琼东南盆地第四纪中央峡谷体系沉积演化与油气前景

Sedimentary Evolution and Hydrocarbon Exploration Prospect of the Quaternary Central Canyon System in the Qiongdongnan Basin

基于琼东南盆地中央峡谷已有钻井和高品质新地震资料,对第四纪中央峡谷体系的外部形态、内部构成、沉积演化过程及其主控因素等进行了系统梳理和研究,明确中央峡谷体系经历了晚中新世侵蚀充填期(Ⅰ期),早上新世平静充填期(Ⅱ期)和第四纪早期回春充填期(Ⅲ期)3期演化阶段,提出控制中央峡谷体系前两期形成的负地貌和物源供给在第四纪峡谷西段仍然存在.进一步研究表明西段早期多物源体系在第四纪变为昆嵩隆起秋盆河单物源,进积型陆坡控制了半限制型负地貌和砂质沉积逐渐向南东迁移,并在第四纪早期(S14)填平峡谷.在此认识指导下首次在峡谷西段浅层发现了3期第四纪半限制型海底扇群,具备"深浅双源供烃-优势通道复合输导-浅层水合物地层封盖-海底扇成藏"的成藏模式,是下一步深水区浅层寻找大中型气田的有利新领域.

Based on the drilling data and new high-quality seismic data of the Central Canyon in Qiongdongnan Basin, the morphology, internal composition, sedimentary evolution process, and main controlling factors of the Quaternary Central Canyon System are systematically studied. The results indicate that the Central Canyon System went through 3 stages of evolution: the erosion and filling stage in the early Upper Miocene( Ⅰ stage), the calm filling stage in the early Pliocene( Ⅱ stage), the rejuvenation stage in early Quaternary(Ⅲ stage), and the evolution of the Canyon System was jointly controlled by tectonic activity and source supply. The negative paleogeomorphy and provenance supply that controlled the formation of the Central Canyon System in the first two stages still existed in the western segment of the Quaternary canyon. The early multi-provenance system in the western segment changed to the single provenance of the Qiupenhe River in the Con Son Swell in the Quaternary,and the provenance supply was sufficient. The progradational continental slope controlled the semi-restricted negative landform and sandy deposition to migrate gradually to the southeast, and the Canyon was filled up in the early Quaternary(S14). Under the guidance of this understanding, three-stage semi-restricted-scale submarine fan groups in the shallow strata of the western segment of the Quaternary canyon are discovered for the first time. These submarine fan groups have superior conditions for reservoir formation and have the new hydrocarbon accumulation model of "shallow-deep dual hydrocarbon source supplying, multiple preferential pathways conducting, shallow gas hydrate sealing, submarine fan below the hydrate stable zone controlling accumulation", and are new fields of large-middle scale oilfield exploration with broad prospects.