Influence of Formation Pressure Variation on Relative Permeability Characteristics of Oil and Water Phase

Abstract

At present, there are still some disputes on the influence of pressure on the relative permeability of oil and water phase in low permeable reservoirs. This text carried out the displacement experiments to study the influences of effective stress and displacement pressure on the relative permeability. The results indicate that: with the decreasing of displacement pressure, the relative permeability of oil and water and the displacement efficiency become poor; the lower the permeability is, the worse the effective permeability and displacement efficiency are; low permeable reservoirs have strong stress sensitivity, the relationship between permeability and effective stress follows power function; when the reservoir energy drops, the effective stress of rock increases, which causes the physical property worse, and meanwhile the flooding pressure decreases, which ultimately reduce the displacement efficiency, so high energy preserving level is the guarantee of improving the flooding efficiency. The results also indicate that the displacement pressure gradient should consider the actual producing pressure gradient after meeting the requirement of π number, otherwise, the testing displacement efficiency may be larger than the actual. The studying results provide theoretical references for high efficiency development of low permeable oilfields.