'SS-Offshore Offloading Systems and Operations' Bonded flexible Oil Offloading Lines, a cost effective alternative to traditional Oil Offloading Lines

摘要

In deepwater offshore fields where spread moored FPSOs are involved, the produced oil is generally offloaded to shuttle tankers via Oil Offloading Lines (OOLs) connected between the FPSO and deepwater buoy. Until recently, two types of Oil Offloading Lines (OOL) were used for the transfer of stabilized crude oil between the FPSO and the offloading buoy: steel pipe or unbonded flexible pipe. Since 2000 Trelleborg and SBM have been working on an alternative offloading solution made of bonded flexible hoses called TRELLINE? (see reference [1]). This product can be adapted to a large range of applications like for the offloading of oil from a MOPUstor to a submerged loading system (SLS). In September 2005, the TRELLINE? was used for OOL for the first time for SNEPCO who decided to supplement the existing Bonga OOL system with one 20" ID TRELLINE? to match with ultra short delivery. In December 2006, the OOL was installed with the SBM vessel Dynamic Installer (see reference [2]). In July 2008, Total Exploration Production Angola (TEPA) decided to use the TRELLINE? for the 18" ID OOLs of the Pazflor field. For Pazflor, the produced oil is exported from the FPSO to the buoy located 1,856m away, via two identical 18" OOLs of 2,070 m long, made of 175 hoses sections each. The OOLs are connected to the FPSO and the buoy by the means of gimbal tables that decouple the tension and bending loading. Specificity of Pazflor Trelline hoses was their hig desing pressure equal to 50 bars that had required intensive qualification and testing program, and making Pazflor export lines a "world-first". Based on past installation experiences on Bonga project (OOL) for SNEPCO in 2006 and on Yme project (SLS) for Talisman Energy Norge in 2008, see reference [3]), a new installation method has been developed. A specifically designed patented equipment was developed to ensure a safe and quick offshore installation. It comprises: 1. An A-Frame designed to upend individual hose from deck to the fire line. 2. An assembly platform designed for vertical assembly of the hoses. 3. A large deployment wheel ensuring the transition from vertical to horizontal of the OOL at the sea surface. In June 2011, the SBM vessel Normand Installer successfully installed the two Pazflor OOLs. The two OOLs were assembled and hooked up in less than 4 weeks (mobilizations included). The TRELLINE? OOL system demonstrated its advantages in term of design, procurement cost, lead time, installation efficiency and operational advantages. It will further demonstrate maintenance advantages.