Several ideas in the construction of submarine pipelines Ma Liangchu's ideas and opinions for suppliers include: straight seam welded pipes, single-layer insulation pipes, pipe laying vessels, pipeline inspection and beach sea pipelines.
With the beginning of the new millennium, the offshore oil and gas situation in China is particularly gratifying to be put into production in the early years of the South China Sea and successfully sent to the Ake gas field in Hong Kong. There are 13 oil and gas fields successively developed, as well as Dongfang 1-1 gas field, Ledong gas field and Weixinan oil field group. Showing a good sign. Since the Pinghu oil and gas field was put into production in the East China Sea, a large oil and gas field has been discovered in the Chunxiao Sanjing, Xihu Sag, 450km southeast of Shanghai. Since the significant discovery of oil and gas in the Bohai Sea from Qinhuangdao 32-6 Nanpu 35-2 Suizhong 36-1, it has also been in the waters near Dagang and Penglai 1-93 and so on have discovered large-scale oil fields with a capacity of 100 million tons, especially Penglai 1-93 can be said to have discovered the second largest oil field in China after Daqing, with reserves exceeding 600 million tons, the prospect is really getting pregnant. The annual production of offshore oil and gas in China has exceeded 15 million tons, and it can reach 30 million tons in the near future. Daqing offshore will soon be able to realize that the oil and gas produced by offshore oil and gas fields will be transported through pipelines except for a few that are shipped directly offshore. Transmitted to onshore processing and delivered to users separately. Therefore, China will have a large number of submarine pipelines to be built in the near future. It is estimated that by 2010, China ’s submarine pipelines, together with the existing more than 2,000 kilometers, will reach a total of about 10,000 kilometers in the construction of submarine pipelines, in addition to the success of the past 20 years. In addition to experience and practice, we must pay attention to creating new experience and new practice combined with the contact with the subsea pipeline in the previous period. Here are some preliminary ideas and views on the construction of China's submarine pipelines for discussion 1 straight seam welded pipe in the past A large number of domestic oil and gas pipelines (except for the newly reconstructed multiple lines), most of which use domestically-made threaded welded pipes. Therefore, several large-scale steel pipe factories in China produce these types of threaded pipes, and some slightly larger diameter steel trunk pipes are more It is so recent that many steel pipe factories have started to produce seamless pipes, but mass production of straight seam welded pipes with generally small diameter and incomplete specifications is being planned. Due to the special environment of submarine pipelines, most of the more than 2,000 kilometers of pipelines that have been built use imported seamless pipes and a few straight seam pipes.
Regarding the use of domestic steel pipes and straight seam pipes in submarine pipelines, as early as around 1990, when the China Classification Society's submarine pipeline system specifications (1992 edition) were compiled, the materials of domestic steel pipes and foreign pipe materials were compared. There are discrepancies in the specifications, manufacturing process and individual chemical composition of the imported pipes, which limits the domestic and international steel main pipes to be analyzed in the design. As long as the targeted adjustments are made during the smelting and manufacturing process It is completely possible to achieve consistency. Therefore, specific regulations have been made in the adoption of domestically produced steel pipes in this code. As for the use of straight seam pipes in subsea pipelines, the domestic and foreign pipeline specifications are very clear. Seamless steel pipes or straight seam welded steel pipes are allowed in submarine pipelines, and straight seam pipes are also widely used abroad. It is also found that there is no clear prohibition on the use of threaded pipes in the domestic and foreign submarine pipeline specifications, but it is implicitly indicated in the text that it can be used as a submarine pipeline. For example, the pipe manufacturing section of the specification states that "the pipe should be seamless or Steel plate or steel strip is rolled and welded into "here" steel plate or steel strip is rolled and welded "
The former is a straight seam pipe, and the latter refers to a threaded pipe. Over the years, people believe that the use of threaded pipe is not recommended in submarine pipelines, and it is accepted by all subsea pipeline designers. There is no precedent for the large-scale use of threaded pipes abroad. It is widely used like a straight seam tube.
In this regard, domestic steel mills and steel pipe factories must produce and manufacture steel pipes suitable for submarine pipelines in accordance with internationally uniform standards and specifications, including slightly larger diameter straight seam pipes. Generally, the price of straight seam pipe is 10% ~ 15 less than that of seamless pipe, which reduces the cost of each kilometer of submarine pipeline by about 5%, and the larger the pipe diameter, the more obvious the price advantage. Therefore, it is more suitable to use straight seam pipes for oil pipelines with a slightly larger diameter (for example, diameters greater than 300 ~ 400mm), and the economic benefits are very obvious. Therefore, the use of domestic straight seam welded pipes is recommended in the construction of submarine pipelines.
