Deng, Huifeng (COOEC Shenzhen Subsea Technology CO., LTD.) | Song, Chunna (COOEC Shenzhen Subsea Technology CO., LTD.) | Miao, Chunsheng (COOEC Shenzhen Subsea Technology CO., LTD.) | Dai, Wanbao (COOEC Maintenance Company)
The subsea pipeline trenching by a pipeline plough introduced to China for the first time is indicated in this paper, which was used in the Ledong 22-1/15-1 Field Development Project performed by COOEC. Proposed to achieve the trench depth of 1.8m, the pipeline plough succeeded trenching along the 24’’export pipeline over an approximate length of 54 km, which was launched in the depth up to 100m. Based on the Ledong project, the equipments, construction procedure and related highlights covered in the pipeline trenching are described herein.
In order to protect the offshore pipeline from potential mechanical damage possibly caused by wave, currents and other uncertain factors, the most effective solution is to make a trench that meets the depth requirements to bury the pipeline. Burial is used as protection to prevent external loading from fishing activity/snags or hydrodynamic loading and to prevent movement of the pipeline during thermal expansion on commissioning (Finch et al, 2000). In 40s-60s of last century, the normal solution was to trench along the pipe with jet equipments when the offshore oil or gas explorations took place in shallow water zone near the coast. In the end of 1960s mechanical trench was introduced in the North Sea for pipeline trenching project. With the exploration activities going to deep water zone which is very complicated in sea situation, the pipeline plough appeared and took an important part in the offshore pipeline trenching project. Although after the 1980s a lot of pipeline ploughs were used for offshore pipeline trenching over the world, a pipeline trenching by a pipeline plough was not carried out in China until a pipeline plough was introduced in the Ledong 22-1/15-1 Field Development Project performed by COOEC in South China Sea in 2009.