[History of the Ocean Sichuan Pipeline] Asia’s largest submarine oil pipeline was completed and put into operation in Maoming, Guangdong

It is understood that the single-point mooring terminal consists of a pontoon that can float on the sea and a pipeline laid on the seabed to connect to the land storage system. China’s first single-point mooring system was settled in Maoming Petrochemical Company in 1994. It is responsible for the task of entering 70% of Maoming Petrochemical’s crude oil into the factory. In the 23 years since it was put into operation, it has received and unloaded 1,003 tankers, and the original pipeline has safely transported a total of 193 million tons of crude oil. In early 2016, Maoming Petrochemical Single Point Mooring began laying a new submarine oil pipeline. The diameter of the pipeline increased from 864 mm to 1219 mm, the design life reached 30 years, and the pipeline's designed oil transportation capacity increased to 15 million tons/year. After more than a year of construction, the construction unit overcame the differences in land and sea construction, the impact of extreme bad weather, and multiple construction technical difficulties to complete the project safely and smoothly. (over)

As of early March, Maoming's 300,000-ton single point has safely unloaded 1,000 domestic and foreign oil tankers. It has been in operation for 22 years and has unloaded 76 types of crude oil. The cumulative amount of unloaded crude oil is nearly 200 million tons. The unloading volume accounts for 70% of the total crude oil processing volume of Maoming Petrochemical. Compared with the transfer at Zhanjiang Port, it has saved a total of 4 billion yuan in transportation costs. After the new pipeline is completed, the diameter of the Maoming 300,000-ton single-point submarine pipeline will increase from the original Φ864 mm to Φ1,219 mm, and the design life will reach 30 years. By then, the crude oil handling capacity of the Maoming single-point point will be increased from the original design capacity of 10 million tons to 15 million tons. * * Improving the terminal unloading capacity of Maoming Petrochemical single-point mooring has positive significance for promoting the local economic and social development of Maoming

　　On May 19, on the offshore waters of Dianbai District, Maoming City, Guangdong Province, the 300,000-ton ocean tanker "Kaichuan" safely transported crude oil from Saudi Arabia to Maoming Petrochemical's third oil tank area through a newly built single-point mooring system and underwater manifold. 　　At noon two days later, the transportation of 260,000 tons of crude oil was successfully completed, and the "Kaichuan" slowly left its berth on the sea under the bright sun. 　　So far, Asia's largest diameter submarine oil pipeline - Maoming Petrochemical's 300,000-ton single-point mooring oil terminal submarine pipeline has been successfully put into operation.

The first project between Guo Xinhui's Sinopec Petroleum Engineering Design Co., Ltd. (formerly Shengli Oilfield Design Institute) and Maoming Petrochemical. 　　After hearing about the Maohai Pipeline Project by chance, the Petroleum Engineering Design Company actively fought for it, actively communicated, and finally contracted the Maohai Pipeline Project in the form of EPC general contracting. 　　This project they undertook as general contractor is not simple. It has been called "Asia's No. 1" since its "birth". 　　It is about 15.49 kilometers long and is Asia's largest submarine oil pipeline with a diameter of 1,219 mm and a flow rate of 9,000 cubic meters per hour. It has a designed oil transportation capacity of 15 million tons per year and can handle more than 70 300,000-ton oil tankers every year. It handles 70% of Maoming Petrochemical’s crude oil loading and unloading tasks. 　　This submarine oil pipeline with the largest diameter in Asia extends all the way to a deepwater "point" in the South China Sea. Because of it, large oil tankers can be moored in the offshore sea and no longer drift. People call this "point" single-point mooring. 　　Single point mooring is an important "point" in the single point mooring system. The single-point mooring system located in the South China Sea is China's first and currently only single-point mooring system. 　　Single point mooring was officially put into operation on November 11, 1994. Over the past 22 years, Singapore, the United States, Saudi Arabia, etc. * * More than 1,000 oil tankers drift here to receive and unload crude oil through single-point mooring. 　　Guo Xinhui's mission is to activate Asia's first submarine oil pipeline, which is to lay 15.425 kilometers of 48-inch submarine oil pipeline and replace a new submarine manifold. The newly laid pipelines are arranged parallel to the original old pipelines, and the pipe diameter is increased from the original 864 mm to 1219 mm.……

　　　When he served as the project manager of a general contracting project for the first time, Guo Xinhui encountered an Asian first - the single pipe diameter of this project was 1219 mm, and the maximum weight after adding a counterweight layer was 33 tons, making it the submarine oil pipeline with the largest designed pipe diameter and the heaviest single pipe in Asia. Even internationally, there are very few submarine pipelines with such large diameters. 　　Since the pipe diameter far exceeds the diameter of conventional submarine pipelines, the design, pipeline coating and weighting, offshore pipe laying construction and subsequent trenching are all the first in China, without any accumulation of experience or reference. This has reached the extreme requirements for offshore engineering equipment and construction technology capabilities. 　　The project was constructed by EPC, a petroleum engineering design company, and Shengli Oil Construction Company was responsible for the construction. The two sides joined forces and clenched their fingers into fists to become the optimal combination. 　　As an outstanding enterprise in the field of long-distance oil and gas pipeline design and offshore oil and gas engineering design, Petroleum Engineering Design Company has rich experience. The construction unit, Shengli Oil Construction Company, is Sinopec's only amphibious oil construction company with first-class professional offshore oil engineering contracting qualifications. It has been involved in submarine pipelines for nearly 30 years and has become a leader in domestic beach and shallow water engineering construction. 　　The construction sea area is located in the South China Sea, with strong winds, high waves, fast currents, and busy shipping. Extremely bad weather once became a "stumbling block" affecting safety and progress. 　　They decided to use the cofferdam method for the construction of the intertidal pipeline, using film bags to blow sand into the cofferdam, placing ton bags outside the weir body to prevent surge impact, and driving steel sheet pile support in the pipeline connection area within the weir body to form a "weir within a weir." 　　They also work with * * The South China Sea Forecast Center of the Ocean Administration has established a meteorological service contract relationship, regularly receives weather forecast information, monitors typhoon trends in real time, and ensures early deployment and effective measures. At 6 a.m. on July 30, 2016, super typhoon "Nida" approached. The project department launched an emergency plan and completed the pipe abandonment and anchor lifting within 15 hours. Production resumed at 8 p.m. on August 5. ； Typhoon "Dianmu" hit on August 18. After research, it was decided to abandon the pipes in place to resist the wind. Production was resumed at 10 pm on August 20.……

