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水平井压裂开发是提高低渗致密气藏产量和采收率的重要手段。低渗致密气藏存在应力敏感性,由于储层压力下降,造成近井地带孔隙度、渗透率等物性参数降低,裂缝宽度减小甚至闭合,地下流体渗流能力下降,影响压裂水平井的开发效果。从室内实验出发,研究了低渗致密气藏应力敏感性,多次升降压进一步加剧了裂缝渗透率应力敏感程度,储层和裂缝渗透率应力敏感损害具有不可逆性。采用压裂水平气井的生产动态分段拟合方法和试井分析研究了应力敏感参数变化规律:随生产时间增加、地层压力降低,地层渗透率逐步降低,压裂裂缝半长逐渐变短,裂缝导流能力下降,表现出较强的应力敏感性。单井动态分析和数值模拟研究表明:随应力敏感效应增强,水平井压裂稳产期采出程度和采收率降低幅度变大;随着配产提高,应力敏感效应影响增强;低渗致密气藏应控制合理生产压差,减少应力敏感对储层的伤害。
Horizontal well fracturing is an important means to improve the yield and recovery of low-permeability tight gas reservoirs. The low permeability tight gas reservoirs have stress sensitivity. Due to the decrease of reservoir pressure, physical properties such as porosity and permeability in near-wellbores decrease, the width of fractures decreases or even closes, and the seepage capacity of subsurface fluid decreases, which affects the development of fractured horizontal wells effect. Based on the laboratory experiments, the stress sensitivity of low permeability tight gas reservoirs has been studied, and the pressure sensitivity to fracture permeability further aggravate the stress sensitivity of reservoirs and fractures. Stress-sensitive damage to reservoir and fracture permeability is irreversible. The production dynamic section fitting method and well test analysis of fractured horizontal gas wells were used to study the variation of stress sensitive parameters. With the increase of production time, the formation pressure decreased, the permeability of formation gradually decreased, the half length of fracturing fractures became shorter, Flow conductivity decreased, showing a strong stress sensitivity. The results of single well dynamic analysis and numerical simulation show that with the increase of stress sensitivity effect, the recovery rate and recovery rate of horizontal well fracturing during the stable production period become larger. With the increase of production allocation, the effect of stress sensitivity effect increases. The reservoir should control the reasonable production pressure difference and reduce the stress sensitivity to the reservoir damage.