青藏高原羌塘盆地海相烃源层的沉积形成环境

羌塘盆地是青藏高原一个最大的中生代海相残留盆地。上三叠统在南、北坳陷为次深海盆地相沉积,发育一套黑色页岩烃源层;下侏罗统和中侏罗统下部为半温暖半干热—温暖炎热气候,在南坳陷南部局部地区也发育了浅海—次深海盆地相黑色页岩烃源层;中侏罗统中部和上侏罗统下部海侵规模扩大,以碳酸盐岩台地沉积为主,台地凹陷是形成烃源岩的主要场所;中侏罗统上部是一套滨海—浅海碎屑岩沉积,泻湖亚相页岩和前三角洲亚相泥岩为主要烃源岩。羌塘盆地中生界海相烃源岩的沉积发育特征与国内外碳酸盐岩大油气田的烃源岩发育特征基本一致,主要是深海—次深海盆地相沉积的黑色页岩、台地凹陷沉积泥灰岩和页岩、泻湖亚相或前三角洲亚相等沉积的页岩(油页岩)和泥岩。

DEPOSITIONAL ENVIRONMENT OF THE MARINE HYDROCARBON SOURCE ROCK IN THE QIANGTANG BASIN, QINGHAI-TIBET PLATEAU

The Qiangtang Basin is the largest Mesozoic marine residual basin in Qinghai-Tibet plateau.The Upper Triassic Formation is sub-abysmal basinal facies deposit in the south and north depressions.A black shale layer developed.The climate in the lower part of Lower and Middle Jurassic Formation is semi-warm and semi-xerothermic to warm and hot.A black neritic to sub-abysmal basinal facies shale layer developed in the southern part of the south depression.In the middle part of Middle Jurassic and the lower part of Upper Jurassic Formation,the scope of transgression increased.Carbonate-rock platform facies deposit is dominant and platform depression is the main place of source rock developing.A littoral to neritic detrital rock deposit is in the upper part of Middle Jurassic Formation.Lagoonal subfacies shale and prodelta subfacies mudstone are the main hydrocarbon sousce rocks.The characterstics of deposition and development of the Mesozoic marine hydrocarbon source rock in Qiangtang basin are similar to the ones in the large carbonate-rock oil and gas fields at home and abroad.Black abysmal to sub-abysmal basinal facies shale,marl and shale depositing in the platform depression and lagoonal subfacies or prodelta subfacies shale and mudstone are the main hydrocarbon source rocks.