Study on the Productivity of Multi-fractured Horizontal Wells in Ultra-Low Permeability Reservoirs

摘要

Based on the equivalent radius model, a productivity model for ultra-low permeability reservoirs was developed, which considered the influence of the threshold pressure gradient and the variable mass flow in fractures, and the effect of threshold pressure gradient, fracture number, fracture half-length, fracture angel, and fracture distribution on the productivity were analyzed.The results show that the greater the threshold pressure gradient, the greater the effect of it on multi-fractured horizontal well productivity, so the threshold pressure gradient must be accounted to evaluate the productivity in ultra-low permeability reservoirs.With the increase of fracture number, fracture half-length and fracture angel, the productivity increases.In order to obtain higher productivity, the angle between the fracture and horizontal well should be between 75 and 90 degree.When the total half-length of the fracture is certain, reducing the fracture interference, the length of the outer fractures should be bigger than that among the inner fractures.The research results provide a scientific basis for the design of multi-fractured horizontal wells in ultra-low permeability reservoirs.