渝东碳酸盐岩区油气运聚体系

HYDROCARBON MIGRATION AND ACCUMULATION SYSTEM IN CARBONATE FORMATION,EASTERN CHONGQING

因受多期构造变动、碳酸盐岩及超压发育等因素影响,渝东地区油气运聚体系有其特殊性。通过对古岩溶发育、成岩作用及断裂的分析,认为油气运移的通道除高孔渗岩层、不整合面、断裂系统外,岩溶系统也可为有利运移通道;浮力与超压释放产生的水动力是油气二次运移的驱动力。运用单井埋藏史、包裹体测温等手段分析了运聚期次和构造期的关系以及各运移期流体势的变化后认为,志留系、二叠系油气在T3末和J2s晚期发生2期大规模运移,志留系油气在燕山晚期张性作用阶段的K1晚期再次在石炭系充注,总体运移指向石柱及其它继承性隆起区;二叠系油气为自生自储型,三叠系油气藏由于燕山晚期以来的张性断裂开启而发生强烈的改造和逸散。

The characteristics of hydrocarbon migration and accumulation system in carbonate formation, eastern Chongqing can be traced from these factors： disturbance of multi-tectonics, lithologic character of carbonate formation and existence of abnormal pressure. Besides of permeable formations, plane of unconformity and framework of faults, karst cave is another important type of migration pathway according to the analysis of paleo-karst cave, diagenesis and fault. Buoyancy and hydropower from release of overpressure drive the fluids to migrate in formation. The relationships between hydrocarbon migration stages and tectonic movements based on the data of burial history of well and fluid inclusions and the changes of fluid potential in all migration periods indicate that： Under the force of buoyancy and hydropower, hydrocarbon in Silurian and Permian migrated extensively in late Triassic and middle Jurassic. Silurian hydrocarbon was injected into Carboniferous again when late Yanshan extension movement took place in the end of late Cretaceous. And its accumulation place is Shizhu and other doming zones. Hydrocarbon sourced from Permian formed reservoir in itself. But hydrocarbon reservoir from Triassic destroyed due to the opened framework of faults.