The YC13–4 gas field in South China Sea is tied into the developed YC13–1 gas field existing facilities nearby. The CRA clad carbon steel gas riser and carbon steel umbilical protective riser are designed and together installed onto the existing jacket of YC13–1 gas field.
In order to ensure the welding quality of the CRA clad gas riser, avoid the high risks of simultaneous operations of production, hot works and installation, and taking into account of natural gas operational conditions of high temperature and high pressure around YC13–1 gas field existing platform, the installation method of dual-risers (gas riser and umbilical protective riser) together onto the existing jacket is used. The CRA clad gas riser and umbilical protective riser are designed, fabricated and precisely assembled on land forming dual-risers upper and lower parts together with fastening clamps based on measuring data of existing jacket correspondingly. The lower part is installed at first and then upper part. Each part is lifted, submerged in water, up-righted under the help of intentionally added buoyancy and then moved close to jacket by winch. The lower and upper parts are joined by bolted flange at last.
The installation of dual-risers together onto the existing jacket for YC13–4 gas field is actually completed within 10 days. This method avoids the close support from the existing platform and works efficiently.
