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82nd EAGE Annual Conference & Exhibition
- Conference date: October 18-21, 2021
- Location: Amsterdam, The Netherlands
- Published: 18 October 2021
101 - 150 of 1137 results
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Improvements in Geologic Modeling Workflows Based on Six Years of Incremental Models at Farnsworth Ccus/Eor Site
Authors R. Balch, R. Will, W. Ampomah and N. HobbsSummaryThe evolution of five versions of a geologic model at Farnsworth unit have highlighted the ability to integrate new interpretations, newly generated data, and feedback from monitoring and simulation efforts into increasingly comprehensive models over extended periods of time, while allowing for useful models at each stage of development. Technical advances in model building and design of comprehensive workflows should aid future projects with the goal of commercial carbon storage at EOR sites.
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Gravity Assisted Steam Flooding (Gasf) For Improving Oil Recovery of Foamy Extra-Heavy Oil Reservoirs
By Z. YangSummaryThis research provides a feasibility and adaptability research of V-H GASF for improving oil recovery of foamy extra-heavy oil reservoirs. In addition, this work optimized the well location and operation parameters of this technology.
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A New Approach to Optimize the Stratal Slices by Using Multilevel 2d Wavelet Transform
More LessSummaryIn this paper, we propose a new approach to optimize the stratal slices by using multilevel 2D wavelet transform. We first interpolate the slice to enable it to be multilevel decomposed. Then, multilevel 2D wavelet transform is applied to decompose the interpolated slice into multiple levels. We further reconstruct the decomposed data within different levels, and re-interpolate the optimal reconstructed slice to the original size. Comparing with the original slice, the final result can be potentially a better alternative to uncover more geologic and sedimentary features of the target zone. Two examples are carried out to validate the effectiveness of the proposed method.
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P-Wave Velocity at Shallow Depths in Sand Dunes and Its Effect on Static Correction
Authors S. Hanafy, A. El-Husseiny, M. Benaafi, A. Al-Shuhail and J. DvorkinSummaryWe address the problem of measuring the P-wave velocity at a very shallow depth in unconsolidated dune sand. Because the overburden stress is very small at shallow depth, the respective velocity is small and the signal is weak. Hence, such data are scarce, both in the lab and in the field. We used in our approach a high-resolution seismic experiment with geophone intervals ranging between 10 and 25 cm. The outcome is a velocity-depth relation in the upper 1 m interval. These results were combined with a conventional survey where the geophone spacing was 2 m. The latter results gave us the velocity profile in the deeper interval between 1 and 7 m, down to the bottom of the dune. The calculated velocities ranging between 87 m/s at a depth of few centimetres to 390 m/s at 7 m depth. This is the first study where such low velocity was recorded at extremely shallow depths in the sand dune environment. The velocity profile thus generated is statistically fitted with a simple analytical equation. We show that using a replacement or tomogram velocities instead of the accurately measured velocity profile may result in 23% to 44% error in static correction.
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Joint Inversion of Porosity and Permeability Based on Velocity Dispersion in 3d Two-Phase Orthotropic Crack Medium
More LessSummaryReservoir parameter inversion is an essential geophysical method to quantify the reservoir volume. Oil-gas reservoirs are often presented as two-phase medium and anisotropic features, which lead to a great challenge for the reservoir parameters prediction. In the abstract, a new joint porosity and permeability inversion technology is proposed for 3D twophase cracked orthorhombic media based on the BISQ mechanism. First, we derive the porous elastic wave equation of 3-D two-phase orthotropic anisotropic medium and build the relationships among porosity, permeability and phase velocity. Then using the genetic algorithm, we conduct the porosity and permeability inversion with single-azimuth velocity dispersion by genetic algorithms, and analyse the influences that the different azimuths velocity dispersion have on the inversion accuracy. Finally, we implement the joint inversion of the porosity and permeability with multi-azimuths velocity dispersion, which makes use of advantages of the different azimuth, and analyze the algorithm stabilization and accuracy.
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A New Generalized Auto-Tune Procedure for Modeling Asphaltene Precipitation by Equation of State
Authors A. Daryasafar, A. Soleymanzadeh and K. ShahbaziSummaryComplex structure of the asphaltene causes many challenges for predicting its phase behavior. Recently, Cubic-Plus-Association (CPA) and (Association Equation of State) AEOS models, which consider association term, are widely used. Although these two models predict phase behavior of the asphaltene properly, they contain different adjusting parameters. Since, most of the methods that have been presented for tuning of the EOS models are time consuming, a generalized auto-tune technique based on the genetic and Monte-Carlo algorithms is suggested in this work. The proposed method of tuning was applied to the CPA and AEOS models. To confirm the applicability of this technique, the amount of the precipitated asphaltene during titration data for two oil samples was predicted by CPA and AEOS. Results demonstrated that the outcomes of the EOSs were properly matched with experimental values of asphaltene precipitation, which proves the appropriateness of the proposed tuning procedure.
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Flow Diagnostics for Fractured Reservoirs with Geomechanics
Authors V. Spooner, L. Gutierrez Sosa, S. Geiger, D. Arnold, F. Doster and A. BuschSummaryFlow diagnostics are a powerful tool, for screening, ranking, and clustering large model ensembles in terms of their dynamic reservoir performance. We have extended the seminal flow diagnostics approach of Møyner et al. (2014) in two ways. First, we account for fracture-matrix transfer processes pertinent to naturally fractured reservoirs. Secondly, we account for coupled hydro-mechanical effects that are can alter the performance of stress-sensitive reservoirs during production. We have demonstrated that by accounting for the underlying hydro-mechanical heterogeneity affecting the flow behaviour, we can choose models that cover a broader range of uncertainty than considering just static metrics.
