Dip-constrained tomography with weighting flow for paleo-canyons: A case study in Para-Maranhao Basin, Brazil

Chen, Guang; Hu, Lingli

doi:10.1190/segam2014-0513.1

Cited by 2 publications

(1 citation statement)

References 3 publications

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“…Thus far, techniques for implementing or improving raybased tomography have dominated discussions of velocity model-building strategy for submarine canyons; analysis relies heavily on the quality and density of the residual moveout (RMO) picks to build accurate high-resolutions models (Fruehn et al, 2015). In addition, different techniques such as pick weighting and layer constraints (Sun et al, 2011;Chen and Shen, 2012;Chen and Hu, 2014), reference horizons and offset-consistent dip constraints (Graham and Richard, 2009, Guillaume et al, 2013, Chen and Hu 2014, have been explored to help invert good models.…”

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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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

View full text Add to dashboard Cite

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Delineating Overburden Anomalies through Dip-Constrained Tomography for Improved Reservoir Imaging in an Offshore Carbonate Field

Waqas¹,

Nakayama²,

Benson³

et al. 2016

Day 2 Tue, September 27, 2016

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Overburden (shallow) anomalies such as channels, sink holes, or karst features pose challenges for seismic time imaging, resulting in an obscured image below the anomalies i.e. pull-ups or push-downs. These anomalies can propagate down to the reservoir masking the image and create structural uncertainties. These relatively small scale (< 1 – 2 km) overburden anomalies cannot be resolved with conventional depth imaging usually, based on migration velocity analysis and residual move out (RMO) minimization only. This paper proposes the application of dip-constrained tomography, in combination with RMO tomography to help resolve these shallow anomalies. Although the method has been widely used elsewhere e.g. in offshore Brazil and North Sea (Chen et al., 2012, Guillaume et al., 2013, Carotti et al., 2015 and Hollingworth et al., 2015), this is the first time it has been applied in a carbonate oilfield in offshore Abu Dhabi. An accurate velocity model is required for seismic depth imaging. The velocity model is optimized using a tomographic technique which is a non-linear optimization process with relevant constraints imposed. The data are migrated using an initial velocity model and common image gathers are obtained. RMO is defined in a cost function and non-linear tomography finds a velocity model minimizing the cost function. An additional structural constraint in the form of an offset-dependent dip constraint is introduced in the cost function for minimizing the misfit between the offset-dependent dip of the events and the expected dip. Dip-constrained tomography was able to obtain a high resolution velocity model in the overburden and provided a robust seismic image essentially free of pull-up and push-down effects in the reservoir. The structural uncertainty in the reservoir was subsequently reduced. Inverting the dip term together with RMO term can potentially correct image distortions e.g. pull-ups and push-downs and focus the image simultaneously. The refined subsurface image can help optimize the reservoir model with less structure uncertainty and can enhance the production profile by providing more flexibility in well design and planning. The methodology was applied on a pilot area which gave quite encouraging results and leads to extend the pre-stack depth imaging to a full-field application.

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Dip-constrained tomography with weighting flow for paleo-canyons: A case study in Para-Maranhao Basin, Brazil

Cited by 2 publications

References 3 publications

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

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

Delineating Overburden Anomalies through Dip-Constrained Tomography for Improved Reservoir Imaging in an Offshore Carbonate Field

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