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Steel Catenary riser and Steel Lazy Wave Riser | Simple configuration Very simple installation Simple pipeline connection at seabed Reduced Number of Components Reduced Number of Cold spots Progressive slope limits the slugging problems at riser bottom. No discontinuity with Flowline Fabrication of the SCR is normally performed as an extension of the pipelay operations If installation by reel-lay vessel accepted, fabrication of the SCR may be performed onshore allowing better conditions for welding activities. Installation of SCR is performed as an extension of pipelaying Installation can be performed by reel-lay vessel, thus reducing installation duration No subsea tie-ins to perform Coiled tubing can be deployed from FPSO for hydrate remediation purpose Change of slopes/elevations is minimized to improve the flowing conditions. Individual production loss in case of one flexible riser major failure, limited to one branch
| Liable to rapid wear at seabed touch down point Unsuitable for shallow water (rigid pipe) High static load at top end connection Wear at seabed can be exacerbated by fluctuations in oil density or slugging causing repeated lift-off and set-down Resistance to dynamics associated with vessel heave Cyclic fatigue at TDP and Top of riser due to vessel motion combined with current and hydrodynamic loads Soil Data Modelisation Requirement for Skid if Gas Lift is required. Potential riser Anchoring (Pipe Walking) at riser bottom Low Local Content High quality weld required Tight tolerances High quality inspection program (AUT) Complex hook-up operations Large impact of fabrication constraints on installation Fatigue damage during installation to be considered , notably if reeled Unlikely pre-laying of SCRs prior to FPSO arrival Heavy pipelay ship required Complex installation of the GL skid if required In case gas lift , efficiency of the artificial lifting should be carefully assessed Pigging operations through the flex joint may be limited to low sea-states. large amount of insulation may be required on the separate gas lift riser. All cold points should be avoided within the injection manifold. The injection module shall accommodate the Flowline expansions. Most critical fatigue zone (TDP) is very difficult to instrument Assessment methods of fatigue damage from the measurements data (extrapolation methods, numerical models calibration) Critical elements of the SCR gas lift injection (if required) module are not recoverable
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Free Hanging Flexible riser | Simple configuration Very simple installation Simple pipeline connection at seabed Compact Little response to dynamic motions (little fatigue) Active Heating system can be integrated No discontinuity with Flowline All manufacturing and product testing activities take place onshore offering good conditions for assembly and quality control of the work. Gas lift and Fiber Optic insertion during fabrication of the riser. The installation of the flexible risers open to a wide range of vessels. Can be wet stored on seabed Change of slopes/elevations is minimized to improve the flowing conditions. During production, the gas lift tubes integrated in the IPB riser may provide heat to the production core pipe. An active heating system (heating cables) can be integrated in the riser structure. Individual production loss in case of one SCR major failure, limited to one branch
| Liable to rapid wear at seabed touch down point High static load at top end connection Wear and risk of birdcaging at seabed can be exacerbated by fluctuations in oil density or slugging causing repeated lift-off and set-down Resistance to dynamics associated with vessel heave Cyclic fatigue due to vessel motion combined with current and hydrodynamic loads Requires long Qualification tests (thermal tests, acive heating, monitoring…) riser Touchdown curvature (Compression > Birdcaging) Clashing Material temperature Limitation Special care should be taken not to damage the outer sheath during installation. In case gas lift , efficiency of the artificial lifting should be carefully assessed . Limited U-value for conventional insulated flexible risers (f 3.0 to 3.5 W/m2K). Potential Plugging of one or several GL tubes (hydrate, sand). Insulation of the gas lift injection fitting is required to avoid cold point. In case gas lift , efficiency of the artificial lifting should be carefully assessed . Limited U-value for conventional insulated flexible risers (f 3.0 to 3.5 W/m2K). Plugging of one or several GL tubes (hydrate, sand). Insulation of the gas lift injection fitting is required to avoid cold point. Fragility of the Fiber optic components under rough conditions Compatibility of intelligent pigging with flexibles
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| Same as flexible riser plus: Simple pipeline connection Mid-water support is relatively stable Good possibilities for multiple line applications High mid-water velocities may be counteracted by a large mid-water buoy with high tension and lateral stiffness Lower seabed wear than a free-hanging catenary
| Same as flexible riser plus: Potential wear at seabed if buoy tension is insufficient Need to control bending at end terminations and at mid-water buoy Mid water buoy must be configured so that it does not move adversely in high mid-water velocities Wear at seabed can be exacerbated by fluctuations in oil density or slugging causing repeated lift-off and set-down. Complex Design of mid-water buoy for deepwater application considering external prerssure.
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| Same as flexible riser plus: | Same as flexible riser plus: More complex connection at seabed Possible yaw instability of mid-water buoy Seabed unit must resist upward forces Complex Design of mid-water buoy for deepwater application considering external prerssure.
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| Same as flexible riser plus: | Same as flexible riser plus: Potential for rapid wear at seabed touchdown (greater than for lazy S but may be less than for free hanging catenary Wear at seabed can be exacerbated by fluctuations in oil density or slugging causing repeated lift-off and set-down. Susceptible to large motions in cross currents Not well suited to slug flow in Riser Not well suited for closely spaced, multi-line applications due to possible interference Potential clashing /hook-up of adjacent lines
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| Same as flexible riser plus: | Same as flexible riser plus: More complex connection at seabed Susceptible to high transverse current velocities Seabed unit must resist upward forces Potential clashing /hook-up of adjacent lines
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