FLNG: Applying Advanced Technology To Bring More Natural Gas to Market

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 25907, “FLNG: Applying Advanced Technology To Bring More Natural Gas to Market,” by Alexander Boekhorst, Bruce Steenson, and Harry van der Velde, Shell, prepared for the 2015 Offshore Technology Conference, Houston, 4–7 May. The paper has not been peer reviewed. The constraints of space and seaworthiness required the designers of Shell’s joint-venture floating-liquefied-natural-gas (FLNG) facility to assemble these technologies in novel configurations. The operator is applying standardization as a philosophy for its FLNG design so that developments can become faster and more cost effective and has also developed an FLNG solution designed for leaner-gas fields that has many similarities to standard FLNG designs. The so-called “FLNG Lean” is able to deliver higher LNG-production capacities. Introduction With a long history in the LNG industry, the operator signed an agreement with a consortium of heavy-industry companies to design and build multiple FLNG facilities and entered the front-end engineering design (FEED) development phase, which focused on the technical requirements of the project. The operator’s Prelude project was the world’s first to make a final investment decision on an FLNG facility in May 2011. The Prelude project is expected to produce 3.6 million t/a (mtpa) of LNG, 1.3 mtpa of condensate, and 0.4 mtpa of liquefied petroleum gas (LPG). Proven Technologies in Innovative Combinations The operator’s FLNG facility itself is large but is still one-quarter the size of an equivalent facility on land. The key components of an FLNG development include standard gasfield components such as production wells, subsea templates and risers, and the floating facility itself. The facility is a full floating production facility with living quarters; gas- processing, -treatment, and -liquefaction facilities; and product-storage and -offloading facilities. All of these are integrated into a single design. All processing operations are carried out offshore, with LNG, LPG, and condensate product exported directly from the facility. Once constructed, the FLNG facility will be towed to the field site where it will be moored for the duration of operations— approximately 20 to 25 years— without being disconnected. The FLNG unit has been designed to withstand extreme weather, including a Category 5 cyclone, and will remain on location during all conditions. The FLNG facility has an internal turret because this configuration is more suitable for fields that require larger and more complex subsea systems and an increased number of risers. Internal turrets are also better suited for harsh metocean conditions. All the subsea connections join the facility by the turret. Production wells on the seabed feed gas and condensate from the reservoirs through a number of flexible risers and a standard fluid-transfer system (swivel stack) into the facility.