The host facility for your subsea project is an open truss spar. The existing fl
ID: 2074592 • Letter: T
Question
The host facility for your subsea project is an open truss spar. The existing flowline risers are steel catenary risers, hung off on SCR porches installed on the spar hull. There are provisions for two extra SCR’s already in place on the hull. While the subsurface team is trying to determine how much oil is producible from these new reservoirs, they have asked the subsea group to tell them how they would tie this back to the host facility.
Question 1: What would be the reasons for requiring another flowline and associated riser system, Explain?
Question 2: If a new flowline and riser system is needed to flow the oil wells back to the host facility, what information do you need in order to decide on how to design and configure the riser system?
Explanation / Answer
ANSWER 1:
Building on the catenary equation that has helped to create bridges across the world, steel catenary risers use this curve theory, as well. Used to connect the seafloor to production facilities above, as well as connect two floating production platforms, steel catenary risers are common on TLPs, FPSOs and spars, as well as fixed structures, compliant towers and gravity structures. While this curved riser can withstand some motion, excessive movement can cause problems.The first type of riser to be developed, attached risers are deployed on fixed platforms, compliant towers and concrete gravity structures. Attached risers are clamped to the side of the fixed facilities, connecting the seabed to the production facility above. Usually fabricated in sections, the riser section closest to the seafloor is joined with a flowline or export pipeline, and clamped to the side of the facility. The next sections rise up the side of the facility, until the top riser section is joined with the processing equipment atop the facility.
ANSWER 2:
RISER CONFIGURATION SELECTION:
configurations typically used in conjunction with Floating Production/Loading Systems. The standard five configurations generally used are: Free-Hanging Catenary, Lazy-S, Lazy Wave, Steep-S, and Steep Wave. Figure 1-a illustrates these typical types of riser configurations. Figure 1-b illustrates a schematic of a new riser configuration proposed by Wellstream for the Alcorn Linapacan Field Development Project.
DESIGN PARAMETERS AND PROCEDURES
The main problem in designing flexible riser systems is the large number of design parameters. The environmental conditions, vessel or calm buoy motions and riser properties are usually well-defined. The main design parameters are the choice of riser configuration, the length of riser, the system geometry and the sizing of buoyancy modules, subsurface buoy or arch. The choice of riser configuration is usually based on economic criteria, position of the wells, wave and current forces, motion response and excursions of the vessel or surface buoy as well. The design procedure can be described as consisting of three stages.
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