Operator : Chevron
Water Depth : 1,300 m / 4,290 ft
Region : Australia
Country : Australia
Located about 43 to 87 miles (70 to 140 kilometers) off the northwestern coast of Western Australia in the Carnarvon Basin and on the Northwest Shelf, the Greater Gorgon area incorporates a number of gas fields in waters ranging from 722 to 4,265 feet (220 to 1,300 meters). With estimated reserves of 40 Tcf (1.1 Tcm) of gas, Greater Gorgon is Australia's largest undeveloped gas resource.
Spanning the offshore blocks of WA-18-R, WA-267-P and WA-268-P, Greater Gorgon incorporates various gas discoveries in the area made over many years. In addition to the massive Gorgon gas field (discovered in 1981), Greater Gorgon includes the wildcat wells of Geryon-1 (1999), Orthrus-1 (1999), Urania-1 (2000), Maenad-1 (2000), Jansz-1 (2000), Io (2001), Chandon-1 (2006), and Achilles (2009), Satyr (2009), among others.
The Gorgon JV, made up of the Australian subsidiaries of Chevron (the operator with 50% interest), Shell (with 25% interest) and ExxonMobil (with 25% interest), plans to commercialize Greater Gorgon through extensive subsea developments, subsea pipelines and an LNG facility onshore Barrow Island for an estimated US $11 billion.
Upstream development plans for Greater Gorgon include subsea completions for both the Gorgon and Jansz fields. These subsea developments will be tied-back to the onshore Barrow Island LNG plant via pipelines and control umbilicals.
The Gorgon JV awarded both the Front End Engineering and Design (FEED) and the Engineering, Procurement, Construction Management (EPCM) contracts for the upstream development to a Technip/JP Kenny 50/50 JV. Awarded in June 2005, the contracts are worth more than US $75 million and include all subsea development, including the pipelines connecting the fields to the LNG facility.
Each well brought into production will have a subsea tree and surface-controlled subsurface safety valve installed. The trees will then be connected to a cluster, which can accommodate up to eight wells. These clusters will then be connected to production centers on the fields via well jumpers.
Subsea development on the Gorgon field includes two production centers in the first phase. One center will accommodate six subsea wells, and the other will be able to accommodate four subsea wells. A 4-mile (6-kilometer) infield flowline will be constructed to connect the two production centers.
Development on the Jansz field includes one production center that will be able to accommodate up to six subsea wells.
Up to 30 subsea wells will be drilled on the Gorgon and Jansz fields during their production lives. Directionally drilled from various manifolds on the field, the wells will range in water depths of 656 to 4,265 feet (200 to 1,300 meters).
As pressure and production decline from the Gorgon and Jansz fields, other fields in the Greater Gorgon area will be tied into the gas processing facility through subsea systems. The lifetime of the Greater Gorgon project is estimated to span 60 years.
ROVs, offshore work vessels and semisubs will be used for inspection and maintenance on the subsea system.
Individual pipelines will connect the subsea production centers on the Gorgon and Jansz fields to Barrow Island through 30-inch-diameter Corrosion Resistant Alloy multiphase flowlines, with mono-ethylene glycol used for hydrate inhibition and depressurization. Additionally, each pipeline will include an umbilical to transport electric and hydraulic power, signals, and chemicals to the subsea development.
The pipeline connecting Gorgon field to shore will measure 40 miles (65 kilometers), and an additional 7 miles (12 kilometers) of pipeline is being built to connect to the LNG facility. The pipeline connecting the Jansz field to shore will measure 112 miles (180 kilometers) with an additional 7 miles (12 kilometers) of pipeline connecting it to the LNG plant.
The subsea developments and pipeline will be controlled by an electrohydraulic multiplex of primary fiber optic communications from a control system at the LNG plant.
Furthermore, development plans include a domestic gas pipeline to shore.
The Gorgon JV submitted a project proposal for the commercialization of Greater Gorgon in 2001. Although Barrow Island has had a major oil field operating on it since 1967, the island is classified as an A-class nature reserve, imposing even more stringent environmental conditions on the project proposal.
The Greater Gorgon project proposal was approved by the Australian government with the passing of the Barrow Island Act 2003 legislation through the Western Australian Parliament in November 2003.
Additionally, the Gorgon JV received state and federal environmental approvals in the fall of 2007 for a two train LNG facility on Barrow Island. Since the JV submitted its first application, the project scope grew to a three train LNG facility with a 15-million-tons-per-year capacity. A revised project proposal has been resubmitted to reflect this increase in production, and the JV is confident that it will receive governmental approval.
Once the necessary governmental approvals have been obtained and FEED on the project is completed, the JV will again evaluate the financial commitment of the project before moving forward with construction.
|Sumber : SubseaIQ|