Electrically trace heated umbilical, a new solution among subsea active heating technologies

摘要

Rarely do we face so many challenging conditions in umbilical design as those encountered in the engineering study undertaken for this electrically heated control umbilical system. The objective of this study is to advance the engineering of an electrically heated control umbilical concept, which will facilitate an initial subsea development. It is intended to combine all the necessary services within a single umbilical structure. In addition to the normal control cables, tubes and chemical lines, the umbilical contains power cables that are used to energise an ETH-PiP and gas lift tubes for downhole injection. The gas lift system faces two flow assurance challenges. Firstly, the production fluid has an elevated wax appearance temperature and in order to avoid cooling of the fluid and wax deposition in the well tubing, the gas shall be injected in the wells at high temperature. Secondly, the injected gas is not dehydrated, which generates corrosion issues and risks of hydrate formation. In order to remediate these issues, based on the experience with heated flexible lines (IPB) and heated pipe-in-pipes (ETH-PiP), Technip & TUS have developed an electrically trace heated umbilical (ETH-U) allowing heating of the gas lift tubes during both injection and shutdown. This umbilical is challenging for its intended use, range of functions, thermal requirements, corrosion resistance, on-bottom stability, product manufacturability, size and installability. In addition to the umbilical structure, the hardware proves to be just as complex at both the platform and UTA due to a need for weak links and emergency disconnect systems in case of iceberg collision. This paper describes the development; design and optimization of a gas lift injection option using an Electrically Trace Heated Umbilical. This technical solution has been proven as feasible from an engineering stand point based on the umbilical design requirements and the flow assurance calculation methodology.