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72nd EAGE Conference and Exhibition incorporating SPE EUROPEC 2010
- Conference date: 14 Jun 2010 - 17 Jun 2010
- Location: Barcelona, Spain
- ISBN: 978-90-73781-86-3
- Published: 14 June 2010
701 - 797 of 797 results
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The Use of Seismic Inversion to Revisit the Reservoir Mapping of a Large Carbonate Brown Field
Authors S. Sharma, M. Pratap, A. Carrillat, B. L. Lohar, R. Bhanja, A. Saha and F. FriedelWe present an integrated seismic interpretation case study of a large heterogeneous carbonate brown field located on western offshore India. In this study, seismic inversion is used as the key driver to revisit the interpretation and mapping of the reservoirs. The seismic interpretation is developed in a stepwise approach, first on amplitude data and then on inversion data for achieving high level of accuracy and consistency in the final structure. This method is applied in order to overcome typical signal ambiguities and wavelet instability encountered across the field. Both relative acoustic impedance (RAI) and absolute acoustic impedance (AAI) derived from post-stack inversion are successively used to refine the interpretation as AAI provides a clearer image of the reservoir and fault compartments. Eventually, fault interpretation is fine tuned on edge enhancement attributes. The final time interpretation is then depth converted via an integrated velocity model based on geostatistical velocity modeling preserving seismic inversion well ties.
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Interactive Static Corrections to Avoid Mis-interpretation of Seismic Data Due to Near-surface Velocity Changes
Authors I. Korotkov, P. C. H. Veeken and V. KozyrevStatic correction computation is an important step in the seismic processing of land and transition zone data. Complex near-surface overburden velocity changes do hamper proper imaging. Geological and physical features (like: permafrost, pinch outs, swamps, sand dunes etc) may introduce irregular travel time delays. Automatic residual static algorithms sometimes fail to resolve these static corrections and thus may give rise to serious mis-interpretation of the subsurface structuration. Costly dry holes have been drilled based on false tectonic structures visible on non-optimal processed seismic data. These errors can be overcome by introducing an interpretation / modeling phase in the determination of the static corrections, using receiver and shot partial-offset stacks. The Interactive Static computation method uses diagnostic partial stacks in various domains to distinguish anomalies caused by drastic lateral velocity change in the shallow subsurface. Case studies illustrate the benefit of such a static correction method.
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Seismic Investigation of the Earth's Crust in the Sub-shelf Zone of North-eastern Russia – Chukot Peninsula
Authors V. L. Kuznetsov, A. S. Salnikov, V. V. Titarenko and V. M. SolovyevOn the territory of north-eastern Russia unexplored by seismic exploration geophysical profiles about 3 000 km long were surveyed. On these profiles DSS data interpreted by conventional methods and seismic tomography gave the first reliable idea of the structure of the earth’s crust down to depth of 45 km. The earth’s crust presents itself typically continental. Seismic-tomography processing of CR data and first CDP waves made it possible to study the structure of the upper heterogeneous earth’s crust in detail and forecast more than ten new ore knots in it, two zones of oil and gas possibilities and a local uplift being of interest in the context of prospecting for oil and gas.The investigation results show that the most reliable information about the structure of the earth’s crust and upper mantle can be mainly obtained by the conventional DSS method and about the structure of the upper earth’s crust in ore areas by high-density observations of the near-field first waves and their processing and interpretation by seismic tomography.
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Local Stretch Zeroing NMO Correction
Authors N. Kazemi and H. R. SiahKoohiWe present a method of normal moveout (NMO) correction called local stretch zeroing (LSZ) method that avoids NMO stretch. This is done by eliminating those theoretical curves that generate interpolated data samples responsible for NMO stretch. The original sampling interval is preserved by zero padding and reassigning of true data samples. The LSZ method eliminates all interfering reflection events at far offsets by optimally selection of mute zone. The results are generally higher frequency than a normal stack and contain less noise. The method loses its efficiency when CMP data is over- or under-NMO corrected. Performance of the method is compared to conventional NMO correction Taner et al. (1969) using both synthetic and real data.
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Applying the CRS Stack Method to Solve the Problem of Imaging of Complex Structures in the Zagros Overthrust, South West
Authors E. Adibi Sedeh, M. Soleimani, J. Mann, H. Shahsavani and I. PiruzImaging in complex structures poses difficulties that could not be solved by conventional processing. In such cases, applying a full prestack depth migration (PSDM) is an alternative. However, this may not be applicable in all situations due to difficult migration velocity model building. The other alternative for imaging in complex structures is to perform poststack migration on a suitable stack section. Using a time section obtained by the Common Reflection Surface stack method could partially solve some of the imaging problems without requiring a prestack depth migration. A seismic data set of a mountainous area from the complex structure of the Zagros overthrust in south west of Iran was processed by the conventional NMO/DMO/Stack. The CMP-stacked section contained a folding system and dipping layers, but both of them not well imaged in the section. Then, the common reflection surface stack method was applied to data. In the CRS-stacked section, the folding and dipping layers were clearly observed. The other reflection and diffraction events at large travel times were also imaged. Therefore, the CRS-stacked section showed that the common reflection surface stack could be used to partially solve some of the problems with complex structures.
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Fourth Order Crs Stacking Method – Examples
By P. ChiraA significant part of seismic processing is carried out by means of stacking of multi-coverage data. Traveltime moveout expressions are currently used to stack reflection and diffraction events and simulate a zero-offset (ZO) seismic section from multi-coverage seismic data. It significantly reduces the amount of data and increases the signal-to-noise ratio due to constructive interference of correlated events. Conventional stacking methods, e.g. NMO/DMO or pre-stack migration depends on one parameter (stacking or NMO velocity) and requires an accurate macro-velocity model to yield appropriate results. The CRS stacking method is based ona second-order traveltime approximation parameterized with three kinematic wavefield attributes. It does not depend on a macro-velocity model. In this work, we tested the Taylor expansion of the second-order CRS conventional moveout formula, so-called the fourth-order CRS stacking moveout formula, to simulate ZO seismic sections. This formula depends on the same three parameters as the second-order CRS moveout formula. Synthetic dataset with noise and real dataset have shown a good performance of the proposed expression compared to the CRS conventional moveout formula.
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Partial 3D CRS Stack
Authors D. Gajewski and M. BaykulovWe performed partial 3D CRS stacks to enhance the quality and regularity of prestack 3D seismic data. Results of the automatic CRS parameter search are used to perform a simple and robust weighted summation. The method is verified on 2D and 3D synthetic datasets. Improved prestack gathers have higher S/N ratio and show better coherence of reflections.
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Complexity of Hydraulic Fractures – The B-value
Authors A. M. Baig, T. I. Urbancic and S. BowmanThe distribution of moment magnitudes for a hydraulic fracture treatment is related to the complexity of the fracture network through the slope of the frequency-magnitude distribution, known as the b-value. Characterizing this complexity relates to effective field drainage and can be used to calibrate predictions of fracture-mechanical models. As the b-value is determined from the magnitude distribution, then it may be glimpsed by using only a single-well observation array. We use the example of a multi-well observation array to validate this observation. The b-value field for the treatment zone is determined and compared against the distribution of microseismic moment tensors to validate that the complexity inferred by the b-value is reflected in the distribution of mechanisms determined by inverting for the moment tensors.
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Microseismic Event Relocation Using Arrival Times and Cross-correlation Coefficients – A Synthetic Study
Authors J. Kummerow and S. A. ShapiroWe present a feasibility study of seismic event location by jointly inverting P and S arrival times and values of maximum cross-correlation coefficients. This work is motivated by the well-known problem that the location by arrival times alone is occasionally only weakly constraint, and inaccurate measurements of arrival times may introduce significant errors in the event location. This in turn degrades, e.g., the mapping of fracture geometries in reservoirs by passive seismic monitoring. We introduce and test an algorithm, that inverts both measured arrival times and cross-correlation values for the hypocenter coordinates. For our test datasets, including realistic simulations of arrival time errors and uncertainties in the relation between waveform similarity and event separation, the source geometry is better recovered compared to the purely arrival time-based location. For high-quality manual picks, the accuracy of the relocated events is improved by more than 20%. In particular, outliers in the event locations can be effectively corrected.
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Microseismic Imaging at KTB
Authors A. Reshetnikov, J. Kummerow, S. Buske and S. A. ShapiroWe have applied our approach for microseismic imaging to the data obtained from the German Continental Deep Drilling program (KTB project). This is a continuous data stream containing induced microseismicity data recorded at a single 3C geophone located at approximately 3.5 km depth. Using P and S time picks we have located 58 microseismic events using data from the borehole geophone and from near-surface stations. Since microearthquakes occur not at the same time, we have managed to separate continuous data stream recorded at the receiver to the number of 3C traces containing waveforms from different events. Using these traces we have produced seismic gather for the microseismicity cloud. We apply our approach to the produced seismic gather and construct 3D images of the seismic data between P- and S- direct waves. There are two focused reflectors revealed within the microseismicity cloud which belong to SE2 reflector. In order to check consistency of the obtained results, we compare our results with seismic attributes obtained from the surface seismic 3D depth migrated image. Obtained result is consistent with seismic attributes by the location and dip, furthermore it provides with more detailed image of the fault zone fine structure.
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Quantitative Analysis of Diffusivity Estimates Obtained from Microseismicity Based on Nonlinear Diffusion
Authors N. Hummel and S. A. ShapiroWe study the influence of pressure dependent transport properties on estimates of hydraulic diffusivity obtained from fluid-injection induced microseismicity. We figure out what kind of diffusivity estimates are obtained from the so-called rt-plot in the case of pressure-dependent transport properties. The nonlinear pore-fluid pressure diffusion equation accounting for power-law and exponential dependent diffusivity is solved in 1D, 2D and 3D. Following the seismicity-based reservoir characterisation approach (SBRC) synthetic clouds of microseismicity are generated. Depending on the particular diffusivity model the signatures of the microseismic event-clouds differ due to the particular pore-fluid pressure profiles. From the spatio-temporal distribution of microseismicity hydraulic diffusivity estimates are obtained and compared with effective diffusivity values. We show that the triggering front is characterised by a square root dependence of time even in the case of microseismicity based on nonlinear diffusion. We found that for weak pressure dependence of hydraulic diffusivity heuristic estimates do not differ significantly from the effective diffusivity values. Even in the case of strong nonlinearity heuristic and effective diffusivity still have the same order of magnitude. Our analysis reveals that SBRC provides reasonable diffusivity estimates after stimulation of the reservoir.
