Role of Well Operations and Multiphase Geomechanics in Controlling Fault Stability During CO2 Storage and Enhanced Oil Recovery

Abstract

AbstractCO2 injection in active oil fields is a technology proposed for industrializing carbon storage operations. However, monitoring CO2 migration, oil recovery, and mechanical deformation within caprock and on faults is a challenging problem in large‐scale storage‐enhanced oil recovery operations due to intersecting faults, multiphase flow effects, and wells with complex production‐injection schedule. We develop and demonstrate a methodology based on our coupled modeling framework to monitor the movement of CO2, hydrocarbons and water, and the associated evolution in mechanical stability of faults during CO2 storage‐enhanced oil recovery in the Farnsworth Unit oil field in Texas, United States. The methodology honors geological, geophysical, and production‐injection data acquired in the field over six decades. Differential depletion from hydraulically isolated fault compartments followed by water and CO2 injection‐induced overpressure causes volumetric contraction and expansion of the reservoir, and changes in the total and effective stresses in the overburden‐reservoir‐underburden complex. CO2 migrates upward to accumulate near top of the geologic structure, and water migrates downward to pressurize the faults. Three‐dimensional changes in the pressure and stress fields in the system lead to changes in the shear and effective normal tractions on three major faults compartmentalizing the field. Evolution in fault tractions is used to compute the evolution in the Coulomb failure function of the faults to quantify induced‐slip tendency under production and injection. We explain the spatial heterogeneity and time variability of Coulomb failure function in terms of well location heterogeneity and well rate variability.