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Book Chapter

Borehole Geophysics and Rock Properties: Rock-physics diagnostics of depositional texture, diagenetic alterations, and reservoir heterogeneity in high-porosity siliciclastic sediments and rocks — A review of selected models and suggested work flows

By
Per Avseth
Per Avseth
1Odin Petroleum, Bergen, Norway. E-mail: per.avseth@odin-petroleum.no.
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Tapan Mukerji
Tapan Mukerji
2Stanford University, Energy Resource Engineering Department, Stanford, California, U.S.A. E-mail: mukerji@stanford.edu.
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Gary Mavko
Gary Mavko
3Stanford University, Department of Geophysics, Stanford Rock Physics Laboratory, Stanford, California, U.S.A. E-mail: mavko@stanford.edu; dvorkin@stanford.edu.
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Jack Dvorkin
Jack Dvorkin
3Stanford University, Department of Geophysics, Stanford Rock Physics Laboratory, Stanford, California, U.S.A. E-mail: mavko@stanford.edu; dvorkin@stanford.edu.
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Published:
January 01, 2010

Abstract

Rock physics has evolved to become a key tool of reservoir geophysics and an integral part of quantitative seismic interpretation. Rock-physics models adapted to site-specific deposition and compaction help extrapolate rock properties away from existing wells and, by so doing, facilitate early exploration and appraisal. Many rock-physics models are available, each having benefits and limitations. During early exploration or in frontier areas, direct use of empirical site-specific models may not help because such models have been created for areas with possibly different geologic settings. At the same time, more advanced physics-based models can be too uncertain because of poor constraints on the input parameters without well or laboratory data to adjust these parameters. A hybrid modeling approach has been applied to siliciclastic unconsolidated to moderately consolidated sediments. Specifically in sandstones, a physical-contact theory (such as the Hertz-Mindlin model) combined with theoretical elastic bounds (such as the Hashin-Shtrikman bounds) mimics the elastic signatures of porosity reduction associated with depositional sorting and diagenesis, including mechanical and chemical compaction. For soft shales, the seismic properties are quantified as a function of pore shape and occurrence of cracklike porosity with low aspect ratios. A work flow for upscaling interbedded sands and shales using Backus averaging follows the hybrid modeling of individual homogenous sand and shale layers. Different models can be included in site-specific rock-physics templates and used for quantitative interpretation of lithology, porosity, and pore fluids from well-log and seismic data.

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Contents

Geophysical References Series

Geophysics Today: A Survey of the Field as the Journal Celebrates its 75th Anniversary

Sergey Fomel
Sergey Fomel
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Society of Exploration Geophysicists
Volume
16
ISBN electronic:
9781560802273
Publication date:
January 01, 2010

GeoRef

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