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Many years of applied research and construction experience has given
Subsea 7 the significant advantage of being a SURF co...
Single Hybrid Riser Steel Lazy-Wave Riser Hybrid Riser Tower Grouped Slor
Un-coupled Risers
Un-coupled riser systems are i...
© Subsea 7, 2014. Information correct at time of going to press.
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4 pg leaflet_riser_technology__reference

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Riser technology - Boião Subsea

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4 pg leaflet_riser_technology__reference

  1. 1. Many years of applied research and construction experience has given Subsea 7 the significant advantage of being a SURF contractor capable of providing all types of riser systems for deepwater and ultra-deepwater installation. Our unique suite of riser and related technologies meet a wide range of specific field characteristics, such as water depth, environmental conditions, host specification, hydrocarbon composition and client preferences. seabed-to-surface Riser Technology technology product overview
  2. 2. Single Hybrid Riser Steel Lazy-Wave Riser Hybrid Riser Tower Grouped Slor Un-coupled Risers Un-coupled riser systems are increasingly being applied in recent deepwater and ultra-deepwater field developments. Hybrid Riser Towers (HRTs) are recognised to have significant benefits for deepwater riser applications in terms of flow assurance, thermal performance and robustness of layout. This latter issue is especially significant when a large number of risers are considered. An HRT provides the required flexibility by avoiding a crowded layout and allowing a progressive deployment. The concept is applicable to deepwater and ultra-deepwater, and to spread- moored and turret-moored FPSO installations. Specific characteristics of the Hyperflow® Hybrid Riser Tower include: • Custom-designed and built for optimum flow performance and adapted to the specific characteristics of each field development • For ultra-deepwater flow assurance (pressure, temperature and heat transfer characteristics) • Highly suitable for remote and hostile environments • Simplifies field layout with no interference between numerous risers • Low in-situ fatigue damage • Additional equipment such as gas lift, separator unit and booster pumps can be incorporated in the vicinity of the riser base. The first HRT application installed by Subsea 7 was Girassol in Angola for Total in 1998. The field, incorporating three HRTs, has been producing for more than ten years to the specified stringent flow assurance requirements. Hybrid Riser Towers have now become accepted as a robust solution for deepwater and ultra-deepwater developments. The latest Subsea 7 HRT technology is currently being applied to Total’s CLOV projects where two HRTs were installed in 2013. Subsea 7 has previously installed three HRTs at the Total Girassol development and one HRT at the Greater Plutonio development, in Angola. Subsea 7 also has experience in designing and installing Single Hybrid Riser towers offshore West Africa by the J-lay method, most recently for the Total CLOV development and previously for ExxonMobil AB15 GG, both in Angola. The Grouped SLOR is a qualified un-coupled riser system developed by Subsea 7 in collaboration with 2H Offshore for deepwater applications and based on the proven single-riser concept. Grouped SLOR is an 'open Bundle' riser solution developed specifically to optimise the riser/vessel interface, production vessel approaches and access for riser inspection and maintenance. It uses a buoyant truss frame to guide the free-standing risers, constraining all risers to move collectively, and thus eliminating the risk of clashing. The Grouped SLOR has great potential for large deepwater developments, which typically have a complex and congested seabed layout immediately adjacent to the production vessel where there are spatial constraints imposed by mooring lines and vessel offsets. Riser systems installed on a worldwide basis by Subsea 7 fall into two categories - those coupled directly to the host facility, and un-coupled systems which in most cases are connected by flexible jumpers. Coupled Risers • Steel Catenary Risers (SCRs) • Weight-Distributed SCRs • Steel Lazy-Wave Risers (SLWRs) • Flexible riser systems Un-coupled Risers • Single Hybrid Riser (SHR) • Grouped SLOR • Hybrid Riser Tower • Buoyancy-Supported Risers (BSR) • Tethered Catenary Riser (TCR) • Catenary Offset Buoyant Riser Assembly (COBRA) Coupled Risers Steel Catenary Risers (SCRs) have been adopted for many field developments and can be installed by all three methods of installation offered by Subsea 7- J-lay, reel-lay and S-lay. Subsea 7’s widespread experience includes the metallurgical-clad riser for the Shell Bonga field by J-lay (six SCRs each 2km in length) and subsequently for the Exxon Mobil Erha field (ten SCRs each approximately 3km in length). Subsea 7 has also installed SCRs by reel-lay in Brazil and the Gulf of Mexico. One of the main challenges in any SCR design is the fatigue performance of the weld, and, with its extensive welding technology, Subsea 7 has developed high-quality SCR welding solutions, especially for metallurgical-clad or lined SCRs. Using the reel-lay vessel the Seven Oceans, Subsea 7 installed the first Steel Lazy-Wave Riser (SLWR) in the BC-10 field offshore Brazil at a depth of 1,800m for Shell International. The overall BC-10 scope included fabrication and installation of seven steel catenary lazy-wave risers, totalling approximately 21km. The main challenges for SLWRs are high-specification welds and installation issues when all the heavy buoyancies are attached to the SCR. Through extensive in-house research and development, Subsea 7 has further developed the Weight Distributed SCR concept, which enhances the applicability of SCRs to harsher environments. In this concept, well-qualified ballast elements are attached at certain sections of the SCR to reduce the stresses around the touchdown point and enhance the fatigue performance of the SCR.
  3. 3. www.subsea7.com © Subsea 7, 2014. Information correct at time of going to press. Buoyancy SCR Mooring lines Jumper Catenary Offset Buoyant Riser Assembly (COBRA) Un-coupled Risers continued The Buoyancy-Supported Riser (BSR) System has been fabricated and is being installed by Subsea 7 for the Guará-Lula NE field development in Brazil under contract to Petrobras. The BSR concept consists of submerged buoys each weighing approximately 2,000 tonnes installed at approximately 250 metres below sea level and anchored to the seabed by eight tethers, two on each corner of the buoy. The buoy supports 27 steel catenary risers of 3.9km which are connected to the FPSO by non-bonded flexible jumpers. This BSR system absorbs the dynamics from the FPSO, resulting in almost no dynamic stresses on the SCRs. Since there is very little dynamic response for the SCRs, mechanically-lined pipe is used for the SCR section, thereby optimising the riser design. Subsea 7 continues to develop further un-coupled riser concepts designed for harsh environments. A recent example is the Catenary Offset Buoyant Riser Assembly (COBRA), which consists of a catenary riser section with a long, slender buoyancy module on top, which is tethered down to the seabed. Similar to the multi–riser BSR, the top of the catenary riser section is connected to the host by a flexible jumper. Tethered Catenary Riser (TCR) Another alternative for deep and ultra-deep waters is the Tethered Catenary Riser. The concept consists of a number of steel catenary risers supported by a subsurface buoy which is tethered down to the seabed by a single pipe tendon and anchored by a suction pile. The system has all the advantages of de-coupled riser arrangements: flexible jumpers effectively absorb platform motions, and therefore the rigid risers and tendon have reduced dynamic excitation. The riser system is designed for between four and eight risers, in addition to a number of umbilicals, and is most suitable for one or two drilling centres. The installation method is similar to the proven method used for the Single Hybrid Riser Tower. Riser Technology For further information contact Stuart N Smith, VP Technology & Asset Development Stuart.Smith@subsea7.com Single Hybrid Riser Buoyancy-Supported Riser Tethered Catenary Riser (TCR)