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Using Spectral Attributes to Detect Seismic Tremor Sources – A Synthetic Study
Authors E. H. Saenger, M. A. Lambert and S. M. SchmalholzA method is presented to detect subsurface seismic tremor sources by analyzing surface data. Spectral attributes of the recorded seismic wave-field at low frequencies are used to map the surface projection of the sources. We illustrate the concept on a synthetic data-set and show how spectral attributes can be used for detecting locations of seismic tremor sources. In a second part we apply the method to an example of hydrocarbon reservoir related tremors. The results show that increased complexity of the subsurface seismic properties and/or the presence of several tremor sources can strongly complicate the interpretation. In addition, the presence of dominant surface noise may mask the signals emitted by the subsurface tremor sources and make it impossible to detect them at the surface without additional processing. F-K filtering is successfully applied to noise-contaminated data and retrieves masked anomalies. Care has to be taken for using a proper data-set and proper processing parameters in order to avoid artifacts introduced by the F-K filter. Although we discuss an application for possible hydrocarbon reservoir related tremors, we believe that the methods can also be applied to any other type of seismic tremor signal.
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3D-imaging of 2D-time Reverse Modeling
Authors B. Steiner and E. H. SaengerTime reverse modeling has become an efficient tool to detect the origin of low-frequency (<10 Hz) seimic tremor signals. Examples of such signals are observed before volcanic eruptions or above hydrocarbon reservoirs. Technical expertise has mainly been developed for 2D application. However, effects from using three-component signals for 2D reverse modeling are still widely unknown. An example is reverse propagation of signals on a plane vertically below a seismometer array. In this case, reverse calculation is performed with the vertical and the horizontal component parallel to the array. The horizontal component perpendicular to the array is dropped. This causes partial loss of particle motion and directivity of the recorded waves. The concept of merging multiple 2D images to one 3D image is presented to meet problems arising from this loss. A synthetic study with a tremor source demonstrates how this source is imaged in different vertical planes. Planes within the distance of two wavelengths from the source render artificial focusing at the horizontally projected source location. However, these artificial focusing points are weak relative to the focusing at the corret location. A source seems to be locatable with 2D reverse modeling and successive analysis in a 3D image.
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Time Reverse Characterization of Sources in Heterogeneous Media
More LessTime reverse modeling (TRM) is applied to localize and characterize acoustic emission using a numerical concrete model. The aim is to transform a method within exploration geophysics to non-destructive testing. In contrast to previous time reverse applications, no single event or first onset time identification is applied. The method is described from a mathematical point of view. So-called source TRM with limited knowledge of boundary values is used in combination with several imaging conditions. TRM localization and characterization using this highly scattering material is feasible using the rotated staggered finite-difference method. We demonstrate the localization of two synchronous acoustic emissions with a limited number of sensors and using effective elastic properties. Source characteristics can also be recovered. The goal is to apply our method to acoustic emissions measured during experiments carried out on concrete and reinforced concrete specimen. Several aspects of the described methodology can also be transferred back to exploration geophysics.
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Relating Acoustic Emission Sources to Rock Failure Around a Borehole
Authors F. Cuisiat, E. Aker, M. Soldal and D. KuehnIn recent years passive high sensitivity seismic techniques have experienced significant technological advancement, and are currently used for monitoring of hydro- and micro-fracture events during stimulated oil recovery and CO2 sequestration sites. Potentially they enable effective tracking of highly localized Acoustic Emission (AE) due to fracture and micro-cracking processes, and detecting fluid flow in fissures and conduits. Our work focuses on relating the AEs to the source mechanisms by computing the moment tensor of events recorded during crack initiation and macroscopic failure around a borehole penetrating a rock sample. The sample is subjected to increasing load in the laboratory using triaxial apparatus and piezo-ceramic receivers to record the emitted AE signals. X-ray Computed Tomography is used after testing to visualize the damage and verify the locations of the AEs. We find that the type of AE source mechanism is more complex than either a pure double couple or a pure mode I tensile crack and includes a combination of the two. In particular, we find that the source mechanisms of events along the borehole are different from events at the macroscopic fracture tip when decomposing the moment tensor into isotropic and deviatoric components.
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Detailed Section of the Lithosphere in Angola Basin on the Seismic Refraction Data with Account of Earth Curvature
By V. B. PiipNew interpretation of DSS data of 1980th in Angola Basin with homogeneous function method gave seismic section of considerably more informative than previous one. Besides of the curvature of the Earth now was taken in account. Asthenosphere diapir exists in the lithosphere on the boundary of transient zone. Thickness of the crust is increased sharply toward continent along several seaward faults. Two layers with increased velocity, rising in the party of continent, are traced in the lithosphere in central part of the profile. Asthenosphere forms steps inclined in direction to continent. Perhaps, blocks of oceanic lithosphere were moved under continent along asthenosphere top by fault with displacement of about 30 km.
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Source Parameters and Epicentral Relocation of The 22 June 2002 Avaj Earthquake
Authors N. Sarmadi and M. GheitanchiThe Changoureh-Avaj earthquake of June 22nd 2002 is the largest shock since the occurrence of the 1962 Buyin-Zahra earthquake in Qazvin province. The ground-motion characteristics during the main shock should be considered for the high safety design of structures in the region. we calculated the ground motion parameters of this event using digital accelerograms Data of Building and Housing Research Center (BHRC) by using Seismosignal and Sigmaplot softwares. The earthquake was recorded by 78 digital accelerographs installed in different points of the area. We used 18 accelerograms which had good signal to noise ratios at a distance range of 26 – 100 km. The maximum acceleration recorded in this event so far is about 0.5g at the Avaj station which is situated 26km from the earthquake hypocentre. We relocated the epicentre of this event and the first 23 aftershocks by using Tehran Seismic Network Data and Hypoinverse Software. A focal depth of 7 km is estimated for the mainshock. Different seismological Agencies such as (IGTU, NEIC, HRVD) reported different location, in this study, results are consistent with the computation results.
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Source Characteristics of the 28th May 2004 Baladeh-Kojur Destructive Earthquake in Central Alborz
By F. GolabiSource characteristics of the 2004 Baladeh-Kojur destructive earthquake is obtained by inverting far field waveform data. The information from field investigation and aftershock activity are considered as supplementary data to constrain the source parameters. The source characteristics of mainshock is explained in terms of at least three major subevents. Rupture initiated in epicentral area with the first subevent and mainly extended towards west in a unilateral manner. The major slip took place during the first 10 seconds and it is concluded that the directivity played main role for producing extensive intensity in the epicentral region. The source mechanism obtained in this study is predominantly trust and is in agreement with the mechanism of other earthquakes as well as the orinatation of tectonic forces in this region. The total seismic moment is calculated to be M0= 4.1×1018 Nm and the total moment magnitude is Mw = 6.3. Although central Alborz had been seismicly active in historical times there was no evidence that earthquakes as severe as this earthquake had occurred in the vicinity of Baladeh-Kojur region during at least the past 100 years.
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Fault-plane Identification by a Geometrical Method – Application to Moderate Earthquake Mw 5.1 Kerman, Iran
Authors B. Hejrani, M. R. Hatami and S. MousaviThis paper introduce a geometrical method called H-C method for fault plane identification. application of this method to Mw 5.1 Kerman, Iran, Earthquake. H-C method is a simple method, immediately applicable when a reliable earthquake location and its Centroid moment tensor solution (CMT) are available. In this study the Hypocenter location is obtained from two different agencies (local and global), ISC and IIEEES. Full waveform inversion for CMT solutions is done by ISOLA package. The result of this study shows that the fault plane of this Earthquake has a North-South dip which is in agreement with Previous Studies of this region (Talebian et al 2006; Hatami et al 2007). Although H-C Method, not yet broadly recognized as a useful tool for fault plane identification, its great potential is in simple linking of the independent pieces of short- and long-period seismic information.
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Anomalies of the Earth’s Magnetic Total Field in Germany – A New Homogenous, High-resolution Compilation
Authors C. M. Krawczyk, G. Gabriel, D. Vogel, R. Scheibe, H. Lindner, R. Pucher and T. WonikWe present the first homogenous map of anomalies of the Earth’s magnetic total field for entire Germany. This high-resolution map is based on 50 individual ship based, airborne or ground surveys that were conducted between 1960 and 1990, and which are complemented by 17 new surveys after German reunification. The corresponding data sets were related to different geomagnetic reference systems, epochs, and altitudes. The new map images the entire anomaly pattern in Germany consistently in an altitude of 1000 m above sea level with the DGRF1980.0 as reference system. For the interpretation of magnetic anomalies the entire coverage of each anomaly including its dipole character is of special importance. Therefore, this homogenized and for the first time complete anomaly data set offers some new insights into crustal structures in Germany. On the large scale, regional tectonic units as the Variscan terranes in south and central Germany or the extent of old Scandinavian crust beyond North Germany as a relic of the collision between Baltica and Avalonia are well imaged by the magnetic anomalies. On the small scale, also details of local structures like the prominent volcanic areas of the Vogelsberg or the Eifel region are well exposed.
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Satellite and Ground Gravimetry – The Innovative Approaches in Studying the Earthquake Nature and Prognosis
Authors S. M. Demianets and M. M. DovbnichOn example of the seismicity of Vrancea zone and the Crimean region the usage possibility of the satellite data (project GRACE) and the ground gravimetry in investigation of the stress-deformed tectonosphere state in studying the earthquake nature and the seismicity zoning is shown.
