Floating Lng: the Challenges of Production Systems and Well Fluid Management

Floating Liquefied Natural Gas (FLNG) units combine gas pre-treatment to tight specifications and natural gas liquefaction that are new to offshore with traditional production systems that are commonly found on oil Floating Production Storage and Offloading (FPSO) vessels. Attention is often focused on the new units, sometimes forgetting that successful operation of the Liquefied Natural Gas (LNG) section requires properly designed inlet facilities and well fluid management. The challenges are greater still in deepwater and harsh environments. Technip has recently completed several front end engineering designs for FLNG projects. There have been many engineering challenges in the inlet facilities and well fluid management systems to ensure smooth delivery of gas to liquefaction. Chemicals injected in the production piping for hydrate or corrosion prevention, produced water and hydrocarbon condensate must all be removed and treated. Although this paper will describe floating LNG projects, it will focus on the challenges in the production systems that must be mastered to ensure proper and reliable operation of the FLNG. In particular, it will present challenges in the inlet facilities including gas, condensate and water handling and treatment. INTRODUCTION For several years, the offshore industry has been evolving from shallow water fixed platforms to deepwater field developments with floating facilities. Several technology gaps have been successfully filled, one of them being the transfer of industrial gas liquefaction from an onshore to an offshore environment. For a FLNG project development, both liquefaction and upstream production approaches shall be combined to maintain the proper operation of the floating liquefaction unit. Traditionally, offshore gas field developments linked to LNG include production facilities, a pipeline to receiving facilities at shore, and liquefaction plant onshore with large marine facilities (port, jetties, breakwater, etc.). What FLNG technology brings to the industry is a combination of all these into a same location, including also a combination of all the constraints previously independently managed. In an offshore environment, topsides weight is a key project driver whatever the support (from fixed platform to floating vessels). Weight affects directly the support size, project cost and stability of floating structures. Today a state-of-the-art large oil producing FPSO has the following characteristics:  Hull Dimensions = 310 m x 60 m  Topsides Weight > 40000 t  Production capacity is close to 200 000 bopd.  Flow from wells ~2000 t/h