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Inversion-Based Edge-Preserving Seismic Denoising with Structural Constraints
More LessSummaryAttenuating random noise while preserving edges and structures in seismic dataset is of great significance for the following seismic inversion and interpretation. From the viewpoint of inversion, the utilization of more information is an effective way to improve signal-to-noise ratio of seismic data. In this study, we adopt simultaneous sparsity constraints of the first-order difference of signals along the structural direction and time direction, described by minimizing the Cauchy function, as a combined constraint term imposed on the time-domain data misfit to propose an inversion-based edge-preserving and signal-preserving noise reduction method. In this way, the redundancies along both time slices and seismic sections are simultaneously considered, and the edges along the spatial directions can be preserved. The performance of the method is mainly dependent on a trade-off parameter and a scale parameter, which makes it easier to obtain a relatively perfect noise reduction result. The applications on two real poststack datasets and a real prestack dataset demonstrated that the proposed method is an effective edge-preservation and amplitude-preservation denoising tool.
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Pore-Level Investigation of the Synergistic Effect of a Novel Thermoassociated Copolymer and Smart Water in Micromodel
Authors A. Maghsoudian, M. Shirazi, A. Esfandiarian, S. Kord and Y. TamsilianSummaryThe synergy between smart water and a thermoassociated copolymer consisting of acrylamide and styrene, poly(AM-co-St), called HSPAM, as a newly synthesized copolymer applicable under harsh reservoir conditions, was investigated for the first time as a promising candidate for enhanced oil recovery (EOR) purposes. In the first part of this study, a set of experimental tests including FT-IR, H-NMR, and TGA were conducted to characterize the chemical structure. Then the rheological behavior of HSPAM was analyzed under harsh reservoir conditions and the results were compared with hydrolyzed polyacrylamide (HPAM) as a conventional polymer. In the second part, the compatibility, contact angle (CA), and interfacial tension (IFT) experiments were conducted with different synthesized smart waters and the best one was selected to conduct the aforementioned experiments in the presence of HSPAM and HPAM. Finally, the flooding experiments were conducted in a carbonate coated glass micromodel based on the results obtained in the previous sections. The experimental results showed that HSPAM performed well under harsh reservoir conditions in spite of HPAM alongside drastically improving the flooding performance in the presence of four times spiked in sulfate seawater (SW4S) yielding an ultimate recovery of about 83% original oil in place (OOIP).
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A Dynamic Sampling Fwi Method Based on 3d Seismic Wave Reverse Illumination
More LessSummaryWith the improvement of migration technology and the deepening of exploration, the geological target of exploration is becoming more and more complex, and the requirement of velocity is becoming more and more strict. So the precise velocity model is critical for high quality seismic imaging. Full waveform inversion (FWI) can be applied to the velocity inversion of strong transversely variable velocity media and anisotropic media. Because of its accuracy for velocity inversion, we can obtain precise subsurface structure by iterative inversion. But for 3D FWI, the seismic data is massive, which gives us computational difficulties. We propose a dynamic sampling FWI method based on 3D seismic wave reverse illumination, the dynamic observation system is established by the seismic reverse illumination facing the geological target, which can reduce the amount of data and greatly improve the calculation efficiency without affecting the accuracy.
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Numerical Investigations on the Transport Properties of Thermal Neutron in Saturated Porous Media with Digital Rock
More LessSummaryIn this research, the digital rock has been constructed with the pileup of the segmented images of X-ray CT data from the carbonate samples. The transport of thermal neutrons has been simulated with the Monte Carlo method to reveal the correlation between the counts difference of neutrons and porosity, to investigate the effects of water saturation. Instead of a detector used in the conventional researches, the 8x8 array detectors are utilized to detect the transmitted neutrons, which can help to investigate and image the anisotropy of pore structure. Based on the simulated results, it is observed that the calculation of porosity with the neutron data can be affected by the anisotropy of pore structure and the saturation. The significance of fluids content in the porosity evaluation can synchronously increase with the increasing of water saturation. Moreover, a new mathematical model has been proposed to relate the counts difference to the porosity and saturation, which can actually be taken as a new method to calculate the saturation with the porosity and the counts difference of neutrons.
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Data-Driven Approach to Quantify Uncertainty in Wellbore Management through Temperature Logs
Authors A. Alkhalaf, I. AlZefzafy, S. Haldar and N. AnsariSummaryWe demonstrate the use of data-driven machine learning model to automate the process of analysing temperature logs to aid with production management in mature fields. Temperature log analysis has many applications such as evaluating formation productivity ( Bird et al., 1965 ), Estimating thermal conductivity (Seto et al., 1991), and skin damage determination ( Schindler et al., 2015 ). We are specifically targeting the use of temperature logs to quantify the risk of a wellbore leak. We built a machine learning pipeline that autonomously quantify the risk associated with every temperature log. The model is trained with hundreds of labelled historical temperature logs. This is motivated by the high number of acquired temperature logs in mature fields and the growing number of aging wells. In addition, Automating the analysis of temperature logs enables us to utilize the rich history of acquired logs to fine-tune well selection for future surveys (e.g. Zangel et al., 2016) and to quantify the risk associated with a given spatial coordinate and operational condition. (e.g. AlAjmi et al., 2015 ). This methodology contributes to a sound well production management strategy in mature fields with aging wells.
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Low-Frequency Impedance Inversion by Using Interpretable Gated Recurrent Encoder-Decoder Networks
More LessSummarySeismic impedance inversion plays an important role in fine characterization of lithology and reservoir prediction. The conventional impedance inversion methods cannot generate low-frequency information during the inversion process. However, the low-frequency components of impedance are highly significant in reducing the multi-solution of the inversion results and for quantitative interpretations. To obtain the low-frequency information of impedance, an interpretable gated recurrent encoder-decoder networks (GRED) for dual-driven impedance inversion is proposed. We consider two supervisors including well-log impedance curves and the corresponding through-well observed seismic data to train GRED. In this proposed inversion method, the low-frequency components are mainly learned from wide-band well-log data. Examples illustrate that the proposed method can obtain satisfied (wide-band) absolue impedance results and its low-frequency trends.
