Gas and water distribution characteristics of water-driven gas process in tight sandstone gas reservoirs: A microscale study by molecular simulation and experiment

Abstract

Predicting gas and water distribution is an essential step in developing gas reservoirs. This study aims to study the characteristic distribution law of gas and water during waterflooding, which are important in wettability alteration to enhance gas reservoir recovery. Herein, we report a novel method that uses molecular dynamics (MD) associated with a microscopic waterflooding experiment to obtain the characteristic distribution law of gas and water in porous media. We show that this approach may better understand the relationship between gas and water in porous media than conventional technologies. The waterfront in the hydrophilic channel is 13.3 Å more advanced than that in the neutral channel, indicating that the water displacement efficiency in hydrophilic channels exceeds that in neutral channels. Meanwhile, the water flows mainly along the walls of the pores and reduces the diameter of the permeate channel in hydrophilic porous media. While in neutral porous media, the above phenomenon is significantly weakened, and the waterflooding front is relatively consistent. Most importantly, the experimental and simulation results are consistent, and a quantitative evaluation of the gas–water distribution in porous media is given. Additionally, technologically, wettability directly affects the distribution characteristics of fluids in porous media, and changing the wettability characteristics of reservoir rocks is beneficial to delaying the waterflooding front. This approach provides an essential theoretical basis for developing water-driven gas reservoirs.

Keywords

• Gas reservoir
• Tight sandstone
• Waterflooding
• Molecular simulation