Poroelastic modeling of basement fault reactivation caused by saltwater disposal near Venus, Johnson County, Texas

Abstract

To assess the potential for fault reactivation in response to wastewater injection near Venus, Texas, we conducted fully coupled 3D poroelastic finite element simulations for a site-specific geomechanical analysis. We find that simulations using the best estimates of in situ stress azimuth and fault orientation, and the Byerlee’s friction coefficient of 0.6 do not predict fault reactivation, in contrast to observed seismicity patterns. Increasing the maximum horizontal stress azimuth by 10° and the basement fault dip by 5°, both within the uncertainty space of the input parameters, and lowering the friction coefficient of the fault in the basement to 0.35, leads to fault reactivation in the basement as observed. Using the same model geometry but a friction coefficient of 0.6 leads to fault reactivation within Ellenburger, which is inconsistent with observed hypocenter depths at Venus. Expanding the model domain from 5 disposal wellbores to 35 increases the excess pore pressure which favors basement fault reactivation. These simulations demonstrate the sensitivity of geomechanical models of fault reactivation in response to injection requiring high-quality field parameters and help refine the azimuths of the horizontal stresses, the basement fault dip, and the basement fault friction coefficient on the basis of earthquake hypocenter temporal distribution.