异常高压气藏气水两相流井产能分析方法

摘要

提出了综合考虑气水两相渗流能力变化、储集层与流体的弹性驱动能量和应力敏感引起的储集层物性变化等因素的异常高压气藏气水两相流井产能分析方法,并结合实例分析了各因素对产气量的影响.基于广义达西公式和质量守恒定律建立了考虑储集层应力敏感和气水两相渗流能力变化的稳态及非稳态渗流数学模型,推导了相应的产气量方程.实例分析结果表明:储集层含水率上升造成气相渗流能力减小,导致产气量降低,在气水两相流井产能评价过程中不能忽视气水两相渗流能力变化对产气量的影响;生产压差较小时产气量随储集层应力敏感性增强变化不大,而生产压差较大时产气量随储集层应力敏感性增强显著减小,对于应力敏感性气藏,初期生产压差不宜过高.%A productivity analysis for gas-water wells in abnormal overpressure gas reservoirs,considering seepage capability changes of gas-water two phases,elastic drive energy of reservoir and fluid,physical property changes caused by stress sensitivity of reservoir etc,is proposed,and the influences of various factors on gas production rate are analyzed by practical examples.Based on generalized Darcy formula and the law of conservation of mass,mathematical models of steady-state and unsteady-state seepage considering stress sensitivity of reservoirs and seepage capability changes of gas-water two phases are established,then,corresponding formulas of gas production rate are deduced.Results of practical example analysis show that:the increase of reservoir water content causes decrease of seepage capability of gas phase,and thus declining the gas production rate,so the influence of seepage capability changes of gas-water two phases on gas production rate cannot be ignored in the process of productivity evaluation for gas-water wells;gas production rate has smaller variations with the increase of stress sensitivity when production pressure drop is small,while gas production rate decreases significantly with the increase of stress sensitivity when production pressure drop is large.Therefore,the production pressure drop of gas wells at the beginning of the development should not be too high for gas reservoirs with high stress sensitivity.