Dynamic Features of Nonaqueous Foam in Fracture Systems

Abstract

The use of foam as a fluid for gas mobility control has become increasingly popular due to its effectiveness. However, the destabilization of aqueous foam by oil has led to a growing interest in nonaqueous foam. Despite this, there have been limited studies on the dynamic features of nonaqueous foam in fractures. In this study, we investigate the impact of roughness and fracture width on the flow behavior of non-aqueous foam using both microscopic visualization and macroscopic core flooding techniques. We also uncover the regeneration and regulation mechanisms of non-aqueous foam, while establishing a control group of aqueous foam for comparative purposes. Our experimental results show that as the roughness of the fracture increases, the pressure difference generated by both foams also increases, but decreases as the fracture width increases. Moreover, the optimal gas–liquid ratio for aqueous foam is 2:1, while that of nonaqueous foam is 1:2. Nonaqueous foam tends to be captured and deformed when transported through rough fracture surfaces. This deformation causes necking separation, which eventually leads to the generation of new foam. Furthermore, roughness anchors the foam, prolonging its stay in the fracture and increasing seepage resistance. The presence of kerosene in the fractured shale core reduces the stability of nonaqueous foam, as evidenced by a ∼23.3% decrease in differential pressure.