酒东、酒西盆地的异同与油气勘探

SIMILARITY AND DIFFERENCE IN GEOLOGY BETWEEN JIUDONG AND JIUXI BASINS OF NORTHWEST CHINA AND PETROLEUM EXPLORATION

酒东盆地和酒西盆地（曾合称为酒泉盆地）都是祁连褶皱系的山前盆地，在同一区域构造应力场控制下发育，有很多相似性。酒西盆地自30年代以来发现了一批浅层油气藏，酒东盆地多年勘探却无重大突破。分析二者的异同，认为：①盆地边界条件不同，导致局部应力作用方式有别，酒西盆地逆冲-褶皱变形强烈，酒东盆地构造变形微弱，中、浅层断裂少；②主要油源层都是深部下白垩统赤金堡组的成熟─高成熟烃源岩；③酒西盆地的深部油气以断裂为通道，运移至中、浅层圈闭聚集成藏，而酒东盆地的油气纵向运移条件差，一般在深部形成自生自储式油气藏。据此提出：酒东盆地主要勘探目的层是黑梁断裂以东深部的下白垩统，营尔凹陷东部的长沙岭构造、下河清构造和黑梁断裂东侧地带是近期的主要勘探目标区；酒西盆地仍有勘探潜力，其西部的青西低凸起有形成志留系潜山裂缝型油藏和白垩系的构造型及地层一不整合型油藏的有利条件，建议钻科学探索井进行评价。

Jiudong and Jiuxi basins are the piedmont basins of Qilian folding mountains. There are a lot of similarities in sedimentarystrata, potential source rocks and evolution history of organic matter between them because their development was controlledunder a same regional stress field. Many oil fields in shallow structures have been discovered in Jiuxi basin since 1930, butnone is discovered in Jiudong basin. Probing their similarity and difference, the authors consider that: (1)Different basinboundary results in different de formational pattern and intensity of the two basins in the action of the same regional stressfield. Thrusting and folding are strong in the Jiuxi basin, while structure deformation is weak and faults in middle andshallow formations are rare in the Jiudong basin; (2)Main potential source rocks are also in deep Chijinpu Formation ofLower Cretaceous in the two basins, which are mature to high mature; (3)Oil and gas could migrate from deep source rock toreservoirs in shallow structure traps along faults in the Jiuxi basin. ln contrast, vertical migration of oil and gas is difficultand oil and gas accumulated in deep reservoirs to form oil and gas pools in the Jiudong basin. The authors indicate that themain formation for petroleum exploration is in deep Lower Cretaceous in the east of fault Heiliang, and the main targetsrecently are the Changshaling and Xiaheqing traps, and the eastern region along the fault Heiliang in Yinger depression,Jiudong basin. In spite of the long procedure of petroleum exploration, there is exploration potential in the Jiuxi basin. Qingxisalient has profitable conditions to form fractured oil pools in Silurian buried hill and oil pools of antiform, unconformableformation traps in Cretaceous. The authors suggest drilling a Scientific Exploratory Well to assess the perspective forpetroleum exploration.