AUTUMN MEETING OF THE ASSOCIATION OF THE HUNGARIAN GEOPHYSICS
ABSTRACTS OF THE PRESENTATIONS
SECTION „A”
„Geosciences in an energy-driven world”
Seismic survey in Sultanate of Oman
László Gombár (GES), István Sebe
(MOL)
In the summer of 2007 the GES company
received a request from MOL Upstream Division to prepare a feasibility study on
the necessary technical and financial conditions at which GES could give a
competitive proposal for 2D seismic survey planned by MOL Hawasina LLC in the
Sultanate of Oman. MOL and GES had to face the challenges as follows:
-to get to know the referring Omani laws and register an
Omani-Hungarian joint venture company
- organization fast and safe forwarding of a full 2D
vibroseis crew from Hungary to Oman
- furnishing comfortable camp facilities and accommodation
for more than 100 people at the time of an oil industry boom
- permitting and data acquisition in the vicinity of the
capital and west from Muscat crossing the most densely inhabited and intensively
cultivated seaside lands
Owing to the effective cooperation of
MOL and GES experts all the necessary preparation procedures and works were
completed between October 2007 and February 2008. Equipment of the vibroseis
crew (about 150 tons) was transported with one route within one day from
Budapest to Muscat by the largest aircraft of the world, the unique AN-225.
Between March and August of 2008 about
950 line km 2D seismic data was recorded at various surface conditions with 240
fold of CDP coverage. Additionally a dynamite test survey was carried out in the
mountainous part of the license area.
Presentation shows the main stages of
preparation and data acquisition works during the project.
Underground Coal Gasification, UCG: the rediscovered
technology and the environment
Kiearan Flockton (White Coal Energy)
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Underground Coal Gasification, UCG is a
well-known technology that has been rediscovered in the last years. It is a
simple chemical process, where restrained oxidation of coal carbon in steam and
limited oxygen current provides methane, hydrogen, carbon monoxide, and carbon
dioxide, CO2 in a natural environment. The processes can be
engineered below the surface to give the best results for the environment while
releasing valuable energy for industry and the populations’ domestic needs.
From the environmental protection point
of view there are technological requirements and possibilities for UCG.
Hydro-geological understanding is crucial to the environmental success of the
technology, and the disposal of the CO2 is another key element of the
reduction of greenhouse gas emission as the CO2 capture is easier and
more economic form syngas. CO2 sequestration and geological storage
is a by-product of the oil and gas industries experience. When bringing these technologies
together, UCG can give us a very high degree of environmental security with
significant domestic energy production.
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Exploring Unconventional Hydrocarbons in the Makó Trough:
Challenges and Lessons
Anita Horváth, Gábor Bada, Péter Szafián,
Ron Wallis (TXM); Orsolya Sztanó (TXM & ELTE)
The latest phase exploration in the Makó
Trough, commenced a few years ago, has focused on the utilization of
unconventional hydrocarbons. Accumulations are regarded as “unconventional” when
they cannot be produced economically except by means of some sort of
stimulation, usually hydraulic fracturing. The model we have developed for the
evaluation of the hydrocarbon potential indicates a significant gas accumulation
in the area of the Makó Trough. The tally of the distinctive attributes of the
hydrocarbon system and the combined analysis of the available geological data
led to the conclusion that the Makó Trough represents an area of active basin-centered
gas accumulation (BCGA), with very significant perspective reserves.
In a BCGA, hydrocarbons do not
accumulate conventionally, in structural or stratigraphic traps, but rather in
cells. Due to the geological setting of the Makó Trough, the hydrocarbon cell
here forms a relatively continuous zone marked by considerable internal
lithological and petrophysical variability. The most prolific parts, called
sweet spots, possess a reservoir potential higher than the average. The
identification of these sweet spots constitutes one of the most important, and
quite possibly the most challenging task of the entire exploration project.
The hemipelagic Endrőd Formation, which
acts as the source rock, contains organic-rich marls in a depth delimited by the
170-230 °C isotherms. These marls constitute the still active hydrocarbon
“kitchen” of the BCGA in the Makó Trough. The top and bottom boundaries of the
cell essentially coincide with the turbidites of the Szolnok Formation and the
top of the pre-Neogene basement, respectively. In light of the fact that
pressure, temperature, and maturity tests have produced rather similar results
in a number of wells in the area, we have reason to believe that the extension
of the Makó Trough’s BCGA is of regional dimensions (>1000 km2). The
thickness and lateral extension of the potential reservoirs yield a cell volume
as great as several hundred km3 – the largest single prospective gas
occurrence in Hungary to date.
Due to its novelty and complexity, the
exploration of this unconventional resource demands the concurrent application
of a wider range of geological and geophysical methods. In this presentation, we
use selected examples to give an idea of where we stand on the way toward
understanding the Makó Trough, particularly in terms of the geometric and
structural features of the basin, the depositional (basin-fill) processes, and
of the maturation history and accumulation properties of hydrocarbons.
The geophysical surveys were
purpose-designed to enable the mapping of the deep sedimentary trough and the
sediments deposited in it. The data acquired to date suggest that the basin-centered
gas accumulation occurred in the Lower Pannonian strata (11-6? Ma). Interpreting
the 3D seismic data, the structural features and sedimentology of the basin can
be studied in excellent resolution, while the integration of the seismic
information with the geological data obtained from the wells allows us to
interpret local well information extensively to gain a deeper, three-dimensional
understanding of the basin.
The sedimentary sequence filling up the
Makó Trough displays distinct stratigraphic units separated by unconformities.
Mapping the top of the pre-Neogene basement provides valuable insight into the
nature of the paleo-geomorphological elements and the sedimentary environment at
the onset of rifting. Paleontological information dates the syn-rift sediments
of the trough to the Late Miocene (Early Pannonian), suggesting that the most
intensive phase of basin evolution here was delayed by a few million years
compared to adjacent areas. For the environmental reconstruction of the
post-rift sedimentary sequence, we start with the assumption that initially a
starved basin existed here, where sedimentation could not keep up with the rate
of subsidence (Endrőd Formation). The basin was then almost completely filled by
the turbidites of a prograding delta system (Szolnok Formation), followed by the
sediments from the pro-delta (Algyő Formation) and the delta plain (Újfalu
Formation). During the Plio- and Pleistocene, the area continued to subside at a
decreased rate, providing a limited accumulation space filled by a thick
sequence of alluvial deposits similar to the paleo-environment of the Tisza
River and its tributaries prior to regulation.
Our modelling of basin evolution in
terms of subsidence, thermal and maturation history based on the results of
geochemical, petrophysical, and paleontological investigations reveals that the
organic matter accumulated in the trough underwent exceptionally rapid
maturation during the last 5 to 7 million years. In fact, source rocks continue
to mature at present time, and the hydrocarbons they generate continue to
migrate and trap. The rather young age of the Pannonian Basin and its
hydrocarbon system makes it quite different from the classic examples of basin-centered
gas accumulation, such as the Rocky Mountains in the U.S. This means that the
exploration and production experiences of those classic examples have but
limited direct application to the unconventional hydrocarbon systems in Hungary.
PHYSICAL-GEOPHYSICAL CONSEQUENCES OF MAGNETIC PHASE
TRANSITION
János Kiss (ELGI, *), László Szarka (GGKI, *), Ernő Prácser
(ELGI), Antal Ádám (GGKI); (*) University of West Hungary, Kitaibel Pál Doctoral
School of Environment Sciences, Sopron
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Crustal magnetism originates from
subsurface regions, where the temperature is lower than the Curie temperature,
since the magnetic materials lose their ferro(i)magnetism at the Curie
temperature and they become paramagnets. Consequently, any geophysical
exploration indicates magnetism only from the sub-Curie temperature range. In
the investigation of magnetic parameters, this geothermal-gradient based
temperature limit means a material- and depth-dependant constraint.
There are various interesting
(petrologic, mineralogical, physical and geophysical) phenomena just below the
Curie temperature. One of them, maybe the most important one, is the sudden
increasing of susceptibility at temperature of the magnetic phase transition.
This phenomenon is called as Hopkinson effect or Hopkinson peak. According to
our hypothesis this phenomenon occurs in the earth's crust, and it generates an
effect which can be observed at the surface as geomagnetic crustal anomalies.
The Conrad discontinuity, which is the
boundary between granite and basalt-gabbroid types of crust, and the boundary of
so called RLC (reflective lower crust) can be found more or less also in this
depth interval. According to some laboratory experiments, the elasticity
parameters, the density and the wave velocity also might have changes in this
depth (or temperature) interval. Furthermore, there are remarkable
magnetotelluric conductivity anomalies also in this part of the crust.
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The Curie depth of different magnetic
minerals can be defined only from the geothermal gradient or from geomagnetic
depth estimation. In the latter case it is possible to determine the depth of
the deepest magnetic sources in the given area, without any knowledge about the
nature of these sources.
In this presentation we provide a
summary about the results of the project “Geophysical consequences of magnetic
phase transition in the earth’s crust” (OTKA-68475).
Relation between the Mecsek and Villány Zones in the
Jurassic based on correlation of successions
Géza Császár, Ágnes Görög (ELTE), Balázs Szinger (MOL)
Essentially the nature of the Triassic
successions in the Mecsek and Villány Zones of the Tisza tectonic unit were
congruous. However the thicknesses of the Karolinavölgy Fm (Mecsek) and the
Mészhegy Fm (Villány) considered as Keuper facies in a wider sense show
difference in order of magnitude. It is triggered probably by the early start of
rifting and the distances between the rift center and the depositional areas. At
the southern margin of the Mecsek Zone along the main listric fault, a rapid
subsidence and an equivalent sediment accumulation went on in the Early
Jurassic. The maximum thicknesses of these formations are as follows: Mecsek
Coal: (1200 m), Vasas Marl: (700 m), Hosszúhetény Calcareous Marl (350 m),
Mecseknádasd Sandstone: (900 m), Óbánya Siltstone (160 m). Intercalations of
conglomerate and breccia beds of carbonate, magmatic and metamorphic rocks are
known from the Upper Triassic up to the lower Middle Jurassic.
The increasing distance between the
source and the accommodation areas, and the increasing water depth resulted in a
decrease of thicknesses of 1 or 2 order of magnitudes in the Middle Jurassic. It
happened together with the change of deposition from siliciclastic to pelagic,
often siliceous carbonatic one. The first traces of rift type volcanism are
evidenced in the middle part of the Upper Jurassic in the form of pyroclastics.
The volcanic activity became intensive in the Berriasian and later continued
with a production of a new (Mecsek) type atoll developed on thinned continental
crust.
