On May 8, 2016, with the cooperation of Shenzhen offshore oil engineering Underwater Technology Co., Ltd. and the maintenance and repair center of China Petroleum Pipeline Bureau, the offshore project team of Shenzhen Shanye Industry Co., Ltd. fought continuously for 30 days and nights, Completed the underwater pressurized opening and underwater structure installation of large-diameter natural gas subsea pipeline connecting Yacheng Hong Kong subsea pipeline kp694 node of Dongfang 13-2 gas field group, which is the leading in China. Shenzhen offshore oil engineering Underwater Technology Co., Ltd. and CNOOC Zhanjiang Branch successively sent letters of thanks to commend Shanye company for its outstanding contribution to Yacheng submarine pipeline maintenance project.
Yacheng 13-1 gas field is located in the sea area about 90km south of Hainan Island. The 28 inch submarine natural gas pipeline in this operation connects the offshore platform of Yacheng gas field and Hong Kong CLP longgutan power plant, with a total length of about 778km and the first pipeline transmission pressure in the world. It is an important gas transmission trunk line connecting the west of the South China Sea, the east of the South China Sea, the Pearl River Delta and Hong Kong, It is the only channel for CNOOC natural gas transmission to Hong Kong and the main source of gas for Hong Kong citizens. It has been supplying gas to Hong Kong China Light and power company for 20 years. The opening at kp694 node of Shanye company is to reserve the output channel for the subsequent Dongfang and Wenchang gas fields after they are connected to the pipeline.
The project has a large opening diameter and high air pressure in the pipe. Because the opening machine needs to pass the pre installed 28 inch ball valve, the opening stroke reaches 3156mm, and there is no finalized opening product in the world. Moreover, the installation and positioning accuracy of mechanical tee for opening and its sealing require extremely high surface finish of submarine pipe. On the one hand, how to safely and efficiently open holes in underwater low visibility and high-pressure environment is an international problem. On the other hand, the project also undertakes the political task of completing within the specified time to ensure normal gas supply and maintain social stability in Hong Kong.
Since the end of 2015, Shanye company has actively contacted the owner for technical preparation, participated in the research on installation process details, land commissioning and training at the first time, put forward many suggestions on optimizing underwater installation and structural transformation, designed underwater fixtures targeted, and improved the construction scheme. After the start of the project, the company gathered the main divers with long-term operation experience in muddy water and adopted a full set of diving equipment in line with international specifications approved by IMCA D023. After 30 days and nights of continuous struggle, the offshore project team has overcome the problems such as tight construction period, poor seabed visibility, high installation accuracy, unstable wind, wave and current, insufficient performance of supporting ship crane and 24-hour uninterrupted operation. We are not afraid of hardships and challenges. We have successfully completed all the assigned tasks according to the requirements of the owner, The construction technology of underwater installation of domestic drilling machine and other auxiliary structures on the in-service natural gas submarine pipeline under the restriction of poor underwater visibility is explored.
Underwater opening of submarine pipeline is an important means for emergency maintenance and pipe network modification. The successful implementation of kp694 underwater installation process of pressurized opening has accumulated a lot of practical experience for the company to carry out similar projects under the conditions of poor underwater visibility in the future. At the same time, it has also driven the R & D and application of tooling equipment such as submarine pipe longitudinal weld grinding and submarine pipe polishing, It has effectively promoted the improvement of the company's underwater engineering strength.
(text / figure: Underwater Engineering Department of Shanye company)