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Edge-preserved 2D Inversion of Magnetic Data – An Application to Makran Arc-trench Complex
Authors L. Namaki, A. Gholami and M. K. HafiziInversion of magnetic data is frequently used for geo-structural investigations. Long airborne flight lines and dense sampling of magnetic field result to very large data sets which in 3D point of view becomes very difficult to be inverted by non-smooth algorithms. In this case, 2D inversion of individual lines can provide good images of subsurface structures along the profiles. In this paper, we are looking for a 2D distribution of magnetic property inside the earth, so divide the area under the profile into a large number of infinitely long horizontal prisms with square cross-section and unknown susceptibility. A fast and efficient non-smooth algorithm based on edge-preserving penalty functions and discrete cosine transform (DCT) is proposed for 2D inversion of magnetic data. A suitable edge-preserving penalty function is used to render the solution unique and stable and to prevent sharp transitions from being penalized. Finally, we inverted a long airborne magnetic flight data in southeast Iran which intersects Makran subduction zone and its related geological structures. Our result shows a deep oceanic crust remnant, beneath the sedimentary cover located at Juzmurian depression, which makes a prominent role in reconstructing whole geological history of the area
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Geophysical Models of the Earth’s Crust Structure of the Northern Urals
Authors P. S. Martyshko, N. V. Fedorova, V. V. Kolmogorova and I. V. LadovskiyThe construction process of Earth crust geophysical model using observed geophysical field leads to solution of the inverse problem, which is classical example of ill-posed problem as its solution is unstable and not unique. It is possible to choose specific variant of density or magnetization distribution if additional information is presented. The purpose of this article is to show the results gained from the study of the structure of the Earth crust in Northern Urals using geophysical methods (seismics, gravics and magnetics).
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Gravity Model of a Transect in the Southern Region of the Central Andes
Authors A. Casas, M. P. Martínez and M. E. GiménezThe present paper describes the interpretation of a gravity profile that extends over a distance surpassing 800 km in Southern Central Andes (Argentina) at 29º18’ South Latitude. A crustal model in accordance with the main regional geologic structures has been obtained from the inversion of gravity data. This model fits with a dominant collision mechanism that affected ancient blocks. Bearing in mind the subhorizontal subduction system of the Nazca plate, the Chilenia, Cuyania, Famatina System, Pampia and River Plate cratons are well recognized. Also, the gravity signature clearly shows the suture zone between the Precordillera and the Famatina Ranges, as well as the shear zone between the latter ranges and the Velasco Range. The maximum crustal thickness determined beneath the Andean Cordillera at this latitude is 69 km, whereas under the Famatina System and the Velasco Ranges the obtained values are, respectively, 56 km and 46.5 km.
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3D Gravimetric Characterization of El Bierzo Carboniferous Basin and Ponferrada Granite, León, NW
Authors C. Ayala, F. M. Rubio, C. Rey-Moral, J. L. Plata, M. I. Reguera, J. L. García-Lobón and K. MotisThe aim of this work is to present the results of a 3D geological model based on probabilistic inversion of structural gravity data. The gravity data was acquired using high resolution GPS positioning for X, Y and Z coordinates. Prior to the modelling, a Bouguer anomaly map has been obtained and interpreted in terms of regional-residual separation, vertical gradient, geophysical lineaments and Euler solutions. The study area comprises El Bierzo Carboniferous Basin and the Ponferrada granite. The deep structure of the basin and the granite morphology has been obtained from the inversion, using information from reflection seismic profiles together with data from wells and density values from rock samples to constrain the geometry and physical properties of the model. The results favour the hypothesis that the western limit of El Bierzo Basin is a vertical fault, NNE-SSW trend, showing small displacement that does not outcrop because is covered by Tertiary sediments and also indicate that the Ponferrada granite extends below the Tertiary cover towards the NW. Next to that granite another subcropping intrusive body has been modelled, deduced from its gravimetric signature. This body can be part of the post hercinic aloctonous leucogranites.
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Magnetic Basement Study in the Barents Sea from Inversion and Forward Modelling
Authors L. Marello /NTNU, J. Ebbing /NTNU and L. GernigonIn the present study we investigate the basement and its relation to magnetic anomalies for the Barents Sea region. Besides conventional magnetic field analysis (e.g. psedudogravity) we perform 3D inversion and 2D forward modelling to characterize the geometry of the top basement and the distribution of magnetization and density. For the 3D inversion the influence of the input parameter have been studied in detail, and large uncertaintie are encountered over some areas. On a regional scale, the petrophysical parameters and not the geometry of the top basement dominate the magnetic anomalies. The 2D models aid to link together the main crustal unit of the Barents Sea, which are expressed by different magnetic basement characteristics, and to compile a map which shows the different basement domains. The resulting map allows us to interprete the possible extension of Caledonian, Timanian, Uralian and magmatic terranes in the area.
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A Brief Summary of Hessian Based Modelling in a Shared Earth Environment
Authors G. Toxopeus and J. W. ThorbeckeValidating an earth model by simulating a migration image is an important step in a shared earth environment. However, the high computational cost of generating 3D synthetic data, followed by the process of migration, limits the number of scenarios that can be validated. To overcome this computational cost, a novel strategy is used where a migration image is simulated by filtering a model. A filter represents one local element of the Hessian, which is obtained by computing the image of a single unit-strength scatterer in a macro velocity model (the impulse response of the filter). One of the key properties of this approach is that the model that describes a target-zone is decoupled from the macro-velocity model that is used to compute a filter. Consequently, different models can be filtered with the same filter. In addition, migration images of, for example, a walk-away VSP dataset or the influence of seismic uncertainties can be simulated. Therefore, these filters enhance a shared earth modelling approach.
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Multi-frequency Phase Coherent Super-resolution Imaging
Authors E. G. Asgedom and L. J. GeliusSuper-resolution imaging of point like geological features is of great interest for analyzing the location of faults and resolving finer details like formation pinch outs. For diffractions from point like features, it has been demonstrated that the time-reversal MUSIC (MUltiple SIgnal Classification) algorithm is able to resolve the location of very closely separated scatterers beyond the classical limit (Lehman and Devaney, 2003; Gelius, 2009). Though this algorithm is efficient for a noise free case, it has been found that it is highly sensitive to the noise level in the measurements. In this paper, we present a modified MUSIC type of algorithm that can handle measurement noise and the phase ambiguity introduced due to singular value decomposition (SVD) by utilizing both the source and receiver side singular vectors and superimposing phase-coherent multiple frequency images. The performance of this new algorithm is demonstrated to be excellent when employed to numerical data associated with two point scatterers superimposed Gaussian white noise.
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Accurate Modeling of Fractured Reservoir Not Using Equivalent Medium Theory
Authors P. Thore and I. TarrassThe presence of heterogeneities (like fractures) in a reservoir can be analysed by the mean of equivalent medium and anisotropy but also with the scattered energy generated. In this paper we show that this scattered energy is quite important on a large scale model were the upscaling used for fracture description is very limited (grid cell size is .5m). Finite Differences (based on a new scheme) and Born Modelling have been used to produce synthetic seismograms.
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Modified Form of Reverse Time Migration Tuned to Multiple
Authors G. T. Schuster, G. Zhan and Y. LuoRecent field tests show the feasibility of achieving superresolution in migration images. To partly realize this with practical exploration data, we introduce a modified form of reverse time migration, denoted as GDM, with an imaging condition tuned to multiple scattered events. GDM imaging of the SEG/EAGE synthetic data shows higher resolution in the migration image, but at the expense of an increased noise level. A limitation is that superresolution property can only be achieved with a highly accurate velocity model.
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Time Lapse Analysis of a Pseudo-3D Surface Seismic Data at the CO2 SINK Project Site, Ketzin, Germany
More LessPseudo-3D surface seismic data (baseline and repeat) were acquired in conjunction with CO2 injection at the Ketzin site. Similar processing steps were used for the baseline and repeat data sets. After processing, stacked profiles from both data sets were compared. No large differences were found on Line 6, and good quality data of line6 starts about 300m away from the injection borehole. On a pseudo-3D profile, with midpoints falling close to the injection point, we observe differences in the two data sets. Our results are consistent with full 3D seismic time-lapse studies over the injection site.
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Measurement of Frequency-dependent P and S Impedance from 2D Data
Authors A. Alshangiti, M. Chapman, A. Wilson and R. ClarkAnalysis of seismic data suggests that hydrocarbon bearing zones are often associated with high values of attenuation; this attenuation is associated with strong velocity dispersion. Due to dispersion, the impedance will be frequency-dependent. A frequency-dependent inversion has been carried out on synthetic data, and the results show that the impedance varies strongly with frequency in the dispersive medium but not in the elastic ones. We carried out this inversion on 2D PP field data, and the results show two consistent strong P and S impedance anomalies along the selected CMPs that might be interpreted as dispersive/reservoir zones.
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Environmental Investigations in Fuka Area Northwestern Coast of Egypt
More LessMany environmental problems may hinder development and investment plans of coastal locations as saltwater intrusion contaminating freshwater reserves of coastal aquifers. This problem is obvious in the poor Bedouin village 'Fuka', Northwestern coast of Egypt. In order to apply cost reduction criteria in parallel with achieving the main target of locating saltwater intrusion locations as well as detecting any of near surface structures; cheap, fast and effective geophysical investigation tools of very low frequency-electromagnetic and DC resistivity had applied and discussed.
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Influence of Invading Phase Breakthrough on Acoustic Response in Multi-phase Saturated Austin Chalk
Authors M. K. Sorensen, I. L. Fabricius and T. HansenThe acoustic response of multi-phase saturated Austin chalk samples are investigated. Consistent high velocities are found which are incompatible with effective media theories proposed. This discrepancy is linked to the existence of fast-tracks composed of high moduli saturation, spanning the sample length. These fast-tracks are supposedly created during the saturation process.
