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82nd EAGE Annual Conference & Exhibition
- Conference date: October 18-21, 2021
- Location: Amsterdam, The Netherlands
- Published: 18 October 2021
21 - 40 of 1137 results
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Elastic Full-Waveform Inversion with Geologic Information for Tilted TI Media
Authors S. Singh, I. Tsvankin and E. Zabihi NaeiniSummaryHigh-resolution velocity models generated by full-waveform inversion (FWI) can be effectively used in seismic reservoir characterization. However, FWI in elastic anisotropic media is hampered by the nonlinearity of inversion and parameter trade-offs. Here, we propose a robust way to constrain the inversion workflow using per-facies rock-physics relationships derived from borehole information (well logs). The advantages of the facies-based FWI are demonstrated on a 2D elastic TTI (transversely isotropic with a tilted symmetry axis) model with substantial structural complexity. In particular, the tests show that our algorithm improves the spatial resolution of the inverted medium parameters without using ultra-low-frequency data required by conventional FWI.
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Geostatistical Interpolation Constrained by Lithofacies
More LessSummaryGeostatistical technologies, which include two-point geostatistics (TPS) and multiple-point geostatistics (MPS), are significant in both geological modelling and geophysical inversion. However, TPS is incapable to characterise complex geological structures, due to the dependency on the variogram. When using MPS in the simulation of the continuous variables such as velocity, the calculation and memory burdens are heavy. We integrate TPS with MPS to release these issues. Based on kriging theory, we present a geostatistical interpolation strategy constrained by the lithofacies probability distribution, which is obtained by MPS. The proposed approach utilizes the advantages of TPS and MPS simultaneously. The model test illustrates the effect of the method on depicting complicated geological structure.
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Homogenization of Hydro-Mechanical Coupling in Shale Matrix
More LessSummaryShale matrix is the main gas storage space, so the development of its Hydro-Mechanical coupling (HM) model is important to macroscopic HM simulation in shale gas reservoir. At microscopic scale, shale matrix is composed of organic and inorganic matter, while the mechanical properties of these two media are quite different, and both gas storage type and transport mechanism are also different in these two media, thus we need to develope different microscale models to describe the HM process in shale matrix. However, microscale models cannot be straightly applied to macro simulation due to their huge calculation cost. In this paper, an efficient upscaling method based on homogenization theory is developed for the HM process in shale matrix, which can accurately represent the microscale characteristics of organic and inorganic matter in macroscale simulations. Firstly, shale matrix is assumed as a heterogeneous poroelastic medium composed of organic and inorganic matter, and according to different storage type and transport mechanism of real gas in these two media, the microscale HM model is developed. Then, the microscale HM model is homogenized to obtained the equivalent macroscopic HM model for shale matrix. Lastly, the accuracy of the proposed method is proved through a numerical examples.
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Optimising Nanoparticles Mixture for Enhanced Oil Recovery
More LessSummaryIn this study, a combined nanofluid based on mixing Silicon-oxide, Aluminum oxide nanoparticles with 2D-smart nanosheet (MAS2DSN) for enhanced oil recovery is developed. The current single nanofluid flooding method for tertiary or enhanced oil recovery is inefficient, especially when used with low nanoparticle concentration. In this work, we show the potential of mixing nanoparticles with two-dimensional smart nanosheets in one patch as a C-EOR agent. The combination of a Mixture of Aluminum-Silicon nanoparticles with 2D-Smart Nanosheet (MAS2DSN) is used to reduce the IFT and altering the wettability of the sandstone core samples even at low concentrations. The IFT decreases up to 0.16 %, and the contact angle measurements show that the wettability of sandstone is changed from the oil-wet to the water-wet in the presence of MAS2DSN. The laboratory core-flooding experiments were conducted in the sandstone core samples saturated with module oil (20 cP). Stable MAS2DSN nanofluid is applied in core-flood experiments using Al2O3, SiO2, and 2DSN at concentrations of 0.05, 0.05 and 0.005 % respectively, resulting in a 22.9% increase in the oil recovery. This work exposes new opportunities for oil production by using a mixture of nanoparticles.
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Gpr Full Waveform Frequency-Space Domain Modeling by the Full Spectral Methods
More LessSummaryAccurate differentiation matrices operators by the full spectral method have been applied to the temporal and spatial domains of the transverse electric (TE) and transverse magnetic (TM) modes of the GPR full waveform. By Fourier transform, these operators are simply complex frequency and wavenumber which must be sampled appropriately to produce accurate results. This full spectral method contrasts with the pseudo-spectral method that transforms only a component (either the time or space) to the Fourier domain and leaves the second component in its regular domain. The finite difference approach supplies its approximate differentiation matrices operator in time and space domains thus leading to inherent truncation error. Convolution of the differentiation matrices operator with the medium parameter is performed; and the inversion of the system of linear equations produce the accurate GPR full waveform modeling results for different permittivity models.
