Phase I of this project will analyze and develop pipeline repair plans and capabilities for spool piece repair and leak clamps for deepwater (1000+ ft) pipelines in the Gulf of Mexico.
The objectives of the Phase 1 project were as follows:
Identify pipeline and flowline size ranges of participants, including insulated and non insulated conventional pipe, as well as pipe-in-pipe options as applicable. In order to understand what repair scenarios will be expected, identify and evaluate expected pipeline and flowline damage conditions, using the damage categories outlined in the MMS database of Gulf of Mexico pipeline leaks.
Provide a technical and cost evaluation of deepwater pipeline and flowline repair alternatives resulting in a recommended repair system for each identified damage condition. Identify potential repair vessels, ROV's and other tools of opportunity.
For the recommended solution, develop conceptual plans and procedures for effecting repairs for each system, including repairs during both construction and operations.
Develop a project execution plan for constructing the recommended system for the next phase of the project.
Perform the background work required to fund the second phase DW RUPE JIP, including procurement, integration of equipment and, where needed, component and SIT testing of the selected system components.
The scope of work under Phase I of the project is complete. This final report (attached) addresses the first phase of a JIP formed for the development of emergency repair capability for pipelines and flowlines in water depths in the 1,000-10,000 ft range in the US Gulf of Mexico. Stress Subsea (SSI) conducted a Failure Mode and Effects Analysis, conducted interviews with suppliers and operators and, included input from the JIP's Steering Committee, to make recommendations for two different repair methods to support the emergency repair of larger diameter pipelines and flowlines, respectively. For larger diameter pipelines the recommendation is to use two 'structural' leak clamps to make spool piece repairs, or use one of the two clamps to clamp a pinhole leak. The use of the same clamp design for either application avoids needing three separate tools. For the smaller flowline repair, the recommendation is to cut the flowline on bottom, lift the ends to the surface to add fittings, and then lay the flowline ends on bottom to join them with a vertical jumper containing twin collet connectors. Major pipe damage and pinhole leaks for the flowlines would be repaired the same way.
Starting with a collection of operator/participants pipe 'dedications', the JIP prepared a Design Basis which served as guidance for various equipment inquiries and requests for quotes. These pipe dedications defined, among other things, size, length, wall thickness, grade and the MAOP of the dedicated pipelines. Interviews were conducted with key deepwater products manufacturers, installation and repair contractors, as well as operators with experience in developing deepwater repair methods. Throughout the project, SSI held 5 project meetings, met with BP and Shell for their views and lessons learned, and met with industry leaders such as Sonsub, Oceaneering, Oil States, Quality Connector Systems, Canyon Offshore and Deep Marine Technology to get their input and advice. SSI also interfaced with companies such as FMC and Grayloc, as well as a number of other smaller sub suppliers.
From the Deepwater RUPE Phase 1 Project, the following conclusions were drawn:
The probability of needing a deepwater repair is low, but the consequences are high. The most likely (non-construction related) damage types are wet and dry buckles caused by anchor snags. Optimum repair solutions for a low-CAPEX pipeline repair and a low CAPEX flowline repair are different. Traditionally a leak clamp and a spool piece connector set are needed for each pipe size. The new paradigm of employing full structural clamps as connectors, and in place of connectors, allows two structural clamps to be used in a spool piece repair or one of the two structural clamps to be used alone for a pinhole leak from a cracked weld. So, two clamps will serve the same function as two connectors and a clamp (pipeline repair scenario only). For pinhole leaks, the most likely cause will be cracked welds, thus full structural clamps are advised to arrest crack propagation (pipeline repair scenario only). Use of structural clamps for pipeline spoolpiece connections does not have field experience, and thus requires structural and SIT type-testing. Use of Collet Connectors with vertical jumpers has already been validated (first by shell) in the GOM, thus the concept needs no qualification testing. Avoiding 'slip on' connectors minimizes elastomer seal damage caused by rough cut ends of the pipe. For flowline repairs, use of collet connectors with inserts minimizes the number of connectors required. Use of deepwater pollution control tents and bags to collect spilled oil during a repair is fraught with problems. Careful placement of lift frames to create containment 'humps' (to lock in the trapped oil in the pipe) during pipe cutting, and use of pumpable plugs during spool piece installation will minimize pollution more effectively than tents and bags. At the conclusion of Phase 1, SSI recommended that a DW RUPE Phase 2 Co-Ownership organization be formed to jointly purchase, store, maintain and manage both pipeline and flowline repair systems, to be dispatched for use by a Co-Owner in making a deepwater pipeline or flowline repair. MMS did not participate in any subsequent phases of this project.