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Sidescan Sonar Data Interpretation for Sediments Mapping in Kandalaksha Bay of the White Sea
More LessThis paper presents the results of annual geophysical, biological, geological and geomorphological research of the seafloor in Kandalaksha Bay, White Sea. Optimal algorithm for interpretation of Hydra sonar data was developed using multivariate statistical methods. Varios types of seafloor were identified (mud, sand, rocky bottom and bottom with a separate standing stones). As the results of these investigations two detailed sonogram sets of attributes were made for the bottom geology imaging.
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Integrated Petrophysical Research of the Complex Reservoir Rocks of the Volyn-Podillia
Authors I. V. Ustenko, S. A. Vyzhva and V. P. BukovskyiLaboratory petrophysical research of the Devonian, Silurian and Cretaceous rocks of the Volyn-Podillia oil and gas-bearing area. Relationships between porosity ratio, density and interval time are determined. The results can be used to facilitate wire line logging interpretation and formation evaluation during detailed field appraisal of the prospective plays of the region.
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Origin of Gas Hydrates Imaged from the Acoustic Basement in the Northernmost South China Sea by Using OBS
Authors J. M. Deng, T. K. Wang, C. S. Lee and C. S. LiuDuring the survey of TAiwan Integrated GEodynamics Research (TAIGER) in 2009, we recovered 36 ocean-bottom seismometers (OBS) along 3 multi-channel seismic (MCS) profiles for investigating the origin of gas hydrates in the northernmost South China Sea off SW Taiwan. In the accretionary prism of the Manila subduction zone, we observed gas hydrates accumulated in the closed areas where were formed by folding imaged from a strong variation of the lateral velocity (3-4.5 km/s) in the acoustic basement. In the continental slope, gas was migrated from the rifting basement to the anticline. The rifting basement with a relatively low velocity of 3-4.5 km/s in the extended continent of the northernmost South China Sea resulted from magma intrusion along normal faults since the paleo-seafloor spreading. We suggest that gas generated in the deeper structures may be migrated along faults to accumulate hydrates in the sedimentary layers.
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The Effect of Carbonate Texture and Pore Types on the Pressure Dependence of Acoustic Velocities
Authors A. A. Hassan and S. VegaCarbonate rocks are often characterized by various pore types and depositional textures that result in complex relations between acoustic velocities and other parameters such as differential pressure (Pd). In this paper, we study the effect of texture and pore shape on a set of thirty groups of velocity-Pd trends from 63 carbonate core plug samples. We found that similar compressional velocity-Pd trends are associated with similar carbonate texture, pore shape and size. However, the effect of texture was found to be less predominant on shear velocity-Pd trends which were more influenced by pore shape.
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Impacting Factors on the Thermomechanical Behavior of Dolostones upon Calcination
Authors A. Panaiotu and D. CiobaneteUntill now, the crystal size was accepted as a major factor in calcination of dolostones: the larger the crystal size, the lower the resistance to decrepitation. This is not entirely true, many metamorphic dolostones with medium-coarse crystal size having better thermochemical properties than fine grained sedimentary dolostones. The reason for this could be related to the shape of crystals and their bounding inside the crystalline aggregate, the amount and type of fluid inclusions, or the presence of impurities or organic matter, aspects emphasized through textural and petrogenesis analyses, chemical composition (X-Ray fluorescence), cathodoluminiscence and UV fluorescence studies.
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Seismic Geomorphology: Tool for Imaging Elements of Depositional Systems
By S. SenguptaSeismic geomorphology is an emerging field of science having a great potential in the hydrocarbon exploration and basin evolution studies. It deals with the integration of geomorphological concepts in the routine seismic interpretations. Aided by various tools like horizontal and vertical seismic slices, horizon slices and seismic attribute studies, geobody identification etc. it forms a major element in the state-of-art interpretation modules. The paper highlights preliminary studies from the East coast of India to know the basinal evolution & tectonic settings of that area.
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Paleo-Mesozoic Development of the Reggane Basin, Southern Algeria
Authors E. Lewandowski, R. Zühlke, H. Jäger, T. Bechstädt, T. Leythäuser and R. AichaKey objectives include sequence stratigraphy of the Devonian basin fill, numerical modeling and basin development during the Paleozoic to Mesozoic. Total thicknesses of the Paleozoic basin fill range between 4500-5500 m. Twelve stratigraphic intervals have been analysed from 2D seismic surveys and well data. Two major pan-African structural domains in the subsurface of the Reggane Basin significantly influenced the Paleozoic basin development: the West African Craton (WAC) and the Hoggar Block (HB). Moderate to high subsidence rates persisted during the Ordovician to Silurian. Subsidence rates slow down until Eifelian and accelerated again until the Devonian-Carboniferous boundary. Initial moderate to high subsidence rates in the early Carboniferous are followed by low subsidence in the late Carboniferous. Basin inversion started at approx. 200 Ma. Maximum paleotemperatures were reached at 250-240 Ma with approx. 200-220°C. Sediment pathways and dispersion widths outline a low-gradient transition from proximal upper shelf areas in the SE to outer shelf areas in the NW. Sediment flux varies strongly in time. The burial and exhumation model indicates, that the paleotemperature development was primarily controlled by regional burial, rather than by a Late Triassic heat flow event (related to Central Atlantic Magmatic Province).
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Petrophysical Properties of Greensand as Predicted from NMR Measurements
Authors Z. Hossain, C. Grattoni, M. Solymar and I. L. FabriciusNuclear magnetic resonance (NMR) is a useful tool in reservoir evaluation. The objective of this study is to predict petrophysical properties from NMR T2 distributions. A series of laboratory experiments including core analysis, capillary pressure measurements, NMR T2 measurements and image analysis were done on sixteen greensand samples from two formations in the Nini field of the North Sea. Hermod Formation is weakly cemented, whereas Ty Formation is characterized by microcrystalline quartz cement. The results indicate that porosity measured by the NMR method underestimates the total porosity of greensand due to the presence of paramagnetic minerals. The surface area measured by BET method and the NMR derived surface relaxivity are associated with the micro-porous glauconite grains. The effective specific surface area as calculated from Kozeny's equation and as derived from petrographic image analysis of Backscattered Electron Micrograph's (BSE), as well as the estimated effective surface relaxivity is associated with macro-pores. Permeability may be predicted from NMR by using Kozeny's equation when surface relaxivity is known. Capillary pressure drainage curves may be predicted from NMR T2 distribution when pore size distribution within a sample is homogeneous.
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Sorption of Magnesium and Sulfate Ions on Calcite
Authors R. Ahsan and I. L. FabriciusAt low concentration, Mg2+ ions adsorb on calcite surface, probably in hexahydrated form. Each Mg2+ ion is replacing two Ca2+ ions. When Mg2+ ion concentration corresponds to that of seawater, the calcite surface becomes covered with Mg-calcite after dissolution of an equivalent amount of calcite. When no Mg2+ ion is present, SO42- ion adsorbs on the calcite surface but is rapidly replaced by Mg2+ if these ions are present.
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3D Folding and Mud Diapirism in the South Caspian Basin
Authors I. Santos Betancor, J. I. Soto and C. E. MacellariWe analyze the deformation and folding history of a single anticline culmination in the South Caspian Basin, offshore Azerbaijan, using a post-stack 3D seismic cube provided by REPSOL. Folding occurred simultaneously to mud diapir perforation and extrusion, and shortening rates vary along the anticline axis. Maximum shortening estimates are inferred in regions pierced by the overpressured mud. A major folding episode occurred during the middle Pliocene (~3 Ma), after the deposition of the Productive Series (Late Messinian-Early Pliocene). Folding rates estimates decreased afterwards since the Late Pliocene, synchronous with the sedimentation of the post-Productive Series (< 3 Ma).
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Structure of Zagros Simply Folded Zone
Authors A. Chalabi, L. Gagala, J. Vergés, P. Keller and N. BangDespite the well exposed anticlines in the Zagros Fold Belt in Dohuk region in the Iraqi Kurdistan, very little is known about their geometry and structure at depth. Using both field data and subsurface data we constructed the first balanced cross-section across this region. The N-S trending section shows the Shiranish monocline and Tawke and Dohuk anticlines ending in the Slevani Plain to the south. The present geometry of the three folds is formed by a combination of thick and thin-skinned tectonics, multiple detachments and inversion tectonics.
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Rock Property Analysis of Malay Basin Mudrocks
Authors L. M. Duffy, A. C. Aplin and M. J. HoesniThe mineralogy and texture of mudrocks from the Malay Basin have been measured to understand the extent to which diagenetic processes drive porosity loss in shales. Previously, sonic and density log data from wells in the region highlighted the possible role of chemical compaction in reducing porosity with permeability and contributing to elevated pore pressures at depth. This study finds change in mudrock properties can be seen in samples from below the interval associated with the onset of chemical compaction and would provide a logical mechanism behind log behaviour.
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Multidisciplinary Approach - Breaking Paradigms in a Mature Oil Field
Authors N. Jaimes Villarreal, A. Ortiz-Fernandez and P. VillamarinIntegrated analysis of seismic attributes (curvature and coherence), log imaging and core descriptions was the keypoint to the identification of a fracture family not recognized before in a naturally fractured reservoir in northeastern Colombia. The importance of this family lies in its high transmisivity of water that invades wells close to these corridors that need to be avoided in new wells to get maximum performance in hydrocarbon recovery. Quality of 3D data made possible to calibrate zones with 2D seismic and core data. Vertical zonation of fractures indicates facies and thickness control in this reservoir.
