滨里海盆地盐下油气成藏主控因素及勘探方向

MAIN FACTORS CONTROLLING HYDROCARBON RESERVOIRS AND EXPLORATION DIRECTIONS IN THE PRE-SALT SEQUENCE IN PRECASPIAN BASIN

滨里海盆地盐下油气资源十分丰富,盆地内目前发现的85%的油气探明储量均分布在盐下层系内。盆地内盐下目前发现的含油层系主要有3套:泥盆系、石炭系及二叠系,其中石炭系是盐下最主要的含油层系。滨里海盆地共发育4个二级构造单元:滨里海南部次盆、东部次盆、西部—西北部次盆及中央坳陷,不同区带成藏主控因素不同。在对滨里海盆地盐下油气基本成藏条件分析基础上,详细分析了不同区带盐下成藏主控因素,指出南部次盆成藏主控因素为石炭系碳酸盐岩的分布及下二叠统盐岩盖层分布;东部次盆为石炭系及二叠系储层的分布;西部及西北部次盆成藏主控因素为石炭系及二叠系碳酸盐岩储层的分布。在成藏主控因素分析的基础上,提出了滨里海盆地盐下下一步油气勘探的方向。

Hydrocarbon resources in the pre-salt is very rich, and eighty-five percent of oil and gas proven reserves is distributed in the pre-salt in PreCaspian Basin. There are three series of hydrocarbon-bearing strata in the pre-salt sediments in the basin. Devonian, Carboniferous and Permian. Among them, Carboniferous is the most important oil-bearing layer system. In PreCaspian Basin, four secondary tectonic units are developed. They are southern PreCaspian Sub-basin, eastern PreCaspian Sub-basin, western and northern-western PreCaspian Sub-basin and Central Depression. In different sub-basins, the main factors controlling reservoir formation are different. Based on analysis of the basic conditions for reservoir formation in the pre-salt succession in PreCaspian Basin, this paper researched into main factors controlling reservoirs in the pre-salt in each sub-basin. Study indicated that main factors controlling reservoir are the distribution of Carboniferous carbonate and Lower Permian salt in southern sub-basin, and distribution of Carboniferous carbonate and Lower Permian clastic reservoir in eastern sub-basin, and Carboniferous and Lower Permian carbonate reservoir in western and northern-western sub-basin. On the basis of analysis of main controlling factors, this paper put forward further exploration directions for the pre-salt in PreCaspian Basin.