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Near Surface Q Compensation and its Effect on Restoring Frequency Consistency
More LessSummaryThe resolution of near surface problems on onshore has a serious impact on the seismic processing results. Due to the different years of seismic data acquisition and large changes in topography, there are serious near surface problems in the Qaidam Basin in western China, especially frequency inconsistencies. For many years, the commonly used method to resolve it is four-component surface consistency deconvolution (SCDEC). Near surface Q compensation technology (NSQCT), because that the absorption attenuation effect caused by near surface velocity and thickness changes is considered, is more physical significance than SCDEC. This abstract first introduces the NSQCT from the surface relative Q inversion and stable absorption compensation algorithm, then designs the parallel processing workflow, and compares the effects of the two methods in solving the frequency inconsistency problem in actual data. The results confirm that the NSQCT in this area has a significantly better effect in restoring frequency consistency than SCDEC.
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Multi-Parameter Pseudo Acoustic Full Waveform Inversion Method in Elastic World
More LessSummaryIn land seismic exploration, low-velocity zone causes the ray path of reflected wave propagating to the detector perpendicularly. Therefore, single-component data is regarded as P-wave data. In this paper, we first derive a new pseudo acoustic wave equation (PAE) in elastic world based on acoustic approximation. Compared with the acoustic modeling, pseudo acoustic modeling has obvious elastic AVO effect and S-P converted energy. Then we propose a pseudo acoustic wave full waveform inversion method for elastic parameters inversion using P-wave data only. The gradients of the misfit function with respect to updating the perturbations of elastic parameters based on PAE theory are derived. A field data example in eastern china is carried out by our new method using only the p-wave data. The results of pseudo acoustic full waveform inversion shows that S-wave velocity inverted is reliable and the passion ratio profile is well fitted to the natural potential logging curve.
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3D Elastic Wavefield Reconstruction Method Based on Optimal Operator Boundary Storage Strategy
More LessSummaryReverse time migration has to store both forward- and backward-propagated wavefield which cost a large of memory, especially in elastic world. Such problems can be solved by wavefield reconstruction method. To reconstruct source wavefield with high spacing accuracy, tradition methods still cost more computer storage. In this study, we propose a 3D elastic wavefield reconstruction method based on optimal operator boundary storage strategy, which cost less storage and reconstruct source wavefield with high spacing accuracy same as previous methods. Our algorithm is success in accurately reconstruct elastic wavefield and reducing 80% of the storage.
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Minimum-Phase Sweep Signal for Phase Controlled Vibroseis Acquisition
Authors I. Korotkov, A. Zhukov and I. DagaevSummaryThe recent development of vibrator electronics allows generating a family of comprehensive sweep signals including phase controlled sweeps. Standard vibroseis acquisition outputs zero phase signals in correlated traces, which require feather mathematical conversion to minimum phase in order to agree with assumption of minimum phase earth response. In proposed method, vibrator controller calculates the minimum phase equivalent of the any desired reference sweep and then emits it to the subsurface. Recorded subsurface response is then correlated with original unchanged reference sweep. Output is minimum phase signal gathers, which are ready for standard processing with minimum phase deconvolution application. This paper demonstrates advantage of direct minimum-phase controlled sweep acquisition to standard acquisition followed by minimum-phase conversion signal processing.
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Investigation and Mapping of Upper Jurassic Delta Channels in Central Part of the West Siberian Basin
More LessSummaryThis paper gives new information about depositional model of Upper Jurassic formation in the central part of the West Siberian Basin. Two main types of sandstones were identified by facies analysis: channel sandstones and sandstones of mouth-bar. The facial classification of well data made it possible to substantially refine the prediction of reservoir properties on the investigation area. Delta channels with increased collector thicknesses and high permeability values were outlined.
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Research and Application of the Efficient Reflection Coefficient Inversion Method Via Toeplitz-Sparse Matrix Factorization
More LessSummaryWe developed an efficient reflection coefficient inversion method based on Toeplitz-sparse matrix factorization. This method can be performed by solving two sub inversion problems alternately. One takes the elements of the Toeplitz wavelet matrixas parameters to be inverted for, and will be solved by effective fused lasso algorithm(EFLA), which guarantees that the computational complexity is much lower than that of fused lasso algorithm. The other takes the elements of the sparse reflectivity matrixas parameters to be inverted for, and will be solved by fast iterative shrinkagethresholding algorithm (FISTA) with backtracking, the parameter of the ratio of minimum non-zero reflection coefficient amplitude to maximum reflection coefficient amplitude is defined to represent the sparsity which makes it easy to choose the parameter for the objective function. The seismic profile can be simultaneously deconvolved into a Toeplitz wavelet matrix and a sparse reflectivity matrix by alternatively solving the above two sub problems. Our tests on the synthetic seismic data and field seismic data demonstrate that the proposed method can effectively derive the wavelet and reflectivity simultaneously from band-limited data with appropriate lateral coherence.
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High-Quality Source Rock Thickness Prediction of Xujiahe Formation in the Western-Central Transition Zone of Sichuan Basin
More LessSummaryThe Xujiahe formation in the western-central transition zone of Sichuan Basin are divided into six members. Source and reservoir are stacked vertically. The first,third,and fifth members are source rocks. In this context,the distribution of high-quality source rock is one of the major determinants of tight gas exploration. The total organic carbon (TOC) is an important parameter to predict the distribution of high-quality source rock. The multi-attribute inversion method is selected optimally to predict the TOC distribution. There are too many 2D seismic lines in study area. According to the prior works, the multi-attribute inversion must be performed line by line. This leads to the following problems:1. It is a heavy and time-consuming workload; 2. The 2D seismic line which is far from the well is impossible to perform multi-attribute inversion. In the view of above, this paper establishes a pseudo-3D seismic survey grid to form pseudo-3D seismic data. Based on this,multi-attribute inversion is used to predict the TOC distribution effectually. The method can improve the utilization ratio of 2D seismic data and greatly reduce the workload. Prediction results shows: the high-quality source rocks of the first, third and fifth member of Xujiahe formation are overall development in study area.
