Hulls For Mega-FPSOs: Achieving Long Life And Performance From Sound Design To Asset Integrity Management

Abstract

TOTAL E&P Branch has steadily become a significant player in the field of Floating (Production) Storage and Offloading facilities, hereafter called FPSOs, key to several oil and gas field developments. Total E&P is present today in more than 43 countries with operated production of 2,9Mboe/d. From its broad experience, Total has capitalized on its technical knowledge, and is willing to standardize hull design whenever possible. A set of "General Specifications" has been developed for FPSO hulls, and is regularly revised. Three main drivers can summarize Total E&P philosophy in FPSO hull standards. First, durability: hulls shall be able to stay on field for the entire design life (typically 20 years) without need for heavy maintenance (and especially dry-docking); second, and as direct consequence of the first, safety: hull design shall always remain inherently safe. This safety by design has consequences on principles of lay-out and robustness to accidental condition and operation. Lastly, hulls shall be easy to engineer and build; our standards are also focused on the project execution phases: risks in terms of schedule and costs shall be mitigated as well through good engineering practices that are recalled to the Contractors. Once the units are in production, the "Floating Units Integrity Management program" is put in place to monitor the units from safety, environmental, operational, maintenance and quality management viewpoints. This in turn provides valuable feed back information for more efficient and standardized designs. Increasing complexity of installations leads to technical challenges, involving multi-disciplinary teams to define clear Company rules. Floating units are and will be a significant part of Total E&P offshore activity. Capitalization of experience gained from various projects and from operations helps to design more efficient and cost effective units. The paper will add a significant contribution in that area. View on Total E&P F(P)SO hulls Look back at our operated installations (combining those of former companies Total, Petrofina and Elf E&P), in the thirty-five year period between 1972 (when our first loading buoy was installed on Djeno (Congo) and now (installation of the mega-FPSO Dalia and loading buoy in 1350m water depth), the figures are as follows:22 SPM (Single Point Moorings, i.e. buoys and fixed loading towers),23 FSO (Floating Storage and Offloading, new-built storage units or converted tankers moored on chains, turrets, rigid arms, or mooring hawsers),6 FPS (Floating Production Systems) comprising 4 FPSO (Floating Production Storage and Offloading), 1 FGSO (Floating Gas Storage Offloading) and 1 TLP (Tension Leg Platform).The last decade was marked by more complex integrated floating units associated as well with an increase of water depth:The year 2001 was marked by the start of production on Girassol Field, through a huge spread-moored FPSO with an offloading CALM buoy in 1,400 m water depth (references [1] to [4] and Figure 1: "Girassol FPSO (Angola 2001)"). Main FPSO characteristics: size 300 m x 60 m x 31 m, storage 2,000,000 bbls, deck 180 m x 60 m with 25,000MT topsides - now extended to 31,000MT with Rosa field development, 16 mooring lines (cable 1.8 km dia 120 mm with 650 m chain at bottom to 17 m suction piles and 200 m chain to surface); tandem offloading is possible as a back-up of the CALM buoy. The FPSO and Buoy are connected with two 16" steel transfer lines.In 2003 Installation of the new built FSO Unity moored by an external turret in Nigeria (see Figure 2) and an export CALM buoy. The FSO Unity is also equipped with tandem offloading as a back-up. Main characteristics of the FSO: hoses 3x24" and one 6" gas line, mooring with 9 chains each 733m long terminated with a 12 ton anchor, FSO size 298,000 dwt, storage capacity 2,400,000 bbls (300 m x 62 m x 32.2 m), water depth 65 m.In 2003 installation of the new built FPSO Farwah moored by an external turret on Al Jurf field (Libya 2003) with offloading of export tankers in tandem mode (see Figure 3). Main characteristics: dimensions 210 m x 44 m x 23 m, storage capacity 900,000 bbls, water depth 90 m.