Study On Influence Of Drilling Damage On Capacity In Tight Sandstone Gas Reservoir

Tight sandstone gas reservoir is abundant, which is the important areas of natural gas producing reserves growth in the future. However, tight sandstone formation is extremely easily damaged in the process of drilling because of its special geological features. Thus, for the protection of tight sandstone formation and improving of gas production in the process of drilling, it’s significant to make a systematic formation damages analysis under different drilling method and study the effect of drilling damage on gas production. Based on formation damages geological features of tight sandstone, through laboratory tests evaluation and production prediction model, the following are the major points and achievements presented in this dissertation:(1) According to statistical analysis of formation damages geological features of tight sandstone and electron microscope scanning experiment evaluation, the paper analyzed the potential damage type of tight sandstone formation in the process of drilling.(2) The paper carried out tight sandstone formation damage experiment evaluation through corresponding evaluation methods, and analyzed the degree of permeability damage under different drilling mode.(3) In view of the drilling fluid invasion depth of mathematical model under different drilling mode, the paper established steady-state productivity prediction model of different drilling formation damage under the condition of barefoot well completion. Meanwhile, this paper established gas production uncertain evaluation method based on Monte-Carlo, and compiled a calculation procedure of gas production probability model by MATLAB. At last, the paper analyzed the influence of drilling damage factors on steady-state gas production.(4) Setting up the dynamic gas production mathematical model in view of gas seepage and rock deformation, and established a simulation method for the real tight sandstone formation by Weibull distribution. This paper solved the dynamic gas production model by COMSOL software, and analyzed the influence of drilling formation damage on dynamic gas production by taking real gas well parameters for example.This study can provide scientific method for formation damage evaluation and production prediction under different drilling mode, and also provide decision-making method for tight sandstone gas reservoir development under reasonable drilling mode.