鄂尔多斯盆地陇东地区三叠系延长组长3油层组石油运移与充注研究

Oil Migration and Filling in the Triassic Chang 3 Member of Longdong Area,Ordos Basin

鄂尔多斯盆地是我国第二大沉积盆地,中生界延长组富含丰富的油气资源。陇东地区位于鄂尔多斯盆地西南部,延长组长3段是该区重要的含油层系。在长3油层组原油特征和油源条件分析的基础上,对长3原油中含氮化合物组成和分布进行了探讨,结合成藏期分析,研究了鄂尔多斯盆地陇东地区长3油层组石油运移特征和注入方向。结果表明,长3油层组原油含氮化合物的分布与组成在纵向和横向上均存在明显的运移分馏效应,较好地指示了该区石油的运移。晚侏罗世至早白垩世,鄂尔多斯盆地延长组长7优质烃源岩进入生烃门限,并开始大量生烃,且以垂向、侧向、垂向-侧向交替式混合运移的方式,从盆地中心和生烃中心向西部和西南侧向运移和充注,油气充注点位于M18、Z71和Z49等井区周边区域。

Ordos Basin is the second largest sedimentary basins,with abundant Mesozoic crude oil resources. Longdong area is located in southwestern Ordos Basin.The Chang 3 oil group of Jurassic Yanchang Formation is an important oil-bearing layer.Based on the characteristics of crude oil and oil-source analysis of the conditions for Chang 3 oil group.Making use of the composition of the nitrogen compounds in crude oil and the changes of the absolute concentration,combining with the research results of the comparison of source rock and oil source correlation,this paper discuses the migration characters and directions of Chang 3 oil group in the Longdong re-gion of Ordos Basin.The results show that in the distribution and composition of nitrogen compounds in crude oil from vertical and longitudinal,there are evident migration and fractionation effects which can be used to indi-cate the regional migration of crude oil better.From Late Jurassic to Early Cretaceous,Chang 7 high-quality source rock had reached generation thresholds.At the same time,there are plenty of hydrocarbons generation which have an lateral migratory extend from the centers of the basin and hydrocarbon generation to the west,the southwest and the northwest,in ways of verticality,laterality and alternation of them.