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5th EAGE St.Petersburg International Conference and Exhibition on Geosciences - Making the Most of the Earths Resources
- Conference date: 02 Apr 2012 - 05 Apr 2012
- Location: Saint Petersburg, Russia
- ISBN: 978-90-73834-23-1
- Published: 02 April 2012
21 - 40 of 178 results
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Prestack Inversion and Probabilistic Lithofluid Classification - A Case Study from the Caspian Sea
Authors S. Klarner, N. Buxton and S. BenkoThe Caspian Sea is currently one of the focus areas for exploration and production in the FSU. Logistically a challenge (large areas with very shallow water) and ecologically sensitive (endemic flora and fauna), it demands operators to develop a sustainable approach to hydrocarbon development in the region. In that context, a better understanding of the subsurface helps to optimize drilling activity as one of the factors having a huge environmental impact. The AVO inversion and probabilistic lithofluid classification approach presented in the current paper, is one of the technologies applied to improve the subsurface understanding of the area in order to optimize the future field development. The workflow includes seismic data improvement by reservoir oriented processing procedures, a comprehensive rock physics analysis on well data, simultaneous inversion of angle stacks, crossplot analysis of inversion results and probabilistic lithofacies classification in the AI-Vp/Vs domain using the established depth dependent rock physics trend. First experience of using a probabilistic approach to quantify the reservoir properties shows that potentially even pore fluids can be estimated from seismic data.
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From Rock Physics Study through Inversion to Seismic Litho/fluid Prediction - A Case Study from Precaspian Basin
By A JangirovIn this paper a new approach is proposed for seismic reservoir characterisation. The workflow shows how rock property trends can be derived, compared with seismic amplitudes and used in prediction of litho/fluid content based on observed seismic amplitudes. The workflow is supported by case study using the data from Precaspian basin.
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Choosing Seismic Dataset with Application of Deterministic Full Stack Inversion
Authors K.E. Filippova, A.A. Kozhenkov, J.L. Debrouх and D.V. IsakovIt is common that several seismic datasets are available on the same project as a result of reprocessing. Different companies may reprocess the same datasets using various technologies and different processing sequence and interpretation team have to choose the most suitable volume for interpretation and reservoir properties forecast. Sometimes it is a really difficult choice.
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Seismic Inversion Potential for Carbonate Reservoir Modeling, as Exemplified by Samara Region
Authors I.A. Babenko, T.V. Nekrasova, V. Sheppard and I. GontarenkoThe paper describes the use of seismic inversion for the purpose of prediction and delineation of oil-saturated reservoir areal Samara region fields.
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SGS-based Stochastic Inversion Workflow for Clastic Thin Layer Properties Recovery in Carbonate Medium
More LessThe problem of recovery clastic layer properties in carbonate medium was solved with Sequential Gaussian Simulation (SGS)-based stochastic inversion. Stability analysis of this workflow results was presented. The estimate of identification possibility low-impedance object in high-impedance medium. Method of assessing sufficient for practice multiple realizations of stochastic inversion was proposed.
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Geology as the Main Factor in Determining the Technology Required in Seismic Inversion and Interpretation
Authors M. Romanenko, D. Kutcheryavenko, S. Iliin, A. Dubok and D. EmeliyanovВ условиях активного развития и применения методик сейсмической инверсии ключом к успешному решению задач прогноза является не столько алгоритм, сколько понимание особенностей геологического строения изучаемых объектов. В рамках работы над одним из производственных проектов мы столкнулись с очень интересным и нестандартным для Западной Сибири геологическим строением изучаемой толщи, которое поставило много нетривиальных задач для акустической и синхронной инверсии. На нескольких примерах с различных этапов проекта показано, каким образом понимание особенностей геологического строения района и целевого интервала может повлиять на методику расчета и интерпретации кубов упругих параметров. В заключении работы даны практические рекомендации, которые могут быть полезны, специалистам работающим в области интерпретации данных сейсморазведки.
