DETAILED ASSESSMENT OF MESO-PALEOZOIC HYDROCARBON SOURCE ROCKS: IMPLICATIONS FROM WELL CSDP-2 ON THE CENTRAL UPLIFT OF THE SOUTH YELLOW SEA BASIN

The well CSDP-2 is the first whole coring deep hole ever drilled on the Central Uplift of the South Yellow Sea Basin. It penetrated many sets of clastic and carbonate rocks from the Late Ordovician Formation up to the Early Triassic Qinglong Formation unconformably under the Neogene. The data of organic abundance, organic types, thermal evolution history, soluble organic matter and hydrocarbon-generating intensity of the sequence confirms that on the Central Uplift there occurs three sets of effective hydrocarbon source rocks: the lipophilic limestone of the Upper Member of the Qinglong Formation, the mudstone of the Upper Ordovician up to the upper member of the Lower Silurian and the oil-gas type limestone of the Middle and Upper Members of the Carboniferous. The effective hydrocarbon source rocks that generated gas are mainly the mudstone and carbonaceous mudstone of the Dalong Formation-Longtan Formation, the stink limestone of Upper Qixia Formation which is rich in organic, limestone of middle-lower Carboniferous and the carbonaceous mudstone in the bottom of Carboniferous. The Mesozoic and Paleozoic total hydrocarbon-generating intensity revealed by the drilling is (20.7619-31.2839)×10⁸m³gas equivalent/km² and its gas-generating intensity is roughly comparable to large and medium-sized gas fields of the world. According to our calculation, the total oil-generating intensity of the oil source rock is (43.076-55.30)×10⁴t/km², and the total gas-generating intensity of gas source rock is (16.4543-25.7539)×10⁸m³/km². The total gas-generating intensity of source rocks is 4-5 times higher than the oil-generating intensity, and the hydrocarbon-generating intensity of clastic rocks is twice higher than that of limestone. High hydrocarbon-generating intensity and abundance of hydrocarbon source layers have provide sufficient materials for a medium-large oil and gas accumulation, showing a good oil and gas exploration prospect of the Mesozoic-Paleozoic in the region of the Central Uplift of the South Yellow Sea Basin.