underwater engineering

underwater engineering

1.  Introduction to COOEC Subsea Technology Co., Ltd.

COOEC Subsea Technology Co., Ltd. (hereinafter referred to as "Shenzhen Company") created a lot of technical innovations in 2009: for the second dynamic cable laying project of Wenchang, the construction period was shortened by 5 days via pooling of resources; for the trenching project of Ledong, the fastest speed of the first time trenching reached 800m/h, creating a plurality of new domestic records; for Huizhou 25-3/1 project, the confinement of conventional technologies was broken, saving a cost of RMB15 million; for PY4 -2/5-1 submarine pipeline replacement project, deep-water suction anchor was installed via ROV for the first time, submarine pipeline was dragged through FPSO for the first time, and was successful at once-through; for LF22-1 oil field disposal project (the first deep-water oil field disposal project in China), the construction period was shortened successfully in completing the recovery of buoys and mooring.

At present, Shenzhen Company holds one DSV, and is ready to buy another DSV to meet the needs arising from its development. This Company itself owns 4 sets of working-level ROVs and 2 sets of observation-level ROVs, and the subsea engineering it is able to undertake includes: installation of single point, hose, submarine base plate and riser; trenching and laying of submarine pipeline and submarine cable; subsea inspection and maintenance; a variety of subsea salvage works.

"HYSY 709" Vessel

2. Subsea Engineering Projects of Shenzhen Company in Recent Years

Table 1. Subsea Engineering Projects in Recent Years


Description of Engineering



Liuhua Oil Field re-production project



PY4-2 hose replacement project



Ledong trenching project



Panyu 4-2/5-1 submarine pipeline replacement project



LF22-1 oil field disposal project



Huizhou 19-2 riser installation project



Second dynamic cable laying project of Wenchang



PY30-1 submarine valve opening project



Ledong expansion bend installation project



Wenchang submarine pipeline rush repair project


2.1 Liuhua Oil Field Re-production Project

In mid-May of 2006, Liuhua Oil Field was attacked directly by No.1 typhoon “Pearl”, resulted in breakage of seven ones among anchor chains, 2 lines of 13.5-inch production hoses and 1 line of 6-inch chemical reagent hose were broken in the sea at a depth of 300 meters. The complexity of re-production of Liuhua Oil Field was at a world class. Upon discovery of such a great complexity, all the well known foreign companies quoted very expensive prices and even harsh conditions. COOEC Subsea Technology Co., Ltd. took the initiative in overcoming the difficulties of harsh natural environment, big degree of difficulty in operation, short of equipment supply, no proven technologies and successful experiences to rely on, and in July 2007, Liuhua Oil Field was put into re-production smoothly after shutdown for more than one year, which created a miracle in the field of international maritime engineering!

Fig. 1

Fig. 2. Subsea Co-operation between ROV and ADS

2.2 PY4-2 Hose Replacement Project

2.3 Ledong Trenching Project

Ledong trenching project was a plow type trenching after the laying of 24"/105 km outgoing transmission pipeline, with a trenching water depth of 100 m. Plow type trenching operation was the first trenching operation ever carried out in China, involving the operating equipment of APP and the DP power vessel. Because of its high-risk nature, trenching has strict requirements on sea conditions and equipment conditions. Both the excessive flow velocity and the DP performance extremes may lead trenching operation to a standstill. Therefore, prior to offshore construction, the project team had mastered the characteristics of velocity and direction of flow and had got familiar with the performance indicators and parameters of the DP vessel, which had laid a foundation for smooth progress of subsequent trenching operation. This trenching operation was scheduled for 31 days, while the actual offshore construction lasted for 26 days, 5 days shorter than scheduled, with a fastest speed of trenching up to 800m/h. It created a number of records for the first time in China: plow type trenching machine was used, trenching water depth was up to 100m and the trenching speed was up to 800m/h.A new business record has been applied for the project.

2.4 Panyu 4-2/5-1 Subsea Pipeline Replacement Project

Panyu 4-2/5-1 Oil Field is located in the South China Sea, about 200km to the south of Hong Kong. The oil field includes 2 wellhead platforms (PANYU4-2, PANYU5-1), from which the crude oil medium was transmitted via 2 subsea pipelines to the underwater base plate (PLEM) separately, and after convergence, was transmitted to FPSO. It also includes two subsea power cables (PANYU4-2 ~ PLEM, PANYU5-1 ~ FPSO).The oil field has an average water depth of about 100m.

In the replacement of Panyu 4-2/5-1 subsea pipeline, the construction of crossing FPSO was the difficult point of the project, involving joint subsea operation of a number of large scale engineering vessels such as pipe-laying vessel, DSV vessel and DP vessel, etc. and at the same time, a normal platform oil production must be guaranteed. The corporate leadership organized technical backbone to conduct solution analysis for many times, and calculated the positions and coordinates of the individual points on the seabed precisely. As the work was prepared sufficiently, the crossing was completed in only two days. The deep-water suction anchor of this project was installed via ROV for the first time, whereby the pipeline was positioned and fixed, which symbolizes that our capacity for marine engineering construction has been further enhanced. In addition, during the implementation of this project, technical staffs have designed an oil collector used to repair submarine pipeline, and have achieved very good results. This method is the first of its kind in China. A patent has been applied for this project, and two new business records with respect to this project will be applied for in 2010.

