Distribution of the Mesozoic in the continental margin basins of the South China Sea and its petroliferous significance

摘要

Based on 40 wells encountering the Mesozoic sedimentary rocks, 52 thousands kilometers of seismic profiles covering most parts of the South China Sea (SCS) and the latest collection of gravity and magnetic data, the distribution of the Mesozoic in the continental margin of South China Sea and the oil and gas exploration prospect are studied. The Mesozoic is distributed in three main areas in the SCS: (1) the area of eastern Pearl River Mouth Basin and Southwest Taiwan Basin, where the Mesozoic buried at 1–3 km deep and 2–8 km thick, is thickest in the Chaoshan Depression and east Dongsha Uplift, and there is a long axis gentle fold in the east of the Pearl River Mouth Basin; (2) Liyue-Palawan Basin area, where the Mesozoic, 2–4 km deep and 2–5 km thick, is thickest in the south depression of the Liyue Basin; (3) Zhongjiannan-Wan'an-western Nanwei Basin area, where the Mesozoic is 3–5 km deep and 2–3 km thick. According to the spatial location relationship between the Mesozoic distribution and deep faults, it is inferred that the Mesozoic distribution is controlled by the eastern Yangjiang-Yitong Shoal fault, Balabac fault and YueDong-Wan'an fault, and affected by the uneven base uplifting and block faulting caused by the Mesozoic Pacific plate subduction to the East Asian continent. The study on the distribution of residual Mesozoic strata, structural traps and source rocks concludes that there are two favorable areas for the Mesozoic hydrocarbon exploration, namely, Chaoshan Depression and Dongsha Uplift in the east of Pearl River Mouth Basin, and south depression in the Liyue Basin. However, the exploration prospect of the Zhongjiannan-Wan'an-western Nanwei Basin area needs further investigation.