Elastic and inelastic deformation of fluid-saturated rock

rsta.royalsocietypublishing.org Research Cite this article: Makhnenko RY, Labuz JF. 2016 Elastic and inelastic deformation of fluid-saturated rock. Phil. Trans. R. Soc. A 374: 20150422. http://dx.doi.org/10.1098/rsta.2015.0422 Accepted: 27 May 2016 One contribution of 12 to a theme issue ‘Energy and the subsurface’. Subject Areas: civil engineering, geophysics, engineering geology Keywords: poroelasticity, drained and undrained response, unjacketed bulk moduli, plane-strain compression, dilatant hardening Author for correspondence: Joseph F. Labuz e-mail: [email protected] † Present address: Laboratory of Soil Mechanics, Chair ‘Gaz Naturel’ Petrosvibri, Swiss Federal Institute of Technology in Lausanne, EPFL ENAC IIC LMS, GC Station 18, 1015 Lausanne, Switzerland. Elastic and inelastic deformation of fluid-saturated rock Roman Y. Makhnenko † and Joseph F. Labuz Department of Civil, Environmental and Geo- Engineering, University of Minnesota, 500 Pillsbury Drive SE, Minneapolis, MN 55455, USA JFL, 0000-0002-7549-0644 In situ rock is often saturated with fluid, the presence of which affects both elastic parameters and inelastic deformation processes. Techniques were developed for testing fluid-saturated porous rock under the limiting conditions of drained (long- term), undrained (short-term) and unjacketed (solid matrix) response in hydrostatic, axisymmetric and plane-strain compression. Drained and undrained poroelastic parameters, including bulk modulus, Biot and Skempton coefficients, of Berea sandstone were found to be stress dependent up to 35 MPa mean stress, and approximately constant at higher levels of loading. The unjacketed bulk modulus was measured to be constant for pressure up to 60 MPa, and it appears to be larger than the unjacketed pore bulk modulus. An elasto-plastic constitutive model calibrated with parameters from drained tests provided a first-order approximation of undrained inelastic deformation: dilatant hardening was observed due to pore pressure decrease during inelastic deformation of rock specimens with constant fluid content. This article is part of the themed issue ‘Energy and the subsurface’. 1. Introduction The presence of pore fluid plays an important role in a wide variety of geophysics and geoengineering problems. These include earthquake precursory processes [1,2], hydraulic fracturing [3–5], water-level changes in wells and tide effects on compressible aquifers [6,7], to name a few. Oil and gas exploration relies 2016 The Author(s) Published by the Royal Society. All rights reserved. on August 30, 2017 http://rsta.royalsocietypublishing.org/ Downloaded from

Elastic and inelastic deformation of fluid-saturated rock

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poroelasticity

drained and undrained

unjacketed bulk moduli

planestrain compression

dilatant hardening