考虑封闭气的水驱气藏物质平衡方程

针对现有水侵模型均为理论推导所得,假设条件多,实际应用效果不理想的现状,通过对定容封闭气藏衰竭开采及水驱气藏定量开采的物理模拟试验,研究了气藏开发过程中的物质平衡和水侵规律。定容封闭气藏衰竭开采模拟试验表明,压力与累计产气量呈线性关系,与理论公式完全吻合,可见模拟试验系统能够模拟实际气藏的开发。水驱气藏模拟试验结果代入物质平衡方程,计算等式两端的结果有所差别,且随着水侵量的增加,这种差别越来越显著,原因在于水驱气藏物质平衡方程未能考虑水体侵入对气藏形成圈闭产生封闭气所带来的影响。通过分析试验数据,在原有水驱气藏物质平衡方程中添加一修正项(即考虑水体侵入产生封闭气的影响),再次代入试验数据,物质平衡方程等式两边比较吻合,可见添加修正项后的物质平衡方程可以有效描述水体侵入对气藏产生封闭气的程度,对水驱气藏水侵量计算和开发动态预测有重要的意义,使物质平衡方程进一步得到完善。

Material Balance Equation of WaterFlooding Gas Reservoir Considering Trapped Gas

Through experimental research of closed gas reservoir depletion and waterflooding gas reservoir development,we studied the material balance and the law of water influx in the water-flooding gas reservoir.The simulation results for depletion of closed gas reservoir showed that there is a linear relationship between pressure and cumulative gas,which is consistent with theoretical formula.So the experimental system can simulate the development of actual gas reservoir.The simulation results for waterflooding gas reservoir indicated that there were some differences between experiment results and theoretical calculation results,which would be more and more prominent as water influx increase.The reason is that in material balance equation it did not take the effect of water influx into account on the trap forming process from reservoir and the generation of trapped gas.Based on the theoretical and experimental analysis,we did modification on the original material balance equation of water flooding gas reservoir,which takes trapped gas into account.The results from newly modified equtions matched experiment data very well.So the added item in the equition can describe the affecting degree of water influx to produce trapped gas,which have important significance in calculating water influx and predict development dynamics of water-flooding gas reservoir.