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Petrophysical Evidences for the Presence of Bornova Flysch Zone in the Gulf of Izmir, Aegean Sea
By A. UyanikSummaryVarious researchers have studied the characteristics of the Bornova Melange, one of the key geological units in Western Anatolia, since mid-1960’s. The outcomes of these studies have revealed that the Cretaceous-Paleocene aged Bornova Flysch Zone is dominated by turbiditic sandstone-shale intercalation bearing km-scale limestone and ophiolite blocks. It is unconformably overlied by volcano-sedimentary succession deposited during the Miocene. The regional angular unconformity between the Cretaceous and Miocene sediments can be clearly observed at the outcrops around the Gulf of Izmir. However, the presence and properties of the BFZ in the offshore portion is not known. In this sense, determination of the presence and extent of the flysch zone and understanding its’ geomechanical properties in the gulf is the main purpose of this study. Rock physics parameters such as; density, Vp/Vs ratio, Poisson’s ratio and pore pressure have been derived from interval velocities. Petrophysical models indicate that the BFZ is present in the gulf and Cretaceous angular unconformity acts as a regional lithological, tectonic and geomechanical boundary. Findings can help to better understand the hydrocarbon potential of the BFZ in the gulf. They are also crucial to predict geomechanical behaviour of flysch type facies, encountered in other regions of the world.
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An Approximate Approach of Ray Velocity and Attenuation in Viscoelastic Anisotropic Media Based on Perturbation Theory
Authors J. Wu, B. Zhou, X. Li and Y. BouzidiSummaryIn viscoelastic anisotropic media, the stiffness parameters, slowness vector, phase, and ray velocity are all complex-valued quantities. The solutions are challenging and very complicated where the eikonal equations are difficult to solve. In this contribution, we propose an approximation for calculating the ray velocity vector and quality factor in viscoelastic VTI and ORT media based on the perturbation theory. The real and imaginary parts of the stiffness matrix are regarded as the background quantities and perturbations, respectively. The perturbation part of slowness vector can be determined through the zero-valued Hamiltonian function and the homogenous ray velocity vector. The numerical results show high accuracy for all types, such as qP, qSV and qSH, of seismic waves in models with strong anisotropy and attenuation. This is also valid even in the special propagation directions of qSV-wave where the wave surfaces are folded.
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Seismic Stochastic Inversion Constrained by Multiple-Point Patterns
More LessSummaryGeostatistical stochastic inversion can provide inversion results with higher resolution and play a significant role in the reservoir prediction. Traditional stochastic inversion is based on two-point geostatistics (TPG), which is unable to describe complex reservoir structures. In this paper, a new strategy is proposed to overcome these difficulties. First, we utilize FILTERSIM algorithm to acquire the multiple-point correlation from the seismic profile. Then, the stochastic simulation is realized under the multiple-point constraint. Finally, combining with Metropolis-Hasting algorithm, the accurate inversion results are acquired. The model test results illustrate the availability and accuracy of the method.
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Experimental Investigation of Using Ionic-Liquids as Alternatives of Surfactants in Enhanced-Oil-Recovery Processes for Harsh Carbonate Reservoirs
Authors A. Esfandiarian, A. Maghsoudian, M. Shirazi, M. Mohammadi, S. Kord and Y. TamsilianSummaryStudies on the Ionic Liquids (ILs) as chemical agents for chemical enhanced oil recovery (CEOR) processes are very limited. The aims of this investigation are fulfilling a gap in the research on IL-based CEOR processes and showing the possibility to use the ILs as an alternative and influential agent on changing the reservoir rock and fluids properties. In this study, three cationic ILs including: 1-hexyl-3-methyl-imidazolium-chloride ([HMIM][Cl]), 1-methyl-3-octyl-imidazolium-chloride ([OMIM][Cl]) and 1-dodecyl-3-methyl-imidazolium-chloride ([DMIM][Cl]) were synthesized for CEOR process. According to obtained data from pendant drop interfacial tension (IFT) measurement tests, the critical micelle concentrations (CMC) of ILs in three different solutions with various total dissolved solids (TDS) include: Low Saline Water (LSW (TDS = 2000 ppm)), Formation Brine (FB (TDS = 195475.93 ppm)), and Sea Water (SW (TDS = 36250 ppm)). Also, some sessile drop contact angle measurement experiments were taken for evaluating the impacts of ILs on the wettability alteration mechanism for dolomite carbonate rock. Finally, several chemical flooding were conducted in dolomite coated micromodel system with dolomite pattern by determining the optimum concentrations of ILs. The recovery factor (RF) results showed that a flooding process after two pore volume injection could recover 80.28% (±1.0) of the original oil in place.
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Machine-Learning-Driven Dispersion Curve Picking for Surface-Wave Analysis, Modelling, and Inversion
Authors A. Kaul, P.J. Bilsby, A. Misbah and A. AbubakarSummaryThe quality of onshore seismic data is strongly affected by the characteristics of the near surface. To compensate for the distortion of travel times of seismic energy, workflows have been formulated to analyse, model, and invert surface waves. This approach requires human-intensive picking of high energy modes on conditioned semblances that represent each analysis location on the dispersion survey. In this work, we designed a globally trained supervised machine learning model to perform pixelwise binary segmentation on semblances using fully convolutional architecture with residual units to pick the fundamental mode – the mode with the highest surface-wave energy. We validated our approach on all the analysis locations of the Cooper Basin in South Australia, and compared the results with current conventional methods used in the industry.
