库车坳陷中生界烃源岩排烃史与资源潜力

Hydrocarbon Expulsion History of Mesozoic Source Rocks and Resource Potential in Kuqa Depression

为揭示库车坳陷油气勘探潜力,利用生烃潜力法分析了研究区烃源岩的排烃史与排烃特征。结果表明:三叠系排油高峰始于23Ma,早于侏罗系排油高峰(12Ma)。古圈闭被破坏,新圈闭形成时间晚于23Ma,不利于来自三叠系的油源聚集成藏。三叠系与侏罗系烃源岩排气量大,且时间与新圈闭形成时间耦合较好,有利于天然气的晚期成藏。三叠系源岩排出的天然气较难突破中上侏罗统的巨厚泥岩,但是该条件有利于天然气在下侏罗统圈闭内成藏。库车坳陷具备发育深盆气藏的烃源条件与致密储层条件,有利于形成大面积的深盆气藏,拜城凹陷与阳霞凹陷的斜坡带是潜在的深盆气藏资源区。

For revealing the potential force of gas and oil exploration in Kuqa Depression,the hydrocarbon expulsion history and the characteristics of hydrocarbon expulsion of the studied area were analyzed by using the method of hydrocarbon-generation potential.The results show that,firstly,the peak of oil expulsion of the Triassic source rocks is started at 23 Ma,it is earlier than Jurassic source rocks(12Ma).At this time the ancient trap was destroyed,and new trap is formed later than 23Ma.It is not beneficial for Triassic source rock accumulation.Secondly,the exhaust volume of the Triassic and Jurassic source rocks is larger,and the exhaust time is coupled better with that of new trap formation,which is favorable for late gas accumulation.Thirdly,the gas of the Triassic source rocks is difficult to break through the giant thick mudstone in middle and upper Jurassic,but the condition is advantageous to the natural gas accumulation in the Jurassic traps.Fourthly,Kuqa Depression developes deep basin gas source conditions and tight reservoir conditions,which is favorable for the formation of large area of deep basin gas reservoirs,and the slope of Baicheng Sag and Yangxia Sag is the potential of deep basin gas resource area.