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Initial Wave Impedance Modeling Method Based on Plane-Wave Destruction
More LessSummaryInitial model is critical to the model-based wave impedance inversion method, and its accuracy directly influences the convergence speed of inversion and the accuracy of inversion results. In this paper, the initial wave impedance modeling method based on plane-wave destruction (PWD) is proposed, the wave impedance information is extrapolated by using of the predict relationship between the traces which is derived from the plane-wave destruction equation, and the Tikhonov regularization is introduced to improve the stability and noise resistance ability of the method. No longer like the traditional modeling methods which need the fine horizon and fault interpretation results, the method in this paper is a seismic data-driven modeling method, the initial model which has a good consistency with the geological rules can be directly established by using of seismic data and well-log properties. The effectiveness of the method is demonstrated by model data test and field data application.
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Mineral Prospecting for Copper-Molybdene Ores in Northern Kazakhstan Using Electromagnetic Sensing and Induced Polarization Technology (EMS-IP)
Authors A. Belova, Y. Davydenko, D. Gurevich, A. Bashkeev, S. Bukhalov and P. VeekenSummaryGeoelectric techniques are applied to identify geobodies in the shallow subsurface (<1km) that correspond to commercial ore deposits (copper-molybdene) in Kazakhstan. A combined CSEM and Induced Polarisation method is chosen to delineate anomalies in the underground. Resistivity and polarisation effects prove diagnostic. The workflow comprises steps like: EM acquisition, quality control and data preconditioning, inversion, interpretation and Principle Component Analysis. Inversion processing is done via a finite elements method solving the Cole-Cole formula simulating Maxwell’s equations. 1D inversion results serve as input for the 3D inversion. Principle Component Analysis (n-dimensional clustering and distance weighting) and computation of composite geoelectric parameters enhance the discrimination power. EM anomalies are circular (hydrothermal injection feature) and/or elongate in shape. Fracture zones and faults provide conduits/barriers and govern hydrothermal processes. Faulting in part controls the outline of the segmented IP anomalies. Three shallow well locations were proposed based on the EMS-IP data. Two of these boreholes demonstrate elevated polarisation phenomena: copper-molybdene metal ore in MN17 and pyrite enrichment in MN16. The mapped geobodies based on EM anomalies give complementary information on volume and distribution of the mineral resources. EMS-IP is a cost-effective investigation tool that deserves more attention in geoscience projects.
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Mud-Roll Removal in Shallow Water Marine Data Using the Curvelet Transform
Authors F. Ahmed, E. Verschuur and C. TsingasSummaryMud-roll comprises of dispersive seismic waves that propagate along the unconsolidated sediment layers at the sea floor in shallow water marine environments, where the water depth is normally less than 30 m. Mud-roll’s characteristics are spatially variable, i.e. the dispersion properties change from one shot to another across a seismic survey area. These complex kinematic properties make noise elimination very challenging using conventional seismic processing workflows. Our proposed method is a hybrid, Curvelet transform-based workflow that takes advantage of conventional seismic processing filtering to estimate the noise components, followed by the Curvelet transform that attenuates the residual noise energy that is difficult to remove with a conventional subtraction algorithm. In this paper, we illustrate the proposed Curvelet transform-based workflow using both synthetic and field data and demonstrate its effectiveness.
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Artificial-Lift Method Screening for One of the Southwestern Iranian Oil Field Based on Fuzzy Logic Approach
Authors H. Asaadian and M. Nazari SaramSummaryThe choice of an artificial lift method in fields that have been faced with declining production has always been a challenge. Therefore, in this paper, by designing a two-stage screening process and using fuzzy logic approach, it is attempted to select the most accurate method for one of the southwest Iran squares. Fuzzy logic will make the ranking system more accurate and more sensitive to the operating conditions of artificial lift methods. By the method ranking with this screening procedure, Electrical Submersible Pump (ESP) and Sucker Rod Pump (SRP) are selected as the priorities.
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Full-Bandwidth FWI
Authors T. Kalinicheva, M. Warner and F. ManciniSummaryWe have run FWI to 100 Hz on raw field data from a deep-water marine towed-streamer dataset. We show that the results are similar to, and are broader bandwidth than, conventionally processed PSDM images. FWI removes multiples and ghosts from the raw data, and can produce a full-bandwidth PSDM reflectivity image in a few days without conventional processing or migration.