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Fluid Circulation in the Llanos (Colombia) and Diagenese
Authors F. Gonzalez, I. Moretti and X. GuichetThe Colombian Llanos constitute the current foreland of the Eastern Cordillera, HC exploration is active near the compressive front (thrusted anticline structures) as in the plain (affected by small normal faults) or eastward near the wedge of the basin. Petroleum systems are known to be efficient but their complete understanding is far to be simple. The role of the water flow within the HC migration and maybe trapping needs especially to be better defined. The water production is very high in many HC fields (up to 75% of the fluid production) and the handling of such a huge quantity of water is a major environmental and economic issue. Question marks are numerous about the origin of this water (compaction, meteoric, other). The water sampled in the HC field is often fresh (not salted). Within this general context, the goal of the presented study is to test a single idea: can this unusual water flux be for a part due to diagenetic processes, namely to the dehydration of the smectite since the tertiary deposit are for large part shales.
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Study of Stratigraphy, Biostratigraphy, Microfacies, Diagenesis, Sequence Stratigraphy and Reservoir Potential of the Fahliyan Formation in the Marun Oil Field, Zagros Basin, Southwest Iran
Authors B. Habibnia, A. Feghhi and H. Amiri BakhtiarFahliyan Carbonate Formation with the age of Neocomian (Lower Cretaceous) is a main reservoir of Khami Group and is extended in whole Zagros Basin. The equivalent formation of Fahliyan Formation in Saudi Arabia, Bahrain and Qatar is Yamama Formation and in Kuwait from older to earlier; Makhul, Minaghish and Ratawi Formations (Setudenia, 1978). Considering Fahliyan performance as a high-quality reservoir and Marun Oil Field as one of the top biggest oil fields in Dezful Embayment, southwest Iran, a detailed study looked quite necessary in this area. This research was mainly done based on petrographic methods. Moreover, well logs were used as a subsidiary tool to assess the reservoir potential of microfacies. After recognition of microfacies and evaluation of lateral and vertical variations (using Walter’s law) depositional model of Fahliyan Formation was proposed. At the final stage, compartments with more reservoir potential were proposed. Generally speaking, the main tasks done through this study are: Study of microfossils (benthic foraminifera and algae), Relative age determination of Fahliyan Formation (based on age of microfossils), Study of different kinds of microfacies, Study of depositional environment, Study of diagenetic processes and Assessment of microfacies with reservoir potential using thin sections and well logs.
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Micro Tremors Energy Distribution before and after Stabilization of the Cave Risovaca in Serbia
By M. VanicCave Risovača is located in center Serbia, near the town Aranđelovac.Because of falling down rock material from walls and ceiling in object in 2007 geophysical research was carried out. Base on micro tremor data object is split on three parts. Last chamber has the biggest amplitude. After that stabilization of an object was done. In December 2009 research is repeated by author. The aim of the research was to conclude how stabilization is the influence on micro seismic properties of the cava, and micro tremors energy amplitudes. According to results of this research stabilization is done successfully.
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Geoelectric Survey of a Roll-over Anticline (Austria)
Authors K. Kelevitz, D. Raáb, E. Dombrádi and D. SpahicWe present the results of the geoelectric tomography carried out in the quarry of St. Margarethen (Austria). The research target was to identify the middle Miocene sedimentary layers by their electric properties, which outcrop in the quarry. Since these layers have different resistivity, we chose 2D multielectrode geoelectric method for the survey. The results of this survey confirm that the strata belong to a roll-over anticline structure. In connection with this structure, a major listric fault has been located to the east, which had an active role in the basin formation.
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Variation of the Crustal Structure Along the Juan de Fuca Ridge from Gravity and Seismic Data
Authors M. Marjanovic, S. Carbotte and M. NedimovicVariations in axial topography and crustal structure are observed along the Juan de Fuca Ridge (JdFR). They may reflect spatial variations in mantle melt supply and delivery of the melt to the crust together with temporal changes, possibly linked to interaction with nearby melt anomalies/hotspots. Here we analyze gravity and multi-channel seismic (MCS) data at the JdFR in order to gain a better understanding of the possible sources for the crustal structure variation in this area. Gravity models for the propagator’s wakes show presence of thinner and probably denser crust that we attribute to the presence of FeTi basalts. In difference, on the younger crust side of the wakes the models show presence of thicker crust at the extent of ~10 km from the wake. The anomalously greater twtt to Moho within the axial region is explained by the presence of thicker crust. Since thickening of the crust and gradual changes of densities within the layer 2b/3 due to the half plate thermal cooling account for less than 60% of the observed anomaly, the remaining ~40% of the anomaly we attribute to the presence of low density body below the crust.
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Method of Electromagnetic Sounding on the Territory of the Ancient Bilar Settlement
Authors A. Gimazov, B. Platov, A. Stepanov and Z. SlepakThe article presents the application of method of electromagnetic sounding for studying of the anthropogenic layer structure on the territory of the ancient Bilar settlement. Field research technique, data processing and interpretation are presented.
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Attenuation Mechanism of Seismic Wave in Chamoli Region of Garhwal-Kumaun Himalayas
Authors A. Kumar, S. Mukhopadhyay and E. Del-PezzoIn this study the S-wave attenuation mechanism is analyzed and intrinsic and scattering attenuation effects are separated. This helps in understanding the physical mechanisms governing attenuation properties of the crust of this region. It has been observed that the Qs−1, Qd−1 and Qc−1 values at all frequencies are comparable. The estimated Le−1, B0, Qi−1, Qs−1, Qd−1 and Qc−1 values show that S-wave attenuation is primarily controlled by scattering attenuation in the source zone of the 1999 Chamoli earthquake. My results also show that for the source zone of 1999 Chamoli earthquake in the Garhwal Himalayas seismic albedo is very high, i.e. attenuation is mainly controlled by scattering attenuation. In conclusion, The extinction length Le varies between about 12 km to about 125 km in the study region. The seismic albedo (B0) values vary between 0.65 and 0.8. B0 values are very large (>0.5) showing that at all frequencies scattering attenuation is the dominating factor causing attenuation of seismic waves. This shows that the degree of heterogeneity is very high for the frequency range considered in this area.
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Croswell Seismic Waveform Tomography for Monitoring the CO2 Injection at Ketzin Site, Germany - Synthetic Data Test
Authors F. J. Zhang and C. JuhlinCO2 injection usually results in small changes in the seismic velocity of the reservoir. To monitor this we need an accurate velocity model of the underground, waveform tomography is a potential tool to solve this problem. In this study, synthetic datasets based on time-lapse cross-well seismic measurements at Ketzin were generated and then waveform tomography was applied to them to check the ability to reconstruct the underground velocity model. Our results suggest that waveform tomography may be suitable for handling the real cross-well datasets acquired at the Ketzin site to monitor CO2 injection.
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Seismic Description of Eocene Depositional System, SW Barents Sea
Authors P. A. Safronova, K. Andreassen, J. S. Laberg and T. O. VorrenThree-dimensional seismic data from the Sørvestsnaget Basin, south-western Barents Sea continental margin are used to investigate a Middle Eocene depositional system. It is composed of sandstones interbedded with mudstones inferred to have accumulated in a deep marine environment. The time-thickness map shows thickness increasing towards the northern part of the study area. Based on the thickness distribution, the source area is inferred to be the Stappen High. A root-mean-square amplitude map displays amplitude variations along the depositional system distribution. An area with increased high amplitudes is interpreted to demonstrate the higher sand content and may contain gas.
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An Integral Geometric Method for Automatic First Arrival Detection
More LessFirst arrival picking is a time consuming step in seismic processing since there is no precise and reliable method has been found for automation of this process so far. Environmental noise originating for instance from raindrops, traffic or electrical noise from power lines can strongly affect in particular energy based picking methods [e.g. Coppens, 1985; Spagnoli, 1991] but also other like methods based on cross-correlation techniques, fractal dimensions [Boschetti et al., 1996] or neural networks [Murat & Rudman, 1992] are influenced. Various automatic first break picking methods were published and have been applied successfully in the exploration industry. But as the datasets grow larger, it is necessary to improve efficiency and speed of the first arrival detection process while maintaining accuracy and further reducing the necessary amount of human intervention. In this paper, a promising automatic first break detection method, Wave Area Ratio (WAR), is presented. That model is used to estimate travel times which are furthermore used as a benchmark for the identification of improper picked travel times.
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High-resolution Reflection Seismic Imaging in the Kristineberg Mining Area, Northern Sweden
Authors M. Dehghannejad, C. Juhlin, A. Malehmir and P. WeihedThe Kristineberg mining area is located in the western part of the Skellefte Ore District, one of the most important mining districts in Europe. As a part of a 4D geologic modeling project, two new reflection seismic profiles were acquired. Although the structural geology is complex, the processed seismic data reveal a series of steeply dipping to sub-horizontal reflections, some of which reach the surface and allow correlation with surface geology. Reflection modeling was carried out to obtain the 3D orientation of the main reflections and to provide insight into the possible contribution of out-of-the-plane reflections. The new reflection seismic profiles have improved our understanding of shallow geological structures in the area and in conjunction with recently acquired potential field data, magnetotelluric data and geological observations will help to refine previous 3D geologic modeling interpretations that were aimed at larger scale structures.
