Geomechanical Modeling to Resolve Velocity Anomalies and Image Distortions below Seafloor with Complex Topography

Birdus, Sergey

doi:10.3997/2214-4609.201400372

Cited by 5 publications

(4 citation statements)

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“…This took into Exploration Geophysics H. Debenham and S. Westlake account the differing overburden pressure of the water column, versus the sediment column (Birdus, 2009). High resolution updates were required in the upper six MBUs in order to resolve large lateral changes in velocity.…”

Section: Model Building For Psdmmentioning

confidence: 99%

Pre-stack depth migration for improved imaging under seafloor canyons: 2D case study of Browse Basin, Australia

Debenham

Westlake²

2014

Exploration Geophysics

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In the Browse Basin, as in many areas of the world, complex seafloor topography can cause problems with seismic imaging. This is related to complex ray paths, and sharp lateral changes in velocity. This paper compares ways in which 2D Kirchhoff imaging can be improved below seafloor canyons, using both time and depth domain processing.In the time domain, to improve on standard pre-stack time migration (PSTM) we apply removable seafloor static time shifts in order to reduce the push down effect under seafloor canyons before migration. This allows for better event continuity in the seismic imaging. However this approach does not fully solve the problem, still giving sub-optimal imaging, leaving amplitude shadows and structural distortion. Only depth domain processing with a migration algorithm that honours the paths of the seismic energy as well as a detailed velocity model can provide improved imaging under these seafloor canyons, and give confidence in the structural components of the exploration targets in this area. We therefore performed depth velocity model building followed by pre-stack depth migration (PSDM), the result of which provided a step change improvement in the imaging, and provided new insights into the area.

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Section: Model Building For Psdmmentioning

confidence: 99%

Pre-stack depth migration for improved imaging under seafloor canyons: 2D case study of Browse Basin, Australia

Debenham

Westlake²

2014

Exploration Geophysics

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“…In practice, we start with building an initial velocity model with the geo-mechanical approach as described by Birdus (2009) to provide a better initial model and then perform several iterations of high-resolution tomography in a topdown, layer-constrained fashion to reduce residual curvature. Dense event picking is essential for highresolution updates.…”

Section: Weighted High-resolution Tomography Workflowmentioning

confidence: 99%

“…This imaging challenge associated with complex shallow geology has been widely observed and various studies have been done to address the issues. Birdus (2009) developed a geomechanical modeling technique to incorporate geostress into the initial velocity model in an area with a complex sea floor. This method serves to provide a better input model for tomography.…”

Section: Introductionmentioning

confidence: 99%

High-resolution tomography for paleo-canyons: a case study in Para-Maranhao Basin, Brazil

Chen

Shen

2012

SEG Technical Program Expanded Abstracts 2012

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The shallow geological complexities in Para-Maranhao Basin, offshore Brazil, characterized by rugose topography and complex V-shaped paleo-canyons directly below the water bottom, bring challenges in velocity model building for prestack depth imaging, especially when using a global grid-based tomography. It is not uncommon to see image distortions, such as non-geological depth undulation and amplitude variations, present after global tomography updates. These distortions can affect the fidelity of reservoir interpretation. Here we propose to use a highresolution tomography workflow with structurally-guided weighting scheme to build a velocity model with better accuracy. The migrated common image gathers are thus flatter, and the image distortions below complex nearsurface overburdens are attenuated.

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“…First, initial velocity models that honor shallow geologic features are very helpful and sometimes critical for tomography to converge quickly to reasonable final models. Birdus (2009) proposed the use of geo-mechanical methods to build initial seabed-canyon models. Arnaud et.…”

Section: Introductionmentioning

confidence: 99%

Velocity model-building challenges and solutions for seabed- and paleo-canyons: A case study in Campos Basin, Brazil

Zhang

Subia

Sun

et al. 2017

SEG Technical Program Expanded Abstracts 2017

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The Campos Basin, offshore Brazil, features complex shallow geology in the forms of pronounced seabed canyons and paleo-canyons. The rapid variations in the velocity field due to these complex shallow geologic features can be difficult for ray-based tomography techniques to resolve, resulting in distorted images in deeper section. Full waveform inversion (FWI) is able to utilize the recorded diving-wave energy to resolve the high-resolution velocity model in these geologically complex areas. Additionally, dip-constrained non-linear slope tomography introduces dip constraints to ray-based residual move-out tomography and is able to capture smallscale velocity anomalies associated with these shallow heterogeneities. A combined workflow of FWI and dipconstrained tomography enabled Chevron to build accurate and detailed velocity models in the Campos Basin, resulting in fewer seismic image distortions. We demonstrate the method using a Campos Basin, Brazil narrow-azimuth streamer dataset.

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Geomechanical Modeling to Resolve Velocity Anomalies and Image Distortions below Seafloor with Complex Topography

Cited by 5 publications

References 0 publications

Pre-stack depth migration for improved imaging under seafloor canyons: 2D case study of Browse Basin, Australia

Pre-stack depth migration for improved imaging under seafloor canyons: 2D case study of Browse Basin, Australia

High-resolution tomography for paleo-canyons: a case study in Para-Maranhao Basin, Brazil

Velocity model-building challenges and solutions for seabed- and paleo-canyons: A case study in Campos Basin, Brazil

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