昌都盆地古油藏的流体包裹体证据

青藏高原隆升与油气保存是当今油气勘探理论与实践面临挑战课题之一。本文利用在昌都盆地采集的51块储层岩石样品,运用流体包裹体系统分析的技术和方法,不仅揭示了工区中生界三叠系和侏罗系在早侏罗世—早白垩世的前陆盆地发育阶段发生4期油气充注,形成了古油藏,而且这些古油藏在新生代的走滑拉分盆地发育阶段遭到破坏而演化成沥青砂岩。同时,在古生界—中生界储层检测到大量纯气相包裹体,并且与高温盐水包裹体共生,暗示工区晚期存在天然气运聚过程。由此认为,昌都盆地以寻找天然气为主;在盆地南部的芒康深凹陷中生界可能是天然气勘探的有利地区。

Fluid Inclusion Evidence of Paleo-oil Reservoirs in Changdu Basin, Tibet

It is one of the challenges to investigate the relationship between Tibetan uplift process and hydrocarbon preservation mechanism in the current petroleum exploration theory and practice. For this study, systematically technique and method of fluid inclusion have been employed to analyze the 51 reservoir rock samples which are taken from the outcrops of Changdu basin in the northeastern Tibet. Eventually, the paleo-oil reservoirs charged with four events during foreland basin stage from the early Jurassic to the early Cretaceous in the Triassic and Jurassic grey fine sandstones have been firstly unraveled, which had been destroyed or cracked into bituminous sandstones during the strike-slip and pull-apart basin stage of the Cenozoic. Meanwhile, abundant pure vapor fluid inclusions with weak white-blue fluorescence and being coeval with aqueous inclusions of high homogenization temperature in trails of sandstones, calcite and quartz veins both in the Paleozoic and the Mesozoic reservoirs, which is surely implying for natural gases migration and accumulation happened widely in basin during the Cenozoic. It is, therefore, suggested that natural gas is the object for seeking and the southern Mangkang depression in the basin with relative good preserving condition would be the favorable site for gas exploration.