页岩气剩余储量评价及提高储量动用对策——以川南长宁页岩气田五峰组—龙马溪组为例

Evaluation of the remaining reserves of shale gas and countermeasures to increase the utilization of reserves:Case study of the Wufeng-Longmaxi formations in Changning area,southern Sichuan Basin

剩余储量评价对气田开发效果评价及进一步提高气田储量动用尤为重要,为此以四川盆地南部长宁页岩气田为研究对象,通过有机地球化学测试、三轴岩石力学实验、数值模拟等方法,从储层展布、剩余储量评价、提高储量动用等方面进行了系统分析。结果表明:研究区平台井控储量采出程度为45%~70%,井均剩余储量为(0.5~1.5)×10^(8)m^(3),局部区域存在挖潜潜力;长宁页岩气田存在3种未动用储量类型:井网部署空白区、压裂未充分改造区和纵向未动用区;在单井剩余储量>1.0×10^(8)m^(3)的区域内,按照地质—工程—开发耦合选井原则,开展重复压裂井优选;优选网状缝发育区且先期部署井间距大于500 m的区域,结合地面井场条件开展同层加密井的部署和实施;储层、岩石力学及数模分析认为,⑤小层为上部气层最优靶体、与下部气层①小层靶体垂向距离>20 m,优选网状天然裂缝发育区、压力系数>1.2、上部气层I类储层连续厚度>10 m的有利区进行错层立体开发,预期可提高平台储量动用率30%。相关认识可为页岩气区块的井网部署策略提供借鉴和参考。

The evaluation of remaining reserves is particularly important for the evaluation of gas field development effect and the further improvement of gas field reserve utilization.Therefore,taking Changning shale gas field in southern Sichuan Basin as the research object,the reservoir distribution,remaining reserves evaluation and the improvement of reserves utilization are systematically analyzed.Methods included organic geochemical testing,triaxial rock mechanics experiments and numerical simulation.The results show that:The distribution of the average remaining reserves of the single well is clarified.The recovery degree of the well-controlled reserves of the platform in the study area is 45%-70%,and the average remaining reserves of the well are(0.5-1.5)×10^(8)m^(3),there is potential in some areas.There are three types of unused reserves in Changning shale gas field:Blank area of well pattern deployment,insufficient fracturing area and vertical unused area.In the area of single well remaining reserves>1.0×10^(8)m^(3),according to the principle of geology-engineering-development coupling well selection,repeated fracturing well optimization is carried out.The area with network fracture development and the spacing between the pre-deployed wells is greater than 500 m is selected,and the deployment and implementation of the same zone infill wells are carried out according to the surface well site conditions.According to the analysis of reservoir,rock mechanics and numerical simulation,sublayer⑤is the optimal target of the upper gas layer,the vertical distance from the lower gas layersublayer①is more than 20 m,the network natural fracture development area is preferred,the pressure coefficient is greater than 1.2,and the continuous thickness of the upper gas layer I reservoir is more than 10 m.In the favorable area,the staggered tridimensional development is expected to increase the platform reserve utilization rate by 30%.The results of this study provide references for the well pattern deployment strategy of shale gas blocks.