阿拉斯加北坡盆地海域油气地质及勘探潜力

Petroleum Geology and Exploration Potential in Offshore Arctic Slope Basin, Alaska

阿拉斯加北坡盆地海域经历了四个主要构造演化阶段,分别为前中泥盆世埃尔斯米尔造山阶段、晚泥盆世至三叠纪被动边缘阶段、侏罗纪至早白垩世裂谷阶段以及中—晚白垩世至第四纪前陆盆地阶段。研究区发育良好的生储盖组合:三叠系Shublik组为主力烃源岩;下白垩统Kuparuk组浅海相和三角洲相砂岩为主要勘探目的层,上白垩统Torok组三角洲砂岩为次要目的层;下白垩统泥岩为区域盖层,且封盖条件好。研究区在构造演化过程中形成了大量圈闭,以大型低幅背斜构造圈闭、构造-地层复合圈闭为主,并发育多套成藏组合。认为北坡盆地海域具有优越的油气成藏地质条件,待发现资源量巨大,勘探前景广阔。前陆盆地挤压构造带、楚科奇海岸、巴罗拱曲等构造圈闭发育区是有利勘探区带。

Alaska Arctic Slope Basin is partly located in land of Alaska and partly in seas. It is shown that the basin has experienced four stages of tectonic evolutions, which are the pre-middle Devonian Ellesmere orogeny, the late Devonian to Triassic passive margin, the Jurassic to early Cretaceous rifting and the middle-late Cretaceous to Quaternary foreland, respectively. A good source-reservoir-cap assemblage develops in offshore area. The Triassic Shublik source rock is the major source rock. The lower Cretaceous Kuparuk neritic and deltaic sandstone is the main target reservoir and the upper Cretaceous Torok deltaic sandstone is the secondary target reservoir. The lower Cretaceous mudstone with good seal condition is regarded as the regional cap rock. A large number of traps formed during the tectonic evolutions, predominantly including large-scaled low-rising anticlinal traps and structural/stratigraphic combined traps, and developing several plays. Based on comprehensive analysis, it is shown that there are excellent geological conditions for hydrocarbon accumulation and enormous undiscovered hydrocarbon resources in the offshore area. The compressional structural belt in the foreland, Chukchi coast and Barrow Arch should be the favorable area of exploration.