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Separation of LS-Epithermal Gold Veins Deposit Alterations by Geophysics in Chucotka Region
By E. ErmolinSummaryA number of epithermal gold-silver deposits are located within Okhotsk-Chukotka volcanic belt (Far East of Russia). LS-epithermal veins with the thickness of several meters can contain up to several hundred tons of gold. The search of covered veins is a complicated task for exploration and it is difficult to solve it without geophysics. The example of successful application of audiomagnitotelluric method in Chukotka region was presented by author. As the result of all data analysis the geophysical prospecting criteria were suggested. Unfortunately, not every found vein is commercial. To increase the chance of finding a new deposit the author set the task to define additional prospecting criteria. The induced polarization (IP) method was used to achieve this goal. The main result of the investigation is that the instrument for separation of alterations types was suggested. The chargeability anomalies at 0.31 Hz and 15 mV/V amplitude are connected with illite chlorite alterations of a deposit core. Illite chlorite alteration of the core deposit is also characterized by high resistivity (up to 2000 Ohm-m) and low magnetic susceptibility. The zones of illite and kaolinite alterations surrounding the deposit core are characterized by reduced electrical resistivity (from 50 to 300 Ohm-m).
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Immiscible Water Alternating CO2 Displacement Efficiency in Layered Water Wet Porous Media
Authors D. Al-Bayati, A. Saeedi, M. Myers, C. White, Q. Xie and M.M. HossainSummaryIn this work, a laboratory test to investigate the influence of permeability heterogeneity and ensuing crossflow on the recovery performance of immiscible water alternating CO2 injection was performed. The results reveal the negative impact of heterogeneity in the vertical direction on ultimate oil recovery from layered cores. Contrary to our previous conclusions about continuous immiscible CO2 flooding, it possible to observe that the crossflow to negatively affect the RF of immiscible WAG in layered samples. This contradiction may suggest that WAG flooding would achieve a stable frontal advance in each layer in non-communication layers.
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Slope Estimation by Convolutional Neural Networks
More LessSummaryLocal dip field has have been widely used in geophysical applications, such as structure prediction, seislet transform, trace interpolation and denoise. The plane-wave destruction (PWD) is the common method to estimate the local slope. However, the PWD is sensitive to strong noise. It is not easy to estimate an accurately local slope from noisy data by PWD algorithm. To estimate an accurate slope from noisy seismic data, we have proposed an architecture based on deep learning (DL). The architecture contains two sections: the convolutional and deconvolutional sections. The conventional section can learn the local features and the deconvolutional section constructs the output using the learned feature to match the target. Numerical tests on two examples demonstrate that the proposed method can obtain a relatively accurate dip field from noisy data.
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Triaxial Induction Tools Responses in Layered Arbitrarily Anisotropic Medium
More LessSummaryDue to different sedimentary environments, the realistic formation shows different electrical anisotropic characterizations. In general, only electrical anisotropy in layered unrotated media is considered, which is not always available in the practical application. With the widespread availability of multi-component induction logging technology, it is willing to solve more complicated electrical anisotropy problems. Therefore, it is important to introduce a universal algorithm applicable for arbitrary electrical anisotropic media. A fast forward algorithm, based on dyadic Green’s function, is proposed to compute the triaxial induction responses under arbitrary anisotropic media. Anisotropic dip and azimuth are introduced to further characterize the complicated electrical anisotropy. Numerical simulations proved the robustness of the algorithm, and illustrated the responses under different electrical anisotropic situations. It can be concluded that anisotropic dip and azimuth could impose great influences on the triaxial induction logging responses. Some important phenomena can be observed, for example, there exist critical borehole dip and critical anisotropic dip in the rotated uniaxial and biaxial media, and the crosscouping magnetic components, Hxy (Hyx) and Hyz (Hzy), are closely related to the anisotropic azimuth. The proposed algorithm could well make up the deficiency of traditional method and reduce the uncertainties of resistivity interpretation.
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3D Characterization of Pore Microstructure and Implications for Flow Transport Property of Tight Reservoirs
More LessSummaryUnconventional hydrocarbons have been considered as important complementary resources to conventional resources, which have been intensely investigated in recent years. Pore microstructure, especially of tight reservoirs, has significant effect on flow capacity, storage capability and recovery efficiency. A comprehensive understanding of pore microstructure is crucial for the prediction of transport property, and thus provides some basis for the evaluation of tight oil potential area. Three-dimensional features of pore network were studied by X-ray CT data analysis, where geometrical and topological parameters were calculated. On the basis of these quantitative analyses, numerical simulations were conducted for demonstrating transport capability.
