Hydrocarbon geological conditions and exploration prospects of Lower Paleozoic in the South Yellow Sea Basin

Drilling, inclusion analysis and geochemical prospecting indicate that oil and gas charging process exists in the deep marine Mesozoic-Paleozoic strata in the South Yellow Sea Basin, which is endowed with a good potential of oil and gas resources.Based on the latest seismic data interpretation of the South Yellow Sea Basin and fully understanding of the latest drilling data in its adjacent Yangtze Platform, the geological conditions and exploration prospects of oil and gas in the Lower Paleozoic are described through systematic analysis on tectonic division of the Mesozoic-Paleozoic marine basins, hydrocarbon accumulation elements and assemblages of Lower Palaeozoic.The results show that: a.The South Yellow Sea Basin is a residual basin formed by the superposition and reconstruction resulting from multi-stage tectonic movements.As the Lower Paleozoic tectonic deformation is weak, the strata are relatively well preserved.The Gaoshi stabilized zone of the Laoshan fault uplift in the middle of the basin constitutes the Lower Paleozoic tectonic stable zone.b.Palaeozoic strata possess relatively superior geological conditions for oil and gas resources, of which the Cambrian source rock is characterized by great thickness and high contents of organic substance dominated by typeⅠkerogen.Metasomatic dolomite and granular limestone are mainly developed in Middle Cambrian to Ordovician, which can be used as better reservoirs.The thick argillaceous rocks of Upper Ordovician to Lower Silurian are widely developed and have good sealing ability, which can be used as a set of regional caprocks.The source-reservoir-caprock combination is well developed in Lower Paleozoic, and several large structural traps and hydrocarbon charging exist in the Gaoshi stable zone.As the structural traps match well with the formation of oil and gas in time and space, and the late structural destruction is relatively weak, the oil and gas preservation conditions are good.Therefore, it can be a favorable area for marine oil and gas exploration in South Yellow Sea Basin.