Productivity formulas of conventional reservoir's well-net are based on single-phase flow or oil-water mobility ratio is 1 under the condition of piston water flooding. But this is not consistent with the actual process in low permeability reservoirs. According to the water driving characteristics of areal well pattern injection-production unit, the flow region is divided into three zones in this paper. Productivity formula is derived based on the equivalent flowing resistance method

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... the low permeability reservoir characteristics of oil-water two-phase flow capacity of the flooding pattern. Compare the productivity formula with the conventional productivity formula. The results show that when the dimensionless liquid production index change little with water saturation, close to 1, the two calculated results are consistent; when the dimensionless liquid production index change great with water saturation, much less than 1, the results of conventional capacity formula are obvious big, and the error calculation is increasing with the decreases of the dimensionless liquid production index; The production formula established is more in line with Mobei low permeability reservoirs.