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77th EAGE Conference and Exhibition 2015
- Conference date: June 1-4, 2015
- Location: Madrid, Spain
- Published: 01 June 2015
81 - 100 of 980 results
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The 4D seismic signature of gas in thin-bedded geology: results from an outcrop analogue model
Authors M.-D. Mangriotis and C. MacBethNumerous examples of reservoir fields from continental and marine environments involve thin-bedded geology, yet, to our knowledge, the inter- relationship between thin-bedded geology, fluid flow and seismic wave propagation remains unexplored. This paper focuses on the 4D seismic signature of gas saturated thin layers, and addresses the challenge of identifying the relevant scales and properties which correctly define the geology, fluid flow and seismic wave propagation in the field. Based on the study of an outcrop analogue for a thin-bedded turbidite, we model the time lapse seismic response to gas saturation changes for different levels of model scale, from fine scale geological grid to upscaled coarse flow simulation grids. Our results show that multiples and converted waves vastly contribute to the measured amplitudes in the case of thin-bedded geology. Hence, any forward/inverse modelling from the flow simulation to the seismic domains involved in quantitative 4D has to take into account thin layers when these are present in the geological setting.
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Results of Using Different Petrophysical Approach in Controlling Fault Seal Analysis in Rengasdengklok Area, Northwest Java Basin, Indonesia
Authors B. Sapiie, I. Gunawan, E. Edward, R.A. Wibowo and P.R. PutraThe standard fault seal analysis using SGR algorithm is relying on two important parameters mainly fault throw and v-shale values. Both parameters are determined from interpretation of seismic and well data through petrophysical analysis. However, v-shale values are highly influenced by clay mineral composition particularly area with complex mineralogy such back-arc basin environment. This paper is presented interesting results of fault seal analysis using multimineral petrophysical approach to get better proportion of clay contents, which in turn gives better results in term of distributions of sealing capacity. Fault seal analysis was conducted using 3D seismic and 95 wells. Clay volume determination is using three types of methods, which are single parameter method using gamma ray log, dual parameter with gamma ray and bulk density-neutron porosity logs, and multimineral model. The calculation of fault attributes based on 3d grid geological models. Throw used in the calculation of SGR. Generally, the SGR value using clay volume from multimineral analysis are less than SGR value by using other clay volume. The result of this study shows that most of the faults are tend to have sealing and leaking potential in specific zones where clay volume model controls the SGR value instead of throw.
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Application of Pyrenean Fractured Carbonate Outcrops for Subsurface Reservoir Characterisation
Authors J.C. Gutmanis and L. Ardèvol i OróThe so-called ‘seismic gap’ remains a major challenge in the appraisal and development of fractured hydrocarbon reservoirs which are generally very heterogeneous in terms of open fracture intensity and connectivity and therefore also in reservoir quality. Acceptable and sustainable well rates largely depends on finding the fracture ‘sweetspots’, but much of the fracture system exist at scales too small to be mapped seismically and too large to be fully determined from well data (ie in the seismic gap). Excellent km-scale exposures of carbonates in the Spanish Pyrenees enables this problem to be tackled head on by studying fractures from micro to macro-scale; their dimensions and distributions provide data for use in reservoir simulation and for guiding well and seismic interpretations. In addition, the influence of mechanical properties and anisotropy on fracture distribution can be examined in detail. The results and principles should be used to underpin and calibrate sub-surface reservoir characterisation.
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Sedimentary Analysis of Rift Related Fan Deltas in the Gulf of Suez Using High Resolution Image Electrofacies
Authors M.T. Taher, S.E. El-Nady, A.E. El-Araby, E.H. Haddad, MN Nassar and H.F. FadlallahThe Gulf of Suez is a failed intracontinental rift that forms the NW-SE trending continuation of the Red Sea rift system. A complete petroleum system is represented by the Miocene syn-rift succession in the Gulf of Suez. The Burdigalian Yusr sand reservoirs, which belong to the Rudeis Formation, were deposited as submarine fans. Sedimentary analysis was performed using the wireline conveyed microimaging tool for electrofacies identification. Two wells, H-27 and HN-1X in H Field, Gulf of Suez, were included in this multiwell sedimentological study. Based on sedimentary structures visible in high resolution image logs, the depositional framework was used to predict reservoir quality and understand the geometry of the Yusr sand members. Prograding deltas with numerous, thick proximal fans were identified in well H-27 as compared with the limited, thin proximal fans, fining up channel fills and interlobe fine grained deposits encountered in well HN-1X. A correlation and paleocurrent analysis revealed the best drilling location in the field and consequently, an exploratory well was drilled in January 2015 based on this study.
