Feasibility of TLP with Tender Assisted Drilling for Northwest Australian Waters – A Case Study

摘要

The objective of the work is to assess the feasibility of a tension leg platform (TLP) dry tree unit (DTU) with tenderassistedrndrilling (TAD) for the harsh metocean conditions offshore North West Australia, characterized by the occurrence ofrntropical cyclones and persistent swells. Making use of the drilling tender vessel's accommodation, power generation, mudrnpumping, cleaning and storage facilities etc. can reduce the production platform topsides weight by up to 3,000 tonnes. Suchrnweight and associated cost savings could become enablers for some of the deepwater gas field developments offshore WesternrnAustralia.rnA TLP configuration is evaluated as the DTU in a water depth of 500 m. The TLP is sized for a specific payload for gasrnproduction. A typical 6-column semisubmersible is configured as the drilling tender vessel (DTV), for which a preliminaryrnTAD mooring system is defined. Hydrodynamic models for the combined DTU/DTV systems are developed and used tornperform extreme response and operability analyses.rnThe coupled TLP/DTV TAD system is analyzed in 1, 10 and 100-year return period environments. It is shown that thernDTU and DTV vessel can be safely moored together by hawsers without collision in up to 10-year return cyclonic stormrnevents. This means that the mooring system operability of up to 99.97% is achievable.rnIn environmental conditions harsher than 10-year return cyclonic storms, the DTV will be disconnected from the DTU andrna full 8-point mooring pattern will be required to moor the DTV to survive up to 100-year return period cyclones.