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Depth Domain Q Estimation and Application - Gulf of Mexico Case Study
Authors A. Elsabaa, D. Stathpoulos, J. Omana, F. Figueira, J. Roth and M. CavalcaSummaryWe present a case study from the Gulf of Mexico where we apply depth-domain Q estimation and compensation using depth-domain match-filter approach.
The goal of this study was to produce a Q-compensated depth migrated dataset with accurate event dynamics, that can be used for subsequent AVO analysis.
The process improved the seismic image resolution and produced more reliable amplitudes versus offset, paving the way to more accurate quantitative analyses of seismic datasets.
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Time-Lapse Topography Inversion from Gas-Plume Monitoring
Authors J. Gunning, S.G. Glubokovskikh, J. Ennis-King and S. JacksonSummaryCarbon dioxide sequestration projects require geophysical monitoring and verification to meet community and stakeholder expectations. Mapping of plume movement is a key component of this obligation. Time lapse seismic provides excellent data on plume evolution, but this imposes the need for subsurface models that consistently predict the observed movement. Seal topography is a primary driver of plume migration, together with fault geometry and permeability. Traditional 3D multiphase flow models are too heavy for use as forward models in inversions for topography, and standard fixed-geometry geocellular models are inconvenient for topographical inversion. Using simplified flow models for plume evolution using topography and plume-thickness variables, we have developed an efficient framework for topography inversion where seismic information on plume thicknesses is available.
The framework relies on a reduced physics model that describes a bouyancy-driven plume via a simple PDE-controlled thickness field conserving volume. Fast and efficient inversion is possible via either adjoint-state methods or full-Jacobian methods based on reduced basis representations. The method is illustrated using field data from CO2CRC's Otway Project in Australia, using plume evolution over a 4 month injection period with pre and post-facto seismic monitoring. The resulting inversion predicts surface topography trends conformable with other sources of data.
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Impacts of Feldspar Dissolution, Calcite Cementation and Clay Growth on Pore Structure
More LessSummaryPrecipitation and dissolution are two mechanisms that alter porosity and pore size, which have vital implications for a host of geological settings, such as hydrocarbon extraction from a subsurface reservoir, carbon sequestration in geological formations and diagenesis in a sedimentary basin. In this paper, we construct parameters to quantitatively illustrate the effects of three major diagenesis processes (feldspar dissolution, calcite cementation, and clay growth) on the pore structure in geological sample though microscope observation and reservoir characterization experiments. Results show that feldspar dissolution and calcite cementation occur preferentially in the connected pores with a throat greater than 1um while clay growth have an impact on throat size less than 1um. At the same, the parameters have an excellent relationship with pore structure, porosity, and permeability, which is of great importance for reservoir physical prediction in study area.
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Robust Elastic Full Waveform Inversion Based on N-th Power Operation and Convolved Wavefields
More LessSummaryThe elastic full waveform inversion (FWI) can use the recorded multi-component seismic data to construct high-precision multi-parameter models of the subsurface media such as P- and S-wave velocity models. However, due to the reasons such as data quality and algorithm limitations, there are still many problems in the promotion and application of elastic FWI method. Aiming at alleviating the influence of low-frequency data absence on the inversion results, we propose a robust elastic FWI method based on the n-th power operation. The n-th power of the seismic data can compress the time-domain waveform and expand its frequency-band. The FWI objective function constructed using the n-th power wavefields shows better convexity. By successively lowering the power during the inversion, we can realize a new multiscale FWI strategy, which is also a data-domain layer-stripping strategy. Seismic data will be more sensitive to the source wavelet errors after the n-th power operation. To mitigate this problem, we propose a robust objective function for elastic FWI using the n-th power operation and the convolved wavefields. Finally, the validity of the method is verified by numerical examples.
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Investigation of the Correlations Between Anisotropic Properties and Kerogen Content in Organic-Rich Shale
More LessSummaryUnderstanding the quantitative responses of anisotropic behaviours in shale, which are induced by kerogen content, is of great significance in assessing hydrocarbon production potential and hydraulic fracturing design. Controlled experiment is difficult to be conducted on natural shales due to their characterizations of high variations. In this work, hot-pressing technique is applied to create well-controlled artificial organic-rich shale (AORS) for quantitatively researches. 11 AORS anisotropic samples with different kerogen content are constructed and machined into prism-like shape where the opposing faces allow for wave propagation along different directions. Quantitative relationships between kerogen content and directional elastic properties (velocities, anisotropic parameters and VP/VS ratio), dynamic mechanical properties (Poisson’s ratio, Young’s modules and stiffness) to the bedding plane are obtained at ambient conditions with ultrasonic experiments. Bedding perpendicular P-wave velocities are more sensitive to the increasing kerogen content than corresponding bedding paralleling velocities. Apparent dynamic Poisson’s ratios? have good agreement with the true dynamic Poisson’s ratio ?31 and ?12 which may simplify real field mechanical problems. At low kerogen content (<10%), VP/VS ratio and kerogen content have linearly negative correlation, and the magnitude of VP/VS ratio which is less than 1.7 may be a significant characterization for high organic-rich (>10%) shale.
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Creation of Lithology and Gas-Bearing Sensitive Elastic Factor Based on Xu-Payne Optimization Modeling
More LessSummaryFaced with the complex lithology and gas characteristics of carbonate rocks, the original acoustic wave curve, density curve, and calculated elastic parameter curves have been unable to identify reservoirs and gas layers accurately. In this paper, we use Xu-Payne optimization modeling method to take the measured P-wave logging as the standard curve, and use the least square method to calculate the lithology content iteratively and obtain the corrected velocity curves and density curve. Next, we use the coordinate rotation method to construct lithology-sensitive density projection factor and identify dolomite reservoirs and limestone reservoirs, and finally we construct fluid-sensitive elastic factors under different lithology reservoirs. In this way, the respective gas layer response characteristics of the dolomite reservoir and the limestone reservoir are revealed, and the threshold is set to provide a basis for the quantitative prediction of subsequent seismic inversion.