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Azimuthal AVO Analysis on High-density ISS®, OBC data, Trinidad & Tobago
Authors P. Paramo, A. Cegna, K. Vincent, S. Cardinez, J. Kommedal and G. AlexanderIn this study we analyse Amplitude Versus Offset (AVO) on different azimuth sectors from a high-density full-azimuth OBC dataset acquired in the Columbus Basin of Trinidad & Tobago. The OBC acquisition covers an area of approximately 1000 km2 of some of the most prolific acreage in the region where some of BP’s major gas fields are located. In some parts of the study area shallow gas is present, often concentrated in shallow stacked sands and creating imaging challenges. The azimuthal AVO analysis is performed on migrated Offset Vector Tiles (OVT) containing up to 1080 traces at each image point and covering azimuth ranges from 0 to 360 degrees and offset ranges from 180 m to 10 km. Reflections with travel paths passing through the shallow gas often lead to lower signal-to-noise OVTs and larger NRMSE values. Azimuth sectors containing such reflections provide a different AVO response than that predicted from well-logs and from observations of azimuth sectors where the data avoided the shallow gas. Here we characterize the variations in azimuthal AVO at different locations, analyse the major factors contributing to these variations, as well as suggest possible solutions for compensating or correcting for these AVO azimuthal variations.
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Multimodel Adaptive Subtraction and Its Application to Multimeasurement Data Acquired in Shallow-water Surveys
Authors K.H. Liu, C. Kostov, F. Xavier de Melo, V. Govindan and G. MiersMany existing adaptive subtraction methods can be formulated as a parameter estimation problem and all of them, although fundamentally different, have a common restriction that the dimension of the unknown parameters must be determined in advance. We propose an adaptive subtraction framework, called multimodel adaptive subtraction (MMAS), that aims to relax this restriction as well as regularize the estimation of the parameters through a generalized information criterion (GIC). We show that MMAS can be applied to the popular least-squares adaptive subtraction (LSAS) method and call the resulting algorithm the multimodel least-squares adaptive subtraction (MMAS-LS). We further extend MMAS-LS to 3D and applied it to the multiple subtraction of a 3D data set from a multimeasurement shallow-water survey. We compare our proposed 3D MMAS-LS method with conventional 3D LSAS and observe that our proposed method is able to preserve the primary events better and achieve the same level of multiple attenuation compared to 3D LSAS, while using smaller or simpler filters.
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Imaging the Near Surface Using Surface-consistent Prediction Operators - Examples from the Middle East
More LessThe scope of this paper is to illustrate how surface-consistent deconvolution operators can help to image the shallow subsurface on land data. Two case studies from broadband, dense, wide-azimuth surveys recently acquired in Oman are presented. The predictive deconvolution operators were computed from an advanced simultaneous inversion of surface-consistent scalars and autocorrelations. Source and receiver operator volumes are compared to the migrated stack of primary reflections. A good match is observed, meaning that surface multiples were captured by the prediction operators. Furthermore, a significant improvement in the imaging of the shallow layers is achieved up to very shallow times. Some structures that are almost invisible on the migrated stack are revealed and the shallow reflectivity is recovered in undershoot areas. A good correlation with a shallow velocity well log is also observed. The deconvolution operators are derived from high fold, good quality reflection data. Therefore, they overcome the usual difficulties of near surface imaging from primaries such as low, irregular near-offset coverage and strong noise contamination. These high-resolution reflectivity volumes can be used as a guide for velocity model building of the shallow subsurface or as an input to internal or surface multiple modelling.
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Multi-dimensional Free-surface Multiple Elimination and Source Deblending of Volve OBC Data
Authors M. Ravasi, I. Vasconcelos, A. Curtis and A. KritskiThe wave-equation approach to signature deconvolution and free-surface related multiple elimination of multi-component ocean-bottom data of Amundsen (2001) has recently been linked to seismic interferometry by multi-dimensional deconvolution (MDD). When applied to simultaneous-source data this method can also unravel and reorganise blended data into sequential source responses. We have generated two blended versions of the Volve OBC dataset and compared the ability of MDD to deblend different types of simultaneous-source acquisitions together with suppressing free-surface multiples. Reverse-time migration of the deblended responses produces seismic images of similar quality to those from truly sequential source data.
