压裂气井水锁伤害解除的数值模型研究

低渗透凝析气藏一般需要实施水力压裂措施后才能进行有效地开发，但大量室内实验和现场实践表明，压裂过程中往往会产生压裂工作液对储层的伤害，特别是在低渗透常压或异常低压油气藏中，压降常常与毛细管力在数量级上大小相当，故在进行一些修井作业及水力压裂后会出现气藏产量递减的现象。在低渗透凝析气藏压裂过程中,压裂液沿裂缝壁面进入气藏后将会产生气水两相流动，改变原始含气饱和度，毛细管压力使得流体流动阻力增加及压裂后返排困难，如果气层压力不能克服升高的毛细管力，就会使压裂液无法排出，出现严重的水锁效应。利用气体饱和水后的蒸发作用解除水锁伤害的机理，建立了压裂气藏水锁伤害模型，并选取岩样进行了研究，结果认为蒸发速度越大，温度越高，渗透率越大，压降越大水锁伤害解除得就越快，压裂气井中的水基流体的滤失会对压裂气井产能造成严重伤害。

A Study on the Numerical Model for Water-lock Removal of Fractured Gas Wells

In general,low-permeability gas condensate can only be effectively recovered by hydraulic fracturing, whose working fluid causes damages to the reservoir formation.Especially in low-permeability,normal or subnormal pressure oil and gas reservoirs,whose formation pressure has comparable order of magnitude with the capillary pressure,gas production decreases after workover or hydraulic fracturing.During the fracturing of low-permeability gas condensate reservoirs,gas-water two-phase flow occurs when the working fluid goes into the formation along the fractures,changing the original gas saturation and increasing the capillary pressure.If the pressure of the gas zones cannot overcome the increased capillary pressure,it is hard for the fracturing fluid to flow back,resulting in serious water-lock effect.In this paper,a numerical model for fractured reservoirs with water-lock effect was built based on the mechanism of gas evaporation after being saturated by water.Rock samples were selected for this study,the results show that the water-lock can be removed quicker under higher evaporation rate,temperature,permeability and pressure decline;filtering of the water-based fluid used for fracturing causes serious damages to the deliverability of the fractured gas wells.