In the Villány Thrust sheet of the
Villány Zone the highly lacunose Upper Triassic is followed with gently angular
unconformity by the 8 m thick Somssichhegy Limestone of Pliensbachian age
(according to Vörös, 2008). After
another long submarine break, the Bathonian to Callovian Villány Fm („ammonite
cemetery”) of 0.4 m thickness deposited. Elsewhere this formation is underlain
by Middle Triassic carbonates. The next sequence (Szársomlyó Limestone Fm)
started in the Oxfordian with planktonic foraminifera-bearing pelagic limestone
and finished in part in reefal carbonate platform environment in the Berriasian.
In between the two zones, in the eastern
continuation of the Görcsöny High, the first sediment is the cherty crinoidal,
radiolaria-bearing limestone of Middle Jurassic, deposited on the metamorphic
Baksa Complex or on the Middle Triassic carbonates. The aim of the presentation
is to try to reconstruct the Jurassic palaeogeographic history of the relevant
zones.
Odd Things in Well Log Interpretation
Bertalan Kiss, József Tóth, Ilona Vargáné-Tóth, István Szabó,
Ádám Spitzmüller
(MOL E&P Formation Evaluation)
On the well logs the rock’s composition,
texture, structure, the type of fluid (water, oil, gas) in pores and its amount
are primarily reflected. In practice, especially in well log interpretation, the
parameters connected to rock’s texture properties can be very interesting too.
These parameters or attributes may appear inconsistent; due to indefinable
concepts, to excessive affection to traditions and to knowledge or information
shortage. These parameters are treated as constants in layers, although known
that vary within certain values.
Examples of the inconsistencies in the
literature that they use the resistivity of the flushed zone (Rxo), the
transition (invaded) zone resistivity (Ri), the uninvaded zone resistivity (Rt /
Ro), the diameter of transition zone (di), but they don’t use the diameter of
flushed zone (dxo). "Over-consistency", or rather an excessive insistence on
identifying with 2 the value of cementation or porosity exponent (mR=2). It is
now proven that the rock texture is quantitatively characterised with its
porosity and cementation or more recently, porosity exponent (mR).
The magic numbers 2 and 3 are very often
used as constants or exponents in functions. Shall we categorise this fact to
the numerology, or it’s just a coincidence that some numbers are equal, for
example mR ≈ Δts/ Δtp, or mR ≈ 2/CP, mR ≈ nR…?
In some cases, the use of "formal logic"
may help, when we only analyse the acoustic travel time – porosity
transformation functions, there are a lot of similarity between the evaluation
of electrical resistivity and determination of shale volume.
The information hierarchy in oil
industry makes an interesting situation (core data, production data, etc.) with
particular attention to the characterisation and evaluation of unconventional
reservoirs.
We wish to introduce some more
unusualness and not confirmed connections, looking for possible petrographic,
physical and mathematical background. The goal of this presentation is to make
an attention on the main problems of well log interpretation, making it easier
to understand and perhaps the development of this expertise. We believe that
from time to time, it is worth and even necessary to return to the roots, and
systematically reflect on the past experience and use them in our further
projects.
Reworking
of old well-logging data in geothermal exploration
Pál Lendvay, László Zilahi-Sebess (ELGI)
The properly calibrated devices are not
always available before interpretation. The regional evaluation often has to be
completed from the well logs measured with logging instruments of different
type, measuring the same physical parameters and having the different depth of
investigation. The available logs had to be homogenized and had to be calibrated
subsequently.
All these processes are permissible
because it can be supposed from the genetics of the region that statistically
similar strata would be compared in the different boreholes. The overlay
of trend-type functions was made finally by co-scaling the curves.
A few boreholes were needed as pillars
for quantitative interpretation having a complete series of logs. The relation
in these boreholes were established by more processes checking each others and
they were extended for the boreholes having less measurements, only one
resistivity curves sometimes.
The resistivity logs of different
investigation depth show the different invasion-state of the same layer. That’s
why the curves have different dynamic ratio. The simplest solution for that
seemed to use the logarithm of resistivity as a relative clay indicator,
similarly to SP or GR curves. The porosity values of the components were
estimated based on the compaction trend. The physical background of it was, that
the electrical conductivity can be considered being directly proportional to the
specific surface, when tortuosity was near
constant.
It became clear that the sonic porosity
is in a very good correlation with the total porosity calculated from nuclear
methods.
Our model consists of two main
lithological components (sand and clay) and three kinds of porosity (free water,
subcapillary water and adsorption water). Both the adsorption water and the
subcapillary one are considered to be in direct ratio to clay content, that’s
why the estimation of volumetrical clay content is very important due to
calculation of effective porosity in our model.
The conclusion from the sand-to-clay
ratio for total porosity can be made only knowing the compaction state of the
sediment. That’s why the test functions for porosity vs depth were created sand
and clay for each.
Heat conduction parameters of the
sediments can be estimated knowing the porosity components but most of the heat
transport is supported by the water flow and it depends on the permeability of
the rock. Permeability can be calculated with the help of modified Timur-equation
based on the ratio of free and bound water.
Handling uncertainty in geology
János Geiger
(University of Szeged, Dept. of Geology and Paleontology, Szeged)
The
uncertainty belonging of geological phenomena can be characterized using several
methods. Most of them relied on probability distribution but recently the theory
of fuzzy sets also appeared in this topic. The traditional way to handle
uncertainty is to derive such estimations which include somehow its effect (e.g.
probability interval around means, standard deviations, and fuzzy numbers).
However there are some possibilities by which the uncertainty can be connected
to the geological evolution of the property analyzed.
This paper
presents how the uncertainty depends on depositional facieses and demonstrates
that, in case of lateral extension, the entropy may be the function of the
geometry of grid cells.
For the
first problem Markov change analysis of some vertical lithological succession is
addressed to the first problem. In this approach three types of entropies are
calculated. Two of them pertain to every state: the first two are relevant to
the Markov matrix expressing the upward and downward transitions, while the
third coincide with the total depositional system. By calculating the second,
third, etc. order Markov sequences (i.e. by powering the initial transitional
probability matrix) and calculating the so called system entropy for each step
an interesting convergence series of the corresponding entropies can be
analyzed. This series converges to the entropy belonging to the limit of the
series of transitional probability matrixes if power goes to infinite. By
comparing entropy series belonging to two identical and one different
depositional facieses it seems to be clear that the form of entropy series, the
speed of their convergence, and the limits are the function of depositional
facieses if the scales are the same.
In the case
of lateral extension one-hundred grid-realizations of a lateral porosity set
were generated by sequential Gaussian simulation. Then the average values, the
width of their probability intervals and standard deviations are calculated for
the first, first two, first three, and finally for the first 100 grids. The
series of means obviously converges, and its limit is the theoretical expected
value of the background population. However the limit of series formed from the
width of probability intervals is not zero. It means that even in the limit
there is a small amount of uncertainty belonging to the information gathered
about the porosity. It open question whether this uncertainty varies with the
depositional genetic, but it can be supposed to be the function of the grid
geometry.
New experiences of logging methods in uranium exploration
in Hungary
Zoltán Balogh,
András Barabás, Béla Szanyi, Jenő Mázik (WildHorse Energy)
WildHorse Energy Hungary, owned by an
Australian company was formed in 2006 with the aim of exploration and production
of radioactive ore. The WildHorse Energy Hungary received an exploration permit
to Bátaszék area and Dinnyeberki area in year 2006. In the Bátaszék area
reconnaissance exploration was started in the summer of 2007 by airborne
geophysical survey. The preparation for drilling exploration was started in the
Bátaszék area and Dinnyeberki area in the fall of 2007. WildHorse Energy Hungary
decided to verify historical drilling data by four new drillholes in the
Bátaszék and one in Dinnyeberki areas. The boreholes were drilled in March of
2008 followed by detailed laboratory assay of core samples. The geophysical
logging survey was completed by two companies.
The purpose of the logging data was to
verify the U quantity and quality of historical results. In order to define the
appropriate method the new and the historically applied methods were also
considered.
Mineral resource assessment (formerly
applied method in Hungarian uranium exploration) is based on the natural gamma
ray logs. The application of this method has to be controlled by assay of
uranium cc. of drill core samples. The control involves the determination of
uranium cc. based on assay and gamma ray log, the relations of Ra/U
disequilibrium, and other circumstances (correction of depth, mud, and collar).
The presentation will show the results
of control borehole logs, Dinnyeberki and Bátaszék area and compare them to the
results of historical borehole logs and other laboratory assays.
Coal seam correlation for the
uniform coal seam numbering and coal quality parameter determination for the
Joint Ore Reserves Committee Code, JORC resources calculation in the East-Mecsek
Coal Basin, Hungary
Mária Hámorné-Vidó, András Madarasi, Ágnes Szamosfalvi,
István Kovács, Erika Szeghy, Henrietta Jencsel, György Paszera (ELGI); Lajos
Németh, László Somos (White Coal Energy)
White Coal Energy requested coal seam
correlation on 9800 coal beds using the coal bed depth, thickness and quality
data of 420 boreholes in the E-Mecsek. The coal seam correlation started with
the seam contraction of coal beds considering the initial cut off conditions in
the previous explorations. Contracted coal seams were counted following the
historical data of old reports and cross sections and the traditional numbering
systems in the given coalfield. The traditional coal seam numbers were
interpreted in geological cross sections of the previous reports and in new
lines of four prospecting regions of Pécs, Hosszúhetény, Komló and the northern
region. We tried to identify the original coal seam numbers in 144 lines where
the basin development was interpreted with the occurrences of regional marker
horizons and facies changes. This method helped us to introduce a uniform seam
code system, which consists of 46 coal seams. Following the basin development
the seam numbering starts from the bottom. The new seam code system was verified
and locally corrected if it was necessary with the second editing of the cross
lines.
The uniform coal seam numbering gave us
the possibility to interpret individual coal quality data of core and cutting
samples with statistical approach. Statistical method gave homogeneous and
robust values to the different coal parameters in a given sub-region and seam
level. This was necessary as the boreholes were drilled in different time period
with different methods and the reliability of individual data was often lower
than the acceptable limit as the stratigraphic and well log data differed from
each other during the sampling. We divided the E-Mecsek into 8 sub-regions and 5
seam group levels. Beside of the lower and upper level the middle most
productive coal seam group level was divided into three parts.
SECTION „B”
„Investigations
at the Bátaapáti nuclear repository”
On the Build-up of the Mórágy Granite Body
Zoltán Balla
(MÁFI)
In the course of the exploration of the
National Radioactive Waste Repository (Bátaapáti, Üveghuta, South Transdanubia)
detailed geological and geophysical surveys were carried out. These resulted in
collection of enormous volume of facts, which were only partly interpreted.
It was established that the main rock
types of the Mórágy Granite Formation can be arranged into the following
succession: porphyritic monzogranite — rarely-porphyritic monzogranite —
contaminated monzogranite — contaminated monzonite — monzonite. They form the
Mórágy Granite Body, which is cut by dikes and fracture zones. The latter have
various infillings.