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Improvised Approach For Seismic-Driven Water Saturation_Trend Prediction- Field B Case Study in Malay Basin
Authors C.L. Lew, H.H. Ismail, B.P. Kantaatmadja and E.A. Jones Jr.SummaryThe motivation of this paper is to predict the water saturation (Sw) trend when away from the well, as one of the elements in determining the hydrocarbon volume and commerciality is the Sw. The Sw can be estimated from the resistivity that being derived from the wireline log (at well location) and electromagnetic (EM) data for field coverage away from the well. An example of the EM data is the controlled source electromagnetic (CSEM). However, the limited availability of EM data coverage in Malaysia has led to this study of evaluating an alternative seismic based approach to predict Sw trend away from well using seismic data. An improvised methodology has been developed to predict the 3D seismic-driven Sw_trend by integrating elastic properties and machine learning technique which allows the prediction of hydrocarbon saturation across the field. The generated 3D seismic-driven Sw_trend is validated by 14 blind test wells, where the results are promising. The methodology allows interpreter to visualize and characterize the distribution of the hydrocarbon saturation across the field, and helps to differentiate between the commercial hydrocarbons from the residual which is essential for economic evaluation and well planning
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Numerical Simulation of Multiscale Fracture Network Two-Phase Flow Based on Finite Volume Method
More LessSummaryCapturing heterogeneity and multiscale in fractured media is important to understand the underlying mechanisms controlling flow behavior as fractures, both natural and engineered, can dominate flow patterns in many types of media. Due to the fractures’ characteristics as heterogeneity, multi-scale and extreme size-to-aperture ratio, they challenge standard macroscale mathematical and numerical modeling of flow based on averaging and Poisson process. This paper presents a numerical method for solving the two-phase flow model of discrete fractures due to the heterogeneity and multi-scale fracture distribution in fractured reservoirs based on the finite volume method. In this context, the paper discusses the control effect of non-uniform distribution of fractures on reservoir water saturation at different scales. Mathematical and numerical modeling related to fracture dimension reduction, multiphase flow and high order upwind scheme are also analyzed on.
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Robust Estimation of Uncertainties of Avo Attribute Anomalies
Authors F. Pivot and M. BouayadSummaryAVO (Amplitude Versus Offset) technique is widely used for de-risking fluids inside prospects. In this extended abstract, the objective was to develop a new family of attributes “confidence attributes” allowing a better understanding of AVO uncertainties. So, with the help of confidence attributes geophysicist could better map parts of the anomalies that are highly robust to the choice of the process parameters. All results are here illustrated on a real deep offshore turbiditic field.
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An OBS Multiple Attenuation Approach Enabled By Signal Apparition Encoded Multi-Source Acquisition: A Case Study
Authors J. Robertsson, F. Andersson, P. Riste, L. Amundsen, M. Cogan and Å. Sjøen-PedersenSummaryOcean Bottom Seismic (OBS) data that are adequately sampled on the source side allow for up/down wavefield decomposition and removal of all surface-related multiples by means of deconvolution of the downgoing wavefield from the upgoing wavefield. However, conventional sequential acquisition of an adequately sampled shot grid can be costly. Instead, simultaneous source acquisition provides a means to both achieve a productivity increase over conventionally acquired data while also enabling the acquisition of a better sampled shot grid. In this paper we present the results from the first 3D triple-source simultaneous source OBS survey acquired using the principles of signal apparition. We demonstrate that the decoded data allows for a simple bespoke OBS processing workflow to be used resulting in high quality multiple-free images.
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Study on Absorbing Boundary Conditions of Viscous Sponge Layers Based on Lattice Boltzmann Method
More LessSummaryThe lattice Boltzmann method (LBM), a kind of mesoscopic method based on kinetic theory, is widely used in computational fluid dynamics and acoustic wave. Compared with the traditional wave equation, LBM has many advantages, such as great ease of implementation, near-infinite potential for the parallelization, flexible handling of boundary conditions and simulating complex phenomena easily. In this abstract, LBM is introduced to simulate acoustic wave propagation with viscous sponge layers (VSL), where the relaxation time, which is related to the kinematic shear viscosity, varies as different functions and the reflected wave absorbing effects are compared. Numerical results demonstrate that the situation when the relaxation time in VSL varies as a cubic function has a better absorbing ability for boundary reflection, which is of vital importance for seismic wavefield simulation by LBM.
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3d Towed Marine Signal Apparition Multi-Source Acquisition Over Troll: Results and Comparisons Against Conventional Production Seismics
Authors J. Robertsson, F. Andersson, P. Riste, L. Amundsen and M. CoganSummarySimultaneous source acquisition offers the prospect of productivity increases as well as the acquisition of better sampled data. Whereas a productivity increase is straightforward to achieve for OBS, it is sometimes less so for towed marine configurations. On the other hand, towed marine configurations significantly benefits from better sampled data in terms of near offsets, wide azimuth, inline sampling and crossline midpoint distribution. These are areas that simultaneous source techniques can directly address. In this paper we present results from the worlds first 3D towed marine multi-source acquisition based on the principles of signal apparition. We demonstrate that signal apparition results in a much better sampled data set resolving individual diffractors in a complex overburden without compromising on SNR when compared to conventionally acquired flip/flop data.
