Installation of Dual-Riser Combination onto the Existing Jacket

摘要

This paper will introduce a new installation method that is so called dual-riser integrity installation.The key idea of this method is to install two risers,a wet gas riser and an umbilical protection riser,onto an existing jacket located at sea of about 90 meters in depth by use of combination of risers and clamps together in order to ensure the welds quality of CRA cladding wet gas riser by fabrication onshore and mitigate the high risks of simultaneous operations of gas production and hot works during splicing of CRA cladding riser in field offshore.The CRA cladding gas riser and umbilical protection riser and Adjustable Clamps are designed,onshore fabricated and precisely assembled into upper and lower dual-riser(gas riser and umbilical protection riser)combinations based on measuring data of the existing jacket.The lower combination is installed at first and the upper combination is followed up.Each combination is lifted in horizontal,submerged in water,up-righted under the help of crane and intentionally added air bags and then moved close to jacket by winches.The lower and upper combinations are connected by bolted flange at last. The installation of dual-riser combination onto the existing jacket of YC13-1 gas field located at water depth of about 90 meters is actually completed within 10 days.This method avoids the direct support from the existing platform and works efficiently.