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Seismic Stratigraphy and Numerical Analysis of the Southern Brazilian Margin
Authors J. Contreras, R. Zühlke, S. Bowman and T. BechstädtThe Campos, Santos and Pelotas basins (offshore southern Brazil) have been investigated in terms of 2D seismo-stratigraphy and numerical basin analysis. The processes controlling accommodation space evolution from the shelf top to the continental rise (i.e. eustacy, subsidence and sediment input) are discussed, and the evolution of the different basins is compared. Main results include: (i) classification of depositional seismic sequences from the syn-rift Barremian to the drift Holocene basin fill; (ii) numerical modeling of the subsidence/uplift history; (iii) forward stratigraphic simulation and quantification of erosion, transport and deposition rates regarding the basin-specific hydrocarbon potential
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Environments of Sedimentation and Distribution of the Jurassic Strata
Authors A. A. Suslova, A. V. Stoupakova and Y. K. BurlinThe Jurassic period characterised by the transgression of the Arctic Ocean with its maximum transgression in the Tithonian, when the organic reach black shales were deposited. During the Early and Middle Jurassic the change occurred from an arid to a humid climatic regime, resulting in increased run-off and the transport of sediments out onto the shelf. The most uplifted areas at Jurassic period were the Svalbard Archipelago, the Central Zone of the Barents steps, Baltic shield, Finnmark platform, Frants Joseph Land, The Novaya Zemlay archipelago and Timan-Pechora anticline. These areas could be the main sources of material. Many of the most important oil and gas reservoirs of the Barents sea basin were deposited during the Early and Middle Jurassic. Eastern and Western part of Barents have been developed simultaneously within the one basin. Thereby that allowed us to mark out five transgressive-regressive regional cycles. A gradual thinning of sequences from east towards west indicates a general increase in accommodation space during deposition towards east. The Jurassic sandstones are one of the main reservoirs on the Barents Sea shelf and have rather good reservoir properties.
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3D Reservoir Model of the Sobrarbe Delta System (Eocene, Ainsa Basin, Pyrenees Foreland Basin) - SobraRes Project
Authors T. Kissner, R. Zühlke and T. BechstädtThe Late Eocene Sobrarbe Delta System developed at the southern margin of the Ainsa basin as part of the Pyrenees foreland basin, northeastern Spain. It shows exceptional lateral and vertical exposure at seismic scale. Continuous outcrops between alluvial plain an basin margin in both time and space allow for high-resolution measuring/sampling of vertical sections and physical/optical tracing of sediment surfaces. This study includes preliminary data from three outcrop transects of 12-25 km each in the direction of long-term progradation and parallel to paleo-coastlines. The ongoing project will further develop and analyze a high-resolution 3D data set of reservoir architecture in the Sobrarbe Delta System with special focus on lateral continuity and vertical connectivity of reservoirs. Improved reservoir models are essential for forward numerical models of sedimentary systems and fluid-flow during subsequent burial. Key objective is the improved understanding of heterogeneities in reservoir facies and petrophysical parameters in foreland basin delta systems by high-resolution outcrop analysis. Outcrop-based data sets are processed with GIS (ArcGIS ®, ESRI 2009). 3D models will be performed and analyzed with Petrel ® (Schlumberger) and compared to producing subsurface delta systems in foreland basins.
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PTT and Deformation Paths Derived from FIAs, Pseudosections and Zoned Garnets and Their Significance
By A. ShahA progression of FIAs (foliation intersection/inflection axes preserved within porphyroblasts) in the foothills of the Colorado Rocky Mountains reveals three periods of garnet and staurolite growth and one growth phases each of cordierite and andalusite. These minerals grew in an overall prograde path, where the growth of garnet was always followed by the formation of staurolite for each FIA. For the last 1 period of FIA development the growth of staurolite was also followed by the development of andalusite and cordierite. The intersection of Ca, Mn, and Fe isopleths in garnet cores for 3 samples, containing FIA set 1, set 2 (1758.8±9, 1720.5±6.1 Ma) and set 3 (1674±7.6 Ma), trending NE-SW, E-W and SE-NW respectively, indicate that these rocks never got above 4kbars throughout the Colorado Orogeny. A slightly clockwise P-T path occurred for this orogeny.
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Sedimentary Response to the Evolution of Mobile Substrates: Examples from Offshore West Africa
Authors A. P. Oluboyo, R. L. Gawthorpe, M. Huuse and F. Hadler-JacobsenUtilizing a regionally extensive 3D seismic volume from the deepwater region offshore West Africa, we present an interpretation of the variability of responses of slope channels to mobile substrate deformation on continental slopes. Within the study area, salt related deformation commenced in the Cretaceous and continues till present day. A series of NE-SW trending, structural dip parallel channel fairways, are initially positioned by elongate pre-Palaeogene salt-cored foldbelts and extensional faults. Typical dimensions of these elongate mini-basins are in the order of 50km length by 10km width. The ensuing interaction of submarine channels and salt structures through the Oligo-Miocene results in increasingly tortuous sediment pathways, blocking and confinement of submarine channel systems over length scales of 10’s to 100 km and development of “shadow zones” devoid of sediment input.
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The Method of Stress State Estimation of Permeable Rock
By V. A. PavlovThe stress state estimation method of deep permeable rock based on hydraulic fracturing and following deformations is developed. Numerical modeling of tests by singular integral equations is carried out. The stress state estimation is carried out by the fracture opening pressure value on a borehole wall and by the magnitude relations of maximum and minimum stress dependence of the borehole cross-sectional area change. The method could be used for a continious monitoring of state change in the chosen point of rock mass in the process of field exploitation.
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Geological Controls on Gas Production: Wissey Field, UK SNS
Authors C. Duguid and J. R. UnderhillZechstein Supergroup carbonates have formed a highly disappointing exploration target beneath UK waters. The Wissey gasfield, situated in the UK Southern North Sea is the first gas field in that region to produce solely from Zechstein Supergroup Carbonates and specifically the Z3 Plattendolomit Formation. Investigation, integrating seismic interpretation with well data analysis has explored the stratigraphy and structural complexity of the Wissey region. Furthermore, the nature of the naturally fractured Plattendolomit Formation reservoir and controls on the observed reservoir quality have been identified and are set in the context of both the Z3 depositional system and the subsequent deformation observed.
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3D Integrated Reservoir Modelling for Upper Safa Gas Development in Obaiyed Field, Western Desert, Egypt
Authors M. Abdel-Fattah, W. Dominik, E. Shendi, M. Gadallah and M. RashedA detailed 3D model of Upper Safa gas reservoir in Obaiyed Field has been constructed by integration of seismic, well log, and core data. Data integration was facilitated by the Petrel, Schlumberger’s reservoir modeling software. The integrated model has been used to support key operational and reservoir development decisions. The cross sections made from the 3D reservoir model in many directions of the study area, show the lateral and vertical extension of Upper Safa reservoir zones and their thickness, facies and petrophysical parameters variations including faults and folds.
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3D Seismic AVO Data Established by the Wavelet Transform Modulus Maxima Lines to Characterize Reservoirs Heterogeneities
Authors S. Ouadfeul and L. AliouaneThe main goal of this paper is to establish reservoirs media heterogeneities by the wavelet transform modulus maxima lines, first we gathered amplitude versus offsets AVO amplitudes at the top of the reservoirs and we calculate the 2D wavelet transform after we calculate its maxima and we estimate the Holder exponent at each one, variation of this coefficient can give more information about the variation of lithology and fluid nature at any direction. Application of this idea at synthetic 2D seismic model shows that application on real AVO seismic data and its attributes can give more ideas about reservoirs heterogeneities.
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Seismic Analysis of Gas Accumulation in the Italian Offshore
Authors A. Mocnik, A. Del Ben, E. Forte, R. Geletti and M. PipanThe Apennine-Maghrebides foreland offers very different geological settings favouring gas accumulation within permeable horizons, depending by lithology and tectonic structures. In this paper we analyze the different relationships that may exist between the deep structures and the presence of gas in the Plio-Quaternary sediments. Processing techniques (AVO and complex attributes analysis) and geological interpretation of some deep crustal seismic profiles in the Italian offshore, let us to make a qualitative study of gas presences finding their correlations with deep structures.
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Variation of Seismic b-value in Central Alborz Mountains, Iran
More LessThe Alborz Mountains is an arc shape fold and thrust belt surrounding the south of the Caspian Sea. The geology of the Alborz Mountains is controlled largely by major thrust faults. The Mosha fault is the most prominent structure in the southern part of the Central Alborz region. It is an active, high dip angle reverse fault with an approximate length of 400 km. Damavand volcano is situated 20 km northwards from the Mosha active fault and lies unconformably upon folds and thrusts. We calculated the frequency-magnitude distribution in the Central Alborz Mountains, Iran. The earthquake catalogue used in this study consists of 895 local events recorded by the Iranian Seismic Telemetry Network from 1996 to 2006. The seismic array consists of 19 permanent stations equipped with 3-components short period (SS1) seismometers. We generated a spatial 3-D variation of b-value in the Central Alborz Mountains. A distinctive area of high b-value is found around the metropolitan Tehran. This result is well consistent with the conspicuous low velocity region derived from local earthquake tomography, coordinate of Damavand Volcano and a geothermal reservoir of 550 km2 in this region.
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Seismic Studies on the Messinian Rocks in the Onshore Nile Delta, Egypt.
Authors M. Barakat and W. DominikThe Nile Delta is illustrated to be an arcuate delta (arc-shaped), as it resembles a triangle or lotus flower when seen from above. The hydrocarbon potential of the Nile Delta sedimentary sequence is limited for the time being to the Neogene formations, trapped against listric fault planes or over tilted fault blocks. The main proven reservoir within the Miocene deltaic sequences of the North Delta Basin is the Abu Madi sandstones (the Messinian Rocks). The Messinian Reflector is a widely known important reflector identified and characterized by an erosional unconformity surface. It is also affected by normal faults, listric faults, secondary antithetic faults and large rotated fault blocks. The time structure maps, velocity maps, depth structure maps as well as isopach maps were constructed by using Petrel Software 2009. The Seismic investigation gives an idea about the structural and stratigraphic characteristics of the onshore area of the Nile delta region by the interpretation of the available 2D seismic data. There are three structural trends identified for the Nile delta: The Tethyan trend, an east-west trend, the north east-south west trend and the northwest-southeast trend.
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Understanding Seismic Anisotropy of Ice in West Antarctic Ice Sheet
Authors B. W. Al-Rumaih, G. W. Stuart, G. E. Lloyd and D. A. AngusA deep understanding of the seismic anisotropy of ice plays an instrumental role in modelling ice flow and its influence on ice sheet melting. To understand predicted seismic anisotropy from aggregates of ice crystals, we use two approaches: forward modelling of seismic anisotropy due to lattice preferred orientation (LPO) and forward modelling of seismic anisotropy due to fluid filled cracks (FFC). We generated a series of geo-mathematical models for various crystallographic distributions in strained ice to provide a tool for interpreting the observed estimates of anisotropy from three-component recordings of microquakes at the base of the Rutford ice-stream in Antarctica.
