川西中段山前带雷口坡组气藏形成条件及过程

利用探井和地球物理资料,系统分析川西中段彭州气田钻探成果和中三叠统雷口坡组天然气成藏特征。川西中段深层有优质的下寒武统烃源岩,雷口坡组微生物型储集层沿山前带呈北西向展布,晚期发育的沟源断层形成的输导体系,早于断层形成的圈闭体系,具备形成大气田的基本条件。川西中段雷口坡组气藏为次生气藏,其天然气来源于下伏古气藏及烃源岩,深层的天然气通过断层向上运移聚集。川西中段雷口坡组的成藏特点为:(1)深层古油气藏发育;(2)微生物储层发育;(3)沟源断层晚期发育;(4)地震促使断层活化;(5)天然气跨层运移成藏。除雷口坡组外,深层应该还存在残余的古气藏,可能赋存的层位为二叠系和震旦系。

Formation condition and process of Leikoupo Formation gas reservoir in the piedmont zone of middle segment of western Sichuan,China

Based on exploratory well and geophysical data,the drilling results of Pengzhou Gas Field in the middle part of Western Sichuan and the characteristics of gas reservoir formation in the middle Triassic Leikoupo Formation are systematically analyzed.There are high quality Lower Cambrian source rocks deep in the middle part of western Sichuan,and the microbe reservoir of Leikoupo Formation is distributed in the NW direction along the piedmont belt.The transport system formed by the late developed trench-related fault is earlier than the trap system formed by the fault,which has the basic conditions for the formation of large gas field.It is considered that the Leikoupo Formation gas reservoir in the middle part of western Sichuan is a secondary gas reservoir and the natural gas originates from the underlying deep Paleozoic gas reservoir and source rock,which migrates and accumulates upward through the faults.The reservoir-forming characteristics of the Leikoupo Formation in the middle part of western Sichuan are related to:(1)development of deep palaeo-oil reservoirs;(2)development of microbial reservoir;(3)development of trench-related faults in late stage;(4)fault activation by earthquake;(5)cross-layer migration and accumulation of natural gas.In addition to the Leikoupo Formation,it is possible that there are residual paleogas reservoirs in the deep layers,possibly in the Permian and Sinian strata.