Impact of stress dependence of elastic moduli and poroelastic constants on earth surface uplift due to injection

Abstract

Hydromechanical models have typically assumed constant stress-independent elastic moduli to estimate, forecast, and history-match earth surface uplift. The effect of stressdependent elastic moduli and poroelastic constant (i.e., Biot coefficient) on Earth surface uplift during injection is investigated in this study. Experimental data gathered for different rock types shows that Biot coefficient and bulk modulus vary in response to Terzaghi effective stress. Stress-dependent elastic modulus was imported to the numerical model representing Berea sandstone. Hydromechanical simulations were performed to model CO 2 injection into the Berea reservoir by incorporating elastic moduli stress dependency. Hydromechanical modeling results show that using stress-independent elastic moduli causes under-estimation of Earth surface uplift due to injection. A decrease in Young's modulus and an increase in Biot coefficient because of injection can contribute to a higher estimated uplift. Neglecting the stress dependency effect could cause an erroneous estimate of potential surface uplift due to injection. The impact of geological properties of Berea and injecting brine instead of CO 2 on surface uplift trend were also investigated.