Comprehensive Experimental and Simulation Studies on Capillary Pressure in Unconventional Production and CO2 Sequestration

Abstract Capillary pressure measurements on shale and tight core samples have revealed that this parameter can reach hundreds or even thousands of psi at reservoir conditions. A high pressure difference between the fluid phases can significantly affect the multiphase flow in the reservoir, but this parameter is usually neglected in analytical and numerical unconventional reservoir modeling. This study presents a systematic and comprehensive evaluation on the coupled effects of capillary pressure and wettability on unconventional production and CO2 sequestration. Mercury injection capillary pressure (MICP) measurements were performed on hundreds of Permian Basin core samples based on facies-driven selection criteria. Both mercury intrusion (pressurization) and extrusion (depressurization) were recorded for all samples to represent drainage and imbibition processes, respectively. The exhaustive experimental dataset was used to create type drainage-imbibition curves for capillary pressure and relative permeability in six dominant facies in the Permian Basin. Systematic field-scale mechanistic simulations were performed to evaluate the effect of all integrated parameters on oil production and sequestration. Simulation results show that capillary pressure decreases water cut in water-wet formations and increases it in oil-wet reservoirs. In a long-term CO2 sequestration scenario, high displacement pressure in the matrix constrains gas propagation and storage capacity in shale rocks.