A 14 mile hydraulic control/chemical injection umbilical links the Troika subsea development manifold to the Bullwinkle platform. This paper discusses the experiences gained through the complete process starting with contractor selection, looking at design standards, manufacturing facilities, inspection requirements and the level of client involvement to ensure technical integrity and a quality product. Introduction The Troika development is an oil field located 150 miles offshore Louisiana in the Green Canyon area of the Gulf of Mexico. Designated as the Green Canyon 244 Unit, the development includes block 200,201,244-and 245. Troika is jointly owned by BP Exploration Inc. (BPX), Marathon Oil Company (MOC) and Shell Offshore Inc. (SOI), with BPX serving as the operator. Fig. 1 shows the Troika field location. Troika is located in 2700 ft of water and features an eight well subsea manifold with five well initially installed in a cluster arrangement. Production from Troika is transported via two 10 inch flowlines for processing on the Shell Bullwinkle platform 14 miles away located on Green Canyon block 65 in 1350 ft of water. The Troika development is control by a multiplexed electro-hydraulic control system operated from the Bullwinkle platform. The control system is linked to the manifold by an electrical and hydraulic/chemical umbilical. The function of the hydraulic/chemical umbilical is to provide high and low pressure hydraulic fluid for all the actuated valves on the manifold and subsea trees, methanol to all the subsea trees and both flowlines and chemicals (paraffin & corrosion inhibitors) to both flowlines. In addition it includes a bleed line for the well annulus fluids. An overview of the Troika field development is given in OTC 8845' and the layout is shown in Fig. 2. This paper takes an overview of the Hydraulic/chemical umbilical and outline some problems experienced with emphasis on the use of super duplex tubing meeting the requirements of ASTM specifications. It looks at what quality program were in place during the manufacture of the tubing, how the problem was discovered, what steps were taken to identify the extent of the problem and how it was overcome. Design Requirements The initial design requirements were established in the conceptual design study completed by Intec Engineering included the line function, fluids, inside diameter, required flow rate and pressure rating. The material selection was based on Shell Offshore material recommendation of either 2507 super duplex or zinc coated steel tubing. The functional and fluid requirements are summarized in Table 1. Contractor Selection The contractor selection process was typical for any major equipment purchase for an offshore project. An inquiry document was prepared with a technical functional specification for the hydraulic/chemical umbilical only defining the inside diameter of each line, pressure rating, material and service/design life. This allowed each bidder to choose what they consider the appropriate design criteria for the wall thickness calculations of the tubing and the configuration of the actual tubes inside the umbilical.

System Description The Foinaven riser and umbilical system comprises of 10 flexible pipes and 2 umbilical and provides production, test, gas injection, water injection and control for two drilling centre. The size and duty of the risers is as follows:- Drill Centre I 2 × 10" Production 2 × 8" Production/Test 1 × 10" Water Injection 1 × 8" Gas Injection I × Dynamic Umbilical Drill Centre 2 2 × 10" Production 2 × 8" Production/Test I × Dynamic Umbilical The design pressure for the system is 3689 psi (254 bar g). The configuration of the risers is a "pliant wave" (figure I) which is anchored to a gravity base structure by tethers and has buoyancy modules distributed along the lower end. The system is designed such that it can be released from the FPSO in extreme emergency conditions. Design Conditions The Foinaven field is the deepest ever application of a "pliant wave" riser configuration and has to withstand very high currents over the full water column of up to 2 m/s (3.9 knots), When combined with the 100 year design wave of 18 m (sign) this provided very harsh conditions for the design of the pipe (figure 2), the critical areas being the vessel interface, where a bend stiffener is required, and at the riser touchdown point where extreme near and far vessel positions resulted in the need for a hold back anchor to prevent pipe movement and subsequent over bending of the pipe. The large waves in the Atlantic also impose severe fatigue loading on the risers, the most critical risers being the gas and water injection risers, due to the high operating pressure within the system. Next to the environmental conditions the next major influence on the system design was the vessel offset. This is closely linked to the design of the mooring system for the vessel which was far more compliant than originally anticipated in the riser design. When procuring a floating production system the risers influence both the sub sea layout as well as the mooring system design. Care must therefore be taken in addressing this interface. If the interface is defined at the riser touchdown the cost benefit of manufacturing flexible flow line jumpers (especially the flow line to manifold jumpers) at the same time as the riser maybe lost. Also for the umbilical, vessel interface was one of the major challenges. The region that experiences the highest loads both with respect to tension and bending is found at the I-tube exist. Bend stiffener design as well as cross-section design is critical. At touch down two clump weights were needed, One main clump weight taking up virtually all the tension, leading to that the touch down area saw no tension at high bending. the resulting catenary below the tether clamp, however, induced such a high bottom tension in the extreme current and far vessel offset cases that the interface joint between dynamic and static umbilical was anchored to a second, smaller slump weight. Its role is to prevent axial movement of the interface joint thereby preventing potential unwanted configuration changes.