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Geomagnetic Measurements of Lazar's Canyon (Eastern Serbia)
Authors I. Mitrovic and M. C. CukavacIn this paper, a correlation between magnetic data and geology of research area is given and it enable adequate geological explanation. Nevertheless, we managed to separate large geological units within the investigation area by modelling of geomagnetic measurements. On the current level of investigations and on the basis of current knowledge, we assumed the position of the regional fault and lithological boundary of two regional geological units. The obtained results does not give possibility of quantitative interpretation, because we need data of other geological and geophysical investigations (susceptibility measurements, detailed geological mapping, gravity method...) for such interpretation. In that sense, these results stay in the domain of qualitative interpretation. Results show very good correlation between geomagnetic data and data of geological mapping and the measured elements of tectonic fabric.
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Inversion of Electrical Resistivity Tomography and Cone Penetrometer Resistivity Data to Map Quick Clay in Norway
Authors S. K. Cornée and A. A. PfaffhuberQuick clay is highly sensitive marine clay deposited during the last glaciation found in North America and Scandinavia. Seeping rain and groundwater may turn marine clay into quick clay by reducing pore water salinity Quick clay can lead to serious landslides as it becomes nearly liquid at failure. Geophysical combined with geotechnical methods are promising to indicate quick clay, and hence potential landslide areas. Joint inversion of electrical resistivity and cone penetrometer resistivity data from a site in Norway with a history of quick clay sliding have been carried out. Surface-, borehole- and further laboratory measurements have further been found consistent within technical uncertainties.
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Creep of Highly Porous Chalk and Biot Critical Frequency
Authors K. A. Andreassen, I. L. Fabricius and N. N. FogedChalk behaves with time dependent deformation when subjected to a load. We review a previously published data set from high pressure oedometer tests and apply a friction factor corresponding to the friction between solid and pore fluid. The friction factor is the Biot critical frequency used in acoustic theory to discriminate between the high and low frequency domains. By doing this we show how test results from dry, oil, and water saturated chalk can be combined in one simple expression.
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Crustal Structure Beneath Hudson Bay from Ambient-noise Tomography - Implications for basin formation
Authors A. E. Pawlak and D. W. EatonThe Hudson Bay basin is the least studied of the four major Phanerozoic intracratonic basins in North America, which include the hydrocarbon-rich Williston, Illinois and Michigan basins. This study focuses on determining how the Hudson Bay basin formed and on regional crustal structure based on ambient-noise tomography. Two hypotheses are tested, the first suggesting subsidence due to eclogite phase transformation and the second suggests subsidence from lithospheric extension resulting in crustal thinning. Results show asymmetric cross-correlation functions, for which we have adopted an alternative method to averaging cross-correlations, yielding better-defined dispersion ridges. Tomographic pseudo-sections show compelling evidence suggesting crustal thinning as the main event in basin formation.
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Velocity Models and Pre-stack Depth Migration of Gas Hydrates on Taiwan Accretionary Prism
Authors B. J. Yang, T. K. Wang, J. M. Deng and C. S. LiuReflection images of the accretionary prism along seismic profiles collected from R/V Maurice Ewing in 1995 and from R/V Marcus G. Langseth in 2009 off SW Taiwan are presented for charactering gas hydrates in this study. Pre-stack depth migrations of the seismic profiles indicate the thickness of sediments about 2-3 km and the depth of the bottom simulated reflector (BSR) about 300 m below the sea floor. Layers of gas hydrate and free gas are about 100 m thick and 80 m thick, respectively. Horizontal velocity analysis of the seismic profiles show a gas-hydrate layer above BSR with a P-wave velocity of about 2100 m/s and a free-gas layer below BSR with a P-wave velocity of about 1800 m/s. Most BSRs are non-continuous in the accretionary prism that may result from the gas dissipation from thrust faults, fractures and severe deformation due to subduction. Gas migrated from thrust faults and accumulated beneath the lower slope of the accretionary prism may result in more clear and continuous BSRs in the lower slope than those in the upper slope of the accretionary prism. The difference of BSRs may be associated with the organic sediments came from the river of Taiwan.
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The Effects of Shear Properties of Heavy Oils on Seismic Response
Authors F. Vasheghani, L. R. Lines and J. EmbletonShear properties of heavy oils can influence the seismic response. This is ignored in the elastic modeling approaches. However, heavy oils are considered Viscoelastic materials and the effects of their shear properties on seismic response can be modeled using Viscoelastic approaches. Variations in viscosity will change the attenuation of seismic waves. Biot – squirt flow relations (BISQ) can be used to relate attenuation and viscosity. One order of magnitude change in viscosity is equivalent to one order of magnitude change in quality factor. The importance of using appropriate models for characterizing the heavy oil reservoirs is illustrated by comparing the elastic and Viscoelastic responses to changes only in viscosity. While elastic models are blinds to such changes, viscoelastic models illustrate great sensitivity to changes in fluid viscosity, therefore have the potential for estimating fluid viscosity in the reservoirs.
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Complex Trace Transformation and its Application to Suppress Random Noise
Authors H. R. Soleymani, M. Nejati, S. M. Arabshahi and M. A. RiahiComplex trace transformation is a useful method for random-noise suppression of seismic data. This method omits the low frequency components of the amplitude envelope of the stacked trace and calculates a new trace using normalized phase information. The method uses very simple equations and has the ability to simultaneously suppress random noise and broaden seismic bandwidth. The only parameter selection required is time window length. time window is an important parameter for complex-trace transformation processes, and controls both bandwidth or frequency content of the output and the noise suppression level. we tried to explain and cover the main aspects of this method by illustrative figures. also effects of this method on noisy traces shown studied with 1-D and 2-D seismic sections.
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Detection of Leaking Using Self-potential on Vidara Dam (Bosnia)
By D. NaumovVidara Lake (Serbian: jezero Vidara) is an artificial lake in northeast Bosnia.Dam leakage was noted that the dam leakage at southeaster zone. The aims of research were to locate a wide zone of leaking and to determine a smaller field of anomalies for future measurements.Conducted measurements confirm and peruse the leakage zone and indicate that the northwestern and middle parts of the dam body are without damage. The basis of these results is now possible to plan further research that will define the 3D model on is needed for repair of the dam.
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NMR as a Tool for Estiamtion of Excess Conductivity in Chalk
Authors M. M. Alam, A. K. Shaik and I. L. FabriciusExcess conductivity arising from CEC could play a significant role in quantification of hydrocarbons in North Sea chalk. We demonstrate the use of T2 as an indicator of excess conductivity, so that NMR logs could be applied to determine excess conductivity in chalk. We found that calcite grains have considerable CEC. Interestingly, excess conductivity in chalk is controlled by the calcite surface rather than by the clay specific surface. Excess conductivity of chalk consequently has positive linear relationship with the specific surface of calcite. The NMR tool could thus potentially be used to calculate calcite specific surface in chalk and from the average value of calcite CEC it is possible to predict excess conductivity.
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Influence of Cementation Factor on Water Saturation in Carbonates of Main Dolomite in North-West Poland
Authors P. Krakowska and M. NiepsujDetermination of hydrocarbon saturation in carbonates is challenge for the geophysical interpretation. Cementation factor is one of the main coefficients in petrophysics which strongly affect water saturation. Its wrong determination causes serious error in water saturation value. In the paper water saturation was determined using two equations: Borai and Shell formula. By using computed water saturation and fluid substitution method theoretical velocities of P-waves and S-waves (also P-wave/S-wave velocity ratio) were calculated. Diversity in P- wave and S-wave velocity is a source information about lithology. In reservoir rocks Vp/Vs ratio may also work as a confirmation of gas saturation.
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Application of Artificial Neural Networks to the Evaluation of Formation Permeability
By P. KurnikANNs enable the recognition of relations between input and output data and the prediction of permeability. The network was created using Statistica and MATLAB Neural Network Toolbox. Permeability, one of the most important reservoir parameters of rocks, defines ability to transmit fluids in porous space of rock formation. Permeability is affected by structure and texture (shape, size, and degree of sorting and cementation), porosity, shaliness and carbonate volume. There is no general formula for permeability calculation on the basis of factors influencing fluid flow in porous rocks. ANNs enable the prediction of permeability.
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Influence of N2/CO2 Injection to the Wettability Behavior of the Coal-water-gas System
Authors N. Shojaikaveh, E.S.J. Rudolph and S.N. AshrafizadehGeological sequestration of carbon dioxide (CO2) is one of the viable methods to reduce the CO2 emission and to stabilize the concentration of greenhouse gases in the atmosphere. Carbon dioxide (CO2) or flue gas (N2/ CO2) injection into coal layers serves the dual purpose to enhance coal bed methane production (ECBM) and to store CO2. Because of the important rule of coal wettability in ECBM efficiency, we have undertaken an experimental study to investigate the wetting properties of different coal types by means of contact angle measurements in a modified pendant drop cell at in-situ conditions.
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Development of Reservoir Characterization Techniques and Production Models for Exploiting Naturally Fractured Reservoirs
Authors I. Oraki Kohshour, B. Habibnia and K. DalvandFor many years,geoscientists and engineers have undertaken research to characterize naturally fractured reservoirs. Geoscientists have focused on understanding the process of fracturing and the subsequent measurement and description of fracture characteristics. Engineers have concentrated on the fluid flow behavior in the fracture-porous media system and the development of models to predict the hydrocarbon production from these complex systems.This research attempts to integrate these two complementary views to develop a quantitative reservoir characterization methodology and flow performance model for naturally fractured reservoirs.The research has focused on estimating naturally fractured reservoir properties from seismic data, predicting fracture characteristics from well logs, and developing a naturally fractured reservoir simulator.It is important to develop techniques that can be applied to estimate the important parameters in predicting the performance of naturally fractured reservoirs.This project proposes a method to relate seismic properties to the elastic compliance and permeability of the reservoir based upon a sugar cube model. In addition, methods are presented to use conventional well logs to estimate localized fracture information for reservoir characterization purposes. This is an important step in developing exploitation strategies for optimizing the recovery from naturally fractured reservoir systems.
