In the development of offshore oil and gas fields in China for nearly 40 years, the design and construction technology of submarine pipelines has made great progress from the initial short-distance submarine pipelines in oil and gas fields to various long-distance platforms and then to onshore submarine pipelines. At present, the development engineering models of offshore oil and gas fields in China are basically all sea and half sea and half land.
China offshore oil industry started in 1960s. In the 20 years before the reform and opening up, offshore oil people were self-reliant. Over the past 30 years of reform and opening-up, China offshore oil industry has achieved leap-forward development through foreign cooperation, introduction and absorption of foreign advanced technology and management experience. More than 30 oil and gas fields have been discovered and developed in Bohai Sea, East China Sea and South China Sea, with an annual oil and gas equivalent of over 50 million tons. With the development of offshore oil industry, great progress has been made in offshore oil and gas storage and transportation. Over the past 20 years, China Offshore Oil Corporation has successively built more than 60 platforms, 1 1 floating production and storage devices, more than 2,000 kilometers of submarine pipelines and 6 onshore oil and gas processing terminals in China. It can be said that after more than 20 years of introduction, study and practice, China engineers and technicians have basically mastered the offshore oil and gas storage and transportation engineering technology within the water depth of 100 meters, and have formed some proprietary technologies and capabilities with China's marine characteristics. However, although China has laid more than 2,000 kilometers of submarine pipelines at sea, there is still a big gap between the domestic design and construction capacity and the international advanced level. In terms of engineering design, foreign companies have formed design technology under the conditions of nearly 3000 meters water depth, harsh sea conditions, complex seabed landforms and geological conditions; However, domestic design units can only set foot in the design of submarine pipelines in the water depth of 100 meters and in the conventional environment; In terms of engineering construction, there are only two pipe-laying vessels in China, and the laying depth is less than 100 meters, especially in engineering inspection and maintenance.
The first submarine oil pipeline in China is an internal submarine pipeline in Chengbei Oilfield jointly developed by China and Japan. The submarine pipeline is a thermal insulation double pipe with an inner diameter of 6 decimeters, an outer diameter of 1.2 decimeters and a length of 1.6 kilometers. The pipeline was designed by Nippon Steel Company and constructed by floating method. 1985 was completed and put into production, and it is still in production. The first long-distance subsea oil-gas mixed transportation pipeline in China is Jinzhou 20-2 natural gas condensate mixed transportation pipeline, which was completed and put into operation in 1992. Pipeline diameter 12 decimeter, length 48.6 kilometers. This is the first submarine pipeline laid by a domestic pipe-laying ship in China. Up to now, the longest submarine pipeline in China is the submarine gas pipeline from Nanhaiya 13- 1 gas field to Hong Kong, which was completed and put into operation at the end of 1995. The pipeline has a diameter of 28 decimeters, a length of 787 kilometers and an annual gas transmission capacity of 2.9 billion cubic meters. Designed by JPKenny Company of America and laid by Seipem Company of Italy. The first submarine pipeline for long-distance transportation of heavy oil in China is the submarine pipeline from Suizhong 36- 1 oilfield central platform to Suizhong onshore terminal, which was completed and put into operation in 200 1 year. The 70-kilometer-long pipeline is a double insulation pipe with an inner diameter of 20 inches and an outer diameter of 26 inches, with an annual oil transportation capacity of 5 million tons. The density of crude oil transported is 0.96g/cm3. The pipeline is completely designed and laid by CNOOC Engineering Company. It was established on the basis of summarizing the experience of submarine pipeline transportation in Suizhong 36- 1 experimental area. 1987 after the discovery of the oil field, in the feasibility study of the oil field engineering scheme, it is discussed to lay a 50-kilometer submarine pipeline to transport offshore crude oil ashore. Finally, after research and evaluation by authoritative experts at home and abroad, it is considered that the crude oil produced in this oilfield has high density and viscosity. At that time, there was no precedent for transporting heavy oil by long-distance submarine pipeline at home and abroad, and the technical risk was great. Especially, the oil field is located in Liaodong Bay, and the temperature is low in winter, so the risk of shutdown and restart is greater. Immediately, the pilot area plan was launched. Through the production test of1993-1998 in recent five years, it is considered that it is feasible to transport high viscosity crude oil long distance with double-layer insulation pipe. The long-distance pipeline has been running normally since 200 1 oilfield was put into production. It can be said that Suizhong long-distance submarine oil pipeline fills the gap of long-distance transportation of high-viscosity crude oil at home and abroad. At present, the natural gas fields developed offshore in China all adopt the half-sea and half-land model. Natural gas produced by Pinghu gas field in the East China Sea, Nanhaiya 13- 1 gas field and Dongfang 1- 1 gas field, after gas-liquid separation and natural gas dehydration on offshore platforms, is transported to onshore oil and gas terminals for treatment through submarine long-distance pipelines, and then sold to onshore users (or industrial or civil). Most oil fields developed in Bohai Sea and South China Sea basically adopt the whole sea engineering model, such as Qinhuangdao 32-6 oil field in Bohai Sea and Huizhou oil and gas field in South China Sea. Oil and gas produced on the platform are mixed and transported to offshore production and storage devices for processing, storage and export through submarine pipelines. In recent years, the development of Bohai Sea and Beibu Gulf oil fields has also begun to adopt the form of half sea and half land, such as Suizhong 36- 1 oil field in Bohai Sea and Weizhou oil field in South China Sea. After the oil and gas produced in these oilfields are separated and dehydrated on the platform, the crude oil is transported to the onshore terminal for processing and storage through the submarine long-distance pipeline, and then exported through the wharf or single point.
