Characteristics of tight oil reservoirs and their impact on seepage flow from a nonlinear engineering perspective

Abstract In order to clarify the characteristics of tight oil reservoirs and their impact on seepage, we conducted a comprehensive analysis of the reservoir characteristics of the Chang-7 tight sandstone using advanced equipment such as X-ray diffractometers and high-pressure mercury injection devices from the perspective of nonlinear engineering. We studied the effect of reservoir characteristics on oil and water seepage. The results show that tight cores are mainly quartz arenite and feldspar arenite with high clay mineral content. They have abundant irregular, disconnected pore spaces and micro-fractures, leading to low permeability and poor physical properties. Tight cores are stress-sensitive, with core permeability decreasing as effective pressure increases. An exponential fitting function can effectively reflect the relationship between permeability and effective stress of tight sandstone cores in this area. As the air-measured permeability of the core increases, the start-up pressure gradient first decreases sharply and then gradually stabilizes. The oil–water two-phase start-up pressure gradient and permeability have a power relationship: G = 5.66 × 10 −4 K −1.42 . For tight cores, a slight increase in permeability can significantly reduce the start-up pressure gradient. This study provides a theoretical basis and technical support for the efficient development of tight oil reservoirs from a nonlinear engineering perspective, which helps to optimize development strategies and provide ideas to enhance tight oil reservoir recovery.