Analyzing start-up pressure gradient of gas phase from the viewpoint of physical concept and experiment,it concludes that the "threshold pressure effect" is the macroscopic reflection of two-phase seepage resistance when gas flows in tight core with high irreducible water saturation,and the capillary pressure curve and the time-varying relative permeability curve are sufficient to describe this phenomenon quantitatively.So gas phase start-up pressure gradient should not be introduced into model.A seepage mathematical model of tight gas considering the time-varying relative permeability curve,reservoir stress sensibility and start-up pressure gradient of movable water is established,and a new numerical simulator is programmed in which the model is solved with fully implicit finite difference method.Comparison testing between the new simulator and Eclipse software shows a good consistency without considering the special mechanism.Simulation results show that time-varying gas water relative permeability curve increases water production and reduces the period of table gas production.Start-up pressure gradient of movable water reduces daily water production and increases the period of table gas production.Reservoir stress sensibility reduces daily water production and accelerates gas well decline.The migration of irreducible water is an important reason for water produdng.The model considering the time-varying gas water relative permeability curve can forecast the well real production dynamics.%从气相启动压力梯度的物理概念和物模实验角度分析认为,气体通过高束缚水低渗致密岩心时的“阈压效应”实质为气水相间渗流阻力的宏观反映,毛管压力曲线与时变的气水相渗曲线足以定量描述该现象,不应引入气相启动压力梯度.建立了考虑气水相渗时变、储层应力敏感及可动水启动压力梯度的致密气渗流数学模型,用全隐式有限差分方法求解,并编制了数值模拟器.对新模拟器进行了退化测试,并利用新模拟器研究了特殊渗流机理对致密气藏开发的影响及气水相渗时变对实际区块的影响,结果表明:不考虑特殊渗流机理时,新模拟器与Eclipse软件计算结果具有很好的一致性;气水相渗时变会增大气井产水量、减少稳产气时间;可动水启动压力梯度会减少日产水量、增加稳产气时间;储层应力敏感会降低日产水量、提早进入递减期;束缚水的运移是气井产水重要原因之一,考虑气水相渗时变更能反映实际气井生产动态.
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