Now it is believed that these rocks
arose due to the mixing of two magmas, the composition of which is represented
by the two extreme members of the rock succession. The product of the more mafic
magma (the monzonite) occur in bodies of cm–km size enclosed in the
monzogranite, which crystallised from the more felsic melt. The hybrid rocks are
the transitional members.
On the basis of the data obtained during
the geological mapping of the land surface, the borehole logging and the tunnel
mapping 8 vertical and 6 horizontal sections were compiled. These give an
imagination of the build-up of the granite body with the following principal
elements:
1. In the middle part of the
approximately 6 km-wide monzogranite strip in the NE part of the Mórágy Block a
longitudinal — NE–SW oriented — 2 km-wide zone enriched in mozonites and hybrid
rocks is located. This zone branches towards the NE and ends. Its continuation
or ending in the SW remained unclear. The main zone is accompanied by a smaller
zone in the NW and two of them in the SE.
2. The zones are composed of monzonite
or hybrid-rock lenses and remind fragmented dikes. These bodies dip towards the
NW at steep angles and are about parallel to the major tectonic zone of the
region, i.e. the Mecsekalja Zone.
3. Within an approximately 2 km2
area explored by drilling the ratio of the monzonite and hybrid rocks arises
from the 37% on the horizon 200 m a.s.l. up to 67% on the 0 m horizon. From the
uniform trend of the rise it can be evaluated that on the horizon about –300 m the monzogranites disappear. This
conclusion is obviously only valid for the explored area and is invalid beyond
it. Nevertheless it is clear that where monzonites are present they intruded
into monzogranites from-below.
Consequently, the mixing of two magmas
took place due to the intrusion of the monzonite magma into the mozogranite
magma as sheet-like bodies. These intrusions were split into branches both along
the strike and upwards. Hybride rocks formed on the rim and in the surroundings
of the monzonite bodies due to the reactions with the country monzogranite.
The monzonite intrusions run parallel to
the Mecsekalja Zone. In a 1-1,5 km-wide strip in the monzogranites along the
Mecsekalja Zone contact metamorphic rocks occur. These show that the original
igneous contact was situated somewhere in the vicinity. Consequently, the
Mecsekalja Zone either influenced the position and build-up of the intrusion or
followed its primary shape and position.
Results of Geophysical Inversions in the Bátaapáti
Project Area
László Sőrés.,
Ernő Prácser (ELGI)
The planned nuclear waste disposal site
near Bátaapáti is one of the areas most extensively studied by geophysics in the
country. To map the Paleozoic granite surface and to resolve the loose sediments
over the granite 841 time domain EM soundings and 51 VES soundings were measured
in a 50x50 m regular grid. Perpendicular to the narrow valleys 15 multielectrode
DC profiles were also measured. Taking into account all available information
(borehole logging data, surface outcrops etc.) a coherent geoelectric model was
created using constrained geophysical inversions. The goal of harmonizing a
multidisciplinary dataset required unique solutions that were not used in
geophysical inversions before.
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Uncontrolled independent 1D inversion of
hundreds of geophysical soundings necessarily leads to un-appropriate results.
There are several expectations that a reasonable interpretation model must
fulfill. The optimization must give a best fitting model, but at the same time
it should not conflict with the general geological knowledge about the area. It
also must harmonize with other types of geophysical and non geophysical data. To
create such a model is not an easy task. There were some corner points
(assumptions) that we could rely on.
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The geoelectric basement (granite) forms a
relatively smooth surface under the hilltops and hillsides, where it is covered
by loess. In the narrow valleys erosion can make the topography really rugged.
·
All over the area the sediments over the
granite surface follow a well defined sequence and resistivity pattern.
·
The top of the sequence is randomly truncated
by erosion.
·
Resistivity is dropping with the depth due to
increasing water and clay content.
Our inversion
strategy was implemented by the following scenario:
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The general layer model of the area, was
determined using electric borehole log data
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At each borehole location geoelectric layers
were determined by joint inversion of electric borehole logs and the adjacent
surface geophysical measurements. The new technique - called “Surface Borehole
Model Optimization” - was introduced during this interpretation project.
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Layer resistivities and thicknesses were
spatially extended over the entire survey area by interpolation. From the
interpolated values start models were generated for all sounding locations.
Inversion were carried out for each station to get the initial granite depth
§
Using the initial granite depth and elevation
values a second generation start model set was created. Truncating the
theoretical layering “virtual erosion” was applied at each station.
§
Second generation start models were used to run
the second batch of inversions.
§
Inversion results were visually checked and
correlated for each South-North and East/West direction profiles. Suspicious or
unacceptable depth and resistivity variations were corrected by restarting
constrained inversions with fixed parameters.
§
2D inversions of 15 multielectrode DC profiles
were rerun with fixed granite depth determined by 1D soundings.
To estimate the error of the inverted
layer parameters several soundings were selected for error analysis. Adding
usual amount of random noise to the same datasets inversions were carried out
100 times and the statistical distribution of layer parameters examined. The
analysis shows that the standard deviation of granite depth is about ± 4 %
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The result of constrained inversion is a
coherent model that gives good correlation between measured and synthetic data,
and is also close to the general expectations. However, there are several cases,
when concept and reality are not in perfect harmony. To visualize the conflict a
“Stress Factor” map was created. This shows the spatial distribution of
difference between the fitting error coming from the constrained model and
fitting error of free inversion. Red spots of the Stress Factor map points to
areas where geophysical data do not respect our geological concept. Possible
reasons: granite surface is not as smooth as expected, 1D model is not
appropriate due to strong 3D distortions, etc.
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Well-logging results at Bátaapáti — from surface
boreholes
László Zilahi-Sebess (Geo-Log &
ELGI) Gábor Szongoth, (Geo-Log) Erzsébet Bánné-Győri (Geo-Log), Attila Galsa
(ELTE & Geo-Log)
During the 10 year period of the surface
investigation we did the well logging in 62 drills, it was about 8000 meter.
There has not been such a big volume complex geological survey in Hungary, and
the well logging has not reached such a big success. Special measurements
(hardly known in Hungary, like magnetic susceptibiliy, acoustic borehole
televiewer, high sensitivity (heat pulse) flowmeter)) were applied during the
project.
The lecture is about the measurements
and the geological, tectonical, and hydrogeological informations gained from it,
especially the own results of well logging like palesoils correlation, granite
weathering crust division, granite crack rating. We have to point out the part
of the acoustic borehole televiewer from the many kinds of results, it helped to
develop the usual measurements evaluation in cracked type rocks.
Well-logging results at Bátaapáti — in-mine investigations
Gábor Szongoth, Sándor Hegedűs (Geo-Log),
László Zilahi-Sebess (ELGI & Geo-Log)
During the tunnel driving, several types
of drill were made to extend the geological, tectonic, hydrogeological and
geotechnical knowledge, but especially to plan and to control the tunnel
driving. The near-horizontal drills caused special technical problems during the
measurements and their interpretation.
Using the experience of the surface
measurements the logging program was reduced, the probes were modified, and the
methodology of the evaluation was worked out.
In this lecture the conditions of the
measurements and the results obtained so far will be presented, which are
especially considerable in geotechnics (rock mass classification).
Magmatic evolution of Mórágy Granite (SE–Transdanubia)
Edit Király,
Zoltán Gulácsi (MÁFI)
The evolution of Mórágy Granite
(SE–Transdanubia, Hungary) — belonging to Tisza megaunit — is outlined by
detailed petrographical, mineral chemistry and geochemical investigations in the
frame of the research project of low- and intermediate-level radioactive waste
disposal.
Hypothesis of migmatites was previously
accepted for the origin of the granitoid complex. The model of magma mixing has
come into the light during this research. The granitoid complex is formed by
mixing and mingling of a felsic and a mafic magma.
In the beginning the felsic and the
mafic melts evolved separated. Monzogranites are developed from a single felsic
melt at the same time as the mafic bodies are crystallised in the early
carboniferous circa 340 million years ago joined the variscan orogenesis. Around
the first rheological threshold, after generation of accessories, biotite and
plagioclase, K-feldspar begins to form, which takes a long period. The mafic
melt could get into the felsic one at that time.
The mafic microgranular enclaves are
developed from a mafic melt characterised by Newtonian liquid and already
contained crystal seeds (titanite, pyroxene, amphibole, plagioclase) when it was
intruded to the felsic melt. The felsic melt caused re-crystallization of early
minerals, which was similar to the contact effect. Afterwards the two melts were
evolved together, however their connections are restricted. The felsic melt had
already visco-plastic behaviour, so the homogenisation was not able to be
completed. As a result of partial mixing of the two magmas, hybrid rocks are
formed as well. Chemical characters of minerals relating to magma mixing are
present only in these hybrid zones. Rock forming minerals (plagioclase,
amphibole, biotite, microcline) and accessories (titanite, allanite) indicate
complex zoning (more mafic zone and rapakivi-like texture) recording the effect
of mafic melt to the monzogranitic magma. There is no such evidence of magma
mixing in the monzogranite or in the mafic enclaves rather mingling is more
characteristic here. Minerals formed from both types of melts can get into the
other melt as xenocryst (pyroxene, amphibole, quartz pool, plagioclase,
microcline) during the mingling. Enrichments in accessories (zircon, apatite,
allanite) and in biotite tables indicate surfaces between the mafic and felsic
melt.
The mafic melt is evolved in discrete
enclave magmas being not in close connection to each other. Therefore the mafic
microgranular enclaves display variable appearances and more diverse whole rock
compositions, especially in TiO2, P2O5.
By the end of the magmatic evolution the
temperature of felsic and mafic magmas became closer and closer to each other.
When the viscosity of the mafic melt became larger the cooling became slower.
Thus the mafic enclaves were increasing of their grain size.
Components still staying in the felsic
melt (Si, K, water vapour and volatiles) get into the mafic melt where apatite
needles are developed after the formation of the major mass. The distribution of
Na2O and K2O, which are related to late magmatic minerals (microcline, acid
plagioclase), does not display any difference between monzogranite and mafic
enclaves. The K overcompensation became significant here as well. It resulted in
K enrichment of rocks originated from primarily K poor mafic magma. The K
overcompensation is petrographically expressed in appearance of late-magmatic,
invasive, poikilitic microcline. This appearance suggests no microcline
previously crystallising from mafic melts.
Migrations and other late magmatic
processes result in similar geochemical characters in monzogranite and mafic
bodies, however REE patterns of monzogranite refer to more differentiated rocks.
The Eu anomaly is more pronounced in mafic enclaves due to the early plagioclase
accumulation from the mafic melt.
Alterations (uralitisation,
biotitisation, sericitisation) are promoted by high K, water and volatile
content of the felsic melt. The late magmatic crystals of microcline protected
their inclusions from the alteration.
