Interaction of a normally-incident plane wave with a nonlinear poroelastic fracture

Journal Article · Tue Sep 24 00:00:00 EDT 2019 · Journal of the Acoustical Society of America

DOI:https://doi.org/10.1121/1.5124691· OSTI ID:1580913

Nakagawa, Seiji ^[1]; Pride, Steven R. ^[1]; Nihei, Kurt T. ^[1]

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1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

While it has been recognized that a large amplitude incident wave upon a dry fracture can exhibit nonlinear seismic wave scattering due to its stress-dependent mechanical compliance, the impact of pore fluid in the fracture and a fluid-filled poroelastic background medium—features common for fractures in the Earth—are not well understood. As a first step toward an understanding of the nonlinear poroelastic response of elastic waves in fractured media, analytical approximate formulas are used for the amplitude and phase of a normally incident plane wave using a perturbation method, assuming a fluid-filled, highly compliant nonlinear interface embedded in a linear poroelastic solid. The stress-closure behavior of the fracture is modeled by nonlinear, poroelastic displacement-discontinuity boundary conditions (a linear–slip interface). The theory predicts that the static (“Direct current,” or DC) and higher-order-harmonic waves produced by the nonlinear scattering can be greatly reduced by the presence of fluid in the fracture. This, however, depends upon a number of parameters, including fracture compliance, fluid properties (compressibility and viscosity), and the permeability of the background medium, as well as environmental parameters such as the initial fluid pressure and stress acting on the fracture. The static effect produces low-frequency fluid pressure pulses when a finite-duration wave is incident upon the fracture—behavior unique to fluid-filled fractures within a poroelastic medium.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1580913
• Journal Information: Journal of the Acoustical Society of America, Journal Name: Journal of the Acoustical Society of America Journal Issue: 3 Vol. 146; ISSN 0001-4966
• Publisher: Acoustical Society of America
• Country of Publication: United States
• Language: English

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