一种评价封闭气藏采气指数、动储量及井间连通性的简便方法  

A simple method for evaluating gas production index,dynamic reserves and interwell connectivity of closed gas reservoirs

作　　者：鹿克峰 苏畅 程超逸 LU Kefeng;SU Chang;CHENG Chaoyi(CNOOC China Limited,Shanghai Branch,Shanghai 200335,China)

机构地区：[1]中海石油(中国)有限公司上海分公司,上海200335

出　　处：《中国海上油气》2023年第4期86-93,共8页China Offshore Oil and Gas

摘　　要：严格地说,封闭气藏中气井稳定采气指数出现在拟稳态流动阶段,通过短时测试求取气井稳定产能时,易受测点压力不稳定或气藏边界不确定的限制。由Blasingame变产量气井拟稳态流动方程可得出:在拟稳态流动阶段,变产量气井采气指数接近常数,将这一结论与封闭气藏压降方程式结合,提出了一种基于日常生产数据,评估气井稳定采气指数、气藏动储量的简便方法。实例应用表明:本文方法流态识别清楚,前期非稳态流动阶段采气指数呈明显“凸”形,后期拟稳态流动阶段呈“水平线”形态,基于“水平线”特征可评价:①处于稳产期,但产量存在频繁波动的常规气井的采气指数与动储量;②产量和压力持续递减的低渗气井的采气指数与动储量;③多井同采气藏井间连通性。研究认为,封闭气藏开发全过程中,气井采气指数经历递增→递减→水平三个阶段,开发早期短时测试求取的往往是递增阶段的瞬时产能,采用本文方法求取的则是拟稳态阶段的真实稳定采气指数。Strictly speaking,the stable gas production index of a gas well in closed gas reservoir occurs in pseudo-steady state flow.The calculation of gas production index is likely to be limited by unstable pressure at the measuring point or uncertain gas reservoir boundaries due to short period of test time.According to Blasingame variable gas rate well pseudo-steady state flow equation,the gas production index of variable gas rate wells approaches a constant in the pseudo-steady state flow stage.By combining this conclusion with the pressure drop equation of closed gas reservoirs,we propose a simple method to evaluate the stable gas production index and gas reservoir dynamic reserves based on daily production data.The example analysis shows that this method can identify flow regimes clearly.The curve shape of gas production index over time shows obvious“convex”in the early unsteady-state flow stage,and it becomes a“horizontal line”in the late pseudo-steady state flow stage.The“horizontal line”can be used to evaluate:①the production index and gas reservoir dynamic reserve of conventional gas wells with frequent production fluctuations but in stable production period;②the production index and gas reservoir dynamic reserve of low permeability gas wells with continuous decline of production and pressure;③the interwell connectivity of gas wells in multi-well gas reservoirs.Results suggest that during the development process of closed gas reservoirs,the gas production index curve has three stages:increasing stage,decline stage and horizontal stage.In early development,short-term testing is usually used to obtain the instantaneous gas production index during the increasing stage,while the proposed method can be used to obtain the true stable gas production index of the pseudo-steady state flow stage.

关 键 词：简便方法 采气指数 气藏储量 连通性 

分 类 号：TE37[石油与天然气工程—油气田开发工程]