Shiyou shiyan dizhi (Sep 2020)
Marine petroleum exploration in South China
Abstract
Marine strata in South China are mainly distributed in the Paleozoic and Mesozoic. The strata are old and the thermal evolution degree is high. It was controlled by the multi-cycle sedimentary and multi-stage structural evolution history. The petroleum basic geological conditions are superior, but the distribution of oil and gas is complicated. Oil and gas exploration has mainly gone through three stages: general survey, structural reservoir, massive lithologic gas reservoir and shale gas exploration. Although major breakthroughs have been made in many fields, the overall detection rate is low. A systematic summary of the early discovery of large gas fields and the new progress of exploration was made in order to clarify the prospects for oil and gas exploration. There is a large potential for marine petroleum exploration in South China. Deep and ultra-deep strata as well as new areas are important breakthrough directions in the Sichuan Basin. The unconventional shale gas reservoirs in the Upper Ordovician Wufeng-Lower Silurian Longmaxi formations and the conventional gas reservoirs in the platform margin zone of the Upper Sinian Dengying Formation in Langzhong-Yuanba, the platform inner beach facies in the Sinian-Cambrian in Tongnanba, the pre-salt strata in the lower assemblage in Qijiang in the southern Sichuan and the reef beach facies in the Permian-Triassic have a total resource amount to trillions of cubic meters, which is expected to achieve a new round of breakthroughs and discoveries. Besides, unconventional shale gas in the Permian and Jurassic and some new targets for conventional gas such as hydrothermal dolomites, karst fissure group, stucco limestones and sedimentary tuffs in the Permian show a great exploration potential. New discoveries continue to be made in complex basin-margin regions in the Sichuan Basin. Shale gas in the residual syncline area and conventional piedmont areas in the basin margin are the main exploration directions. The periphery of ancient uplifts and the progressive deformation area in the southern periphery have weak structural deformation, and the preservation conditions are favorable with a certain exploration potential, and are expected to become a strategic succession area for oil and gas.
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