Prospective prediction and exploration situation of marine Mesozoic-Paleozoic oil and gas in the South Yellow Sea

Abstract

The South Yellow Sea Basin is a large sedimentary basin superimposed by the Mesozoic-Paleozoic marine sedimentary basin and the Mesozoic-Cenozoic terrestrial sedimentary basin, where no oil and gas fields have been discovered after exploration for 58 years. After the failure of oil and gas exploration in terrestrial basins, the exploration target of the South Yellow Sea Basin turned to the marine Mesozoic-Paleozoic strata. After more than ten years' investigation and research, a lot of achievements have been obtained. The latest exploration obtained effective seismic reflection data of deep marine facies by the application of seismic exploration technology characterized by high coverage, abundant low-frequency components and strong energy source for the deep South Yellow Sea Basin. In addition, some wells drilled the Middle-Upper Paleozoic strata, with obvious oil and gas shows discovered in some horizons. The recent petroleum geological research on the South Yellow Sea Basin shows that the structure zoning of the marine residual basin has been redetermined, the basin structure has been defined, and 3 seismic reflection marker layers are traceable and correlatable in the residual thick Middle-Paleozoic strata below the continental Meso-Cenozoic strata in the South Yellow Sea Basin. Based on these, the seismic sequence of the marine sedimentary strata was established. According to the avaliable oil and gas exploration and research, the marine Mesozoic-Paleozoic oil and gas prospects of the South Yellow Sea were predicted as follows. (1) The South Yellow Sea Basin has the same sedimentary formation and evolution history during the sedimentary period of the Middle-Paleozoic marine basin with the Sichuan Basin. (2) There are 3 regional high-quality source rocks. (3) The carbonate and clastic reservoirs are developed in the Mesozoic-Paleozoic strata. (4) The three source-reservoir-cap assemblages are relatively intact. (5) The Laoshan Uplift is a prospect area for the Lower Paleozoic oil and gas, and the Wunansha Uplift is one for the marine Upper Paleozoic oil and gas. (6) The Gaoshi stable zone in the Laoshan Uplift is a favorable zone. (7) The marine Mesozoic-Paleozoic strata in the South Yellow Sea Basin has the geological conditions required to form large oil and gas fields, with remarkable oil and gas resources prospect. An urgent problem to be addressed now within the South Yellow Sea Basin is to drill parametric wells for the Lower Paleozoic strata as the target, to establish the complete stratigraphic sequence since the Paleozoic period, to obtain resource evaluation parameters, and to realize the strategic discovery and achieve breakthrough in oil and gas exploration understanding.