五墩凹陷侏罗系地层发育特征及沉积体系分析

Development Characteristics and Sedimentary System Analysis of Jurassic Stratum in Wudun Sag

摘要: 钻探揭示，敦煌盆地五墩凹陷是以侏罗系为勘探目的层的中新生代残留凹陷，在侏罗系内见低产油流，预示五墩凹陷具有较好勘探潜力。研究表明，该区的地层发育与沉积演化特征决定了油气的成藏富集及勘探方向。根据五墩凹陷内钻井、地震及露头等资料，总结侏罗系发育特征，分析中–下侏罗统沉积体系，并与周缘诸盆地侏罗系进行对比，认为五墩凹陷侏罗系各组段发育齐全，芦草沟和南湖等地出露下侏罗统大山口组；中–下侏罗统沉积时期，物源受凹陷北部北山、南部三危山和东部物源体系控制，五墩凹陷由山前断陷转为凹陷，水体逐渐加深，气候由温暖湿润转为炎热干燥。凹陷内中央洼陷带是有利烃源岩及储层发育区带，并且源储匹配关系较好，是下步油气勘探有利目标区。

Abstract: The drilling data revealed that Wudun Sag of the Dunhuang Basin was a residual sag of the Middle Cenozoic in the Jurassic stratum as exploration target, the low production oil flow was recovered in the Jurassic stratum, which indicated that the Wudun Sag had a better exploration potential, the study found that the direction of exploration and accumulation of oil and gas depended on the stratigraphic development and sedimentary evolution in this area. According to the drilling, seismic and outcrop data from Wudun Sag, the development characteristics of the Jurassic stratum were summarized, the sedimentary systems of the Middle and Lower of Jurassic were analyzed, which were compared with the Jurassic stratums of some basins nearby, it was considered that each formation and interval of Jurassic stratum were developed completely in Wudun Sag, Lucaogou and Nanhu outcrops exposed Dashankou Formation of the Lower of Jurassic. In the sedimentary period of Middle and Lower of Jurassic, the provenance was controlled by the Beishan Mountain in the north, Sanwei Mountain in the south and source systems in the east of the Sag, the Wudun Sag has changed from piedmont fault depression into a sag, the water gradually deepened and the climate changed from warm and wet to hot and dry. The central sub-sag is a favorable source rock and reservoir development zone in the sag, and has a good matching relationship between source and reservoir, which is a favorable target area for oil and gas exploration at the next stage.