The effect of Biot coefficient and elastic moduli stress–pore pressure dependency on poroelastic response to fluid injection: laboratory experiments and geomechanical modeling

Abstract

AbstractBiot coefficient and elastic moduli are typically assumed to have a constant value for analyzing poroelastic effects of fluid injection. To investigate the stress–pore pressure dependency of Biot coefficient and elastic moduli, we conducted a series of laboratory experiments on a porous dolomite core sample from a reef in Michigan basin. We varied the confining stress as well as the pore pressure in the experiments. Then, modeling was performed using analytical poroelastic solutions and a coupled two‐phase flow‐geomechanical numerical simulation (for CO2 injection). The modeling results show that the variability of Biot coefficient and elastic moduli should be included in the geomechanical modeling to accurately predict the poroelastic responses of injection (i.e., stress changes and surface uplift). Using a constant stress‐independent Biot coefficient elastic moduli, which is the assumption in poroelastic modeling, leads to underestimation of the stress change and surface uplift due to injection compared to a realistic stress–pore pressure dependent Biot coefficient, which is updated at each time step of injection modeling. Modeling results indicate that decreasing elastic modulus combined with Biot coefficient increase due to the fluid injection could lead to a larger surface uplift and stress changes in the reservoir. In addition, the stress changes and uplift due to injection are a function of initial in situ stress due to Biot coefficient and elastic modulus stress–pore pressure dependency. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.