Constitutive Characteristics of Relative Permeability of Tight Sandstone Gas Reservoirs Based on Data-Driven Analyses

Relative permeability is critical for describing two-phase flow mechanisms in tight sandstone gas reservoirs. Although massive efforts have been devoted to investigating the influencing factors of tight sandstone relative permeability, no unified understanding resulted from its complex petrophysical properties. Thus, elucidating the constitutive characteristics within relative permeability is essential for comprehending complex and even contradictory two-phase flow phenomena. In this study, we collected and collated 238 experimental relative permeability data groups, statistically analyzing their constitutive characteristics. Results show that the maximum water relative permeability is significantly smaller than the maximum gas relative permeability (krg,max). Interestingly, krg,max values larger than 1.0 are identified in tight sandstone gas reservoirs. The crossover relative permeability and saturation (krc and Swc) are mainly distributed in 0.01–0.02 and 70%–100%, respectively, suggesting exceptionally poor two-phase flow ability. Moreover, irreducible water saturation (Swi) larger than 75% causes an extremely small two-phase flow region (Swt). Larger maximum relative permeability corresponds to smaller Swi and Swc, and larger Swt. Strong hydrophilicity inhibits two-phase flow. The influences of porosity and absolute permeability on relative permeability were also characterized. The two-phase flow region is constrained due to tiny pore size and high hydrophilicity, thus the effect of absolute permeability on relative permeability becomes pronounced.