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

Abstract

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

A Parametric Study on the Innovative Coupling Arm Connecting the Coupled TAD-TLP

“…Limited literature on the interconnection between two floating structures could be found. Xia and Taghipour (2012) investigated the feasibility of a TLP with TAD using a semisubmersible tender vessel for filed developments offshore North West Australia. They still applied the hawsers as interconnections between TLP and TAD.…”

Nonlinear hydrodynamic characteristics of multi-body platform system

“…There are also some studies on the hydrodynamic interaction between two floating platforms in a multi-body platform system. Xia and Taghipour [19] conducted an eigenvalue study of Tension Leg Platform (TLP) with a tender assisted drilling (TAD) in longitudinal motion of the two bodies in the multi-body system. Choi et al [20] conducted an experimental study on TLP and Semi-sub's motion response characteristics.…”