A new physical model for the pressure sensitivity of unconsolidated sands

Matthew Saul; David Lumley

doi:10.1071/ASEG2012ab119

ISSN: 2202-0586
E-ISSN:

oa A new physical model for the pressure sensitivity of unconsolidated sands
Authors Matthew Saul^a and David Lumley^b
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^a The University of Western Australia, UWA (M004), 35 Stirling Highway Crawley, Perth, WA, , Australia, [email protected] ^b The University of Western Australia, UWA (M004), 35 Stirling Highway Crawley, Perth, WA, , Australia, [email protected]
Publisher: Australian Society of Exploration Geophysicists
Source: ASEG Extended Abstracts, Volume 2012, Issue ASEG2012 - 22nd Geophysical Conference, Dec 2012, p. 1 - 4
DOI: https://doi.org/10.1071/ASEG2012ab119
- Published online: 01 Dec 2012

Abstract

Summary

Knowledge of the pressure dependencies of rock properties in unconsolidated sands is important for accurate time-lapse feasibility studies, pore pressure prediction, and reservoir characterization. A key problem that arises in determining such pressure dependencies is an accurate model at low effective stress. We propose a double exponential model to describe the pressure sensitivity of the bulk modulus (K) or shear modulus (G) for unconsolidated sands. The physical basis for our model relies on observed porosity-depth trends in unconsolidated sands, and the concept of critical porosity. Our new model matches laboratory measurements on unsaturated sand samples that have a range of grain size distributions and compositions. Grain size distribution data is first used to estimate critical porosity, which is then used as a zero effective pressure constraint in the data fitting process. We show that our new model more accurately predicts pressure sensitivity near zero-effective pressure compared to current methods, and is thus more accurate for situations in which core measurements at low effective stresses are not available.

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2012-12-01

2026-01-18

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References

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Article Type: Research Article

Keyword(s): critical porosity; fluid substitution.; pore pressure prediction; Pressure sensitivity; time-lapse seismic; unconsolidated sands

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oa A new physical model for the pressure sensitivity of unconsolidated sands

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