Pore-scale systematic study on the disconnection of bulk gas phase during water imbibition using visualized micromodels

Abstract

When water imbibes into tight rocks, the disconnection of bulk gas phase will significantly impact the performance of gas recovery. In this work, we have conducted a systematic micromodel study on the disconnection of gas phase during water imbibition. Seven types of micromodels were designed that can geometrically mimic basic pore structures of a tight sandstone. Then, we conducted capillary-dominant imbibition experiments and analyzed the effects of pore geometry and pore-throat ratio on the transient evolutions of gas–water interfaces. Our pore-scale results reveal that snap-off and bypassing flows are the two main mechanisms that determine disconnection and entrapment of the gas phase. Moreover, we qualitatively linked the pore-scale two-phase displacements to the core-scale “permeability jail” phenomenon (i.e., nearly immobile of non-wetting and wetting phases across a wide range of saturation values). Our study will enrich the knowledge of entrapment behaviors of the gas phase during water imbibition into tight formations.