In addition, a number of long-distance submarine pipelines have been laid offshore China, as shown in Table 37- 1.
Table 37- 1 China Offshore Submarine Long-distance Pipeline
In recent years, it is the peak year for offshore oil engineering construction in China, especially with the large-scale development of offshore natural gas, nearly 2000 kilometers of submarine pipelines have been put into construction. See Table 37-2 for the main long-distance pipelines.
Table 37-2 Main Long Distance Pipelines
In addition, China has made great progress in submarine pipeline technology, many of which have reached the international leading level. In this respect, the research on new technologies such as multiphase mixed transportation of submarine pipelines is particularly prominent, and it is believed that China will have greater development in the future world offshore oil storage and transportation. Multiphase mixed transportation technology has a broad market application prospect in China, and the main factors restricting the application of multiphase mixed transportation technology are the imperfection and applicability of the technology itself. China's oil industry urgently needs a set of long-distance multiphase mixed transportation technology with strong applicability to improve the economic benefits of offshore oil fields, beach oil fields, desert oil fields and remote peripheral oil fields, thus providing technical support for the oil industry to implement the low-cost strategy.
Second, the floating production oil storage device
Since 1986, the first offshore floating production and storage device Hope was put into use in Nanhai 10-3,1floating production and storage device has been put into use in offshore oil and gas field development. Friendship floating production oil storage device was put into use in Bohai BZ28- 1 in 1989, which is the first offshore oil storage device designed and built in China. Floating production and storage device is a single point mooring system developed on the basis of oil tanker. The oil and gas produced by the wellhead platform is transported to the single-point device through the submarine pipeline, and then enters the floating production oil storage device for processing, and is exported regularly. The four floating production and storage devices used in Bohai Sea were all designed and built by China. 1989- 1992 The oil storage capacity of the three units put into operation is 50,000-70,000 tons, and the oil storage capacity of Century is 10000 tons. Qinhuangdao Oilfield was put into production in 2002, reaching 6.5438+0.5 million tons. The mooring equipment of floating production and storage devices used in Bohai Sea area are all soft rigid arm mooring systems. This design is mainly aimed at the special situation of shallow water in Bohai Sea and ice floes on the sea surface in winter. Five of the six floating production and storage devices used in the South China Sea were converted from old oil tankers by foreign companies. Nanhai Endeavour was put into use in Wenchang Oilfield in the South China Sea in 2002. It is a 654.38+500,000-ton floating production and storage device designed and built by China. The device is moored by an internal turret system, and the floating production and storage device used in the South China Sea basically adopts similar mooring devices: the floating production and storage device is a simple and reliable offshore device, which integrates oil and gas treatment, refined oil storage and transportation and people's daily life; 1997 Lufeng oilfield put into production adopts the combination of underwater wellhead system and floating production and storage device, realizing the idea of developing the oilfield by one ship.
In June 2009, Haiyang Youshi 1 17, the largest offshore floating production and storage device in China, was put into operation in Penglai 19-3 Oilfield. The device, also known as Bohai Pengbo, has a hull size of 323m× 63m× 32.5m and is one of the largest floating production and storage devices in the world.
Third, oil tankers.
