南海北部陆缘盆地深水区油气勘探前景

DEEPWATER HYDROCARBON POTENTIAL ALONG THE NORTH CONTINENTAL MARGIN ,THE SOUTH CHINA SEA

南海北部陆缘盆地深水区位于琼东南盆地中央坳陷带和珠江口盆地珠二坳陷,从盆地演化史来看,两盆地均经历了裂陷和裂后两大发育阶段.南海北部陆缘盆地深水区具有良好的石油地质条件:发育始新统-渐新统湖相泥岩和渐新统半封闭浅海相泥岩两套主要烃源岩;存在始新统-下渐新统河流-三角洲相砂岩、上渐新统-下中新统扇三角洲-滨浅海相砂岩和台地碳酸盐岩以及中新统半深海-深海相浊积砂岩等3套主要储层,其中中新统半深海-深海相浊积砂岩储层是深水区最有潜力的勘探目的层;发育多种类型的圈闭,从层位上看,下第三系以构造圈闭为主,而上第三系则以岩性圈闭为主;发育大量油源断层、多个不整合面和大面积连通砂体,构成了良好的油气输导体系,有利于油气聚集成藏.与国外已获油气发现的陆缘盆地深水区相比,南海北部陆缘盆地深水区具有相似的构造、沉积演化特征和相应的成油条件,目前南海北部深水区勘探程度尚低,有效勘探面积和勘探潜力巨大,因此具有良好的勘探前景.

Along the north continental margin,the South China Sea,the deepwater areas are located in the central depression zone of the Qiongdongnan Basin and Zhu Ⅱ depression of the Pearl River Mouth Basin,and both basins underwent two evolution phases (rifting and post rifting).There are excellent petroleum geology conditions in these deepwater areas:(1) Two sets of main source rock developed in Eocene Oligocene lacustrine mudstones and Oligocene semi closed neritic mudstones; (2)There are three sets of reservoir in Eocene Lower Oligocene fluvial/deltaic sandstones,Upper Oligocene Lower Miocene fan detaic/litteral neritic sandstones and platform carbonates and Miocene bathyal turbidites,with the Miocene turbidite facies most important; (3)Multiple types of trap have formed,with Paleogene dominated by structural traps and Neogene by stratigraphic traps; (4)Numerous faults,unconformities and wide connected sandbodies have constituted good migration pathways,which is favorable to hydrocarbon accumulation.Comparing these deepwater areas with the foreign deepwater basins with oil and gas dicoveries,it can be recognized that similar structural and sedimentary features and petroleum geology conditions exist along the north continental margin,the South China Sea,and these deepwater areas are hopeful of exploration prospect due to low exploration activities, wide exploration area and great exploration potential.