Abstract: Low permeability reservoir is not only of existence of threshold pressure gradient, but also could be deformed when the reservoir permeability exponentially decreases with formation pressure decline. This phenomenon most occurred in reservoirs with abnormal pressure and low or super-low permeability. Based on the pseudosteady state theory of non-Darcy flow and deformed media percolation and relative flow behavior equation of oil and liquid phases, the three-phase flow IPR curves with maximum flow rate point in low permeability and pressure sensitivity oil reservoir are derived, by which the allowable minimum flowing pressure in oil well o reservoir can. be calculated. Also, combining with the production data from Puxi oil field in Daqing, the threshold pressure gradient, deformation cofficient, drainage radius, average formation pressure and water cut that affect the reservoir productivity are studied. The results show that the threshold pressure gradient, deformation coefficient have remarkably influences on the reservoir productivity and the allowable minimum flowing pressure. This method can be used to effectively evaluate and forecast the variation of productivity in oil reservoir with low permeability and pressure sensitivity, meanwhile, provide bases for determination of reasonable flow pressure and routine of work as well as sufficiently displaying well flow capacity.

Key words: low permeability reservoir, threshold pressure, starting pressure, stress, productivity, influence, effect