This paper presents the technical challenge and solution of a deep-draft semi-submersible production platform with condensate storage and DP shuttle tanker offloading in LS17-2 gas field development in the South China Sea. The oil and gas field development infra-structure in the SCS is very different from that in the GoM, with almost no oil export pipeline and very few gas export pipelines available for tieback. Specific to LS17-2, gas can be exported through the existing Yacheng -Hong Kong dry gas pipeline, but not for the associated condensate production. For the condensate production, a new-built oil pipeline is technically feasible but economically unattractive. A floater with condensate storage is cost effective but technically challenging. Production semi-submersible with condensate storage and offloading is finally selected after comparison among various development options.
There are only two Semi-submersible production units in the world with dead oil storage today. The challenges facing condensate storage includes safety risk, complex hull marine system, global performance, frequent ballast and de-ballast operations, etc. This paper presents the design methodology and safety solutions of condensate storage in semi-submersible production unit. Another development challenge is condensate offloading. Shuttle tanker with Dynamic Positioning system is recommended because of its low cost and feasible technology compared with other alternatives. In addition, the shuttle tanker operation damage case should be considered and the collision analysis is done to ensure the hull structure's safety. Various hull shapes, storage concepts and topside configurations are investigated. The paper also presents platform layout suitable for mooring, SCRs and platform operations in the SCS. The overall sizing solution is a fit-for-purpose solution considering the Chinese shipyard integration and fabrication capability. The deep draft Semi-submersible production floater with storage and offloading concept received Approval in Principle from ABS, and is planned for the LS17-2 gas field development.
LS17-2 gas field is located in the Continental Shelf, about 150 km southeast of Sanya city of Hainan island, 95 km from the existing subsea dry gas export pipeline from YC13-1 to Hong Kong. The water depth is 1220∼1560m.
