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74th EAGE Conference and Exhibition incorporating EUROPEC 2012
- Conference date: 04 Jun 2012 - 07 Jun 2012
- Location: Copenhagen, Denmark
- ISBN: 978-90-73834-27-9
- Published: 04 June 2012
941 - 948 of 948 results
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Variations of Moho Depth in Zagros, Central Iran and Alborz Zones Using P and S Receiver Functions
Authors N. Mohammadi, F. Sodoudi and A. Gholamir methods to detect the Moho depth variations within Iranian plateau. Due to the different deformation zones existed in the study region, our results show significant variations of the Moho beneath the Iranian plateau. Moho depth beneath Central Alborz is observed around 55±2 km, which is interpreted related to the shortening of the collision of Arabian–Eurasian plate. Moho depth decreases to 37±2 km beneath Central Iranian Plateau indicating less affected by the lithospheric thickening resulted from the collision. Our observations depict the increasing of the crustal thickness beneath the UDAM and SSZ zones along the lower latitudes, which implies that the convergent rate increases from NW to SE across the Zagros collision zone.
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Modelling of Fracture Strength Distribution in Elastically Heterogeneous Rocks
Authors C. Langenbruch and S. A. ShapiroModelling the stress conditions inside hydrocarbon and geothermal reservoirs is important to predict fracture behaviour during the injection of fluids. We analyse the influence of elastic heterogeneity on stress and fracture strength distribution in rocks. Therefore, we simulate the distribution of elastic modules inside a reservoir rock as a 3D fractal random medium according to parameters obtained from sonic well logging data. Using an ABAQUS finite element stress analysis model we determine the stress field inside the rock volume. By applying geo-mechanical considerations we then compute the fracture strength distribution and analyse relations between elastic modules stress state and fracture strength. The stress modelling analysis performed in this paper suggests that the stress state in elastically heterogeneous rocks can be highly heterogeneous. Our modelling study according to elastic heterogeneity derived from sonic well log data along the KTB main hole results in a broadly distributed fracture strength between -10 to 20 MPa. We find strong relations between elastic modules, stress state and fracture strength, which can be applied to predict the stress distribution in hydrocarbon and geothermal reservoirs and the occurrence probability of fluid injection induced seismicity.
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Random Sampling Data Interpolation with Weighted Matching Pursuit (WMP)
Authors X. Wang and H. Z. WangSeismic data interpolation can be done by an inverse Fourier transform if the Fourier spectrum of regular and un-aliasing seismic data is well estimated. The pseudo random sampling of the seismic data in time-space, which is based on a regular pattern, yields a F-K spectrum in which the aliasing looks like white noises. Therefore, restoring the F-K spectrum of the regular and non-aliasing data is similar a process of de-noising in F-K domain. A new method which is called WMP is introduced. This method is based on fast MP algorithm with a weighted operator formed with the Radon spectrum of seismic data by assuming that the events are linear. The noise can be removed clearly with the help of the weighted operator, which is proven by numerical examples. The method can be easily extended to high-dimensions.
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Spatial Distribution of Trap Types Relative to the Regional Structural Framework, Baffin Bay, Offshore Greenland
Authors P. W. Bradbury and K. FrontThe Baffin Bay area offshore northwest Greenland represents a vast frontier exploration province. The aim of this work has been to create a new structural elements map for the region and assess the spatial distribution of trapping styles within a more detailed framework. The assessment was carried out using a large TGS 2D seismic database (>200,000 km2) acquired between 2007 and 2010 and associated gravity and magnetic data. The main basins in the area are the Melville Bay Basin and Kivioq Basin. In these basins and surrounding areas five distinct trap styles comprise the majority of closures. The trap styles include 1) Tilted fault blocks associated with Cretaceous to Palaeocene rifting. 2) Anticlines formed through differential compaction situated over basement highs. 3) Anticlinal closures formed through regional compression during Palaeogene uplift and localized compression in hangingwall fault blocks. 4) Hangingwall anticlines formed during Palaeogene inversion of normal fault blocks. 5) Stratigraphic traps comprising fans and pinchouts. More than 80 closures have been identified from a high level screening within Cretaceous to Palaeogene levels. The structural style, interpreted age of formation and areal extent of the mapped closures is reviewed.
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Facies Characterization by Seismic Texture Analysis Using Grey Level Co-occurrence Matrix Based Attributes
Authors C. G. Eichkitz, J. Amtmann and M. G. SchreilechnerThe grey level co-occurrence matrix is a measure of the texture of an image. It describes how often different combinations of pixel brigthness values occur in an image. Based on this, several textural attributes can be calculated. In this work we developed a principal workflow for the calculation of these attributes. To decrease computational times we adapted calculation methods previously used for image classification of sea ice images. This workflow – including the enhanced calculation methods – is applied on two 3D seismic data sets from sedimentary basins. Different attributes and calculation parameters are tested to define channel systems and faults. The first tests show good results for the identification of both. Especially channel systems can clearly be identified. Additionaly, it is possible to directly extract channel-geobodies from the grey level co-occurrence matrix-based attributes.
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Regularized Full Waveform Inversion Including Prior Model Information
Authors A. Asnaashari, R. Brossier, S. Garambois, F. Audebert, P. Thore and J. VirieuxIn this study, we propose a regularized time-domain Full Waveform Inversion (FWI) scheme based on a two-term model penalty in the misfit definition: the Tikhonov term to ensure smoothness and a prior model term to attract the inversion toward a given direction. We illustrate that the prior model could reduce the sensitivity of inversion with respect to a non-accurate initial model. This procedure delivers a robust model as compared to ''classical'' FWI and can help inversion to solve the cycle-skipping problem. In the Marmousi dataset application, an investigation was done to identify the respective influences of initial model and prior model in complex media. Finally, we propose a simple dynamic approach based on a first derivative of the objective function curve to take out gradually the effect of the prior model in the inversion scheme, once the cycle-skipping problem has been solved.
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A New Technology to Meet Tight Gas Formation
More LessWe develop a new method to accurately determine gas saturation in tight gas reservoir using a three detector neutron logging tool with pulsed neutron source. This tool obtains the thermal neutron counting ratio R13 between near and far detectors and the ratio R23 between the middle and far detectors. With this method, the difference D between R13 and R23 is related to gas saturation and porosity. Monte Carlo simulation is used to evaluate the performance of the tool. The simulation results are analyzed with the new method to estimate gas saturation. The result shows that D can be used to determine gas saturation and using D to determine gas saturation has higher sensitivity than other ratio of thermal neutron counts or other difference of ratios. Another finding is that D logging response is affected by factors such as lithology, shale content, formation water salinity, borehole fluid, borehole size which should be corrected in the log data interpretation. We have applied the new method to process log data from two wells, yielding reliable interpretation result. The field data application result validates our new method and demonstrates its potential value and prospect in the gas saturation evaluation for tight gas reservoirs.
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