|Graphic of Prelude FLNG. Click to enlarge.|
The Board of Royal Dutch Shell plc has made the final investment decision on the Prelude Floating Liquefied Natural Gas (FLNG) Project in Australia (100% Shell); Shell will now start detailed design and construction of what will be the world’s first FLNG facility. (Earlier post.) Moored some 200 kilometers offshore Australia, the FLNG facility will produce gas from offshore fields and liquefy it onboard.
Gas resources are found all over the world in remote offshore accumulations that are too costly or difficult to develop. In Australian waters alone there is an estimated 140 trillion cubic feet of such stranded gas, according to a 2008 report by the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Shell FLNG technology will make it feasible to develop such resources, since it reduces both the cost and environmental footprint of their development.
Having the gas-processing and gas-liquefaction facility located at the site of an offshore field removes the need for: gas-compression platforms; long subsea pipelines to shore; near-shore works, such as dredging and jetty construction; and onshore construction, including roads, storage yards and accommodation facilities. FLNG can also accelerate LNG developments; an FLNG vessel can be ordered at an earlier stage of appraisal of a new gas field, with less guarantee of production longevity than needed to underpin an onshore greenfield investment; if and when the gas resources in the first field are exhausted, the FLNG can be redeployed to another field.
From bow to stern, Shell’s FLNG facility will be 488 meters long, and will be the largest floating offshore facility in the world. When fully equipped and with its storage tanks full, it will weigh around 600,000 tonnes – roughly six times as much as the largest aircraft carrier. Some 260,000 tonnes of that weight will consist of steel—around five times more than was used to build the Sydney Harbour Bridge.
Despite its proportions, the facility is one-quarter the size of an equivalent plant on land. Engineers have designed components that will stack vertically to save space. The operating plant, for example, will be placed above LNG storage tanks. They also came up with the idea of using cold ocean water to help cool the gas, avoiding the need for extra equipment on deck. An assembly of eight one-metre diameter pipes will extend from the facility to about 150 m below the ocean’s surface. It will deliver around 50,000 m3 of cold seawater each hour. This helps to cool the gas from below the facility, saving deck space.
Our innovative FLNG technology will allow us to develop offshore gas fields that otherwise would be too costly to develop. Our decision to go ahead with this project is a true breakthrough for the LNG industry, giving it a significant boost to help meet the world’s growing demand for the cleanest-burning fossil fuel. FLNG technology is an exciting innovation, complementary to onshore LNG, which can help accelerate the development of gas resources.—Malcolm Brinded, Shell’s Executive Director, Upstream International
The facility will be secured in place by one of the largest mooring systems in the world. Four groups of mooring lines will anchor it to the seabed. The system allows the facility to turn slowly in the wind, absorbing the impact of strong weather conditions, while remaining moored over the gas field. It is designed to stay moored at sea even during the most powerful cyclones, saving production days that would otherwise be lost on disconnecting the facility and moving it off the field.
Three 6,700-horsepower engines will sit in the rear of the facility. Two of these will operate at any one time to turn the facility out of the wind and allow LNG carriers to pull safely alongside to load. The facility’s storage tanks will be below deck. They can store up to 220,000 m3 of LNG, 90,000 m3 of LPG, and 126,000 m3 of condensate. The total storage capacity is equivalent to around 175 Olympic swimming pools.
Ocean-going LNG carriers will offload liquefied gas, chilled to -162 °C and shrunk in volume by 600 times, and other products, directly from the facility out at sea for delivery to markets worldwide. Until now, the liquefaction of offshore gas has always involved piping the gas to a land-based plant.
Shell has progressed the Prelude FLNG project at a rapid pace, with first production of LNG expected some ten years after the gas was discovered.
The FLNG facility will tap around 3 trillion cubic feet equivalent of resources contained in the Prelude gas field. Shell discovered the Prelude gas field in 2007.
Some 110,000 barrels of oil equivalent per day of expected production from Prelude should underpin at least 5.3 million tonnes per annum (mtpa) of liquids, comprising 3.6 mtpa of LNG, 1.3 mtpa of condensate and 0.4 mtpa of liquefied petroleum gas. The FLNG facility will stay permanently moored at the Prelude gas field for 25 years, and in later development phases should produce from other fields in the area where Shell has an interest.
Beyond this, our ambition is to develop more FLNG projects globally. Our design can accommodate a range of gas fields, and our strategic partnership with Technip and Samsung should enable us to apply it progressively faster for future projects. We see opportunities around the world to work on other FLNG projects with governments, energy companies and customers.—Malcolm Brinded
The Prelude FLNG project will be the first Australian upstream project in which Shell is the operator. Australia is one of Shell’s key growth provinces, and Shell’s upstream investment in Australia should reach some $30 billion over the next five years, including the Prelude and Gorgon projects, and on-going exploration and feasibility studies in the country.