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Decoding the Impact of Tidal Influence vs Burial Diagenesis in the Fogelberg Discovery, Halten Terrace, Norway
Authors P. Milstead and C.J. LowreySummaryFogelberg is a deep, high temperature discovery on the Halten Terace, offshore Norway with reservoir in sandstones of the Jurassic Garn Fm deposited in tidally reworked sand bars. During appraisal of the discovery a DST test indicated that the reservoir properties were poorer than indicated by previous wells and that there were boundary effects close to the wellbore. This presentation will show how analysis and integration of a full spectrum of sedimentological, petrophysical and petrographic data was used to understand the controls on reservoir quality and take them forward into the reservoir model. The work indicated that depositional facies is a key control on reservoir quality and that an understanding of the tidal bar architecture is critical to modeling flow. A high density of stylolites associated with 2D dunes resulted in significant permeability anisotropy and flow tortuosity. A local sector model (LSM) was built around the relevant well and DST results were matched on the small scale before upscaling to a full field model.
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Quasi-Elastic Full-Waveform Velocity Inversion with Density Constraints
Authors S. Greenwood, V. Valler, T. Hallett, C. Wang, C. Hanitzsch, B. van de Bilt and I. JonesSummaryUnder the acoustic approximation, reflection amplitude is considered to be proportional to interval velocity change across an interface (vi2-vi1) rather than impedance change (ρ2vi2- ρ1vi1). If density is changing slowly, usually increasing gently with depth of burial, then this approximation is often acceptable. However, as discussed in this study, for layers where the velocity increases whilst the density is decreasing significantly, the acoustic approximation in reflection FWI will result in the delivery of a low-velocity estimate rather than the correct high-velocity values for the layer. Here we employ quasi-elastic propagators (permitting density change but not dealing with shear mode conversion and propagation), to help mitigate this problem.
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Geological Modeling Based on a Morphing Algorithm
Authors M. Bouayad, F. Pivot and M. LopezSummaryGeostatistical methods such as MPS (Multiple points statistics) are able to reproduce complex geological shapes, while honoring well data from so-called training images. However, depending on the complexity MPS technique struggles to achieve realistic reproduction. It is the case for complex geological context as turbiditic systems. To overcome the lack of MPS technique for turbidites, we have developed a new morphing algorithm in order to populate rough 3D geomodels with realistic geological information from 3D training images.
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Geological Equiprobable Multi-Models for Resources Assessment. Carson, Bonnition and Salar Basin, NL, Canada
Authors E. Le Guerroué, P. Jermannaud, G. Perez-Drago, B. Lebreuilly, T. Pichot, P. Chenet, D. Norris, E. Gillis and R. WrightSummaryThe underexplored Carson Basin appears prospective for oil and gas, after new regional seismic data uncovered plays and leads that are tested using data-calibrated, equiprobable alternative models. The objective was to provide petroleum resource estimates through data interpretation, and 3D basin modelling. Modeling was setup in order to account for alternative realistic (geologically possible) models.
Stratigraphic and petroleum system models were constructed and calibrated to well and seismic data to account for less constrained parameters such as: 1) the geodynamic evolution of the basin (drowning timing). 2) the lithological content away from well constrain. 3) the carbonate factory production efficiency or 4) the source rock deposition and preservation potential.
Some scenarios were discarded for not honoring well data, interpreted seismic feature and HC occurrence forecasts. Ultimately the resource assessment was accounting for 11 fully calibrated geologically realistic end-member models.
The HC volume estimates were derived from the individual results of each outcome attached to a given alternative scenario with different HC charge. resources in place (unrisked volumes) are estimated to 4.0 Bboe (P50). The Probability of Geological Success is estimated 11% characterizing a medium to high risk exploration area.
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Spatially Correlated Reflectivity Reconstruction via a Two-Step Scheme
More LessSummarySparse spike inversion (SSI), imposes a sparseness constraint term along seismic trace, can evidently broaden the effective band of seismic data. However, this method frequently suffers from instability and poor continuity issues due to neglecting of the spatial dependence among reflectivity at adjacent traces. Although some methods add a lateral constraint item into cost function to consider above spatial correlations, the complicate coupling effect between the triggered two trade-off parameters severely limits the algorithm’s performance. We develop a two-step multichannel reflectivity inversion algorithm (TS-MRI) to retrieve spatially correlated reflectivity while avoiding opting for the two weights simultaneously. In the first step, we apply SSI to fast obtain sparse reflectivity estimation. In the second step, we exploit the result from SSI, a data-driven structural constraint term, and a least-square framework to reconstruct multi-trace reflectivity. The reflection structure characteristics (RSC) estimation plays a key role in building the structural constraint term, which has ability to map the spatial geometrical association in data into inverted reflectivity image. A model and a field data examples confirm the merits of TS-MRI than SSI on guaranteeing the continuity of structures and protecting weak events.
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Six Years Exploring Offshore Newfoundland and Labrador: Insight From Forward Stratigraphic Modeling to Petroleum System Assessment
Authors P. Jermannaud, E. le Guerroué, D. Thomas and G. Perez DragoSummarySince 2014, Nalcor Energy lead with Beicip-Franlab independent resource assessments of the different offshore Newfoundland and Labrador areas ahead of calls for bids.
Each project aimed at conducting an integrated resource assessment study, including the use of Forward Stratigraphic Modeling (FSM) tool.
FSM allows defining and characterizing reservoir, seal and source rock distribution and their heterogeneity in time and space, by assessing the interaction between accommodation space, sediment supply and transport through simulations of various sedimentary processes.
Calibrated to well and seismic data, the model allows testing hypotheses on depositional environment, accommodation history, estimation of eroded sediment volume, sedimentary source dynamics, and sedimentary object styles.
These resource assessments showcased the added value of FSM for oil & gas exploration with:
- definition of the petroleum plays, based on the 4D distribution of main organic-prone sediments, reservoir and seal with respect to the stratigraphic framework;
- generation of 4D Geocube ready for petroleum system modeling to further test hydrocarbon generation/expulsion/migration modeling;
- sensitivity analysis approach, which consisted of testing alternative scenarios of basin subsidence, erosion and sedimentation.