Highlights of project:
1) The suction anchor was installed via ROV for the first time in the industry, whereby the pipeline was positioned and fixed, and crossing FPSO;
2) Subsea pipeline was dragged through FPSO for the first time by Shenzhen Company, which symbolizes that our capacity for marine engineering construction has been further enhanced.
3) Riser is installed using small scale DP vessel, saving large scale crane ship resources and achieving full use of ship resources.

2.5 LF22-1 Oil Field Disposal Project

Lufeng 22-1 Oil Field is located at the edge of the Pearl River Mouth Basin, with a water depth of 330m. It includes underwater control facilities, booster pumps, five production well heads and one FPSO Muning. The operation for disposal of this oil field was in 2009.

This is the first deep-water offshore oil field disposal project in China. During the first phase of the maritime construction, all the contents of the operation were completed smoothly as scheduled. The smooth completion of the first phase of the project symbolized another major breakthrough in the development of Shenzhen Company in the field of deep water operation, and is of great significance to the deep water development of Shenzhen Company.

2.6 Huizhou 19-2 Riser Installation Project

Huizhou 19-2 Platform is located at Huizhou waters of the South China Sea, with a water depth of 107m. In Huizhou 19-2 riser installation project, since an emergency deployment of large scale crane ship “Huatianlong” were required for other projects such that HZ19-2 riser installation could not be supported, Shenzhen Company made a decision temporarily and bravely to adopt innovative technology via emergency deployment of HYSY709 to install a riser of 113m by small scale DP vessel, replacing the originally planned “Huatianlong”, with the construction period shortened by 7 days as compared with the same period the year before. The successful practice of the project proved the feasibility of this technology, breaking the situation of riser installation by relying on large scale crane ship in construction.

2.7 Second Dynamic Cable Laying Project of Wenchang

The installation of dynamic cable from Wenchang FPSO single point to Wenchang 19-1A platform is a single point project in the South China Sea. The second dynamic cable has a total length of 2,635m, in which the dynamic segment is 307m in length, including 26 balancing weight and 32 buoyant blocks. This completion of this dynamic cable laying symbolized the overall completion of Wenchang Oil Field development project, thus the offshore production of Wenchang Oil Field has entered a new phase.

Shenzhen Company attached great importance to the laying of this dynamic cable, and conducted repeated demonstration prior to the construction. It overcame the difficulties of small space and complicated equipment within single point cabin and extreme high requirement on FPSO position limiting, optimized the deployment of its existing ship resources, limited the position of HYSY116 using two tugboats each with a capacity of over 10000 HP, with the power positioning vessel 709 as the main operating vessel and the RECORDER as a saturation diving support vessel, and completed the laying operation in only 4 days.

This is the project that Shenzhen Company undertook dynamic cable laying operation independently for the first time. Shenzhen Company overcame a series of difficulties, such as limited experiences and large-scale equipment resource constraints, and completed this cable laying operation at high efficiency. This construction obtained a wide range of favorable comments from owners, improving the reputation and brand image of Shenzhen Company in the South China Sea market and played an active role for Shenzhen Company to further expanding the South China Sea oil field market.

2.8 PY30-1 Subsea Valve Opening Project

The opening of PY30-1 subsea ball valve symbolized that PY30-1 Oil Field was put into production smoothly. In order to ensure that the ball valve placed on the seabed for more than 1 year could be opened smoothly, Shenzhen Company went all out to brainstorm a solution and eventually opened the valve successfully at once-through.

2.9 Ledong Expansion Bend Installation Project

In Ledong expansion bend installation project for external transmission pipeline, we overcame the natural factors of high perennial water flow rate in this water area, and, after achieving successful installation of the expansion bend at once-through, we had a pressure testing and pigging on the pipeline directly and put it into production successfully.

2.10  Wenchang subsea pipeline rush repair project

Rush repair of subsea pipeline has always been one of the businesses in which Shenzhen Company has very mature technologies. It only took us 13 days to perform the offshore construction, from December 14 to December 31 with 5 days excluded for avoiding typhoon, of leakage inspection and repair project for pipeline from Wenchang 14-3A to 8-3A upon receipt of commission from owner to smooth completion of rush repair task, ensuring that Wenchang Oil Field was put into production smoothly. Shenzhen Company demonstrated sufficiently its abilities in respect of subsea pipeline rush repair once again and won high praise from the owner.

Staff Channel   
Copyright © 2009 OFFSHORE OIL ENGINEERING CO.,LTD. TO-DREAM legal Notice China National Offshore Oil Corporation Site Map Recuitment