Under the guidance of the national energy transportation security strategy, by 20 10, China tanker fleet will carry 50% of the crude oil imported from China every year, and the capacity of China tanker fleet needs to be rapidly expanded from the current 9 million dwt to160,000 dwt, so it is imperative to build China's own ocean-going tanker fleet and even a "super fleet".
Analysts believe that it is a huge and complicated project for a country to build its own supertanker fleet, which needs the policy guidance of the competent government departments and the cooperation of shipping, petrochemical, shipbuilding, finance and other related industries. At present, several domestic shipping giants have basically established strategic cooperative relations with the largest crude oil importers in China, such as China Petrochemical Group and Sinochem Group, and signed long-term transportation contracts.
China * * * has seven oil transportation enterprises, among which COSCO Group, China Shipping Group, China Merchants Group, China Foreign Trade Transportation Group and Yangtze River Shipping Group are the "five national giants", and there are two private enterprises, Hebei Ocean Shipping Group and Dalian Haichang Group. There is also a special Taishan Petrochemical Company, which is a private enterprise that started in the mainland and registered overseas.
The construction of oil tankers is more related to the development of deepwater oil and gas fields in China.
The development of deep-water oil and gas fields is becoming the main growth point of the world oil industry and the hot spot of world scientific and technological innovation, and it is the development trend of the world offshore oil. The world's drilling depth reaches 2967m, the submarine pipeline laying depth reaches 2150m, and the oil field operation depth reaches1853m. According to relevant data, from 2000 to 2004, four new deepwater facilities 1 14 were built in the world, and deepwater drilling 1400 wells were completed. Installation of more than 1,000 sets of underwater oil production devices 1, laying of deepwater submarine pipelines and risers 1, 2000 km; The world's major oil companies have invested $56.6 billion in the exploration and development of deepwater oil fields, and the deepwater production capacity has increased by 1 times. Strictly speaking, China does not have the ability to independently develop deepwater oil fields. For more than 20 years, through foreign cooperation, China has basically mastered the engineering technology of developing various oil and gas fields with water depth less than 200 meters. Liu Hua Oilfield is the deepest offshore oilfield in China, with a water depth of 330m. It was developed by Amoco Oil Company of the United States on 1996. The production system consists of a semi-submersible production platform and a floating oil storage device, which adopted many of the most advanced technology combinations in the world at that time. The eyes of the whole world are turned to the deep sea. Oil production in West Africa, the coast of Brazil and the Gulf of Mexico has started, and China's oil and gas prospects are also pinned on deep water. South China Sea in China is rich in oil and gas resources. It is estimated that the water depth of large gas fields in the South China Sea is between 200 and 300 meters, and the water depth of offshore oil bidding blocks is between 300 and 3000 meters. Therefore, going deeper is not only the development trend of offshore oil in the world, but also the strategic goal of offshore oil in China. Deepwater development is different from shallow water and needs more advanced technology and technology combination. The conventional deep-water submarine pipeline laying of platforms and floating devices can no longer adapt to the new environment technically or economically, and the previous offshore operation devices and technologies need more advanced equipment such as dynamic positioning and ROV to complete.
The operation of China's large oil tanker fleet is in its infancy. At present, most shipping companies are mainly committed to speeding up the development of fleet size, but in terms of safety management, they are in a relatively backward state compared with internationally renowned companies.
There are no clear restrictions on the navigation of single-hull tankers in China's sea areas, and there are no restrictions on the entry of single-hull tankers in China at present, which undoubtedly increases the hidden danger of oil spill accidents at sea in China and makes China's offshore waters face greater oil pollution risks.
For pipelines and piping systems, the deeper the water, the greater the water pressure and the greater the response of the riser system. The greater the water pressure, the more serious the buckling propagation of submarine pipeline. More seriously, submarine pipelines and risers in deep water are much heavier than those in shallow water, and their connection, traction and installation are much more difficult than those in shallow water.
The temperature in deep water area is relatively low (3 ~ 4℃), and sodium crystals and hydrates are easy to form in oil and gas pipelines, which brings severe challenges to pipeline flow guarantee. The thermal stress caused by high temperature transportation is the main reason for the overall buckling (mainly lateral serpentine buckling) of the pipeline.
Fourth, the development trend.
There are two trends in the development of offshore oil fields in China, one is to develop into remote marginal small oil fields, and the other is to develop into deeper waters. The development, popularization and application of some new technologies will play a key role in the development of remote marginal oil fields, which represent the development trend of offshore oil fields.
