Deformation of fluid-saturated porous rock

Abstract

In-situ rock is often fully saturated or at least has a high fluid content. The presence of pore fluid can affect both the elastic response and the inelastic deformation process. However, testing of fluid-saturated rock is not typically performed, even though rock-fluid interaction is critical in many applications, such as oil and natural gas exploration and recovery procedures. Experimental techniques aimed at the measurements of the parameters that govern the deformation of fluid-filled porous rock were developed. Berea sandstone was tested under the limiting conditions of drained, undrained, and unjacketed response. Saturation methods were applied to the rock at pore pressures of 3 - 4 MPa. Hydrostatic loading and compression experiments, both conventional triaxial and plane strain loading, were performed on the sandstone to investigate isotropic and transversely isotropic poroelastic behavior. Measured parameters were used to calibrate a constitutive model that predicts undrained inelastic deformation from the drained response. The experimental data shows good agreement with the model: the effect of dilatant hardening in undrained triaxial and plane strain compression tests under constant mean stress was predicted and observed. Suggested experimental methods can be, and have been already, implemented for testing rock from the field. Moreover, the developed techniques are applicable for the prediction of deformation and induced seismicity in fluid-filled rock utilized for CO2 sequestration.