2 Single-layer thermal insulation pipes Looking at the subsea thermal insulation oil pipelines that have been built in China, the double-layer thermal insulation structure developed abroad more than 40 years ago is generally used, that is, the inner pipeline and the outer casing are all made of steel. The design of this structure is characterized by a steel outer tube with a large diameter and a thick wall. This structure, because the inner tube and the outer tube are made of steel, the problem is that the steel used for the pipeline is very large, and the steel used for the outer tube is 1.2 to 1.5 times more than the inner tube; second, this double-layer tube insulation structure Although it has a good thermal insulation effect, it makes the pipeline construction and laying more difficult and doubles the cost, and its cost is much higher than that of a single-layer thermal insulation pipe. For example, if the steel outer tube of the double-layer tube structure is replaced with a single-layer insulation tube of a polyester jacket tube whose structure is basically unstressed, the cost can be reduced.
Single-layer insulation pipes are allowed in the specification of submarine pipeline systems. Eighty or nine single-layer insulation pipes were used overseas at sea more than ten years ago. As stated in the specification: "Hot-transport submarine pipelines are generally insulated with foam plastic, plus protective steel "Sleeve or plastic protection sleeve" 99 here is "Foam insulation plus plastic ePu technique and experience to obtain practical experience and information in the country / test enkibookmark2 protection sleeve", which is the use of single-layer insulation tube analysis submarine heat transmission pipeline The problems or doubts encountered during the single-layer insulation pipe may be as follows: First, the aging durability of the polyester jacket casing in the seawater environment should be explained. When the steel outer casing is not perforated, the life is generally better than The jacket casing is longer, but it is 20-30 years relative to the design life of the submarine pipeline. The two are basically the same. Because the jacket casing is resistant to aging and durability in seawater, domestic and foreign research results have shown that its life can be compared with the design life of the submarine pipeline. matching. In Canada, there have been reports of experimental results of jacket casings in seawater with anti-aging and durability for more than 25 years, and the single-layer insulation pipes used in seawater abroad have been used for more than 20 years in the early years. This polyester jacket sleeve has light weight, good water tightness, easy processing and no pollution. It is very suitable as a protective tube for a single-layer insulation pipe; the second is the prevention of the joint (or interface) between the jacket sleeve sections Seepage tightness and installation speed problems The interface between the heat insulation material of the steel pipe joint and the welding sleeve and the jacket casing. The anti-seepage tightness of this joint is completely used after the thermal expansion sleeve and the special joint plug push tool are used. This can be properly solved in this respect. CNOOC Engineering Design Company and Beijing Chemical Engineering Design Institute and other units have special research and specific formulas and design schemes. Due to the use of thermal expansion sleeve technology, the speed of the inter-segment repair will not affect the normal Pipelaying progress; the third is the problem of the firmness of the adhesion between the jacket casing and the outer concrete weight layer and the mutual removal of the "two-layer skin". It is believed that when the weight layer may be partially broken, the piece of weight layer will fall off and lose negative buoyancy. Doubts, according to the oilfield technical inspection missions of the Ministry of Petroleum in the past few years, they visited Italy and other countries to specifically conduct field visits to the production line of jacket and casing outer coagulation weighted layer. Poor adhesion and smoothed off "two-skin"
However, when the long pipe section of the pipeline is under-drawn, the friction between the weight layer and the base soil is slightly larger, and the stress portion of the pipeline traction causes a moment with the friction force, which may cause the insulation layer to tear during the traction process. This point can be avoided when the long pipe section of the pipeline is underdrawn as long as it is careful. For the sake of caution, single-layer insulation pipes are used in submarine pipelines. First, you can take 1 ~ 2 kilometers long as the test section. The test section can be jointly carried out with a foreign company to jointly carry out the test, and then be fully promoted on the basis of absorbing foreign technical experience through cooperation. The application of single-layer insulation pipes for submarine pipelines in China has changed the history of using steel outer casings for many years and changing the structure of double-layer pipes to single-layer insulation pipes is also a reform attempt.
