Liwan Gas Project: First South China Sea Deepwater Completions Campaign

Abstract

Abstract Husky Energy installed 14 " frac-pack?? lower completions, 10 sub-sea horizontal trees, and 7 upper completions utilizing two 6-th generation deep water semi-submersibles in Block 29/26 of the Pearl River Marine Basin (PRMB) South China Sea between June 2011 and January 2013. On average, the lower completions, tree installation and upper completions required, 12 days, 2 day and 24 days, respectively. The water depth ranged from 650 m to 1450 m. Introduction In 2004 Husky Energy signed a production sharing contract with the China National Offshore Oil Company (CNOOC) for Pearl River Basin South China Sea deep water Block 29/26 which is 320 km south of Hong Kong (see Figure No. 1). In April 2006, the exploration well Liwan 3-1-1 was drilled in 1500 meters of water discovering the Liwan 3–1 gas reservoir. A 6th generation semi-submersible being built in South Korea was contracted for 3 years (plus 2 × 1-year options). Drilling re-commenced in November 2008 and by November 2011, 26 wells were drilled consisting of 10 exploration wells, 10 appraisal wells and 6 development wells. Six wells were drill stem tested. Three fields with gas-bearing sandstone reservoirs were discovered; Liwan 3–1, Liuhua 34–2, and Luihua 29–1 (See Figure No. 2) Regional Geology The Liwan 3–1 field is located in 1300 to 1500 m water depth within the Baiyun Sag of the Zhu 2 Sub-basin. The two nearest fields are the Panyu 30–1 gas field and the Liuhia 11–1 oil field located 64 km north-west and 102 km northeast, respectively. The PRMB lies on the northern continental shelf of the South China Sea. The Liwan structure developed during the early Miocene. The organic-rich sediments on the Wenchang formation, middle to upper Eocene, are considered to be the potential source rock for the reservoir. The tectonic events during the Oligocene-Miocene period which affected regional sea levels led to significant changes in the drainage framework of the Pearl River, provenance of sediments and depositional environments. Following these tectonic events, thermo-subsidence occurred in the Baiyun Sag and the depositional environment changed from a continental shelf with neritic deposition to a continental slope with deep-water deposition. The main hydrocarbon bearing reservoir, Zhujiang formation, in the Liwan 3–1 Gas field is a turbidite basin-floor fan. The lithology is predominantly claystone and siltstone with local thin deep-water sand stone units. During the Nanhai movement in Late Oligocene most parts of the PRMB were uplifted and partially eroded to form a wide regional unconformity surface. As a result of subsequent sea level rise most portions of the Baiyun sag exhibited shallow marine sedimentation. During subsequent regression, delta profradation occurred primarily in the south Uplift Belt in the southern part of the Baiyun Sag. The Zhuhai Formation, found beneath the Zhujiang formation, is characterized by excellent reservoir quality, deltaic-shallow marine sandstones.