Keywords: 
• low permeability reservoir /
• non-linear seepage flow /
• COMSOL software /
• square inverted nine-spot pattern /
• fractured fissure

Abstract: The non-linear seepage law is shown by the fact that, when fluid flows at a low rate, the seeping rate is not in a straight line with the relation curve of pressure gradient and is not through the original point, that is, when the pressure gradient is relatively small, the fluid seeping rate may be zero. The smaller the permeability of a reservoir is, the more obvious the non-linear seepage feature is. In order to understand the law of non-linear seepage in low-permeability oilfields and its effect on oilfield production, a single-phase uncompressible fluid stable seepage differential equation was inferred based on the continuous model which described the low-rate non-linear seepage law. Meanwhile, the COMSOL software which is widely used in fluid mechanics was used to simulate the square inverted nine-spot pattern seepage law of low permeability oilfields. The COMSOL simulation result clearly shows the difference in distribution of flow lines of square inverted nine-spot vertical well pattern and fracturing pattern as well as equipotential line and the law of changes of pressure affected area with fracture length and the angle between the fracture and well array during fracturing. The simulation result shows that, under non-linear seepage, the equipotential line is not circularly distributed. After a straight well is fractured, the pressure affected area increases apparently. The fracture length and the angle between the fracture and well array both will affect the pressure affected area.