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Could CO2 Storage Site Performance Be Compromised by Palaeo-Gas Migration Conduits in the Overburden?
Authors G. D. Nicoll, M. Naylor, A. J. Cavanagh, S. Geiger and R. S. HaszeldineFormations below the North Sea are proposed as a major repository for anthropogenic CO2 to mitigate climate change. Two such sites are already operational offshore Norway. Large areas of the North Sea are known to have leaked natural gas over geological time, so are these areas suitable for CO2 storage, given that geological heterogeneities and natural gas palaeo-migration pathways could serve to compromise CO2 storage sites in the longer term? We have identified similar features at the Utsira CO2 storage site offshore Norway, thus we use this site as a case study to investigate whether CO2 leakage is possible and if so under what conditions. We evaluate the main uncertainties affecting this storage site and present a risking methodology and screening tool that could be used to assess future storage sites and minimise the risk of compromise due to inappropriate site location.
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Fracture Characterizations from Well Testing Data Using Artificial Neural Networks
Authors R. Eslamloueyan, B. Vaferi and S. AyatollahiDual porosity model refers to those reservoirs which have two different media. The interporosity flow coefficient (λ), and storativity ratio (ω). Well testing analysis is used to estimate reservoir parameters that are used in the reservoirs description. Pressure derivative plots corresponding to different value of λ and ω, are dissimilar. Derivative plots are used to design a model based on ANN to estimate λ and ω. In this study the capability of Artificial Neural Network to estimate λ and ω from well testing data has been investigated. Well testing data for dual porosity reservoir have been generated and converted to derivative plots. The best configuration of ANN has been selected by a trial and error procedure through applying different training algorithms and changing the number of neurons in the hidden layer. Using this procedure, a two-layer ANN model has been found as an efficient tool to estimate ω and λ. The trained ANN has been validated using the test data not been used in the training data set. The results have shown that the ANN is capable of estimating λ and ω using derivative plot obtained from the reservoir simulation as well as the information obtained from the literatures.
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A Poroperm Function To Evaluate the Dynamic Pore Connectivity of Porous Media
Authors M. I. Al-Mossawy and B. DemiralThe pore connectivity affecting the permeability can be called the dynamic pore connectivity, to distinguish it from the average pore connectivity determined by the technique of digital image processing. Digital image processing of the porous media can not evaluate numerically the dynamic pore connectivity. Neithalath et al. (2006) have derived a factor from Kozeny-Carman equation to characterize the enhanced porosity concrete according to the relationship between the porosity and permeability, called the hydraulic connectivity factor (ßH). This factor included conductivity factor, specific surface area of pores, and pore shapes factor. In order to find new relationships between the porosity and permeability, a different model has been used in the present study. A capillary-bundle model was developed to represent the porous media and to derive two relationships between the porosity and permeability. Either of these relationships can be used to characterize the porous media according to their dynamic pore connectivity. One of these relationships had been modified to a function called poroperm (Pp) to be with the same units of permeability. Applying Pp and ßH to characterize seven sandstone cores yielded an excellent matching.
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Reconciling Well-test and Production Data in Mapping Permeability-thickness Trends
By A. PetrovDuring a field development process, one of the parameters used to decide the in fill well locations is permeability-thickness (kh) map. This map can provide us with overall trends in the conductivity of the formation as well as information about optimizing water flood patterns. One difficulty typically observed in generating kh maps is a prominent display of "bull's eyes". The values of kh can change dramatically from well to well, which causes problems in interpolation of these values. Sometimes, because of large discrepancies, the overall patterns are hard to discern and well planning is more difficult. In the proposed work, we developed a procedure for capturing the trends in kh maps by removing the bull's eyes. The kh values are determined by two methods: use the production data and using simplified procedure, determine the value of kh or evaluate well test data and determine the kh values. The procedure was validated by applying it to a large oil field located in Siberia with successful application of in-fill well program.
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Diffusion-to-telegraph Equation Conversion to Analyze Pressure Transient Behavior
Authors A. Moaddel Haghighi and Y. FallahzadehFor many years, pressure propagation in porous media has been the main tool of oil and gas reservoir characterization. Almost all available related petroleum literature states that Instantaneous-Action-at-a-Distance (IAD) is a natural part of diffusion process and it's a "particular behavior of the linear diffusion equation which indicates an infinitesimal change in pressure everywhere in the reservoir following a disturbance at the wellbore". For the first time in the filed of well testing,we have converted a Diffusion equation to its equivalent Telegraph equation. Initial conditions are reconstructed from those of diffusion equation. Here, through a simulation study, we examine the early time behavior of a 1D diffusion equation and its reconstructed conjugate telegraph equation to study the possible discrepancies these two equations may have. This can light up the way to more rigorous study of pressure transient analysis in well testing for better reservoir characterization. The simulation we have conducted is the first try to examine effect of finite speed of pressure propagation in telegraph equation in comparison to the infinite speed of disturbance propagation in diffusion equation which for many years has been a matter of controversy among petroleum engineers.
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An Experimental Study to Minimize Capillary End Effect During Flooding in Porous Media
By M. AhmedCapillary end effect arises from saturation discontinuity existing at the outlet face of the porous medium during a flow test. This phenomenon results in a saturation gradient in the flow system. This results in errors in the calculated relative permeability of the porous media. Accurate relative permeability measurements are essential for many applications. It was observed that the length of the rock affects the measured values. At the end of this study, the optimum length of rock and the flow conditions for our application to minimize the capillary end effect was identified.
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The Use of VSP and Well Data To Design De-multiple Techniques
More LessIn this project, VSP and well log data are used to assess multiple activity on 3D land seismic data. Synthetic VSP data were created using well log data. Observations from these synthetic data are used to determine whether well log data are sufficient to understand the multiple wave field or VSP data are required; whether the multiples identified from the borehole can be used to design de-multiple filters and what is the optimum multiple attenuation technique to use.
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3-D Seismic Ray Tracing on Irregular Tetrahedral Grid
Authors D. M. Molodtsov and Y. V. RoslovWe apply shortest-path method of seismic ray tracing to irregular tetrahedral grid, which is useful for modelling highly heterogeneous media with complex geometry of interfaces. To combine low computational complexity with satisfactory accuracy we introduce specially organized interpolation of traveltimes on the second-order grid. The algorithm is extended on multiple arrivals. Performance of the algorithm is studied in numerical experiments.
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Outcrop-seismic-core Plugs Correlation in a UAE Cretaceous Carbonate
Authors A. H. El Husseiny, S. A. Al Mesaabi, S. Vega and M. AliIn this study, we investigate potential correlation between rock properties and seismic to better understand factors that affect seismic response in UAE Cretaceous carbonates. We correlate geological and geophysical parameters at three different scales: outcrop, seismic and core plugs. We acquired a 2D seismic line on the top of an outcrop. From the same outcrop we examined 17 core plugs. We found that acoustic velocities decrease with increase in fracture density. This result was supported by the outcomes of the outcrop-seismic correlation where changes in fracture density were found to be the main cause of reflection events in these carbonates.
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The Hough Transform for Seismic Profile Interpretation
More LessWe use Hough transform for seismic interpretation, by detecting parameterized shapers through mapping from the image space into the parameter space. We apply the Hough transform for the parabola detection in the real seismic data. Before the transform we use an erosion operator to delete the non-useful information and keep the useful information as much as possible. The result shows a good match between the original image with the detected image.
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Gravimetric Monitoring of the Base of the Mosque Kul Sharif
By A. AbdullinThe research task was determination of facilities of gravimetric method in research of the influence of groundwater on the base of the mosque Kul Sharif. The survey using several gravimeters was carried out, error estimate of measurements was done, and all the obtained data was analyzed. The conclusion is that research of the groundwater influence on the basement of the mosque can be carried out using gravimeters of Scintrex type, which provide high precision. It’s reasonable to carry out research over a longer period of time and take the necessary steps for strengthening the foundation.
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First Time Arrivals Tomography
By N. BelayouniThe tomography consists on detecting the variation of the accoustic waves velocity in the formation in the near subsurface. Within this work, we established a new algorithm of first time arrivals tomography that considers the advances in the IT domain and meets the expectations of geologists and geophysicists in term of ease of parametrization. The work is divided essentially in three parts. We began by resolving the direct problem which consists in calculating the first arrivals time for a given source and velocity model by dicretizing the eikonal equation on a Cartesian grill. Then, we resolved the inverse problem which consists in determining the velocity model which best fits observed times on surface by the method of adjoint state. Finally we added the a priori information in the Least Squares cost function to refine the inversion results.
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New Development for Model Selection Criteria in Reservoir History Matching
Authors M. M. Rafiee and F. HaefnerHistory matching, which is to find a suitable model, such that the simulator correctly predicts the future production, is absolutely needed for a real reservoir simulation. From mathematical point of view the selected model should be minimized in terms of objective function -OF- (necessary condition for model selection) and also the condition of parameter uniqueness (sufficient condition for model selection) must be fulfilled in a successful reservoir history match. Although the value of minimized OF in normal practice get smaller with increasing the number of parameters, the comparison of OF values does not show the unique solution. In this work we developed Penalized Objective Function (POF) strategy based on penalization concept of OF and principle of parsimony, to avoid over-parameterization to find out most probable unique solution for reservoir history matching. The new strategy (POF) has been implemented successfully on field case and could be applied generally for different deterministic model concerning the reservoir engineering decision.
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