　　During the 436 days of construction in the waters of the South China Sea, where "three-foot waves rise even if there is no wind", Guo Xinhui and his team's mood was just like the sea surface of the South China Sea. 　　On June 8, 2016, after arriving in the construction sea area, the on-site construction problems still brought unprecedented challenges to the Shengli 902 engineering ship that had been in service for many years. Due to the unfamiliarity with pipelines and weight in the early stage, the initial welding qualification rate was low and the equipment failure rate was high. 　　The general contracting project department proposed to use SRIMAX fully automatic welding throughout the entire process. “At sea, it is the first time in China that such a large-scale submarine pipeline construction has been carried out using all-position automatic welding. ”Qian Mengxiang, manager of Shengli Oil and Marine Engineering Services Company, said. In the end, a total of 1,280 welding joints were welded throughout the entire submarine pipeline, and the one-time welding pass rate reached 98.51%. 　　Since the new underwater manifold needs to replace the old underwater manifold in situ, the owner requires that the elevation and orientation of the new manifold's opening must be basically the same as the original manifold. According to the owner's requirements, the installation error must be kept within 200 mm, and the tilt angle must be within 2 degrees. For welding joints on the sea, it is not easy to achieve this accuracy by placing them on the seabed. 　　The distance between the new pipeline and the old pipeline that is still in operation is only 50 meters, and the new manifold components weigh 82 tons and are 41 meters long. They are irregular components. The side assembly of such large components and the precision control of the manifold installation position are two difficulties and are also the key control objectives of the entire project. Taking into account minimizing the underwater workload and potential leakage points, the project team proposed a plan to newly design the submarine pipeline and underwater manifold to be welded above the water surface and then lowered as a whole. 　　However, during the process of dismantling and lifting the old manifold, the mood of the project team went through two roller coaster-like processes from high excitement to extreme depression - when the old manifold was dismantled and lifted for the first time, two floating cranes were lifted at the same time. When the old manifold, which had been installed on the seabed for 23 years, was lifted out of the water, all the people on site and those on shore who were paying attention to the project were very excited, and everyone was looking forward to the exciting moment. 　　When the manifold was hoisted nearly 10 meters from the water, the cutting point connected to the pipeline was still more than one meter away from the predetermined position. At this time, the waves increased to more than 1.5 meters. Because the two ships could not keep synchronization under the action of the swell, and the shaking was very severe, to ensure safety, they had to put the manifold back into the seabed. The mood of the project team also fell to the bottom. 　　Two days later, the second attempt to lift was still unsuccessful. Everyone laughed and said that the old manifold had been serving on the seabed for 23 years and was too deeply attached to leave. The construction period was not waiting for anyone. On the basis of summarizing and analyzing the experience of the first two failures, a ship was used for the third hoisting. It took one day to finally successfully hoist the old manifold onto the barge. The old pipeline pipe mouth was blocked and then lowered to the seabed again, clearing the way for the subsequent installation of new pipelines and new manifolds. 　　After actual measurement, the manifold installation error was 270 mm in the longitudinal direction and 310 mm in the lateral direction, which was completely within the acceptable range. The actual inclination was 0.3 degrees in the longitudinal direction and 1.5 degrees in the lateral direction. It has completely exceeded pre-installation expectations. “The single-point submarine pipeline was successfully put into operation, creating a miracle in China's single-point history. I give you a thumbs up!" Cai Shiliang, general manager of Maoming Petrochemical Port Division, said excitedly.

On the 2nd, the Maoming Petrochemical single-point submarine pipeline hidden danger management project completed the construction of the most difficult first crossing of the landing section, including the assembly, welding, testing, and anti-corrosion of the first crossing, and began earthwork backfilling. Because the first crossing of the landing section is at the junction of water and land, welding construction is the most difficult. Since late August this year, the cofferdam filling and filling work at the first crossing of the landing section has been carried out simultaneously with the laying of submarine pipelines. However, due to bad weather and sea conditions and constant strong cold air, the cofferdam filling and filling construction has had twists and turns and the progress is slow. In order to speed up the progress, the construction party continued to increase the investment of personnel, equipment and other resources, and the preparation work for the cofferdam construction area was completed on December 21. On December 22, the assembly, welding, testing, and anti-corrosion of the first crossing of the landing section were completed, and earthwork backfilling began. According to the plan of the construction company, all operations on the remaining 33 crossings on the shore of the landing section will be completed by mid-January 2017. After the offshore pipeline section was laid 1.5 kilometers away from the single-point submarine manifold, the operation was suspended, waiting for construction to meet the manifold in March next year.

What is single point mooring? Single point mooring is an important "point" in the single point mooring system. The single-point mooring system located in the South China Sea is China's first and currently only single-point mooring system. Single point mooring originates from the English "Single Point Mooring". In short, compared with fixed docks, its biggest feature is that the mooring method is "point", that is, large oil tankers or very large oil tankers can be moored at a deep water "point" on the offshore sea surface, and then carry out loading and unloading operations.