3 Pipelaying ship People familiar with the construction of China's submarine pipelines are aware that the only existing pipelaying ship in China is the 109 ship in the Bohai Sea, which is originally used goods. It is an old-fashioned old-fashioned new generation pipelaying ship. In this way, many pipe laying tasks have been completed in China over the years, which is really indispensable, but it is an old ship after all, due to performance limitations, its pipe laying work has poor adaptability, and many pipe laying projects dare not dare to match Therefore, several domestic pipelines with large water depths and long distances are contracted by pipe laying ships of foreign companies, making the only pipe laying market in China often at a disadvantage of equipment and retreating from the hand should be a pity in the past. In the face of the current excellent offshore oil and gas situation in China, it is time to strive to equip as soon as possible practical new-type pipelaying vessels suitable for various sea areas and sea depths of more than 100 meters in China. It can be a semi-submersible, can be a hoist-pipelaying multi-purpose pipelaying vessel. An investment of about 80 million to 100 million US dollars can basically meet the pipelaying practice of these years. The newly equipped pipelaying vessel must be able to It is suitable for laying large and small pipes in groups, laying multiple pipes with similar calibers, and the possibility of laying three pipes with similar calibers at the same time. This is extremely important for increasing the speed of submarine pipeline construction and reducing the cost of pipeline laying. With the equipment and service of the pipe ship, it will soon change the pattern of the domestic pipe laying market. Especially in the development of the East China Sea oil and gas field, it will play a bigger role. As long as the ability of the newly equipped pipe laying vessel allows, it is expected to develop and occupy the Southeast Asian international market. In the future, pipeline inspection should be listed as one of the main contents in the submarine pipeline construction procedures. Pipeline inspection is an important part of monitoring and management of operating pipelines. With the successive development of offshore oil and gas fields in China, submarine pipelines have developed rapidly. In order to protect the sea, only busy with pipeline construction and transportation of oil and gas, we must pay more attention to the monitoring and management of operating pipelines. It is first proposed here that pipeline inspection is one of the necessary procedures when the submarine pipeline is completed, accepted and put into production in the future. Just like the two oil and gas pipelines of the South China Sea Ako gas pipeline and the Pinghu Lake, various intelligent detection pigs for pipeline inspection, as well as supporting technical equipment and professional equipment for pipeline inspection operations at sea are also urgently needed. made. In this regard, recently, when constructing a technical equipment and professional team for submarine pipeline inspection, as well as the matching subsea pipeline repair technical force, you can first find partners at home and abroad, introduce technology and funds, and enable pipeline inspection as soon as possible. Form strength with pipeline repairs. Just like the Pinghu pipeline, first determine the exact location of the fault point through pipeline inspection technology, and then use the internationally-recognized submarine pipeline repair technology to repair and put into operation in a relatively short period of time. Starting from submarine pipeline monitoring and management, pipeline inspection In addition to the first inspection before the pipeline is completed and accepted and put into production, it is necessary to conduct regular pipeline inspections as the pipeline runs. At present, the Ministry of Petroleum is targeting land pipelines. Under the auspices of the pipeline technology inspection center affiliated to its pipeline bureau, The main pipelines on land are carrying out planned pipeline inspections. The inspection results reflect the internal conditions of the pipelines in a timely manner, which also eliminates some hidden dangers of accidents that were not noticed, guaranteeing the safety of pipeline operation and reducing losses. Therefore, the experience of inspections on land pipelines Remind us that submarine pipeline inspection is a necessary technology and one of the important means to ensure the safe operation of submarine pipelines.
5 The Tanhai pipelines have many onshore oil and gas fields adjacent to the sea and extending to the sea. For example, all major oil fields along the Bohai Sea have a large beach area. Most of them hide oil and gas. Therefore, the Dagang and Shengli oil fields along the Bohai Sea The Liaohe Oilfield has plans and actions for development in the beach sea. The annual oil and gas production in the beach sea area has already begun to take shape, and some have millions of tons of ocean, wormwood and submarine pipelines. layout. Due to the flatness of the Bohai Beach area in 1997, the Ministry of Petroleum ’s infrastructure system prepared the enterprise standard for the beach-sea pipeline system specification, which showed that there are indeed many difficulties and problems encountered in the construction of the beach-sea pipeline, the most important of which is the rationale The beach section of the beach-sea pipeline is long, and some are almost all of the beach-sea pipeline. Most of the gentle slopes in the beach area are several kilometers long, where the water is shallow and almost all are in the tidal zone. The soil is generally soft and soft like swamps. Deep in the shore, it is difficult for operators and machinery to enter. Therefore, regular pipe laying barges are often Can not be approached due to water depth restrictions; such as the huge amount of excavation of the pipeline canal with the dredger, which is neither economical nor difficult to implement; the use of amphibious excavation machinery, the operation efficiency is low, the existing equipment can only excavate a few per shift Ten cubic meters, with the daily tide, part or most of the excavated trench will be silted and leveled; using shore traction or reverse traction at sea, due to the long beach and soft soil, the anchorage and towing line of the pipeline traction , Pulley block, etc. are difficult and complicated to configure and set up; the use of high horsepower winches and traction bar seat bottom traction, one may cause safety and risk when traction bar seat bottom, and sometimes due to insufficient anti-slip force when sitting bottom Little effect Sometimes in order to overcome the problems in the laying of the beach and sea pipelines, people are forced to consider again the construction of embankments and the integrated landing scheme of the trestle and some submarine pipelines to build embankments on the shore. The increase of the base soil bearing capacity, can build sand ballast stone throw cushion and sand drainage facilities to play well, or with paving geotextile engineering and technical measures to carry out. The slopes on both sides should be protected against wind, waves and ice. The arrangement of the trestle of the pipe trestle mainly considers the effects and effects of waves, currents, tides, etc. and the most submarine pipeline part thrown by the winter ice icing. It can be produced on the pipe laying barge, and the pipe laying barge is used for reverse traction. Finally, the scheme of laying the landing pipeline on the trestle bridge is not an economic scheme, but it can overcome the problems in the previous laying, so it can still be used as one of the feasible schemes for laying the beach pipeline.
The above preliminary ideas and views may be more importantly missed, please correct me
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