(1) Research and popularize multiphase flow technology. By using multiphase pump and multiphase mixed transportation, the gathering radius can be enlarged, marginal oil fields can be incorporated into the established gathering and transportation system, existing existing facilities can be fully utilized, investment and operation costs can be reduced, and the development of marginal small oil fields can be economical and effective. At present, the application of multiphase pump on land has been gradually popularized, but it has not been applied in the construction of beach oil field. With the continuous development of metering technology, the traditional separated metering device will be gradually replaced by non-separated metering device. At present, dozens of commercial products have been used in offshore oil fields abroad, while China is currently in the stage of development and testing.
(2) Develop light, small and efficient equipment. Due to the limitation of the area and quality of offshore platforms, some light, small and efficient equipment will be more and more used in offshore oil fields. Although China has made some progress in the development of liquid-liquid cyclone equipment, there is still a big gap compared with foreign countries. Therefore, the development of light, small and efficient equipment is still the trend of offshore oilfield technology development.
(3) The platform structure is diversified and lightweight. Platform construction occupies a considerable proportion in offshore oilfield development investment, and domestic and foreign countries are committed to developing light platform technology to reduce investment costs, which is the development trend of platform construction technology.
(4) Submarine pipeline technology and other supporting technologies. The popularization and application of submarine pipeline laying technology and single-wall pipeline transportation technology, as well as supporting technologies such as riser technology, underwater tieback technology, safety and environmental protection, are the technical development trends to reduce the development cost of offshore oil fields in the future.
(5) Vibration and safety analysis of offshore platforms. This is also the basic theoretical research that the development of optical platform needs to be improved.
(6) Research on supporting technology of deep-sea oilfield development project. Underwater connection technology and multiphase flow technology are the development trends of deep-sea oilfield development technology.
(7) Deepwater oilfields are increasingly using FPSO for offshore oilfield development. It may be a choice and trend to use FPSO to develop marginal oil fields in remote deep water areas of offshore oil fields in the future.
Sino-foreign cooperative development of oilfield technology has a high starting point and is at the advanced level in the same period abroad. But on the whole, because China's offshore oil industry started late, there is still a considerable gap compared with foreign advanced level. For example, the underwater processing technology and equipment (such as riser technology and underwater production facilities) in deep-sea oil fields mainly rely on imports, and the efficiency, miniaturization and skid-mounted equipment still need to be further improved compared with foreign countries. The platform structure is diversified and the development of simple platform technology is immature, which are the directions for future scientific research. In the case of relatively insufficient investment in scientific research in China, we should establish the idea of doing something and not doing something, and actively and steadily adopt new technologies and equipment. To do something is to develop some projects with low investment, high efficiency and urgent need on site, such as light platform technology, miniaturization, high efficiency and skid-mounted equipment development, multiphase flow technology and so on. Inaction does not mean inaction, but some technologies with high investment, high risk, mature foreign development and leading technical level, such as underwater tieback technology, underwater production facilities, multi-diameter intelligent pig technology, corrosion monitoring technology, underground separation and so on. For example, China's FPSO manufacturing technology is a typical example of rapidly reaching the world advanced level by introducing foreign advanced technology, digesting and absorbing it for its own use.
Starting from the requirements of combining technology development with production practice, the technology development at this stage should focus on solving the following technical problems:
(1) In the transformation of gathering and transportation technology of offshore marginal oil fields and established oil fields, the mixed transportation pump technology is actively promoted, the gathering and transportation radius of offshore oil fields is increased, and some marginal oil fields are included in the established gathering and transportation system, so that the marginal oil fields can be economically and effectively developed.
(2) Accelerate the research and application test of multiphase flow miscible transportation and non-separation metering technology, and apply it in offshore oilfield construction as soon as possible.
(3) Develop and popularize small reinforced concrete platforms with oil storage capacity and reusable bucket foundation platforms.
(4) Referring to the experience of foreign light and small platforms in developing marginal oil fields, combined with China's national conditions, develop and study light and small platforms suitable for offshore oil field construction conditions in China, including: carrying out risk assessment research on light platforms, compiling design specifications suitable for light platforms, and improving the quality of designers.
(5) Learn from the characteristics of light miniaturization and integration of foreign process equipment, and further develop light miniaturization, integration and high efficiency equipment that is more suitable for offshore oilfield construction in China.