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VSP Kirchhoff Migration with Structure Constraint
By X.M. ZhaoPrestack Kirchhoff depth migration is commonly used in borehole seismic imaging. Its application in this scenario is limited by insufficient coverage of the data acquisition configuration. In this paper, we combine the existing VSP Kirchhoff migration/imaging technique with the structure dip information from a newly developed structure tensor analysis, resulting in a new workflow for the VSP migration/imaging. The workflow allows us to better image both the structures in the vicinity of borehole and the far-field dipping events away from borehole. We tested the workflow with the HESS salt model and confirmed the results with the reverse-time migration (RTM). The results demonstrate that, even with the conventional Kirchhoff migration, combining structure dip information not only reduces ambiguities of the imaging result but also allows for imaging dip structures (e.g., fault) in the far borehole region. The proposed method with structure constraint provides a useful extension of existing VSP imaging capabilities.
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Dynamic Pore-scale Imaging of Reaction in Heterogeneous Carbonates Using a Synchrotron Pink Beam
Authors H.P. Menke, M.G. Andrew, B. Bijeljic and M.J. BluntWe present an experimental method whereby ‘Pink Beam’ synchrotron radiation is used in X-ray microtomography to investigate pore structure changes during supercritical CO2 injection in very heterogeneous carbonates at high temperatures and pressures.The raw images were binarized and the magnitude of dissolution was identified on a voxel-by-voxel basis. This information was used to extract pore-by-pore dissolution data.
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An Efficient High-density Kinematic Invariant Picking Method for Stereotomography Based on Structure Tensors
More LessThe efficiency and effectiveness of the stereotomography is highly dependent on the quality of its data space, the so-called kinematic invariant. The structure tensor is a very robust tool for the slope estimation. In this abstract, we present a highly efficient high-density kinematic invariant picking method based on structure tensors. Compared with the conventional slope search methods, the presented technique can improve the computational efficiency by one or two orders of magnitudes which will greatly enhance the applicability of the stereomography.
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Shallow Water Multiple Elimination (SWME) on Broadband Data
More LessSurface Related Multiple Elimination (SRME) has been approved to be an effective demultiple tool for marine data processing. However, it breaks down when applied to shallow water data mainly because 1) missing or contaminated near-offsets lead to inaccurate multiple models; 2) the cross-talk of short-period multiples deteriorate the matching filter during the adaptive subtraction; 3) the spectrum of the multiple model is distorted by the extra source signature. This paper proposes a new approach that combines a model-based method and a conventional SRME to serve the means of shallow water multiple elimination (SWME). The advantages include: 1) replacing the water-bottom Green's functions with broadband wavelets predicts the correct amplitudes of the multiples; 2) limiting the aperture of the Green's functions to the distance where the critical reflection occurs suppresses the artefacts in the multiple model and lowers the cost; 3) Simultaneously subtracting both the receiver- and source- side water-bottom multiples significantly improves the efficiency; 4) a following SRME helps remove the residual non-water-bottom multiples. A broadband 2D line offshore Santos, Brazil is tested with the proposed approach. It has prominently outperformed the legacy processing that used SRME and Tau-P deconvolution years ago.
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Improving Multiple Removal by Cooperative Matched Filtering
Authors S. Costagliola, M. Codazzi, P. Mazzucchelli and N. BienatiThe suppression of multiple events is a crucial task in seismic marine data processing and several multiple elimination techniques have been addressed in the last 20 years. Both model-driven as well as data-driven methods has been successfully developed to deal with various kind of subsurface structures and using different physical-mathematical approaches. Best results are often obtained by cascading different removal tools, each one focused on a single family of multiple events. However, this kind of processing scheme weights down the adaptive filtering task that has to be performed in each chain step with a consequent increasing of primaries corruption. In this paper we present an integrated subtraction scheme that allows to jointly remove different kind of multiples, predicted from as many techniques, simultaneously.
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Comprehensive Prediction for Fractured Carbonate Reservoir in the Tarim Basin
More LessAlthough increasingly employed for estimating both fracture density and orientation by the industry, the P-wave pre-stack anisotropic inversion using pre-stack azimuthal data is only effective for predicting fractures with a similar orientation, but essentially incapable of predicting multiple sets of fractures with different directions. In comparison, numerical simulation of tectonic stress field is proven to be a feasible way in overcoming this shortcoming. In this paper, these two methods are integrated to comprehensively characterize the complex fractured carbonate reservoirs in the Tarim Basin. As a result, both the single set of fractures and multiple sets of fractures are reasonably characterized, suggested by the good agreements with FMI information and geologic settings. This research could find its value in complex fracture reservoir prediction.
