Simulation of solvent treatments for fluid blockage removal in tight formations using coupled three-phase flash and capillary pressure models

Abstract

Water and condensate blockage near production wells in unconventional reservoirs can significantly reduce oil and gas production rates. This paper presents a new approach for more accurate modeling of liquid blockage in tight oil and gas reservoirs and investigates the use of solvents for blockage removal. A cubic equation of state is used to model mixtures of solvent, hydrocarbons and water that form up to three phases. The three-phase flash model is coupled with a three-phase capillary pressure model to account for the effect of capillary pressure in confined space. The capillary pressure function includes the impact of several important petrophysical properties such as pore size distribution and wettability. A compositional simulator is used to demonstrate the importance of the new phase behavior model. Single- and multi-cycle processes of methanol, dimethyl ether or CO2 injection are simulated to remove liquid blockage and increase production rate in tight oil/gas reservoirs. Simulation results show that DME is more efficient than methanol and CO2 for removal of liquid blockage in tight oil/gas reservoirs because DME is miscible with both oil and water under the simulated reservoir conditions.