The Shtokman Gas Condensate Field (SGCF) is located 610 km from Murmansk in the Barents Sea. The water depth at location is around 340 m. The offshore facilities of the SGCF Phase 1 development will include ice-resistant ship shape disconnectable turret moored floating platform (FP). Significant sea ice invasions occur at Shtokman in approximately 3 out of 10 years, on average. Icebergs may also occur in the SCGF area. Ice and iceberg management are planned to support the FP operations. The present paper describes the methodology to assess performance, operability and risk of the FP in waters where occasional invasion of sea and glacial ice is anticipated. Introduction Challenges with ice-related design and operating philosophy for the Shtokman FP have been described in [Ref. 1]. In brief, the main challenge is to achieve an appropriate reliability level and at the same time minimize operational downtime at acceptable costs. Table 1 summarizes the main ice-related challenges as identified in the pre-FEED and updated during the FEED, categorized by the accidental scenarios. Actions have been taken in order to address the challenges and quantitatively assess the risks. It shall be emphasised that no attempt was made to target the design of individual components to achieve the target reliability level for the entire system, i.e. floating platform with respect to ice actions. This is simply because it would have been too speculative given all the uncertainties involved. On the contrary, it was decided early to establish challenging but realistic design targets for the main systems (e.g. hull, mooring and disconnection system) and in parallel, work on design of the operational measures, including assessment of their efficiency and reliability. Further, quantitative operability and risk assessments of the entire system have been performed to evaluate potential needs for optimisation. The objective of this paper is to present the approach developed and used for assessing performance, operability and risk of the Shtokman Floating Platform with regard to sea and glacial ice. The content of this paper is based on numerous studies performed to provide input for the Final Investment Decision.
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.
The Shtokman Gas Condensate Field (SGCF) is located 610 km from Murmansk in the Barents Sea. The water depth at location is around 340 m. The offshore facilities of the SGCF Phase 1 development will include ice-resistant ship shape disconnectable turret moored floating platform (FP). The design of the hull has been driven to be inherently safe, to resist the environmental condition, and minimize risk of repair over the 50 years operating duration. Introduction The SGCF is located 610km from Murmansk in the Barents Sea, around 73º latitude North and 44º longitude East. The water depth at location is around 340 m and the reservoir is 2000 m below the mudline. The field reserves are estimated to be 3700 GSm3. The gas reservoir covers a geographical area of approximately 1 400 km2, and is approximately 48 km long by 35 km wide. The field will be developed in three phases, the expected daily production of each phase being around 70 million Sm3 per day. SDAG owned by Gazprom (51%), Total (25%) and Statoil (24%) will operate the development of the First Phase of the SGCF. The area is a harsh Arctic environment that can be covered by sea ice and is also known for its icebergs and experiences long periods of darkness during the winter months. Facilities in this region can be exposed to very low ambient air temperatures (including wind chill), snow and icing that require winterisation measures to be taken. The offshore development of Phase 1 of the Shtokman Gas Condensate Field development consists of the following main elements (see Fig. 1):The Floating Platform, including hull, mooring, accommodation, process (oil, gas, water as needed), gas export facilities (compression and metering) and associated control systems.The Subsea Production System (referred to as the SPS).The Umbilicals, Flowlines and Risers (UFR) to gather production from SPS and transport it to the Floating Platform and to connect the Floating Platform to pipeline to shore.The Export Trunklines. After various conceptual initial studies, Shtokman Development AG has concluded to design the floating platform as a turret moored disconnectable and ice resistant ship shaped floating platform. The FP design operating life is 50 years. The present paper describes the main principles of design of the hull that form the frame for further optimization by contractors.
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