Study On Seepage Flow In Long Fracture And Well Pattern Optimization In Low Permeability Reservoirs

Due to the poor reservoir properties and small pore throat radius of low permeability reservoirs,problem about water injection and oil production often occurs,which seriously affects the stable production and increase of production,and the benefit is poor.Large-scale fracturing creates long fractures to form high conductivity channels,which can achieve effective water injection development.However,there are still some deficiencies in the research of long fracture conductivity,seepage law and development parameter optimization.This paper carried out the related research to solve the above problems,which provided a certain theoretical support for long fractures.In this paper,considering above factors,combined with fractal theory,the methods of elastic mechanics and equivalent seepage,we thought of the fracture filled with proppant as the combination of capillary channel,quantitatively described the influence of fracture roughness and tortuosity on fluid flow,and referred relevant scholars research on the dynamic changes of the proppant,established the fracture conductivity prediction model considering fracture roughness and tortuosity.By establishing a typical injection-production model,the seepage law and development advantages between two fractured wells were studied.Finally,the geological parameters of typical reservoir were selected to optimize the well pattern parameters,fracture parameters and injection-production parameters.The results show that the flow in the rough and tortuous fracture will form vortices on the bulge of the fracture wall,which will reduce the effective flow area of the fluid and the conductivity of the fracture can be reduced by up to 40.2%,compared with the flat and smooth fracture.Due to a series of dynamic changes such as proppant embedding,deformation,crush,and diagenesis,the conductivity can be reduced to 20%of the initial value at a closing pressure of 50 MPa.With the increase of fracture penetration ratio,the flow form between injection well and production well gradually changes from radial flow to bilinear flow,which can minimize the pressure loss caused by radial flow.The optimal well pattern for the typical model is 500 m×200 m staggered well network,the optimal oil-water well penetration ratio is 0.4,the optimal fracture conductivity is 260×10^-3μm²·m,the optimal injection-production ratio is 1,the reasonable oil production rate is 2.2%,the optimal pressure maintaining level is 1.1,and the synchronous water injection development is expected.