Anisotropic velocity model building using rock physics: Comparison of compaction trends and check‐shot‐derived anisotropy in the Gulf of Mexico

Bachrach, Ran; Liu, Yangjun Kevin; Woodward, Marta; Zradrova, Olga; Yang, Yi; Osypov, Konstantin

doi:10.1190/1.3627619

Cited by 27 publications

(6 citation statements)

References 3 publications

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“…Also, the anisotropic parameter variances are smaller for low velocities than for high velocities. This anisotropic trend has been calibrated and validated with well data in this study area (Bachrach et al 2011b). The stochastic results are fit to a multi-Gaussian distribution for different velocity ranges.…”

Section: Methodsmentioning

confidence: 65%

“…Build a prior mean (initial) model with a compacting shale model, calibrated with all available well data in the area (Bachrach et al, 2011b). 2.…”

Section: Methodsmentioning

confidence: 99%

“…A mini-basin was selected for this test, where the compacting shale model is expected to be valid. The workflow started with building an initial VTI model using a compacting shale model, calibrated with all available well data in the area (Bachrach et al, 2011b). After the deterministic rock physics model was built, stochastic rock physics modeling was performed to generate the prior model covariance function.…”

Section: Case Studymentioning

confidence: 99%

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Application of the Rock Physics Model in Anisotropic Seismic Velocity Model Building and Quantitative Reservoir Structural Uncertainty Analysis: Gulf of Mexico Case Study

Yang¹,

Osypov²,

Bachrach³

et al. 2013

All Days

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Accurate anisotropic seismic velocity model building is the key to the success of seismic depth imaging projects in complex geological settings. Tomography has been an industry standard velocity model building tool for decades, but simultaneously solving for P-wave velocity, epsilon, and delta with surface seismic data only is an underdetermined inverse problem and unstable. The ambiguity in seismic migration velocity model leads to structural uncertainty in seismic image and is carried over to uncertainty in reservoir modeling. In this paper, we introduce a new method using rock physics compaction modeling of sandy shales to constrain the anisotropic tomography. An effective-media rock model was calibrated with well data for sedimentary basin and was used to build initial vertical transverse isotropy (VTI) velocity models. By running a stochastic simulation of the rock physics model, covariance functions were extracted from possible combination of to P-wave velocity, epsilon, and delta as a priori information to constrain the following anisotropic tomography updates and uncertainty analysis. The case study area is in the Green Canyon in the Gulf of Mexico. The results show that we can successfully constrain three parameters of tomography with the prior information from rock physics. We also performed seismic uncertainty analysis to assess the non-uniqueness of the tomography solutions. 500 velocity models with equivalent residual move out were generated and used to map migrate the reservoir structures. The gross rock volume P10, P50 and P90 were calculated from these 500 realizations to demonstrate the reduction of uncertainty from the rock physics constraints.

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Section: Methodsmentioning

confidence: 65%

“…Build a prior mean (initial) model with a compacting shale model, calibrated with all available well data in the area (Bachrach et al, 2011b). 2.…”

Section: Methodsmentioning

confidence: 99%

Section: Case Studymentioning

confidence: 99%

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Application of the Rock Physics Model in Anisotropic Seismic Velocity Model Building and Quantitative Reservoir Structural Uncertainty Analysis: Gulf of Mexico Case Study

Yang¹,

Osypov²,

Bachrach³

et al. 2013

All Days

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“…Locally, the lithology determines the correlation/covariance among the VTI parameters. These correlations can be measured by stochastic rock physics modeling using the well logs as input (Bachrach et al, 2011). Figure 1.8 shows the rock physics objective function based on a compacting shale model.…”

Section: Ray-based or Wave-equation-based Tomographymentioning

confidence: 99%

“…As an example, the Gulf of Mexico is populated with large shale deposits. Therefore, rock physics principles can be used to estimate the range of anisotropic parameters considering a compacting shale model (Bachrach et al, 2011). As demonstrated in Appendix B, the rock physics stochastic modeling for shale anisotropy shows that in the shallow sediments, a high velocity zone is generally collocated with sand layers where the anisotropy is low.…”

Section: Wemva With the Rock Physics Regularizationmentioning

confidence: 99%

Wave-equation migration velocity analysis for VTI models

Li¹,

Biondi²,

Clapp³

et al. 2014

GEOPHYSICS

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Wave-equation migration velocity analysis (WEMVA) is a powerful technique for robust velocity model building when the subsurface is complex and the starting model is far from true. However, this traditional isotropic WEMVA technique cannot explain anisotropic wave phenomenon, which has significant effects when the reflectors are steeply dipping and/or the waves are traveling at large angles. Furthermore, errors in the anisotropic parameters cause similar defocusing as errors in isotropic velocity. Any defocusing caused by anisotropy may be translated to false updates in the isotropic velocity, which lead to further mispositioning and misinterpretations. However, simple extension of the isotropic WEMVA to the anisotropic medium cannot provide an unique and reliable solution due to the nonlinear and underdetermined nature of the anisotropic model building problem. Many anisotropic models with vastly different geological interpretations may explain the surface seismic data equally well. This thesis addresses these issues by including anisotropic effects in WEMVA and by integrating other useful information from geology and rock physics to better regularize the inversion. First, I extend the isotropic WEMVA method to the anisotropic medium to evaluate and update the anisotropic Earth models. Instead of the industry standard ray-based tomographic methods, the anisotropic WEMVA technique uses wavefields as information carrier to handle both the complex subsurface and the frequency-dependent behavior of the wave propagation. I include the geological information using steering filters to regularize the gradients. Both synthetic and field 2-D examples show that the anisotropic WEMVA technique can resolve the errors in both velocity and anisotropic parameters. Consequently, the migration images are vi

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Quantitative Analysis of Geopressure for Geoscientists and Engineers

Dutta

Bachrach

Mukerji

2021

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Geopressure, or excess pore pressure in subsurface rock formations that is higher than the hydrostatic pressure, is a worldwide phenomenon which impacts hydrocarbon resource estimation, drilling and drilling safety in operations. This book provides a comprehensive overview of geopressure analysis bringing together rock physics, seismic technology, quantitative basin modeling and geomechanics. It provides a fundamental physical and geological basis for understanding geopressure by explaining the coupled mechanical and thermal processes. It also brings together state-of-the-art tools and technologies for analysis and detection of geopressure, along with the associated uncertainty. Prediction and detection of shallow geohazards and gas hydrates is also discussed and field examples are used to illustrate how models can be practically applied. With supplementary MATLAB® codes and exercises available online, this is an ideal resource for students, researchers and industry professionals in geoscience and petroleum engineering looking to understand and analyse subsurface formation pressure.

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Anisotropic velocity model building using rock physics: Comparison of compaction trends and check‐shot‐derived anisotropy in the Gulf of Mexico

Cited by 27 publications

References 3 publications

Application of the Rock Physics Model in Anisotropic Seismic Velocity Model Building and Quantitative Reservoir Structural Uncertainty Analysis: Gulf of Mexico Case Study

Application of the Rock Physics Model in Anisotropic Seismic Velocity Model Building and Quantitative Reservoir Structural Uncertainty Analysis: Gulf of Mexico Case Study

Wave-equation migration velocity analysis for VTI models

Quantitative Analysis of Geopressure for Geoscientists and Engineers

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