Abstract: The ratio of producers'productivity to injectors' injectivity for areal well pattern can greatly affect the choice of reasonable injection mode. With the increase of productivity injectivity ratio, the ratio of injection-production wells should be added properly. With prnductivity much lower than injectivity, inverted nine-spot injection pattern is the optimum selection; with productivity-injectivity ratio approaching 0.25, four-spot pattern will be proper; with productivity close to injectivity, five spot injection pattern will reach higher production rate. The simple formula for calculation of reasonable ratio of injection-production wells is presented. It is suggested that with mobility ratio of low permeability reservoir of less than 1, adopting inversed nine-spot injection pattern is improper, and several main adjust-ment modes for inverted nine spot injection pattern are introduced in this paper.

Key words: areal well pattem, water flooding, four-spot well pattern, five-spot well pattern, nine-spot well patter