South Pars Phases 2, 3 and 6, 7, 8 Gas Field Development - An integrated Design Approach

摘要

This paper discusses the South Pars Gas Field Development which is located approximately 100km off the south west coast of the Islamic Republic of Iran, in the Persian Gulf. J P Kenny has been responsible for the free span assessment and buckling mitigation design of the Phase 2 and 3 subsea pipelines for Doris / Total as well as the detailed design of the Phase 6, 7 & 8 subsea pipelines of this development for SADRA/ STATOIL. In each case identical wellhead not normally manned platforms will transport 3-phase wet gas to the shore via parallel routed 110km, 32" trunklines, each with a 4" MEG injection piggyback, in a maximum water depth of 85m. The key challenges of these projects were related to the high inlet temperature, for a large diameter pipeline, of 89°C, and a 40km section of exceptionally rough seabed along each pipeline route. These factors gave rise to significant pipeline buckling and free spanning issues. J P Kenny designed a snaked-lay pipeline configuration to alleviate the potential lateral and upheaval buckling problems, thus relieving the excessive effective axial compressive force within the pipeline by introducing a number of pre-determined buckle sites. The robustness of the design was demonstrated using the developments defined in the Hotpipe JIP. For the phase 6,7 and 8 pipelines post lay re-analysis of the as-laid pipelines using in-house 3D FE software confirmed the acceptability of the design prior to operation. The exceptional roughness of the traversed seabed produced nearly 450 predicted free spans for the three Phase 6, 7 and 8 trunklines in the operational load case. Using DNV OS-F101 and RP-F105, and in collaboration with STATOIL, J P Kenny completed a full fatigue limit state assessment of each individual span in order to reduce the extent of the free span intervention required during installation.