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The Detailed Facial Model of Complex Clastic Reservoir Based on Geostatistical Inversion Results
Authors K.E. Filippova, P.G. Ponomarenko, I.S. Tsybulkina, V.M. Vingalov and S.V. LyagushevРассмотрены возможности использования геостатистической сейсмической инверсии для уточнение строения залежи и выделения зон выклинивания и литофациальных изменений продуктивного интервала. Данная методология может быть успешна применена для уточнения строения пластов месторождений Западно-Сибирской нефтегазоносной провинции.
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Electroacoustic Logging and Joule Heating
Authors B. Plyushchenkov and A. NikitinIt is well known that electromagnetic field excites acoustic wave in a porous elastic medium saturated with fluid electrolyte due to electrokinetic conversion effect. Pride's equations describing this process are written in isothermal approximation. Update of these equations, which allows including influence of Joule heating on acoustic waves propagation into account, is proposed here. This update includes terms describing the initiation of additional acoustic waves excited by thermoelastic stresses and the heat conduction equation with right side defined by Joule heating. Results of numerical modelling of several problems of propagation of acoustic waves excited by an electric field source with and without consideration of Joule heating effect in their statements are presented. From these results, it follows that influence of Joule heating should be taken into account at the numerical simulation of electro-acoustic logging and at the interpretation of its log data.
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Deep Fracture Imaging Using Dipole Acoustic Data
Authors A.O. Bolshakov, D.J. Patterson and C. LanCharacterizing acoustic fractures in reservoir rocks is important because these fractures provide critical conduits for hydrocarbon production from the reservoir into the wellbore. The standard method uses shallow borehole imaging services, both acoustic and resistivity, which image the intersection of the fractures at the borehole wall. Cross-dipole technology has extended the depth of evaluation some 2 to 4 ft around the borehole by measuring the fracture-induced azimuthal shear-wave anisotropy. A recently developed shear-wave reflection imaging technique provides a method for fracture characterization in a much larger volume around the borehole with a radial extent of approximately 70 ft. This technique uses a dipole acoustic tool to generate shear waves that radiate away from the borehole and strike a fracture surface. The tool also records the shear reflection from the fracture. The shear-wave reflection, particularly the SH waves polarizing parallel to the fracture surface, is especially sensitive to open fractures, enabling the fractures to be imaged using this dipole-shear reflection data. We use field examples to demonstrate the effectiveness of this shear-wave imaging technology that maps fractures up to 70 ft away and even detects fractures that do not intercept the borehole.
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Inversion of 1D VES Data Using New a Technique Called Recursive Ant Colony Optimization (RACO)
Authors Y. Arora, D.K. Gupta, J.P. Gupta and U.K. SinghIn this abstract a new algorithm is proposed named Recursive Ant Colony Optimization (RACO) for inversion of 1D VES data. RACO is derived from a more general global technique known as Ant Colony Optimization (ACO). In this new algorithm, results obtained from first run (first depth) are fed to next run (next depth) which is called recursion. The level of recursion of the process is defined by the term “depth” and hence directly affects the accuracy of the results. Advantage of using the recursion in this algorithm is that the convergence of the problem becomes exponential which is linear in ACO thus this approach become different from its general form. This code is written in C++ which makes it more time efficient. To make this algorithm stable it is tested on synthetic data of 3 layers earth model and 5 layers earth model. Both of the examples chosen are difficult to delineate due to presence of high resistive layers (K-type and HKH-type curve). Then this method applied to field data from Satkui and Tangasol region of Midnapur district of West Bengal, India. Results obtained after completion of the inversion process are found to be in agreement with the available results.
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The System of Adaptive Well Log Data Interpretation in Geological Modeling
Authors A.N. Petrov, D.A. Kozhevnikov, K.V. Kovalenko and I.S. DeshenenkovWide spread application of 3D geological modeling, oil and gas field development practices resulted in substantiation of the necessity for transition from the traditional concept of “absolute pore volume” to the concept of “effective pore volume”. This could be achieved with the geophysical and logging data algorithms interpretation and procedures system directed to the determination of reservoirs dynamic characteristics with high vertical resolution united with principles of adaptability and petrophysical invariance of reservoirs. Adaptive petrophysical models make possible the quantitative estimation of effective porosity and effective/phase permeability. Formation parameters, which characterize the content of bound water in the matrix and cement, maximum possible total porosity and effective porosity, relations between effective porosity and effective permeability are estimated according to outcomes of petrophysical modeling. Effective porosity is calculated with the standard logs data interpretation. The distribution of reservoir properties in three-dimensional space is carried out with geostatistical simulation techniques. Application of effective porosity to prediction of relative permeability and capillary pressures with log data was realized as an important task for field development design. The test of the proposed technology is conducted on a large number of wells worldwide. Formations consist of clastic fine-grained sandstones with complex cement mineral composition.