- regional-scale assessment of the geological risk (Common Risk Segment mapping).
- prospect-scale assessment of the geological risk, coupling FSM with Seismic Reservoir Characterization.
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Seismogeological Characteristics and Petroleum Potential of the Siberian Platform Arctic Regions and the Laptev Sea
Authors V. Kontorovich, A. Kalinin, L. Kalinina and M. SolovevSummaryAccording to modern schemes of oil and gas geological zoning, the Arctic regions of the Siberian Platform cover the Anabar-Khatanga and Leno-Anabar oil and gas regions, are located in the extreme north of the Siberian Platform in the north-east of the Krasnoyarsk Region and north-west of the Republic of Sakha (Yakutia). 16850 km of MOGT seismic profiles have been worked out on this territory and deep wells have been drilled in the continental part, a complex analysis of which allows us to build regional models of the geological structure and to clarify the oil and gas potential of this region at a new level.
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The Validity of 2D Models in Thermal Simulation
More LessSummary2D cross-sectional simulation models of the subsurface have been used to investigate processes like reservoir souring, EOR, water flooding, CO2 storage potential and processes in geothermal projects. This paper investigates the validity of these 2D models with a special focus on simulation models that include thermal processes.
Investigation of the validity of 2D models shows that 2D cross-sectional models do not properly reproduce fluid flow or heat flow in an injection-production system. Even though 3D models also carry uncertainties, with 2D models, unnecessary errors are introduced. Therefore, 2D models are not recommended for investigating thermal processes like geothermal projects and reservoir souring simulation.
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Seismic Wave Numerical Simulation in Seafloor Cold Seepage Plume Flow With Bubbly Liquid Acoustic Equation
More LessSummarySeafloor bubble plume in cold seepage is closely related to the distribution of natural gas hydrates, and they can indicate the boundary of the hydrate stable zone, which is an important area of energy exploration in the future. At present, the seismic response of cold seepage plume flow is mainly carried out by numerical simulation. However, the acoustic velocity model with the bubble medium and the random medium theory cannot universally describe the physical properties of the cold seepage, and acoustic wave equation adopted in previous methods is not applicable for the accurate seismic wave numerical simulation. In order to accurately simulate the seismic response and analyze the seismic response characteristics of seafloor cold seepages, the Keller-Miksis bubble vibration model is proposed to describe the motion state of bubbles under the action of acoustic wave. Considering the interaction between bubbles, the new process of cold seepage bubble model is established. On this basis, bubbly liquid acoustic wave equation is introduced into the seismic wave numerical simulation in seafloor cold seepage. The numerical results indicate that the new equation can simulate the cold seepage plume flow in precise term.
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Deep Embedded Clustering As a Seismic Attribute: A Case Study of 2D Crustal-Scale Interpretation
Authors M. Mezyk and M. MalinowskiSummaryDeep embedded K-means clustering algorithm is applied to several 2D crustal-scale seismic profiles to highlight the distribution of reflections and investigate the complexity of geological structures better across the profiles. Such clustering proves to be a great interpretation asset for long, regional profiles, helping to delineate various crustal units.
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A New Q Estimation Method Based on Logarithmic Spectral Simultaneous Inversion
More LessSummaryFrequency domain Q estimation methods usually pick two reflections at different traveltimes, and estimate Q according to the variation of their amplitude spectra. However, the variation of the amplitude spectra is not only affected by the target layer, but also affected by the overburden, which lead to error of Q estimation results. We have developed a novel Q estimation method, called logarithmic spectral simultaneous inversion (LSSI), to address this problem. This proposed method account for the effect of the overburden by picking another adjacent reflection, which is used as a constraint for the Q value estimation in the overburden, and separating attenuations from different layers according to the traveltime through the process of inversion. Q values of both target layer and overburden are estimated simultaneously. Model test and field data application indicate the validity of the method.
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Intelligent Seismic Deblending Based Deep Learning Based U-Net
More LessSummaryBlended acquisition can help improve the acquisition efficiency or enhance the data density. However, blended seismic data which contains information of multiple sources, should first be separated for traditional seismic data processing steps. Thus, we propose a U-net based intelligent deblending algorithm, combined with the traditional iterative strategy in this abstract. The proposed method can obtain the optimal parameters through self-learning while it should be selected by trial and error in traditional method. We train and valid the U-net by using a set of synthetic data with labels, and then parts of field data with labels are used to finetuned it. Finally, the finetuned U-net is used for intelligent deblending of the left field data. The deblending performance is promising compared with the curvelet transform based thresholding method, which demonstrates the validity of the proposed intelligent deblending algorithm in deblending accuracy, stability and efficiency.
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Correcting For Imperfectly Sampled Data in the Iterative Marchenko Scheme
Authors J. Van IJsseldijk and K. WapenaarSummaryThe Marchenko method retrieves the responses to virtual sources in the subsurface, accounting for all orders of multiples. The method is based on two integral representations for focusing and Green's functions. In discretized form these integrals are represented by finite summations over the acquisition geometry. Consequently, the method requires ideal geometries of regularly sampled and co-located sources and receivers. However, a recent study showed that this restriction can, in theory, be relaxed by deconvolving the irregularly-sampled results with certain point spread functions (PSFs). The results are then reconstructed as if they were acquired using a perfect geometry. Here, the iterative Marchenko scheme is adapted in order to include these PSFs; thus, showing how imperfect sampling can be accounted for in practical situations. Next, the new methodology is tested on a 2D numerical example. The results show clear improvement between the proposed scheme and the standard iterative scheme. By removing the requirement for perfect geometries the Marchenko method can be more widely applied to field data.
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