HDD Ashore Crossing for CNOOC Yacheng13-1 Submarine Pipeline Gaolan Branch
On June 14,2018, Huayuan completed shore pulling of a submarine pipeline by using HDDTechnique for the first time domestically, and innovated a brand-newconstruction technology for onshore/offshore pulling of submarine oil/gaspipelines.
Gaolan Branchof CNOOC Yacheng 13-1 Submarine Pipeline is the first project whose shorepulling was successfully completed by using Horizontal Directional Drilling(HDD) technique, resolving such difficulties as large difference of elevations,complicated topography along the coast, obstacles of live pipelines in vicinity,and huge waves of the sea; reducing cost and construction time; ensuring theaccomplishment of subsequent follow-up works. The Client CNOOC and the EPCContractor gave a high appraisal to Huayuan for its excellent performance.
Gaolan Branchof CNOOC Yacheng 13-1 Gas Pipeline, is one of CNOOC’s projects for developingthe Gas Fields in the South China Sea. After completion of this project, GaolanTerminal will be connected with the Gas network of Hong Kong, eventuallyforming vast gas transmission networks on the sea which can link up the Easterngas fields and Western gas fields, and connect Eastern Terminal, GaolanTerminal and Hong Kong Terminal. Gas sources and their transmission then can beflexibly, efficiently deployed in large scale.
The HDD entrysite is located within Gaolan Terminal, which belongs to parts of CNOOC’sdeep-water gas field in the South China Sea; the daylight-point site is locatedat the seabed. HDD crossing chainage length is 876m, with 100m of maximumvertical depth, the level difference between the entry point and daylight pointis 60.6m, the φ610mm×δ22.2mm pipeline is coated with 3LPP anti-corrosion layersHuayuan company was thecontractor of the HDD ashore crossing works of the submarine pipeline, whosework scope included surveying, design and construction. Facing theunprecedented working situations, without any experiences to follow, Huayuanvaliantly participated the challenges, persevered in technical innovation, andmade full use of its superiority of technological advantages. According todeferent strata formation, deferent stages of pilot drilling was carried out,and when enlarging / smoothing the borehole, forward reaming method was used. Lastlywith the assistance of pipe-laying ship, the pipeline was directly pulled backinto the borehole. Some brand new working methods or techniques were innovated,e.g. conquering such difficulties as high abrasiveness and hardness of thegranite / quartz vein, which wore the drill bits severely; and cuttings bedsformation due to drilling fluid Lost Circulation when forward reaming; andeccentric borehole formation at the interface of hard and soft zones.