After the felsic melt has reached the
second rheological threshold early faults and synplutonic dykes appear. The
leucocratic segregations and dykes are intruded in several phases into the just
solidifying granitoid complex. They are clearly distinguished from both
monzogranite and mafic enclaves by depleted REE patterns and large negative Eu
anomalies.
A greenschist facies mineral association
of actinolite, albite, prehnite and epidote appeared in leucocratic segregations
as well as Ba-infiltration in K-feldspars can be related to the synmagmatic
deformation.
The formation age of the Mórágy Granite: new LA-SF-ICP-MS
U-Pb isotope constraints
Balázs Koroknai, Edit Király, Gyula Maros (MÁFI), Axel Gerdes
(Institute of Geosciences, Altenhoferallee 1, 60438 Frankfurt am Main, Germany)
The Mórágy Granite — located in the
south-eastern hilly foreland (Mórágy Hills) of the Mecsek Mts. — represents the
volumetrically most important surface outcrop of the crystalline basement in the
northern part of the Tisza mega unit. The crystallization age of the microcline
megacryst-bearing biotite-monzogranites and mafic enclaves of predominantly
monzonitic composition is in dispute. Radiometric dating both by conventional
(multi-grain) and single grain U-Pb analyses of zircon — separated only from the
monzogranitic rock types up to now — yielded controversial results.
Balogh et al. (1983) first determined an
U-Pb age of 365±8 Ma using a zircon-titanite isochron, which is in agreement
with the U-Pb evaporation ages (377±5 and 363±13 Ma) obtained on single zircon
crystals by Klötzli et al. (1999). Later on, Klötzli et al. (2004) separated two
age groups: zircons of „normal” magmatic habit (S24–25 typology after Pupin)
show an age of 354±5 Ma, whereas tabular zircons (S4 typology) yielded an age of
339±10 Ma. This latter one was also proposed as the presumable emplacement age
of the pluton. The older ages (~500, ~620, 1150–1200 Ma) from some zircon cores
and xenocrystic domains were considered as inherited components deriving from
older crustal fragments. Recently, Shatagin et al. (2005) proposed — in contrast
to the previous opinions — a pre-Variscan age of 405±4 Ma for the Mórágy Granite
based on conventional U-Pb investigations on multi-grain zircon fractions.
Confused by this controversial age data
we carried out a detailed research (4 samples, 64 analyses) using LA-SF-ICP-MS
(laser ablation-magnetic sector field inductively coupled plasma mass
spectrometry) U-Pb isotope analyses on oscillatory zoned domains of zircon
grains both from microcline megacryst-bearing monzogranites and its mafic
monzonitic enclaves, furthermore from a hybrid monzonite. Such a complete
sampling of the most important rock types of the pluton for radiometric dating
was never carried out before. Our aim was to compare their crystallization ages
and history, furthermore to constrain better the magmatic evolution of the
pluton.
The results deriving from the
monzogranitic rock group imply an age of 337±1,5 Ma for the emplacement and
magmatic crystallization of the Mórágy Granite. This result is unambiguously
confirmed by the concordia (339±3 Ma) and mean 207Pb/206Pb ages (343±9 Ma) of
zircons from cogenetic mafic enclaves (monzonite) dated for the first time in
this study. Rarely preserved, internal domains of zircons from monzogranites
show U-Pb ages around 355–359 Ma, suggesting also an early stage of zircon
crystallisation with uncertain geological background. On the other hand, no
relic, old cores were found in the investigated samples, presumably due to
(almost) complete resetting of U-Pb isotopic system during the main magmatic
event.
Eight concordant analyses on single
titanites from a hybrid monzonite resulted in a concordia age of 332±3 Ma, which
is in accordance with the lower closure temperature of titanite, and indicates
moderate cooling of the pluton. The presented ages clearly confirm the
assignment of the Mórágy Granite to the Variscan orogeny (to its main Lower
Carboniferous orogenic phase) and exclude a pre-Variscan origin.
Morphology, types and internal zoning of
zircon from Mecsek Mountain granitoids resemble very much that of the
ultrapotassic durbachites and associated rocks from Bohemian Massif. These rocks
most likely formed by melting of metasomatised and enriched lithospheric mantle
and all were emplaced shortly after the granulite-facies metamorphic peak in the
Bohemian Massif (ca. 340 Ma).
Brittle shear zones and structural evolution in the
Mórágy Granite
Gyula Maros,
Balázs Koroknai, Antonyina Dudko (MÁFI), Kadosa Balogh, Zoltán Pécskay (MTA
ATOMKI, H–4026 Debrecen, Bem tér 18/c)
The Mórágy Granite is located in the
southeastern part of the Mecsek Mts. It is part of the Variscan crystalline
basement of the Tisza megaunit. The pluton consists of microcline megacryst-bearing
biotite-monzogranite and mafic enclaves of monzonitic composition as end
members, and hybrid rock types of these mingled end members. In the late
magmatic phase leucocratic dykes intruded the pluton. Cretaceous trachyandesite
dykes crosscut the pluton, too.
The deformation history of the pluton
began in the magmatic phase and continued under ductile deformation conditions
during cooling. This phase resulted in the genesis of mylonitic ductile shear
zones. The transitional brittle–ductile deformations formed “pseudo-mylonitic”
shear zones which were inherited by the later brittle deformations in many
cases. On the other hand, the location of a brittle shear zone is often
determined by a rock boundary between rocks of different petrology.
The brittle deformation manifests in
individual fractures and fracture zones. These latter ones are of complex
fracture, fault rock and infilling structure. Based on their phenomenologic
architecture an evolution series could be established. The less evolved type is
the dense fracture bunch, one step further is the sigmoidic duplex of
deformation fish of various size, the next is a shear zone with cataclastic or
brecciated core and the most evolved type is the multi-cored shear zone with
fault gouge of S–C foliation (Maros 2006). The more and more evolved shear zones
are results of multiphase deformations.
The whole size of the most evolved shear
zone type varies from a few decimetres to several tens of metres. The symmetric
or asymmetric damage zones make the bulk volume of the zone, the core zone(s)
span from only 2-3 centimetres to half a metre in width. In most cases various
but mainly carbonate infillings developed in the shear zones. These infillings
are often recycled as breccias by subsequent movements.
The material of the core zones is mainly
argillaceous with various amount of feldspar and quartz debris.
The density of the major zones varies in
the research area. The best continuous outcrop conditions are given in the
shafts. The average distance of them in the shafts is 50-70 metres.
The determination of the amplitude of
the movements is problematic for lack of marker layers. In the scale of the
shafts a few metres drop could be proved. The largest zones could imply drops
from a few tens to a few hundred metres.
The orientation of the zones is
essential to figure out the stress field history and to draw the structural
sketch of the territory. The oriented data sources of the zones are different.
More than one hundred data came from deep boreholes oriented by the ImaGeo®
corescanner system with the help of borehole televiewer measurements (Maros et
al. 2004). A few tens of zones were determined in surface outcrops and another
few tens in the shafts. The right orientation of a zone is unambiguous in a big
quarry or in the shafts, principally in the cases of the correlated zones
between the two shafts, but in cores it is not easy to determine not only the
orientation but even the exact place of the zone. We present a complex method to
determine the depth of a zone in a borehole, and a method to orient the zones
with the help of master faults.
The main polarized strike maximums are
NE–SW, E–W and NW–SE and a minor is N–S.
Detailed microtectonic, XRD, DTG and CT
investigations from several core zone samples prove the presence of cataclastic
flow and S–C foliation in the fault gouges. The <2
m
illite fraction was separated in borehole and shaft samples for K/Ar age
determinations which yielded Mesozoic, predominantly Cretaceous ages (Pécskay
2007, Kovács-Pálffy & Földvári 2004).
The core zone formation is assumed to be
related to a cataclastic collapse of the rock texture due to deformation, which
increased the permeability of the zones and therefore the intruding fluids
caused intense alteration which lead to the shear concentration to a fault core
zone dominated by fine-grained argillaceous material and mineral debris. This
material suffered a pervasive S–C foliation due to the deformation renewals (Maros
& Koroknai in Balla et al. 2009 in press).
Geological documentation of the Bátaapáti inclines
László Gyalog,
Gyula Maros, János Borsody, Judit Füri, Gáspár Albert, Klára Palotás, Balázs
Musitz, Zoltán Gulácsi, Amadé Halász (MÁFI)
During the underground reserch aiming at
the National Radioactive Waste Repository (Bátaapáti, Üveghuta) and the
establishment of the project permanent geological-tectonical documentation was
carried out. The drifting was preceded by preborings of different measure. In
the case of the inclined shafts (1723.5 and 1772.5 m in length) and the joint
shafts (junctions and chambers, 400.3 m in length), preboring was carried out
only in one of the inclines without detailed documentation, however, several
borings starting from the shafts were documented. In the second stage, when the
main gates and their junctions were drifted (altogether 642.7 m), the drifting
was preceded by preborings documented in detail.
The documentation of the inclines was
done principally on the headings and walls due to the drifting technology. In
the first stage of the underground documentation the photos of the heading and
the actual walls were taken from the supported part of the shaft (similarly,
part of the measurements on the walls were done from here), then the
measurements on the heading were done with the help of the printed photos after
supporting the walls.
The photos were taken by the
self-developed ImaGeo® Photorobot. It assembles the photo montage of
the heading and the walls of 28 photos; the picture of the actual wall-section
was produced also of these. The distance of the individual photos from the
Photorobot was determined by programmed laser measurements. After the geodesical
calibration of the heading, the photos and the assembled photo montage obtained
xyz coordinates. In this way the photo montage made by the Photorobot could be
evaluated on an oriented 3D surface. The evaluation of the photo montage was put
into a database vectorially fixed to the photos.
The result of the documentation was a
large number of products. A 1:100 scale geological figure was made of all
headings together with a photo base and geological evaluation. A 1:100 scale
wall map was drawn of the inclined shafts and a 1:200 scale map of the main
gates.
Besides, geological maps of different
scales were drawn of the inclines and their surroundings. As a basic
documentation, the 1:200 scale geological map of the shafts was compiled (in 2
metres height of the shafts), on grounds of it a 1:1,000 scale shaft map
extended an 80–100 m distance from the shafts. Finally, the geological map of
the main gates and their vicinity was presented in 1:5,000 scale in the level of
the gates (0 m asl).
The shafts were drifted in the rocks of
the Mórágy Granite. They were crossed by Cretaceous alkaline volcanite dykes in
some places. In the first 600 m porphyritic monzogranite was the dominant rock
type. Later, in greater depth, hybride and monzonitic rocks became more
frequent.
The tectonic elements were correlated in
the 1:200 scale map between the inclines running 30 metres from each other and
also between the main gates. We became familiar with the typical orientations,
changing from place to place, the infillings, the main features of the fault
zones, and the characteristic impermeable zones in the shafts.
