克拉2异常高压气田开采特征影响因素分析

Analysis of factors influencing production characteristics of Kela 2 overpressured gas field

异常高压气藏与常压气藏的开采特征明显不同 ,边底水侵入、储集层岩石膨胀以及束缚水膨胀均是重要影响因素。研究储集层膨胀驱动能量大小时 ,存在采用常岩石压缩系数还是变岩石压缩系数两种观点。克拉 2气田岩石覆压试验结果表明 ,本区岩石压缩系数在原始条件下要比压降后期高 5～ 10倍。显然 ,考虑储集层膨胀作用时 ,采用变岩石压缩系数更符合实际情况。应用AdelMElsharkawy提出的气藏物质平衡方程 ,将低估异常高压气藏边底水侵入、储集层膨胀以及孔隙束缚水膨胀等驱动力的作用。考虑各种影响因素改进了气藏物质平衡方程 ,使之能更准确地反映不同压力阶段各驱动机制所提供驱动能量的大小。研究表明 ,采用根据异常高压气藏开发初始阶段数据作出的压力与采出程度关系图进行预测 ,有可能过高估计气藏的地质储量和剩余可采储量。

The production characteristic s of overpressured gas reservoirs are obviously different from that of normal-p ressure gas reservoirs. Water influx from associated aquifer, formation rock exp ansion and connate water expansion are important influence factors. In studying the drive energy of formation expa nsion, there are two different views of using constant or variable rock compress ibility. The result of rock load experiment of Kela 2 gas field shows that the o r iginal rock compressibility is 5-10 times higher than that of the late period o f pressure decline. Therefore, using variable rock compressibility is more close to the real production performance. The material balance method offered by Adel M. Elsharkawy may underestimate the drive energy of water influx from associate d aquifer, formation expansion and connate water expansion of overpressured rese rvo irs. This paper presents a modified gas material balance that can more accuratel y express the drive energy of every drive mechanism at the different pressure st ages. The study shows that incorrect extrapolation of early data may result in s erious overestimation of original gas in place and remaining recoverable reserve s.