RESEARCH EXPERIENCES AND APPLICATION OF SEISMIC EXPLORATION TECHNOLOGY TO THE MESOZOIC– PALEOZOIC MARINE STRATA IN THE SOUTH YELLOW SEA BASIN

The South Yellow Sea Basin is the only large sedimentary basin without oil and gas fields discovered so far in the offshore area of China. There occur two sets of strata, the continental Mesozoic-Cenozoic and the marine Mesozoic-Paleozoic, for hydrocarbon exploration. The marine Mesozoic-Paleozoic strata are thick and widely distributed. However, the quality of seismic data is always a problem which restricts effective oil and gas exploration. The marine Meso-Paleozoic basin is characterized by deep burial, complex basin-forming background, and strong tectonic deformation in the later stage. The research of seismic exploration technology for the Meso-Paleozoic has experienced three stages of progress: seismic geological research, tackling key technical problems, and technical breakthrough and application. In the first stage, seismic geological conditions and rock physical properties were analyzed. Then, with the help of continuous updating of geophysical prospecting vessels, in addition to seismic instruments and equipment, the seismic acquisition parameters are continuously improved through large number of theoretical simulations, targeted physical simulations and continuous offshore trials. As the results, the seismic exploration technology called “HRS” took place, which broke the “bottleneck” of the seismic data interpretation for the marine Mesozoic-Paleozoic strata in the South Yellow Sea Basin. This technology is characterized by high coverage, low-frequency and strong source energy. By using this technology, three sets of seismic reflection markers which can be continuously traced and seven reflection surfaces were identified on the Laoshan Uplift where the original reflection of the marine Mesozoic-Paleozoic strata are blank. Upon the basis, stratigraphic sequences were established, residual basin tectonic units revealed, and the oil and gas prospect areas predicted. The Gaoshi stability zone of the Laoshan Uplift was selected as a favorable exploration target. Key structures were delineated, and drilling targets locked. The works mentioned above made clear the direction and conditions for further exploration and the breakthrough of oil and gas exploration in the new strata of the South Yellow Sea Basin. The “HRS” seismic exploration technology has great significance for expanding the spatial areas of hydrocarbon exploration in offshore China, and push forward the exploration and development of oil and gas resources in deep offshore areas. The technology may be used for oil and gas exploration in the sea areas with similar seismic and geological conditions in the other part of the world.