Characteristics of hydrocarbon accumulation and exploration potential of the northern South China Sea deepwater basins

Abstract

Although the huge potential of the northern South China Sea deepwater basins has been proven by a series of discoveries that followed the exploration breakthrough of well LW 3-1-1, recent drilling and other studies have demonstrated the uniqueness and complicated nature of hydrocarbon accumulations of the deepwater basins there. Based on a review of previous work and the latest exploration activities and studies, the purpose of this paper is to discuss the critical controls for hydrocarbon accumulations in the deepwater basins of the northern South China Sea. A terrestrial-marine transitional coal-bearing source rock is proposed to be the primary source rock for the deepwater basins. A marine source rock, which was first identified as contributing to hydrocarbon generation in this region, probably plays a significant role in the deep-and ultra-deep water basins south to the Pearl River Mouth and Qingdongnan basins. The shelf margin delta depositional systems in the Baiyun Sag, sourced from the Pearl River, are currently primary exploration targets in the deepwater part of the Pearl River Mouth Basin, whereas the western Red River deltaic-submarine fan depositional systems, initially proven by drilling, are the possible major exploration reservoirs in the Qingdongnan deepwater areas. Current deepwater exploration targets at the large-sized structural traps and deep and ultra-deep areas in the south of the Pearl River Mouth and Qingdongnan basins will be the future exploration focus. Deepwater exploration activities and relevant fundamental studies, supporting and promoting each other, are of great importance to the national energy supply of China, the basic regional studies of the South China Sea, advancements in technology, and development of related deepwater industries, and will safeguard national sovereignty and territorial integrity.

The dynamic mechanism of post-rift accelerated subsidence in Qiongdongnan Basin, northern South China Sea

“…Qiongdongnan Basin, located at the western end of the northern continental margin of South China Sea, is mainly composed of a shelf and adjacent deepwater depressions, rich in oil and gas resources (Zhu et al 2012;Zhang 2010).…”

Sedimentary facies and the rifting process during the late Cretaceous to early Oligocene in the northern continental margin, South China Sea

“…The late Cretaceous to early Oligocene formations in the northern SCS margin are proven as main source rocks, in which the lacustrine deposits are dominantly oil prone, and the marine and paralic ones are gas prone (Zhu et al, 2012). As discussed above, the early to middle Eocene locally distributed lacustrine Lingtou Formation in the QDN basin and widely distributed lacustrine Wenchang Formation in the PRM basin were developed during the second episode of rifting.…”

“…The continental breakup and ocean-floor spreading processes of the SCS have been investigated extensively (Tapponnier et al, 1982;Taylor and Hayes, 1983;Ru and Pigott, 1986;Briais et al, 1993;Wang et al, 2000;Hall, 2002;Ren et al, 2002;Hsu et al, 2004;Wang and Li, 2009;Li et al, 2014). A lot of work has been done to study the hydrocarbon-bearing conditions of the basins in the northern SCS margin (Chen et al, 2003;He et al, 2006He et al, , 2009Zhu and Mi, 2010;Zhu et al, 2012;Shi, 2013;Zhang et al, 2013). Many hydrocarbon fields have been found in this area, with a recent oil-equivalent production up to 2000 × 10 4 m 3 per year .…”

Deeply buried ancient volcanoes control hydrocarbon migration in the South China Sea

“…Deposition during the subsequent period of post-rift thermal subsidence (Early Miocene-Present), was dominated by very fine-grained, pelagic and hemipelagic strata, which provide an excellent regional seal (Zhu et al, 2009 the Early-Middle Miocene (Zhu et al, 2009). These faults, together with highly permeable unconformities and mud diapirs, provided the main pathways for hydrocarbon migration in the northern SCS (Zhu, Zhong, Li, Xu, & Fang, 2012). These faults, together with highly permeable unconformities and mud diapirs, provided the main pathways for hydrocarbon migration in the northern SCS (Zhu, Zhong, Li, Xu, & Fang, 2012).…”