Development of Cyrogenic Marine (In-Water) LPG Export Hose Escravos Gas Project

Abstract

Abstract A cryogenic marine hose has been developed for exporting LPG at minus 43 degrees C as part of the Chevron Nigeria Escravos Gas Project for Chevron Nigeria Ltd. and the Nigerian National Petroleum Company. The LPG will be stored in a permanently moored floating storage and offloading (FSO) system. Environmental conditions require mooring the export tanker in tandem with the FSO. To transfer the LPG from FSO to export tanker, a program was initiated to develop a floating marine cargo hose suitable for this application. This will be the first application of such. The development program was conducted in three phases, 1) Engineering, 2) Prototype Hose Construction, and 3) Prototype Hose Testing. The development program was designed to establish confidence in deploying the hose; the test program addressed a wide range of conditions. The development program was successfully completed and manufacture is underway for field deployment in early 1997. Introduction Chevron Nigeria Ltd. (CNL) produces approximately 400,000 bbl of oil per day, most of it coming from the Escravos area, offshore Nigeria. Along with the oil is a large quantity of associated gas which is flared. To reduce flaring and to recover the gas and condensates, Phase 1 of the Escravos Gas Project (EGP) was initiated by the joint venture partners, Nigerian National Petroleum Co. (NNPC 60%) and CNL (40%). Figure 1 depicts the field layout and the EGP phase 1 Development Plan. The EGP consists of three major elements:New Gas Gathering, Compression and Personnel Platforms.New On-shore Gas Processing and Extraction Plant.New LPG Floating Storage and Offloading vessel (FSO) and a Dedicated Shuttle Tanker. Associated gas from the Okan and Mefa fields, two of the many in the Escravos area, is recover& by the new gas gathering and compression platform. The gas is pumped to the onshore gas processing plant where the recovered gas is processed to produce condensates (which are blended with crude oil for export), natural gas (piped for domestic use in Nigeria) and liquifiedpetroleum gas (LPG, which is pumped offshore to the FSO for refrigeration, storage and export). The subject of this paper is the program undertaken to develop marine (in-water) LPG hose for transferring the LPG at approximately minus 43 degrees C from the FSO to the shuttle tanker for export to market. Reasoning for Embarking on the Hose Development Program During the project definition and conceptual design stage, several configurations were evaluated for storing and exporting the LPG. The configurations evaluated included a deepwater harbor with export terminal and offshore storage and export via an FSO. The offshore storage and export option was selected as the optimal solution.