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Determination of Capillary Pressures and Relative Permeabilities with Well Logging Data
Authors A. Petrov, D.A. Kozhevnikov, K.V. Kovalenko and I.S. DeshenenkovIn oilfields development process it is necessary to determine attitude of fluidal contacts performedby the deposit area on the base of geological, geophysical and petrophysical data integration add‐in advanced well logging techniques. We propose new capillary model, controlled by a single parameter that is closely related to permeability. Developed model allows more accurate determination of the displaced fluid share at a given capillary pressure during drainage in comparison with analogues. Saturation estimation algorithm based on proposed model was proposed. The advantage of the algorithm is the possibility of hydrocarbon saturation reliable prediction in case of resistivity logging is non-informative due to the low vertical resolution in the layers of low width and anisotropic reservoirs. In practice, Burdine and Brooks-Corey model as the most common approximations of relative permeability curves are used. But these models describe laboratory core measurements data poor in low relative permeability area. New analytical approximations for more detailed and accurate description of relative permeability curves was obtained. Description results show that proposed model has better accuracy in comparison with known analogues. Relative permeabilities can be used for prediction of the brine share in production volume with Leverett function and have great practical importance for field development design.
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Velocity Detection by Duplex Wave Migration
Authors N. Marmalevskyi, S. Gorbachev, Z. Gornyak, G. Dubrova and B. LinkThe sensitivity of the duplex wave migration to the wave propagation velocities is considered. On the field 3D data, the evaluation criteria for detection of correct velocity assignment are shown for the duplex wave migration based on the Kirchhoff integral The opportunities of definition of velocity in thin layers, which thickness is less than length of a seismic wave and complicated with permeable fractures corridors are considered.
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Velocity-less Pre-stack Time Migration in Application to Hard Rock Environments
Authors K. Tertyshnikov, A. Bóna, R. Pevzner and B. GurevichReflection seismic techniques have a number of limitations to get suitable images in hard rock environment. Many seismic migration algorithms need to know the values of propagation velocity of acoustic waves. In sedimentary basins, where layers are usually continuous reflectors, that information could be obtained directly from acquired data, but there are many steeply dips and lack of the horizontal boundaries in hard rock media. In this way, the estimation of velocity model is a really difficult task. Here we describe the velocity-less pre-stack time migration in application to hard rock conditions and demonstrate the results on synthetic data.
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Non-linear Analysis of Low-frequency Microseismic Background
Authors S.B. Turuntaev and O.Y. MelchaevaLow frequency seismic data were analyzed with the help of non-linear Grassberger-Procaccia method. Two data sets were considered: microseismic background inside and outside gas field (“passive” method) and the microseismic background recorded before and after vibrations over an oil field with complicated unknown boundaries (“active” method). It was found, that an application of non-linear methods has to be done with caution. Only the analysis of the records containing pulses allowed to distinct the microseismic background inside the gas field from the background outside the field. The analysis of the records obtained after the vibrator works showed an appearance of deterministic component in the microseismic background after the vibrations at several studied points. Two wells were drilled in proposed points, and the both were successful.
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Incorporation of Multiples for Migration Velocity Analysis with VSP Data
Authors D.A. Nasyrov, D.A. Kiyashchenko, Y.V. Kiselev, B.M. Kashtan and I.V. AbakumovWe demonstrate the original method for the migration velocity analysis with VSP data. The method is based on the use of surface-related multiples jointly with the primary reflected data for the VSP imaging. Velocity updates are carried out by matching the images obtained by using different types of waves. To do it automatically we introduce a cross-correlation type objective function and develop a maximization algorithm based on the adjoint-state method. We show that maximization of the cross-correlation of the images built on different types of waves allows to retrieve the velocity parameters. At the same time the refinement of the velocity model could lead to significant improvements of the seismic images.
