Research on Areal Sweep Efficiency for Rhombus Invert 9-spot Areal Well Pattern of Low-permeability Reservoir

Based on the water flooding theory of low-permeability oil reservoir,the areal sweep efficiency formula for calculating the rhombus invert 9-spot pattern is deduced by the basic formula of low velocity non-Darcy flow and by the flow line integral method and by element analysis method.Accordingly,areal-sweep-efficiency of the injection-production well group can be calculated.It is also applicable to the square invert 9-spot pattern.The application range is wider than the square invert 9-spot pattern.The areal sweep efficiency of one low-permeability reservoir of the Ordos Basin is calculated by the method.The result is close to the real value.