SECTION „C”
„Deep seismic investigations”
Importance of Crustal Structures in Mineral Exploration
of the Athabasca Basin, Canada
Zoltan Hajnal, Bhaskar Pandit, Brian Reilkoff (U. of
Saskatchewan, Canada); Ernő Takács (U. of Saskatchewan & ELGI); Irvine Annesley,
(JNR Resources, Canada);Donald White (Geological Survey of Canada); Alistair
McCready, Dale Wallster, (Hathor Exploration Ltd. Canada)
Modern multifold reflection techniques
were introduced to the Athabasca Basin through the activities of the Canadian
National LITHOPROBE Program in the mid 1990’s. Since then, several very
successful 2D and 3D surveys were carried out, mainly in the eastern segment of
the uranium exploration and mining district, leading to discovery of significant
new ore deposits. Within this region of the basin, predominantly horizontal
sandstones and conglomerates of the Manitou Falls Formation constitute the
sedimentary fill. The crystalline basement lithologies comprise highly folded
and interleaved Paleoproterozoic meta-sediments and Archean orthogneisses.
Despite this apparently simple geology, complex seismic signatures are generated
at the sandstone-basement unconformity, which is the location many of the
economic deposits. Contact(s) between fresh sandstone and comparable basement
rocks generate strong and simple seismic signals. Interfaces between altered
sandstone and variably-altered basement segments (regolith) all reduce the
strength of the reflectivity; and in combination with zones of fracture density
variations, lead to complex multi-cycle wave patterns. Results from in-situ
geophysical and geological logs, and rock-property measurements reveal that the
reflectivity within the basin fill strata is dominantly controlled by porosity
variations; and also, in part, by post-depositional hydrothermal alteration
zones and grain-size lithological changes. Most of the alteration zones are
associated with ore deposits and seismically recognizable through local
anomalous velocity variations. All of the known deposits are also associated
with complex and dipping basement fracture zones. These highly porous fault
systems formed the conduits for the mineralized fluid migration. Numerous
examples from different regions of the basin illustrate that the seismic method
is not only capable of imaging these sub-basement structural environments, but
also can map lithological changes within these regions. Correlation of these
structural architectures to deep seismic sounding results reveals that they are
reactivated faults of the earlier tectonic systems which were established by the
convergence processes of the Trans-Hudson Orogen. Seismic attribute analyses of
2D sections and 3D data volumes have great potential in providing additional
constraints in mapping and identifying the mineralized zones of the structurally
controlled unconformity-type uranium deposits.
Active extrusion of the Pannonian fragment and related
seismicity in the Eastern Alps and the Dinarides – proposal for future
cooperation
Ewald Brückl (Vienna University of Technology)
Recent controlled source and passive
seismic experiments improved our knowledge about the lithospheric structure of
the Eastern Alps and their transition to the Pannonian basin and the Dinarides
substantially. The fragmentation of the Moho into a European, Adriatic, and
Pannonian block controls and the kinematics of tectonic movements, especially
active extrusion of the Pannonian fragment to the east. According to these
models seismicity along the dextral strike slip faults in the northern Dinarides
should be linked to seismicity along the sinistral strike-slip faults in the
most eastern part of the Eastern Alps. Data from ALPASS, CBP, and the ongoing
ALPAACT (Seismological and geodetic monitoring of ALpine-PAnnonian ACtive
Tectonics) allow for accurate earthquake location and calculation of magnitude
and seismic slip in the wider Vienna Basin area. We propose similar efforts in
the APLPASS-DIPS area to test the new tectonic hypotheses.
Lithospheric structure at the contact of the Dinarides
and Pannonian basin obtained from 2‑D seismic and gravity
modelling on the Alp07 profile
Franjo Šumanovac, Jasna Orešković (ALP 2002 Working Group,
University of Zagreb, Croatia)
ALP 2002 was big international seismic
experiment that focused on the lithospheric structure of the Eastern Alps and
surrounding area. Profile Alp07 is one of several refraction and wide angle
reflection profiles located in the transition from Adriatic microplate, through
Dinarides to Pannonian basin. The 300 km long profile Alp07 stretches in Croatia
in the WSW–ENE direction from Istra to the Drava river at Hungarian-Croatian
border, approximately perpendicular to the direction of the Dinarides and the
main faults in the Adriatic region, including a contact between the Dinarides
and Pannonian basin.
Two-dimensional seismic modelling was
done using tomographic inversion and ray tracing technique. The Moho depth is
the greatest in the area of the Dinarides, reaching about 40 km. The depth in
the Pannonian basin area range from 30 to 20 km, and is the least at the end of
the profile. The boundary depth changes rather suddenly, thus making evident the
uneven relief. In order to obtain more reliable data on the crustal composition,
the 2‑D gravity modelling was also performed. The layer boundaries were retained
from the seismic model as there was no need to change them during modelling,
since varying densities in the model produced a good fit to the data.
A geological model was constructed based
on both geophysical models. Three types of the crust were found along profile:
the Dinaridic and the Pannonian crusts that are separated by a relatively wide
transition zone. The Dinaridic upper crust is characterised by low seismic
velocities and densities, but its lower crust has high velocities and densities.
The Pannonian crust can be seen as unique layer characterised by both low
seismic velocities and densities. Large lateral and vertical changes in
densities and seismic velocities can be found in the transition zone. Troughs in
seismic model at the level of Mohorovičić discontinuity are interpreted as major
faults in the lithosphere. Three main lithospheric faults were identified: in
north-eastern part of the Dinarides, under the Sava depression, and under the
Drava depression. The first one may be considered as a result of subduction of
the Adriatic microplate under the Pannonian segment. Similar movements are also
defined within the transition zone, where the Pannonian segment is gradually
rising over on the Adriatic microplate.
ALPASS-DIPS seismic experiment — Receiver functions
analysis on the Alp07 profile
Franjo Šumanovac, Jasna Orešković, Darko Dudjak (University
of Zagreb, Croatia), Endre Hegedűs, Attila Csaba Kovács (ELGI)
ALPASS-DIPS (Alpine Lithosphere and
Upper Mantle PASsive Seismic Monitoring
- DInarides-Pannonian Segment) is a passive
seismic monitoring project located at the contact of the Dinarides and
south-western part of the Pannonian basin. The project is continuation of the
successful active source seismic experiment ALP 2002. The major goal of the
project ALPASS-DIPS is to apply passive seismic methodology in research of the
lithospheric processes and structures related to the transition area between
Dinarides and the Pannonian basin. Despite many geological and geophysical
studies in this area, tectonic and structural relations have not yet been fully
explained. Therefore, this study is yet another attempt to offer a contribution
toward a better understanding of the lithospheric and upper mantle structure in
this area. To reach this goal, P receiver functions are computed from
teleseismic events recorded by temporary seismic stations.
Most of the stations (12) were deployed
along the profile Alp07 (seismic line from the ALP 2002 project) stretching from
Istra, over the islands Cres and Krk, passing near Karlovac and Zagreb to the
border with Hungary. The geophysical model of the crust beneath the Alp07 line
is already constructed and the deployment within passive seismic experiment
along profile Alp07 provides the opportunity to compare the results of the
natural and controlled source experiment. Two more temporary stations were
deployed in Istra, to the Slovenian border, and one in the Pannonian part, near
Slatina. The earthquake recording stations
consisted of three-component,
shortperiod sensors and data were collected during the period of 18 months.
From seismic recordings events with
epicentral distances between 30° and 90° were selected and they are mainly with
NE and SE backazimuth. The teleseismic P receiver functions are calculated from
Ps waves i.e. converted P to S wave at the velocity discontinuities. First,
receiver functions are computed for individual temporary stations and later
stacked along Alp07 profile to obtain 2-D lateral variation of major velocity
interfaces in the crust and upper mantle. The velocity model of the crust and
crustal thickness are taken from the results of the active source experiment.
The Moho depth obtained from receiver functions analysis generally agree well
with results of the active source experiment. From both data sets, crustal
thickness is the greatest under the Dinarides, and the thinnest in the Pannonian
basin area. Exceptions are two stations located in the transition zone between
the Dinarides and the Pannonian basin where agreement is less. This could also
be the evidence that transition zone is heterogeneous, characterised by complex
tectonics and strong lateral and vertical changes in velocities. Those stations
will need to be analysed in more details.
SECTION „D”
„Past, present, future
in mineral prospecting”
selected passages from old times documents of geophysics
and geology
Éva Zsadányi (MBFH)
Nowadays the lecturers, fascinating
their audience, present their presentation of scientific topics using high level
technique of displaying on professional softwares. Looking back to the past of
“displaying” we just have a smile on the presentation methods and achievements
of the technique though those in their own age were up to date. Our
grandchildren will remember to our achievements very possibly with the same
smile.
The public archives of the Hungarian
State Geological, Geophysical and Mining Data Store (archives, repository)
operated by the Hungarian Office for Mining and Geology gives an insight into
the expert materials for more than a hundred years.
Historic and sometimes odd things (at
least, for us) of geoscience expertise, presentations, and language used will be
presented from the old reports of geology, geophysics and mining.
Historic values of the repository are
indisputable. You can find it there, for example, the first domestic report on
bauxite prospecting (by E. Vadász, 1921). The first (standardized) geophysical
report (using magnetic profiling and Wenner-type geoelectric soundings) was
written by B. Vishinsky in 1952. Guidelines for the salt and oil prospecting
were laid down by prof. L Lóczy from 1932.
The old hand-painted colour maps
inevitably have an artistic value. The computer generated colour maps
represented a large jump forward in the seventies, while the 3D presentation
methods gave new vistas in the eighties. Not only the presentation but the
language of the reports changed interestingly as well (it is observable not only
in the Hungarian, but the English and German texts, too).
The author recalls the „good old times”
presenting several documents from the Archives, maintained by the Office for
Mining and Geology.
Looking back the Iharkút geophysical prospecting: what we
did then, what could we do now?
Kristóf L. Kakas, consultant geophysicist
 |
At the backyard of an Iharkút cottage
exactly 35 years ago, in the autumn of 1974 a drilling hit a small bauxite body,
the first of the nearly 30 ones, forming the Iharkút-Németbánya bauxite
occurrence. This is a memorable date in the history of domestic bauxite
prospecting, because from the first productive well on, the synergy of the
geophysical prospecting and the geological/borehole exploration was attained:
the vast majority of the bauxite bodies were found by geophysical mapping, and
the geological results (novel exploration models) formed an application complex
of the geophysical methods, more effective than before. The presentation gives
first a historical overview on the Iharkút exploration, and the role of ELGI
experts in this work.
