孟加拉湾西侧盆地群油气地质特征与勘探潜力

Hydrocarbon Geological Characteristics and Potential Prospect of Basins in Bengal Gulf West

通过对孟加拉湾西侧盆地群的板块构造演化、地层层序发育、烃源岩—储层—盖层等石油地质要素开展详细分析,可知该盆地群先后经历了前裂谷期、裂谷期、后裂谷期等3个板块构造演化阶段,并在后期随着南亚大陆的整体向北漂移演变为被动大陆边缘盆地群。根据区域板块演化与地层发育特征,可将该盆地群的地层划分为前裂谷、裂谷和后裂谷3套巨层序,在各个巨层序内部能够识别出7个三级层序、6套成藏组合。从该被动大陆边缘盆地群的油气地质特征可知,深层的前裂谷巨层序内部二叠系—三叠系河道砂岩、裂谷巨层序内部的白垩系河流相、三角洲相河道砂岩、深水地区后裂谷巨层序内部的被动陆缘盆地中发育的第三系河道、三角洲和深水浊积砂岩是该盆地群下一步主要勘探目标。

The analysis of plate evolution,stratigraphy development,factors of source,reservoir and seal of passive continental margin basins in Bengal Gulf West reveals that the basins have experienced three rift development phases,i.e. pre-rift,syn-rift and post-rift phases,and they developed into passive continual margin basins in the late post-rift phase with the India Plate drifting to north. According to plate evolution and stratigraphy sequence features,the basins could be subdivided into pre-rift,syn-rift and post-rift mega-sequences,seven third-level sequences and six reservoir accumulation associations. Current exploration activities are mainly concentrated on Tertiary sequences of onshore and shallow offshore area. Studies on evolution and geological features of passive continental margin basins in Bengal Gulf West result in conclusions that further petroleum exploration prospects should be Perm-Tri channel sandstone of Pre-rift sequence,Cretaceous delta and fluvial sandstone of Syn-rift sequence,sub-water channel sandstone of passive continental margin Tertiary and deep water turbidity sandstone of post-rift sequence.