RESEARCH OF THE OIL-GAS SOURCE AND FORMATION OF THE POOLS IN THE SHALLOW BED OF THE SHENGBEI SAG, THE TUHA BASIN

By the comprehension correlation of the crude oil carbon isotope,light hydrocarbon,oil-rock biomarker,the paper indicates that the oil-gas in the shallow bed are mainly provided by the Shuixigou Group coal seam of Middle-Lower Jurassic series,and some areas are mixed with the hydrocarbons generated from lake facie shale of the Middle Jurassic Qiketai Formation in the Shengbei Sag,Tuha Basin.In the meantime,it shows that the fault passed through the regional cover(J2q-J3q) is a key to migration and collection of the oil-gas in the shallow bed.Furthermore,the author thinks that the time and way of the oil-gas migration and collection are different in the different areas,which is the characteristic of capturing oil-gas in stags to form pool,example for,Hongnan structure belt,which is later for the shallow oil-gas to migrate,and mainly redistributed that the oil-gas has collected in middle Jurassic,and is secondary oil-gas pool.But,as for Shengbei structure belt,which is earlier for the shallow oil-gas to migrate,and is mainly the low-mature hydrocarbons of the Shuixigou Group coal seam to be captured.