The role of cracks in the nonlinear interaction of a P-wave with an S-wave

Malcolm, Alison and Fehler, Mike and Tencate, James (2015) The role of cracks in the nonlinear interaction of a P-wave with an S-wave. SEG Technical Program Expanded Abstracts 2016, 2016. pp. 3327-3332. ISSN 1949-4645

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Abstract

Cracks play a key role in our ability to produce oil and gas, from micro-scalecracks that enable permeability in tight formations to faults and fractures that compartmentalize reservoirs; our ability to sense and understand them remotely is thus of key importance. We explore the role that cracks play in the nonlinear interaction of propagating waves. We present a laboratory experiment in which a strong S-wave slightly changes the velocity of a lower amplitude P-wave, and use a rock sample with aligned fractures to demonstrate that this signal is strongly dependent on fracture orientation. We build on the linear slip theory to show that the propagating S-wave is indeed able to open the cracks that the P-wave velocity will be most sensitive to. This gives firm, direct evidence that cracks are a controlling factor in the nonlinear elastic properties of rocks, and opens up the possibility of using such signals to remotely map fracture orientations.

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