Apart from the really fortunate
circumstances, the success of the integrated exploration was the result of
several factors. From one side, novel geoelectric methods were applicable that
time, personal and organizational conditions for all-of-the-year geophysical
data acquisition were available, first (and not handy) computers started to
work. From the other side, the Bauxite Prospecting Company professionals became
familiar with and, what is more, recognized the use of geophysical results. The
Iharkút story has effectively supported the aspirations of ELGI to purchase new
instrumentation, while the then-powerful industry gave significant orders to the
Institute.
|
The second part of the paper asks a
question: if the task now would be to explore this occurrence, what methodology
could we apply? Over the past decades (mainly due to the nearly unlimited
penetration of computers) the applicability of some geophysical methods is
altered. Although the question is hypothetical (since currently there is no
bauxite prospecting in this country), we think that with precise magnetic
profiling, with geoelectric tomography, and Turam-type transient (TEM) mapping
one could detect covered bauxite bodies more quickly, more cheaply and more
reliably. This, of course, is not our merit: not we, geophysicists have been
smarter, but possibilities increased.
This paper would serve the memory of the late Gy. Károly and
L. Szabadváry,
key persons at the Iharkút prospecting
Geological expert tasks of the Hungarian Office for
Mining and Geology
István Farkas
(MBFH)
By 1 January 2007 the Government
integrated the Hungarian Geological Survey into the Hungarian Mining Office, and
thus established the Hungarian Office for Mining and Geology, which is the
successor of both predecessors.
The task of the new office is to perform
the state’s duties in connection with mining and geology, in the same way as its
predecessor organizations have done. The merging does not reduce the tasks to be
carried out.
In 2008 the government made an official
review on the administrative orders of the authorities, with special regard to
the tasks of the involved professional authorities. The decrease in the number
of participating expert authorities in favour of increasing the expedition and
efficiency of authority work was the objective of the study. Only authorities
should be involved in the procedures which are really affected.
The 306/2008. (XII. 31.) Governmental
decree provides the elimination and modification of the involvement of each
expert authority. The decree regulates the conditions for assistance, determines
the special issues as well as designates the first and second degree
administration levels.
The paper presents the case types where
the Hungarian Office for Mining and Geology or its regional agencies (mining
inspectorates/captainships) act as expert authorities in geologic matters. It
also shows the professional issues connected to geology in which the expert
authority standpoints can be issued.
The Hungarian Geological, Geophysical
and Mining Data Storage ensure the geological background for the authority work.
From the beginning of 2008, data storage is located in Columbus street,
Budapest. The paper presents the new data storage and the new possibilities of
data services via the Internet.
Functional Discrepancies in the Measures Connected with
Mineral Prospecting and Mining Developments
László G. Somos, chartered consultant
In these Autumn Meetings of geosciences
it is considered as unusual practice to present remarks on legal approximations
about exploration, development and exploitation of mineral resources.
While the new (1993/XLVIII) Mining Act
(together with its amendments) has represented significant importance in the
regulation of mining activities, numerous mining contractor or investor, either
domestic or foreign, confronted with the fact that in the frame of our market
economy it is not so easy – sometimes impossible – task to initiating mineral
exploration or exploitation activities during the last 16 years. This debating
study should try to clear the most important motives, arguments and barriers of
this situation.
We are dealing with the state/public
ownership position of mineral resources (incl. geothermic energy) and with the
functional barriers of the adaptation of this kind of ownership. There is a huge
conflict between rules of estimations of the value of land in the surface and
the value of the mineral commodity below the surface. Several articles of the
Mining Act refer to the substantial importance of the Technical Operation Plan
(TOP). All phases of the exploration, development, and exploitation process are
laced with the existence of a correct and approved TOP, meantime the new demands
in the Government Order No. 96/2005 – in effect by an exaggerated manner -
constrain the real potential of the mining contractor.
There are stipulated specific licensing
requirements for hydrocarbon exploration, development and exploitation in the
Mining Act. According to the recent Mining Authority practice this specific
requirements are – among other requirements – applied for coal seam “coal bed
methane” explorations, too.
We try to treat questions related with
the requirements of land ownership problems (tenement register problems). We
bring on several contradictory exploration, and/or mining plots data published
at the website of Mining Authority. There are articles with contradictory
contents, and wrong glossary definitions in the Mining Act.
The cited practical examples are based
in real data, but then, respecting the business interest of the mining
contractors, we dispense with the concrete areal or denomination identification
of the pertinent contactor or investor.
SECTION „E” „Oil and gas
prospecting”
Aggradational to
progradational sequences of the slope and sand delivery to basin center in the
Makó trough: Integration of 3D seismic volumes and well-logs
Orsolya Sztanó (TXM @ ELTE), Péter
Szafián, Gábor Bada, Anita Horváth (TXM)
Investigating the manner and pace of
shelf-margin progradation is a key to understanding the depositional history of
basin-fill sequences. The sequences constructed as the slope deposits of the
Algyő Formation were studied on an extensive, high resolution 3D volume of 45-50
km long seismic sections acquired in the Makó Trough, parallel to the
paleo-transport direction. Corresponding lithology of the slope and basin center
deposits were given by seven well-logs.
Sediments from the source area were
partly accumulated on the wide, flat-lying shelf of Lake Pannon, while
other portions were passing through the slope to the deep basin center. The
height of the slope was 250-300 m based on correlated well and seismic data. In
plan view, the slope was a 5-7 km wide belt, with a gradient of 1-2°.
The transport processes, rate of deposition, and rate of sand delivery to the
basin in front of the slope were determined by the slope gradient as well as by
grain-size composition and the volume of sediments. The result was the
sequential construction of the shelf margin: aggradation with subordinate
progradation, followed by high-rate progradation.
In “traditional” models of sequence
stratigraphy, the main stage of sand deposition is the shelf during periods of
aggradation, and the basin during periods of progradation. In the Makó Trough,
however, the opposite trend was observed. During aggradation – indicated by
rising shelf-margin trajectory – the shelf builds up from superimposed deltaic
lobes comprising coarsening-up units a few dozen meters thick. Meanwhile, the
shale-prone slope is constructed mainly from prodelta and subordinately
shelf-margin delta sediments, resulting in continuous high amplitude
reflections. The majority of the sand, however, is transported further to the
basin trough canyons and channels by clayey-sandy effective turbidity currents,
and deposited either as extended or slope-detached thick turbidite lobes up to a
distance of 20 km. Thus the vertical accretion of the basin floor equals that of
the shelf region. During progradation, when the shelf margin trajectory is
approximately horizontal, the slope is shown by weak-amplitude, reflection-poor,
chaotic units made up of alternating shales and sandy units. Deposition occurs
on the lower part of the slope and at the slope-toe region. Reflections downlap
within a distance of 10 km. Thus the sediments of the shelf-margin deltas are
sand-rich with low clay content, producing non-effective turbidity currents of
short-distance transport. Consequently, the thickness of coeval basin-centered
sediments remains negligible.
The sequence-stratigraphic subdivision
of Lake Pannon sediments has been a matter of debate for more than 20 years.
Based on our observations in the Makó Trough, it seems safe to say that neither
third nor fourth-order sequences built up of LST, TST and HST as “traditional”
models predict can be designated. Instead, the shelf-margin is constructed of
alternating aggradational and progradational units. The sequence boundaries are
represented by surfaces of maximum regression, these overlain by 1-2 reflections
thick transgressive units, thick aggradational early highstand, and
progradational late highstand reflections. The relative lake level rose
continuously at varying rates. Relative level drops larger in amplitude than the
seismic resolution did not occur, thus lowstand fans and wedges did not develop
either. Sand delivery to the basin center is characteristic during the early
highstand, while the slope-toe becomes the main locus of deposition during the
late highstand and maximum regression.
Fast and cheap pre-stack migration in 3D
Ferenc Horváth, Miklós Körös,
László Németh (GES)
Acquisition of up-to-date 3D surveys
requires investments of several 100 millions or billions HUF and the oil
companies would like to see the results and the turnover of their money as soon
as possible. Pre-stack data processing of the several 10 million recorded
channels can take months even with the recent high speed and high capacity
computers.
Our clients many times prefer rather the
promptness than the fine tuning of the data processing. They want to see the
seismic image of the earth’s interior as soon as possible though it is not the
perfect and final one.
This request led us to develop a so
called „fast and cheap” (FC) technique for the 3D pre-stack migration
processing.
There were two points where the
turnaround time could be reduced:
All the usual data checking and test
procedures have been omitted in the processing centre; - pre-stack processing is
started on data channels provided by field QC processing.
Pre-stack migration velocity space
determination is based on groups of CDP gathers along a not very dense grid,
which can be much faster than doing it along in-line stack sections. At the
selection of appropriate migration velocity it is acceptable to follow the
curvature of reflection arrivals. The acceptable CDP fold is provided by the
pre-stack algorithm itself.
The presentation shows the effectiveness
of FC technique on examples and compares results obtained by FC and normal
pre-stack 3D migration processing on the same recorded dataset.
Options of multiple drilling in the Mako Trough
Tibor Balázs, Zsolt Feczkó, Gary
Lavold (TXM)
As some of you may know, Falcon/TXM has
been actively exploring the options of bringing the basin-centered gas
accumulation (BCGA) in the Makó Trough under production. Over the past few
years, Falcon/TXM has taken strides toward utilizing this significant
prospective gas reserve. The years following the development of the play have
been dedicated to locating and drilling 4 wells on the flanks and 3 on the basin
centre based on 3D seismic survey data. The data obtained from these wells in
turn have been used to refine the model set up on the basis of the 2D and 3D
survey results. Drilling these wells has reconfirmed a fact that had been widely
known for some time: the reluctance of the Makó Trough to give up its riches.
In order to reach the BCGA cells, the
wells need to penetrate to great depths of 3500 to 5500 m. Drilled in
high-temperature, overpressured rock cells that are also compacted and have poor
permeability and porosity to boot, the wells will not be capable of economically
feasible production until after hydraulic fracturing has been performed. Mainly
due to the poor permeability, BCGA wells have a drainage area of a rather small
radius compared to conventional wells, albeit one that is much longer
vertically.
While these challenges clearly entail
financial consequences, the economy of production will to a large extent depend
on well pacing. As to increasing that spacing, the obvious solution is to drill
several wells from the same single site – a process known as multi-pad drilling.
Many modern drilling rigs today come
capable of being skidded from cellar to cellar using a simple hydraulic system
even with a drill pipe stand in the mast, and those that do not can be
retrofitted for that capability with relative ease.
The ideal distance between the cellars
in the same common concrete basement is 4 to 6 meters. In the simplest
configuration, which is the linear one, the substructure and the mast with the
stand can be skidded from one cellar to the next, in hours rather than days,
while everything else – the tank system, pumps, generators etc. – remains in
place. It can be said, therefore, that the number of wells that can be drilled
in a linear multi-pad configuration without rigging up and down will be
determined, in addition to the well pacing, by the pressure loss in the hoses
and lines and the maximum length of the flow line. This yields 4 to 6 wells that
can be drilled with a single rig up/rig down. A four-well cluster already
represents significant economy of time and thus significant savings.