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A New Reverse Time Migration Method for Viscoacoustic VTI Medium
Authors Y.M. Qu, J.P. Huang, Z.C. Li and W.Z. DengBased on a single SLS isotropic media theory, we deduce the second-order quasi-differential equation and extend it to develop viscoacoustic reverse time migration algorithm for VTI medium. Our method use the pseudo-spectral method to calculate numerical simulation. We introduce a regularization operator to eliminate high frequency instability caused by the backward propagation. In the meantime we build a stable reverse time propagator to achieve the amplitude compensating reverse time migration for viscoacoustic VTI medium. The imaging result of HESS model suggests that the viscoacoustic VTI RTM method proposed in this paper compensates the loss of seismic energy and corrects the anistropic effect on seismic propagation. So we get accurate and reliable amplitude-preserving imaging section.
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Elastic Envelope Inversion
More LessWe developed the elastic envelope inversion method. The envelope of the wavefields carries ultra low frequency information which can be used to recover the large-scale component of the model, and the initial model dependence of waveform inversion can be reduced. We derived the misfit function and the corresponding gradient operator for elastic envelope inversion. Numerical tests using synthetic data for the Marmousi II model proved the validity and feasibility of the proposed approach. The inverted p-wave velocity and s-wave velocity from the combined (EI+WI) envelope inversion plus waveform inversion indicated that it can deliver much improved results compared with regular elastic full waveform inversion.
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Vibrator Harmonics - Noise or Signal?
Authors H. Akhondi-Asl and P.L. VermeerSeismic vibrators generate the desired (fundamental) signal and its harmonics. After standard correlation processing using the pilot sweep, harmonics appear as a form of coherent noise preceding each seismic waveform. The harmonics might alternatively be treated as supplementary signal energy by replacing the correlation with source-signature deconvolution using an estimate of the ground force applied by the vibrator. In principle, this could provide: 1) bandwidth extension; 2) improved signal-to-ambient-noise ratio; and 3) reduced harmonic noise contamination. This paper discusses the practical reality with a view to setting reasonable expectations. With modern vibrator equipment, the harmonics are typically relatively weak in comparison to the fundamental signal. For most surface-seismic surveys, we should not expect that harmonics can be used either to broaden the bandwidth of the data beyond what the fundamental delivers, or to increase the signal-to-ambient-noise ratio. Source-signature deconvolution using an estimate of the ground force can be a suitable method to reduce harmonic noise, and collapse the harmonic energy onto the seismic waveforms associated with the fundamental. A limitation is the accuracy of the available estimate of the true applied ground force. In our experience, meaningful ground-force QC can be automated and driven by the seismic data itself.
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An L1-norm Constrained Data Regularization Using Radon Transform
More LessSeismic data regularization and interpolation from data sampled irregularly and sparsely along the spatial directions becomes an important step in the seismic data processing flow. Unsuccessful regularization leads to imaging artifacts and bad predictions for the multiples, adversely affecting the performance of the multiple elimination. In this paper, a new data regularization method that derives from the Radon transform by using the L1-norm constrained sparse inversion has been proposed, and then the efficiency and robustness of the approach are demonstrated with a test on synthetic data. It is shown that this approach gives good results for regularization and upsampling, even for spatially aliased data.
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Synthetic Seismic Modelling of Outcropping Carbonate System of the Maiella Mountain (Central Apennines-Italy)
Authors V. Mascolo, G. Rusciadelli and I. LecomteSummarySeismic models of outcrops can contribute effectively to the interpretation of seismic data. In fact, they are essential for qualifying petroleum targets, because they bridge a critical gap in both resolution and scale between architectural geometries observed in outcrops and in seismic data. Synthetic seismic reflectivity models were generated from outcrop of the Maiella platform-slope-basin transition (central Apennines of Italy) with the aim to define the seismic response of resedimented slope deposits. The preliminary synthetic seismic sections are a combined result of field-work, literature research of the petrophysical parameters and computer simulation with the ray-tracing modelling methods.
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Depth Scaling Strategy for the Noise-included Inverse Problem
More LessSummaryWe propose a depth scaling method to mitigate the sensitivity of the elastic full waveform inversion (FWI) to random noise, which is designed introducing flexible damping factor in the Levenberg-Marquardt method. When the damping factor is constant over iterations, FWI can be severely affected by noise distributions over depths. In our depth scaling strategy, inversion starts with large damping factors, and then semi-automatically decreases according to the tendency of errors as the iteration goes on. With the flexible damping factors we can control the parameter-update regions so that shallow parts can be mainly updated in the early iterations and the parameter-update regions can move to deeper parts at the later iterations. Numerical examples for a simple graben model show that our depth scaling strategy yields more robust inversion results for noisy data than the conventional FWI using a constant damping factor.
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