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

Hydrocarbon resources in the pre-salt is very rich,and eighty-five percent of oil and gas proven reserves is distributed in the presalt 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.