The costs can be further reduced by
regarding all the wells drilled from the same spot as a single drainage area,
and by planning stimulation, fracking and other jobs on a rolling schedule so
they can proceed from well to well without interruption or loss of time. One
potential benefit of this method is keeping the rig drilling away while fracking
or even production testing is under way on another well that has already been
completed.
Advanced Seismic Acquisition and Processing – aims and
results of a research project
Péter Scholtz, Zsuzsanna Nyári (ELGI)
Synthetic
dataset with harmonic noise contamination. From left to right: original
trace (above) and its spectrogram (below), estimated upper harmonic
components, trace after filtration. |
In view of the world’s rising energy
demand and in the absence of breakthrough carbon-free technology, a portfolio of
options is needed to manage the risk of global climate change. All sustainable
options must be developed and used. Capture and geological storage of carbon
dioxide arising from chemical and combustion processes is a relatively new
possibility that is rapidly gaining support.
The application of Advanced Seismic
Acquisition and Processing techniques is an effective tool in support of CCS.
The current common technique in seismic exploration on land is based on multiple
vibratory sources and grouped geophone receivers. The grouping is required to
attenuate unwanted coherent noise, to reduce ambient noise and to increase the
input signal level. This kind of acquisition and pre-processing technique is
both robust and uncomplicated, but it suffers from limitations. The major
drawbacks are the degradation in spatial and temporal resolution due to the
simple summing in the group formation of the sources and receivers (intra-group
differences, inappropriate filter response), and the usage of a theoretical,
rather than true, signal in the pre-processing.
There are several methods already
developed to overcome the described limitations, but they either do not give
satisfactory results, or are too complicated to utilize successfully. In our
research activity (ASAP – Advanced Seismic Acquisition and Processing – EU Marie
Curie TOK ...) we were aiming to solve some of the problems in the existing
methods by looking for suitable signal analysis tools, analysing the vibratory
source signals, studying their behaviour (special attention was given to the
distortion), and developing source signal estimation tools to be used with
source signal separation techniques.
|
We have studied the level of harmonic
distortion during signal generation. We have compared different estimates of
source signal components, originating from various data types (vibratory
accelerometer data and geophone data at several offsets), investigated their
differences and the causes.
We have also modelled the vibrator –
earth coupled system and studied the applicability of vibratory accelerometer
data based methods to estimate near-surface properties of the earth (layer
velocity, thickness) for static correction.
We have investigated the possibility to
compensate for the intra-array static and offset difference caused high
frequency signal loss during the seismic acquisition. By a simple optimization
technique, when the vibrators are started with delays, we can reduce the
detrimental effect of inaccurate signal summing.
Simulated Annealing and Genetic
Algorithm based harmonic noise suppression methods were developed, too. These
techniques could be applied during slip-sweep acquisition measurements, when the
quality and/or productivity enhancement is important. The optimization processes
help to reduce the correlation noise due to signal distortion.
In Hungary current applications are for
the definition of the sub-surface for nuclear waste repositories, and for the
mapping of the sub-surface for geothermal potential. Exploration of hydrocarbons
will also benefit from these advances, and it is noted that this industry has a
current major interest in CO2 storage.
The research were
made possible by the support of the Marie Curie Host
Fellowships
for Transfer of Knowledge (TOK) Development Host Scheme (contract
no. MTKD-CT-2006-042537).
The Basement of the Tertiary Formations on the
Battonya-Pusztaföldvár Ridge
Marianna R. Tátrai, Tamás Bodoky, Attila Csaba Kovács (ELGI)
In Battonya region a detailed
investigation of the geological structure of the area has been carried out based
on former seismic and well-log data with a view to geothermics. The studied 3D
seismic data provide very good information on the structure of sedimentary
formations and on the topography of the Tertiary basement.
In the area the basement of Tertiary
formations are formed almost entirely from Palaeozoic rocks of the
Battonya-Pusztaföldvár ridge. On them Miocene beds can be occasionally found
mostly in basement depressions. The Tertiary basement appears everywhere by
clear, well recognizable reflection arrivals in the seismic data. However, in
the study area tectonic events of the basement happened during or after the
basin evolution could not be identified by seismic data.
On the southern part of the area the
erosion surface of the Tertiary basement is in an uplifted position, while
towards the north it slowly deepens. The investigated region extends beyond the
area of the Battonya-Pusztaföldvár ridge and reaches its steep slope falling
down towards the Békés Basin
On depth map of the basement the bearing
has a direction of W-E. The surface of the ridge is dissected by northward
directed erosion valleys and canyons bound occasionally to pre-rift structural
movements. An especially deep (occasionally with a depth of 300-350 m) valley
system can be found in the middle of the northern part of the region. The
dip-magnitude version of the basement map emphasizes the edges of valleys and so
former watercourses are clearly outlined.
The region was well surveyed by 2D
seismic lines (65 profiles), too. To control the results also they have been
interpreted and the basement has been mapped based on their data, too. Comparing
the basement maps resulted by the two different data sets it is obvious that the
one got by 3D data provides much better resolution.
SECTION „F”
„Geologic risks, risk management”
Remediation Experiences of Mecsek Uranium Mines
András Várhegyi (MECSEK-ÖKO), Zorán Gorjánácz (MECSEKÉRC),
János Somlai (Pannon University, Radiochemical Institute, Veszprém)
The remediation programme of Mecsek
uranium mines has been completed by the end of 2008. The treatment and cleaning
of mine waters and contaminated, tailings pond origin waters and the long term
monitoring still progress as well. All the remediated areas could be categorised
into two groups: on areas without any restriction the reconstruction of original
natural background radiation levels and removal of any pollutant is essential
requirement. On restricted areas certain kinds of human activity is restricted
(human residence, food production etc.) to ensure the population dose limit and
to protect the environmental isolation of radioactive material.
The long term monitoring started with a
4–5 year after-care monitoring and continued by a real long term control period,
revised 5 annually and the necessary interventions are made.
Several technical and radioprotection
difficulties have been arisen during the remediation works, for example using
radioactive mining waste for road construction, radioactive pollution of surface
streams, radon filtration from underground mining cavities etc. Those problems
were successfully treated by proper risk calculation and practical use of ALARA
principle. In our presentation that cases are to be briefly introduced.
Gas geological modeling of transport of mofette gases in
soils
István Csige (University of Debrecen - Institute of Nuclear
Research, Department of Environmental Physics, 4026 Debrecen, Bem tér 18/c);
Sándor Gyila (Hospital of Cardiology Covasna, 525200 Covasna, M. Eminescu 160)
 |
Deep in the lithosphere, little is known
about the transport mechanism of the mofette gases, which seep towards the
surface from depths of occasionally more then several tens of km. There are
indications that the gases can make this long journey even in a few months. On
the other hand it is more accessible to study the transport of these gases in
the near surface soil layers. In this work the dynamics of mofette gases seepage
near surface has been studied theoretically and experimentally. Model
calculations of transport of heat, groundwater and pore gases in the vadose zone
near the surface were done and compared with results of experimental
measurements. Seasonal and semi-diurnal variations of flux of mofette gases from
a 20 meter deep bore hole were observed and linked to variations of relevant
weather parameters. |
Ensuring Balance in the Borehole of High Pressure High
temperature (HPHT) Wells
István Bánhidi, Sándor K. Szabó (TXM)
The objective of this presentation is to
demonstrate those technicalities, which are oriented towards the assurance of
prevailing borehole balance during the planning and exploration phase of
unconventional reservoirs. According to the above statement, the following
topics will be explained in detail during the presentation:
§
TXM Oil and Gas Exploration LLC – aimed to
introduce the exploration drilling of unconventional reservoirs.
§
Aspects of HPHT well design; plan verification
in relation to balance restoration (kick tolerance).
§
Wellhead, BOP, and Choke Manifold
configurations in HPHT wells.
§
Testing formation strenght and its function
(e.g. LOT and FIT).
§
Significance of pore pressure prediction whilst
drilling.
§
Restoring balance and well control
technicalities of HPHT wells.
Integrated Geophysical Investigation of the Dunaszekcső
Landslide
László Zilahi-Sebess, Attila Csaba Kovács,
Tibor Gúthy, Endre Hegedűs, Róbert Csabafi (ELGI)
On the 12th of February, 2008 the loess
cliff at Dunaszekcső slipped down approximately in 300m length and subsided more
than 10 m in a 30-35 m wide strip at the side of the river Danube. After a
couple of hours the crashed and destabilised mass of loess pushed off a small
river shoal into the Danube, forming a peninsula a day after. On the request of
the Hungarian Office for Mining and Geology, the Institute investigated the site
with passive and active seismics as well as with cone penetration tests (CPT).
On the 17th of February a (passive)
seismic monitoring network of six units was established. With these continuously
recording equipments the observation and registration of very weak,
nanoseismical signals of the site was carried out. After observing several
seismic emissions of very low energy, two source areas of seismic noises were
identified. CPT was carried out on four sites, two locations at the foot of the
slipped loess wall and other two locations north of this area, which is
untouched by the landmass movement. Based on the recorded CPT logs and two
earlier drill holes we outline the simplified structure of the loess sequence.
In the beginning of March seismic
measurements with active source was performed along two lines, one at the foot
of the hill along the slipped mass of loess and another one at the top of the
undisturbed loess plate approximately parallel to the other line. On the seismic
tomography the slipped block of loess can be well identified. At the northern
margin of the landslide based on the result of the reflection processing — down
to 300-350m— can be identified a significant deep structural zone, which can be
recognised also on tomography and even at near surface on the correlation of CPT
logs.
SECTION OF POSTER PRESENTATIONS
Fabric analysis of block-and-ash flow deposits of Merapi
volcano (Central Java, Indonesia) by using a photo-statistical method
Dávid Karátson (ELTE, presently at Geowissenschaftliches
Zentrum der Georg-August Universität Göttingen); Ralf Gertisser, Sylvain
Charbonnier (School of Physical and Geographical Sciences, Keele University,
Keele, UK)
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The latest eruptive episode of Merapi
volcano (Central Java, Indonesia) in 2006 produced a series of dome-collapse
pyroclastic flows in the Gendol river valley and adjacent areas on the volcano’s
southern flank. The largest of these flows on 14 June 2006 reached a distance of
~7 km in the Gendol river valley and caused two fatalities and destruction in
the village of Kaliadem. The valley-filling block-and-ash flow (BAF) deposits in
the Gendol river valley constitute nine overlapping lobes that were formed by
successive high-density, ground-hugging basal avalanches, generated during and
after the major dome-collapse events on 14 June. They are massive mixtures of
decimetre- to metre-sized blocks set within a fine lapilli to medium ash-grade
matrix and characterised by steep, bouldery and clast-supported fronts.
Variations in grain size and surface morphologies of the basal avalanche
deposits from the individual block-and-ash flow events are related to different
depositional facies, resulting primarily from effects of channel confinement,
slope and pre-event topography.
