Abstract:

Analyzing the conditions of the Mesozoic-Paleozoic cap rocks in South Yellow Sea Basin provides the basis for oil and gas resource evaluation in the study area. By full use of existing drilling, well log and seismic data, this paper analyzed the cap-rock conditions based on the analysis of structure, stratigraphy and sedimentology in the basin and its adjacent area. The results suggest that five sets of cap rocks have developed in the Mesozoic-Paleozoic in South Yellow Sea Basin, including the argillaceous rocks of the Longtan-Dalong Formation, the muddy limestone and gypsum rocks of the Lower Triassic, the lacustrine argillaceous rocks of the Lower Cretaceous, and two sets of argillaceous rocks of the Lower Cambrian and the Lower Silurian described by seismic interpretation and regional correlation. Whether the existing cap-rock condition in the basin is good or not plays a key role in the Mesozoic-Paleozoic oil and gas preservation. The cap-rock condition in the Lower Paleozoic as a whole is superior to the Upper Paleozoic. For the Upper Paleozoic, the cap rocks of the Qingdao depression are better than the Yantai depression. In contrast, cap rocks of the marine Mesozoic are generally poor.

Key words: South Yellow Sea Basin, cap-rock condition, argillaceous cap rock, Mesozoic-Paleozoic oil and gas reservoir