摘要
早奥陶世在广阔的鄂尔多斯浅水陆表海碳酸盐台地内发育了米脂内台地坳陷。它是由台地内部差异沉降和海平面上升的共同作用下形成的。坳陷经历了三次主要的海进—海退旋回,构成了三套生储盖组合。坳陷的构造稳定性决定了其圈闭型式以地层圈闭为主。作者建立了该坳陷发育的地质模型,并提出其可能存在的四种地层圈闭类型。
Mizhi intra-platform depression developed on the broad shallow water carbonateplatform in Ordos epeiric sea during Early Ordovician.The area of the depression is about 70000 km^2.It was formd by the combined effect of both the differential subsidence of theplatform interior and the rise of sea level.The evolution process can be divided into threeperiods(lower Majiagou,upper Majiagou and Fengfeng).Each period can be subdividedinto three stages.The first stage differential subsidence occurred in the platform interior,and sea level rose;the second stage,intense differential subsidence and evident rise of sealevel resulted in formation of Mizhi intra-platform depression;the third stage,differentialsubsidence weakened gradually,the sea level fell,and the depression was filled.Theevolution of Mizhi depression underwent three large-scale transgressive-regressive changesand formed three supercycles and three stratigraphic sequences corresponding respectivelyto lower Majiagou,upper Majiagou and Fengfeng Formations.Three perfect source-reservoir-cap assemblages were formed from the dark organic-rich micrite at the top ofthe transgressive limb of each supercycle to the evaporite at the upper part of the regres-sive branch.Mizhi intra-platform depression is a gas-bearing sag because of high organicmaturation.Recently,the significant discovery of gas in Fengfeng sequence indicatesthat intra-platform depression has great potential to accumulate gas.The gas accumulatedin porous dolomite reservoirs related closely to palaeokarst.A geological model shows thatfour types of stratigraphic traps existed in the depression.
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
1992年第3期293-302,共10页
Oil & Gas Geology
