A new fluid factor based on rock matrix modulus separation and its application

Abstract Effective fluid factor construction is crucial for identifying hydrocarbon in reservoir predictions. However, the coupling of pore fluids, rock matrix, and porosity jointly influences the elastic properties of rocks, which limits applicability of fluid factors related to elastic attributes. We derive a new fluid factor to separate the differential responses of the elastic modulus among the saturated rock, dry rock framework, and rock matrix. Based on the influence pattern of matrix modulus, porosity, and pore structure on the dry rock modulus, the effects of porosity and the rock matrix are eliminated by using the ratio of pore structure parameters. The difference between the dry rock bulk modulus and the saturated rock bulk modulus is introduced to highlight the effect of pore fluids, thereby obtaining the ratio of shear modulus and bulk modulus based on matrix modulus separation, which is the fluid factor MKRM. Rock-physics model tests on sandstone reservoirs indicate that MKRM is more sensitive to the pore fluid types than parameters such as P-wave impedance, Vp/ Vs, Poisson’s ratio, λρ, and the Gassmann fluid term f. In field data application, MKRM successfully distinguishes oil and water zones, significantly improving the accuracy of fluid identification in sandstone reservoirs.