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Deep Learning for Salt Body Detection: A Practical Approach
Authors B. Consolvo, B.P. Consolvo, P. Docherty and J. UwaifoSummaryInterpreting salt bodies in the subsurface is a challenging manual task that can take weeks to complete. Obtaining accurate picks of salt is very important, because errors in the placement of salt can result in severe degradation of the seismic image. To meet the challenges of speeding up imaging workflows and retaining accurate salt picks, we evaluate three deep learning approaches: a 2D window-based convolutional neural network, a 3D window-based convolutional neural network, and finally a 2D “U-Net” approach. A 3D seismic volume from the deep-water field Julia in the Gulf of Mexico was used to test these approaches. The Julia field has complex salt structures with overhangs and inclusions, and the thickness of salt can reach up to 5 km. The U-Net architecture proved to be the most accurate of the three methods tested, predicting the placement of salt at 98% accuracy, as compared to the human interpretation. Beyond accuracy, U-Net also proved to be the fastest, requiring only 3.5 hours to predict salt on the 3D seismic volume. The results presented here along with other recent studies of deep learning for salt interpretation represent a clear shift in the seismic interpretation workflow.
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A New Acoustic Assumption That Mitigates the S-Waves Artifacts in Orthorhombic Media
Authors M.M. Abedi and A. StovasSummaryApplication of acoustic orthorhombic media can be considered as a modern standard in industrial 3D seismic data processing and modeling stages. However, the presence of significant S-wave artifacts that are associated with the conventional acoustic anisotropic media harms any application that need pure P-wave propagation. Accordingly, we propose a new acoustic assumption for orthorhombic media that mitigates the S-waves artifacts by zeroing the S-waves velocities along the symmetry planes. The accuracy of the new approach compares well with the conventional approach, but the new approach further complicates the governing equations. Noticing the algebraic complexity of the eikonal equation obtained in the new acoustic orthorhombic media, we also propose a rational approximation that simplifies the eikonal equation.
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An Improve Convolutional Auto-Encode Denoising Method
More LessSummaryWe evaluated an improve Convolutional Auto-Encode method for seismic data denoising. The method learn extremely complex functions to effectively attenuate noise by learning and extracting features from a large amount of training data set based on statistical techniques. However, the large quantity of training point pairs may increase the burden of memory and computation during the training. To solve the problem, we develop entropy sampling to select the effective training point pairs and reduce the training set based on the texture complexity. That is, complex texture regions represent the dominant characterization of the seismic data, and these regions are sampled with higher probability as training data set. Numerical illustrations on 2D seismic data show that the proposed method reduces the training data pairs as much as possible to improve the efficiency of training, while ensuring accurate denoising results.
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A Quantitative Estimation Method of Cement Clay in Clayey Sandstone and Its Rock Physics Application
SummaryWhen building the rock physics model for clayey sandstones, it is very important to know the contact type and content of cement clay in clayey sandstone for correctly understanding the influence of the cementation on acoustic velocity of clayey sandstone and how to reasonably establish rock physical model. At present, there is no laboratory method to directly quantitatively estimate the content of the cement clay, which leads to large errors in predicting acoustic velocities when using the cemented sands model for cemented sands formation because of the over-estimated of the cement clay. In this paper, a method for distinguishing cemented clay is proposed by observing the contact relationship and relative distribution between clay and particles in thin sections. The cement clay is used as the input parameter of the constant cement model. The comparison shows the velocities error predicted in our method is 20% lower than the original model, and the predicted results are significantly improved. The method proposed in this paper is a suitable rock physics model for weak cemented formation. It can predict acoustic velocity to identify favorable reservoirs and quantitatively evaluate reservoir parameters by combining seismic and logging data.
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Q-Compensated Least-Squares Reverse Time Migration of Different-Order Multiples
More LessSummaryMultiples have longer propagation paths and smaller reflection angles than primaries, so they cover larger illumination area. Therefore, multiples can be used to image shadow zones of primaries. Least-squares reverse time migration of multiples can produce high quality images with fewer artefacts, high resolution and balanced amplitudes. However, viscoelasticity exists widely in the earth, especially in the deep-sea environment, and the effect of attenuation on multiples is more serious than primaries because multiples have longer propagation paths. To compensate for Q attenuation of multiples, Q-compensated least-squares reverse time migration of different-order multiples is proposed by deriving Q-compensated born modeling operators, Q-compensated adjoint operators and Q-attenuated demigration operators for different-order multiples. Based on inversion theory, this method compensates for Q attenuation along all the propagation paths of multiples. A stabilization operator is introduced to suppress exponential high frequency noise. Example on a modified attenuating Sigsbee2B model suggests that the proposed method can produce better imaging result than Q-compensated least-squares reverse time migration of primaries and noncompensated least-squares reverse time migration of multiples.
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