Quantification of the impact of pore pressure on relative permeability curves utilizing coreflood unit with gamma ray scanning capability

Abstract

Physics of multiphase flow in porous media at Darcy scale heavily relies on the concept of relative permeability. Moreover, relative permeability is an important input parameter for numerical reservoir simulation for multiphase flow in porous media. Often fixed set of relative permeability curves is applied for the entire complex large-scale reservoir models whilst the pressure typically declines during a field’s production. In this study, we are experimentally focusing on investigating the effect of high pressures on relative permeability curves.We use a state-of-the-art custom-made relative permeability steady-state flow system with integrated gamma-ray scanning. We limit the fluids to a model oil, brine, and rock to avoid any secondary effects of fluid-rock interactions, such as wettability alteration, asphaltenes, and gas-dissolution, miscibility, and interaction of phase behavior and flow. We run the relative permeability scans at a fixed temperature (isotherm) and at several pore pressure values (isobars), such as 2000, 4000, 6000, and 8000 psi with fixed and variable net confining pressures. To be able to perform the analysis more diligently, we observe the in-situ phase saturations via two methods: mass balance and gamma-ray scanning. The resulting relative permeability curves are then compared to each other to examine the impact of pressure. We did not observe significant pressure effect on relative permeability measurements in simple model system used in this work, where minimal fluid-fluid and fluid-rock interactions occur. However, the outcome of this work should not be extended to more complex systems where strong fluid-fluid and rock-fluid interactions take place, such as gas flooding with strong solubility effects, and chemical flooding.Systematic analysis of the pressure effect on relative permeability is extremely scarce in the literature, even though the pressure varies significantly in the reservoir during the lifetime of the field. Therefore, it is essential to understand pressure effect on relative permeability under well controlled laboratory conditions. The outcomes of this paper may help engineers to improve their model predictions during field development and therefore decision-making processes.