Significant breakthrough in proprietary deepwater natural gas exploration in the northern South China Sea and its inspiration

In 2014, Zhanjiang Branch of CNOOC Limited obtained high oil and gas flows (160 × 104 m3/d) in Well LS 17-2-1 in northern South China Sea. The tested formation is the Neogene Upper Miocene Huangliu Fm. This is the first self-explored natural gas field in deep water area in China. Exploration in this area underwent three periods: (1) Reconnaissance exploration period (before 2002): Limited by techniques, the major exploration was in shallow water areas; (2) Foreign cooperative exploration period (2002-2012): As the discovered reserve scale was small, and there is no economic benefit, the partners successively gave up their exploration equities in the deep water area of western South China Sea; however, the high quality source rocks and reservoirs were confirmed in the deep water area of the South China Sea, revealing the mask of hydrocarbon exploration in this region; (3) Self-exploration period (since 2013): Relying on national science and technology major projects and its scientific research and production, Zhanjiang Company of CNOOC conducted several scientific researches on seismic data acquisition and processing, high-quality reservoir distribution, key factors for hydrocarbon accumulation in deep water areas, optimized and confirmed Lingshui 17-2 structure as the first drilling target, and obtained significant exploration breakthrough. Lingshui 17-2 structure is located in the Ledong-Lingshui section of the Central Canyon. Its major target layer is the Huangliu Fm. Its total thickness is over 150 m, with sandstone ratio of 75.4%, maximum single layer thickness of 52 m, porosity ranging 30.0%-33.7% (31.5% averagely), permeability ranging 293-2512 mD (633 mD averagely), belonging to reservoir with ultrahigh porosity and high-ultrahigh permeability. The exploration breakthrough in Lingshui 17-2 shows the giant potentiality of hydrocarbon exploration in this deep water area.