The paper describes a design family for 'ship to ship' and 'ship to shore' transfer systems for LNG. The common design philosophy is explained and each configuration is described briefly. Auxiliary systems and equipment are discussed as are operational procedures.A case study is presented for a near shore LNG terminal, comprising a marine transfer system in combination with a regasification plant and a salt dome storage cavern. The regasification plant and the salt dome storage cavern are treated extensively.The systems described will greatly advance the implementation of offshore terminals for LNG. Although new, all of the components used are proven and have been applied in LNG terminals and offshore loading systems longtime.
This paper describes the conceptual design of an offshore liquidified natural gas (LNG) import terminal based on the "Bishop Process," sited on Vermilion block 179, offshore Louisiana. The Bishop Process comprises direct regasification of LNG in the dense phase and storage of the gas thus produced in salt caverns. (For conversion factors of units commonly used with LNG, please refer to Table 1.) The operating principles of this process are discussed, as well as the design considerations for the regas, storage, and send-out facilities. The single-point mooring (SPM) system for the offloading of LNG carriers is described, as well as the verification process thereof. The foreseen marine operations at the terminal are explained, and the work done confirms the technical and economical feasibility of the concept.
The paper describes the conceptual design of an offshore LNG import terminal based on the 'Bishop Process', sited on Vermilion, block 179, offshore Louisiana. It clarifies the Basis of Design for the complete terminal and describes the design and verification process followed for the Single Point Mooring ystem for offloading of LNG. The work done to date confirms the technical and economical feasibility of the concept. Although new in configuration, most of the individual components have been in use for LNG terminals and SPM systems for a long time. Introduction The US is currently by far the world's largest gas market. Of the current supply 85% is produced within the US, and 15% is imported; 98% from Canada and only 2% in the form of LNG. Whereas US demand is expected to grow with 2% per annum, the current U.S. gas production shows an increasing intrinsic decline rate and more undiscovered gas reserves are needed each year to keep up with demand. E&P operations in new frontier areas (e.g. the Alaskan North slope) are unlikely to be allowed in the near future and gradually the realization is dawning that only large scale LNG imports can meet the expected demand and stabilize the price of natural gas. In its annual outlook for 2004 the US Energy Information Administration predicts that LNG imports will grow from a modest 0.2 tcf in 2002 to 4.8 tcf or 15% of expected total supply by 2025[1]. Although new liquefaction projects for gas are being sanctioned, community concerns, congested ports, security and cost considerations are seen to frustrate the development of significant increases in capacities to receive LNG in the US but also in Europe. This paper describes the conceptual design for an offshore LNG import terminal based on the 'Bishop Process', which is developed as part of a research project sponsored by the US Department of Energy's National Energy Technology Laboratory. Ten companies, ranging from operators, mid stream companies, contractors and equipment vendors are participating in this project. The objective of this cooperative research is to design, construct, field test and evaluate the performance of key components of a salt cavern based LNG receiving facility and to describe their application in LNG receiving facilities in the Gulf coast and North-East US. Salt cavern based LNG import terminals have material advantages over tank design terminals in capital costs, operating costs, volume of storage, send out rates, security, and acceptance by the community[2]. As a consequence of the abundant appearance of salt formations found in the Gulf region in combination with hydrocarbon accumulations, the concept has very high potential in this region: not only is the connecting infrastructure to the US gas distribution system in place, it is also underutilized because of declining production and thus there is capacity available to handle large volumes of LNG imports.
Bluewater's Haewene Brim Floating Production Storage and Offloading (FPSO), moored by means of an internal turret mooring system in the central North Sea since 1998, ran out of its original 15 years design life. Good field performance and the tie-in of another field resulted in a targeted lifetime extension for the FPSO of 18–20 years. In the late 90s a number of turret mooring systems, with a typical design life of 15 – 20 years have been installed in the North Sea. A number of these, currently or in the near future, might also be subject to lifetime extension programs. The technical challenges experienced during the lifetime extension project of the Haewene Brim FPSO mooring system will be discussed in this paper. The main objective for the lifetime extension program of the mooring system was twofold: to design a mooring system which allows for continuous operations for the extended lifetime and to maximize the utilization of existing components. A number of the findings, steps of the design process and challenges are described in this paper and solutions are presented. This is complemented with a discussion regarding mooring integrity issues (birdcages in spiral strand wire sections) faced with over the last few years, which made it more challenging to fulfill the original design life and to design a new mooring system within the targeted boundary conditions.
Mooring systems remain an important component of an overall field development. There are numerous sources in literature describing challenges with mooring systems as well as potential solutions. The goal of this paper is to present a number of new technologies which can be applied jointly in an integrated framework to monitor integrity of subsea mooring components. The paper will cover (1) direct tension measurements using Vibrating Wire Gauges, (2) warning systems based on anomaly detections from GPS measurements and (3) mooring line force estimation method and fatigue using time-domain simulation methods. Vibrating Wire Gauges are a potential alternative to the use of in-line load cells or inclinometers for measuring mooring line tensions. These sensors have a proven track record in the Geotechnical Industry. A sensor dedicated for the offshore industry has been developed. The main benefit of this type of sensor is the ease of retrofitting in an offshore environment. Long-term stability tests and dynamic tests were executed and will be presented. Procedures for installation and maintenance were developed. GPS measurements have widely been used in the industry to identify mooring failures. Post-processing methods of these measurements range from application of watch circles to Artificial Neural Networks. However, there remain important challenges with performance of these warning systems under the influence of environmental loads. The authors will show a basic concept which can overcome these limitations. High accuracy floater position and motion measurements can be used in combination with a numerical model to determine mooring line forces in the field. This approach combines the numerical models used in the design with onboard integrity and maintenance procedures. The technical and organisational challenges of such approach are discussed. An onboard system able to capture system drift is used to update the numerical model and correct for deterioration of the mooring system over time. In-service measurements have been used to demonstrate and validate the concept. The methodology has been implemented and installed on an offshore asset which will become active in Q1 2019. A number of industry solutions for mooring line integrity methods have been compared. All presented solutions have a role in the total mooring subsea integrity management program. Integration of these components together or supplemented with numerical analysis can be used to develop an overall mooring subsea integrity management plan and philosophy.
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