Abstract: Permian Lucaogou Formation(P₂l)in Jimusaer(JMSE)sag of Karamay oilfield is a typical representative of tight oil reservoirs in Junggar Basin.Staged fracturing technology is commonly used to improve the productivity of single well.While previous researches were more concentrated on the cases of vertical fractures,the vertical fracture model could not explain the actual data in the blocks.At the same time,the theoretical and experimental studies show that horizontal cracks are easy to form during the process of fracturing according to the matching relationship between natural fracture azimuth and geostress.Therefore there is a lack of theoretical guidance in study area.Based on the law of conservation of mass and considerations of starting pressure gradient,pressure sensitivity and finite conductivity fractures,a dimensionless mathematical model has been set up to study the flow in the multistage horizontal fracturing fractured well in dual porosity and single permeability reservoir in this paper.And numerical solutions of the model are obtained by using implicit diffe-rence method and conjugate gradient algorithms.The effects on unsteady productivity of starting pressure gradient,formation heterogeneity coefficient,interporosity flow coefficient,pressure sensitive coefficient,conductivity and the number of cracks are studied through numerical simulation in turn.Research results show that the fracture parameters and formation parameters affect the productivity curves.So it is necessary to consider both fracture parameters and the pressure decline reasonably,as choosing an appropriate fracturing scheme to obtain maximum productivity.

Key words: starting pressure gradient, double porosity media, multistage fractured, horizontal fracture, productivity analysis, tight oil reservoir