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Improved Depth Imaging by CRS Signal Enhancement in Input Shot Gathers
Authors G. Gierse, G. Eisenberg-Klein, H. Trappe, J. Pruessmann and M. ZehnderNoise suppression and signal enhancement prior to prestack depth migration (PreSDM) may significantly increase the resolution of the depth image, and the effectiveness of the PreSDM workflow. The Common-Reflection-Surface (CRS) technique was previously used for this enhancement of seismic prestack data, providing so-called CRS gathers with regularized CMP and offset coverage, and with a strong noise suppression. These CRS gathers considerably improved the depth image in Kirchhoff PreSDM but were not suited for shot-based PreSDM algorithms. This case study now presents a straightforward way to produce geometry-preserving CRS gathers that similarly increase the signal-to-noise ratio. In a first implementation, CRS prestack data interpolation is performed at the existing trace locations providing a straightforward and automatic preservation of the original shot geometry. Application to 3D seismic land data demonstrates the improved signal-to-noise ratio and resolution both in the geometry-preserving CRS shot gathers, and in the corresponding QC stack. As in the Kirchhoff migration of regularized CRS gathers, such enhancements are expected for Reverse Time Migration of CRS shot gathers as well.
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Band-limited Ray-tracing through Rugose Interfaces
Authors C.E. Yarman, X. Cheng, D. Nichols, K. Osypov and M.I. ProtasovStandard ray-tracing is a very efficient way of approximating wave propagation for small wavelengths, or, equivalently, high frequencies. Furthermore, it is still valid when the medium parameters and the wavefields are smooth on the scalelength of the width of the Fresnel volume (Kravtsov and Orlov, 1990). Standard ray-tracing validity conditions break down in the vicinity of an interface when there is high contrast between the two sides of the interface and/or the interface has a complex structure. In this study, we present a new band-limited ray-tracing method that aims to overcome some of the limitations of standard high-frequency ray tracing in complex velocity models that contain complex interfaces. With a modest increase in computational cost, the method presented captures the wave kinematics that are comparable to finite-difference wave propagation with higher fidelity while staying within the ray-tracing framework, without requiring processing or alteration to the original model.
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3D Velocity Model Building Based on Diffractions
Authors S. Dell and D. GajewskiDiffracted events are of great importance in the seismic processing because they allow to identify the presence of small heterogeneities, truncations, faults. However, to reliable interpret such subsurface features caused by diffractions, the letter ones should be properly imaged. An inherent part of the imaging is therefore a migration velocity analysis which should be tuned to diffractions. Moreover, imaging of diffractions is inherently a 3-D problem. In real geological environments one can not expect diffractors to be located below 2-D profiles. The 3-D effects of diffractors located transverse to the profile line leads to a smeared and less reliable diffraction images. We present a method for 3-D velocity analysis based on diffracted events. We perform migration velocity analysis by evaluating the semblance norm along diffraction traveltimes both in the depth and time domain. Finally, we perform Kirchhoff type of poststack migration with estimated velocities to validate the presented velocity analysis.
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Interval Anisotropic Parameter Estimation from Walkaway and 3D VSP Data
By E. BliasThe purpose of this paper is to present a new method for interval VTI anisotropic parameter estimation above and within VSP array. Above receiver array, the method utilizes duplex downgoing multiples (multiples with two reflections: from the boundary and free surface) for estimation of a layered depth velocity model above the borehole receiver array. A three-term NMO approximation function is used to estimate NMO velocity and a non-hyperbolic parameter. Dix-type inversion is applied to the three parameters to invert them to interval Thomsen anisotropic parameters ε, δ above the receivers. Velocity gradient influence is analyzed analytically. It is shown that in many cases we can neglect its influence on anisotropy estimates. Within the VSP receiver array, the method creates a virtual horizontal reflector at each receiver depth by calculating reflected traveltimes as a sum of two first breaks from the symmetrical source points. For 3D or multi-azimuthal walkaway survey, this approach is generalized for a model with horizontal homogeneous orthorhombic layers.
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