In order to refine the deposit facies
architecture and improve our understanding of particle transport and deposition
of BAF flows within the framework of granular flow systematics, a
photo-statistical method was applied to the 2006 Merapi BAF deposits. At first,
high-resolution photos of BAF deposits possibly parallel to flow were taken.
After photo-improvement and transformation into TIFF files, the resulting images
were analysed by Geo Orient 9.2 and UTHSCSA ImageTool 3.00 software, that were
previously used successfully to obtain detailed and reproducible directional
fabric data.
The purpose of our fabric analysis is
twofold: (1) to infer the relative distance from the vent via vector length (R),
which is the best measure of fabric strength of gravity-flow deposits and (2) to
point out fabric strength differences for various depositional facies.
R is defined as the resultant vector
length of clast alignment (between 0 and 1) computed from clast angles visible
on a vertical outcrop face. It was found previously that volcaniclastic
mass-flow deposits develop a relatively strong fabric already at 0.5-1 km from
source; for BAF and other pyroclastic flows, R is ~0.45. A preliminary analysis
of a parallel-to-flow main BAF unit yielded a R=0.6 mean vector length, with
clasts being scattered between 92-272o. The very strong fabric
suggests well-developed shear stresses that may be due to the high concentration
of clasts in a cohesive flow. Further comparative analysis is in progress.
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Information Management in Complex Geophysical Prospecting
Projects Supported by Data Structures and Tools of the KINGA Portal
Gergely Detzky, László Vértesy, Ágnes Gulyás, László Sörés
(ELGI)
In consequence of the latest
developments in productivity and methodology of the field geophysical data
acquisition technology the resulted data quantity is greater in sense of amount
and diversity as well. Such a large prospecting projects as the investigation of
radioactive waste deposition site in Bátaapáti, demands an effective and
distributed geophysical data management based on coherently standardised data
structures.
Even though the effective development
application capabilities and many internet based IT solutions are present to
fulfil the requirements articulated by the recent geophysical data utilisation,
there were no strong international results up till now in standardisation and
integration of the complex geophysical data service management technology.
ELGI has participated in the
international GEOMIND (Geophysical Multilingual Internet-based Data Service),
and in the domestic KINGA (Key for Internet-based Geophysical Data Access)
projects. Both projects aim the development of internet based geophysical data
services in order to facilitate the satisfaction of the claims in an up-to-date
way. The efforts of the ELGI resulted formulations of the geophysical metadata
profile and general data model compatible with existing international standards
for GIS metadata (ISO 19115) and European INSPIRE directive for geoscientific
data. Practical applicability of these data structures is approved by that great
number of different geophysical information types already seamlessly represented
in these two service systems.
Currently, internet environment on the
client side of the KINGA portal provides functions to perform GIS searching and
alphanumeric selection based on metadata attributes, followed by download of
information from entire repository of geophysical data of ELGI. At the same time
the IT tools facilitating a convenient remote data management are also form an
integrated part of the KINGA system.
Pliocene-Pleistocene drainage network in the Makó Trough:
Mapping on 3D seismic data
Anna Horányi, Orsolya Sztanó (TXM & ELTE), Péter Szafián,
Gábor Bada, Anita Horváth (TXM)
The Makó Trough is one of the deepest
Neogene depressions of the Pannonian Basin. From 12 to 5 Ma, sediments of Lake
Pannon accumulated, whereas later, starting from the Pliocene, rivers coming in
from the Alps and Western Carpathians were feeding the trough. Across most of
the basin, the Pliocene-Pleistocene fluvial-alluvial sedimentary beds, formed
over a period of approximately 5 million years, reached a total thickness of
over 2000 m. These beds carry exceptionally detailed information that can be
used, through the mapping of former larger river beds, to draw conclusions with
respect to paleo-hydrography, paleo-climatology, structural-sedimentary
evolution, and the dimensions and connectivity of potential reservoirs.
This thick and extensive alluvial
sequence and the meander network can be mapped, enabling us to track
chronological changes in high resolution from the regression of Lake Pannon to
the Quaternary on the 3D seismic data (two-way travel time between 1700 and 500
msec), and on well logs. The horizons and individual meanders on the alluvial
plain can be studied in time slices in terms of various seismic attributes such
as amplitude, lithology, and similarity. Also, the channel fill sequences from
some of the greater rivers can be superbly identified in individual wells.
The most prominent features of the
hydrography are the bends of the typically meandering rivers, whose dimensions,
tortuosity, and flow direction vary in time and space. Initially, following the
southward shift of the delta plain, when alluvial sedimentation is well under
way across the basin, in the western part of the basin we find river bends with
an amplitude of 2 to 3 km and highly tortuous rivers running NNW to SSW,
parallel with the axis of the basin. The smaller streams running parallel to
these follow the same structural trend. Later, both the degree of tortuosity and
the bend dimensions seem to be decreasing (to an average amplitude of 0.8 to 1-3
km), due to a less wet climate and/or the shifting of the depocenter. About 700
m below the surface in the north-western corner of the trough, bends with
amplitude of 4 to 5 km appear some time during the early Quaternary, followed by
smaller rivers with 1-1.5 km bends to the south. All of this seems to suggest
that, from this point on, the principal river of the region no longer travelled
through the Makó Trough.
Core investigations in the exploration of unconventional
hydrocarbon systems: The key to success?
Anita Horváth, Péter Szafián, Gábor Bada, R. Wallis (TXM),
Orsolya Sztanó (TXM & ELTE)
Multidisciplinary core investigation
plays a vital role in the evaluation of the unconventional hydrocarbon
accumulation in the Makó Trough. Gas occurrence is normally associated with
tight sand reservoirs. Their petrophysicial assessment may well prove to be the
key to future success for all stages of exploration and production from reserve
estimations to selecting the optimal stimulation methods (hydraulic fracturing).
Combining a poster with a display of
core samples, this presentation is aimed at introducing a wider professional
audience to the rocks identified in the Makó Trough. The presented cores were
drilled from formations constituting the main targets of exploration, including
the pre-Neogene basement, the overlying syn-rift sequence, and the Endrőd and
Szolnok Formations. The poster provides an overview of lab test results on these
cores for porosity, permeability, pore size distribution, specific pore surface
area, water saturation, rock mechanic parameters, fractures, etc. These results
are supplemented by well logs and FMI images, as well as macroscopic core
descriptions.
The presentation is intended to
demonstrate the importance of a detailed and multidisciplinary study of cores in
the following fields:
- reconstruction of sedimentary
environments;
- effect of diagenetic processes;
- reconstruction of tight sand texture
on the scale of pore space;
- natural fracturing;
- role of rock mechanics in drilling and
hydro-fracturing.
The use of seismic attributes in the interpretation of
the Makó Trough 3D seismic dataset
Péter Szafián, Anita Horváth, D. Hoyer,
Gábor Bada (TXM), R., Young (eSeis, Inc., 1155 Dairy Ashford, Suite 600,
Houston, TX 77079, USA)
The hydrocarbon exploration activity of
TXM Ltd strongly relies on the data acquired through some 1,150 km2
of 3D seismic survey in the Makó Trough area. Since the relatively simple
geometry of the trough is associated with a rather complex and diverse
lithological composition, and exploration efforts mainly focus on unconventional
gas accumulations, our main objective is a high accuracy spatial mapping of the
critical petrophysical and geological attributes (e.g. porosity, (over)pressure,
lithology), and the construction of a complex 3D geological-geophysical model. A
significant part of the information required for this job is hidden in some way
in the seismic data, and – using cores, well logs and VSP results – can be
unfurled from the reflected seismic waves.
Our poster presents the seismic
attributes determined using well data and pre-stack seismic data (e.g. AVO type,
absorption, lithology, interval velocity, pore pressure, effective porosity,
coherence), and demonstrates how they can help geological interpretation and
hydrocarbon evaluation of the Makó Trough.
Presenting a spectrometer for natural and
neutron-activated gamma-rays
Ferenc Henézi
(Karotázs Kft,
7634 Pécs, Kővirág u. 39)
TEXT ON WORK
/ SZÖVEG MUNKA ALATT
Application of Weighted Integral Mean Method to detect
near surface lateral changes
Réka Kavanda (University of Miskolc, Department of
Geophysics, 3515 Miskolc)
One of the main challenges in the
environmental work is the exploration of the vertical and lateral inhomogenities
at the near surface. The most common solution of these exercises is the
geoelectric methods, especially the vertical electrical sounding (VES).
In this study the 1,5D function
inversion was used to process the observed data, in which the Weighted Integral
Mean Method was applied as well. The main idea of function inversion
methods is to describe geometrical (thickness) and physical (resistivity)
parameters of the layers along the profile with functions expanded in series. At
first the function coefficients with an inversion technique were determined, and
then the local physical and geometrical parameters of the model were computed
point by point along the profiles.
The 1.5D inversion is the iterative
inversion LSQ algorithm using functions expanded series, 1D forward modeling is
applied on the VES measurement positions, and parameters of an approximately 2D
geological structure are estimated. That’s why it is called 1.5D. The Weighted Integral Mean Method is the
developed variation of the Integral Mean Method, which regards a narrow interval
of the VES point instead of one parameter value under the point. so that the
influence of the parameters are less and less at the result.
The trials of synthetic data prove the
pertinence of the methods. The results of the data processing of the same VES
measurements are more accurate then the results of 1D method. According to this
study, the 1.5D inversion method is good for delineating the inhomogeneous
vertical and lateral structures and determining their qualitative geoelectric
parameters, but the lateral changes of the model were specified with Weighted
Integral Mean Method in case K-type VES curves.
The applied inversion methods can be
effectively applicable in the geological, hydrological, geotechnical and
environmental works.
INVESTIGATION OF COAL SEAM GEOMETRY WITH DELAUNAY TRIANGLE NET
András Madarasi, György Paszera (ELGI)
As part of
the investigation on the utilization of the coal seams
of East Mecsek by gassing, ELGI – mandated by
White Coal Energy Kft –
standardized the classification of the coal layers.
A database was built with
some data of the coal seams, derived from the
boreholes. The variability of the geometry of the coal
seams and coal yard groups was displayed
in a new way – on Delaunay triangular grid formed by the
boreholes – by using the compiled database.
Geoelectric tomography in fractured magmatic rocks
András Madarasi, Balázs Füsi, Ernő Prácser (ELGI)
As
part of the Radioactive Waste Handling Ltd’s subsurface exploration program on
Hungarian National Radioactive Waste Repository for the final disposal of low-
and intermediate-level radioactive waste – mandated by Mecsekérc Corp. –
geoelectric tomography was performed
on the final part of the descending tunnel
(adit) of Bátaapáti site.
Tomographic
data were processed with several
2D and 3D inversion methods. Apparent resistivity distribution in the plane of
the tunnels was estimated by the inversion. Presenting
the inversion results and the processing strategies, results are compared
with geological data and the results of seismic tomography.