(A) the general structure and characteristics of flexible hose
1. General structure of flexible hose
The flexible hose used in submarine oil and gas pipeline system generally consists of five parts:
A. sealing material. Commonly used nylon 1 1. At 85℃, this material has a life expectancy of 30 years and good elasticity. Or adopt HID9300 high-density polyethylene, the ultimate tensile strength of this material can reach 400%, and it has good seawater environment resistance.
B. reinforcement materials. Stainless steel is often used for steel reinforcement armor, and 3 16L stainless steel is generally used as the skeleton under internal and external pressure, which has high corrosion resistance. Or carbon steel parts are used to bear hoop force and axial force.
C. thermal insulation materials. Polyurethane foam is the most commonly used. The material has low thermal conductivity and good thermal insulation performance, but its melting point is low, so it can't be extruded and bonded with steel bars badly. At present, a modified polyurethane foam has been developed, which can overcome the above shortcomings by extrusion. Due to the brittleness of thermal insulation materials, the thickness of single layer should not exceed 40mm, otherwise the flexibility and strength of the hose will be affected.
D. anti-slip and wear-resistant materials. In order to prevent excessive sliding and wear, synthetic materials are placed between the layers of reinforced steel sheets to tightly grasp the steel sheets and play the role of anti-slip and anti-wear.
E. external protective materials. High density polyethylene is usually used because it has good corrosion resistance and mechanical damage resistance.
Figures 15-2 1 and 15-22 show the structural diagrams of two typical hose bodies. The former is a flexible hose lined with nylon material, which transports corrosive medium under normal pressure, while the latter is a high-pressure flexible hose for strengthening treatment and heat preservation.
2. Characteristics of flexible hose
A. the length of the pipe section is infinite. Because the pipe-making process is continuous production like cable, the length of this pipe section is only limited by the size of drum and roller and the ability to install lifting equipment. Compared with steel pipe, it can greatly reduce the workload of pipe section connection and avoid the link with weak interface quality.
Figure 15-2 1 figure 15-22
B. it is convenient to lay and install. Laying and installing flexible hoses at sea does not require a special pipe-laying ship. Generally, with a little modification, a high-power tugboat can be used to lay and install flexible hoses, which is as simple and fast as laying cables, greatly reducing the cost of laying and installing at sea.
C. It has good internal and external anticorrosion performance and thermal insulation performance, and has better mechanical strength performance and durability than steel pipes.
D. It has enough negative buoyancy, and can meet the stability requirements of submarine pipelines without digging trenches or adding additional counterweight coatings.
E it has stronger resistance to hydrodynamic force and vibration fatigue damage than steel pipe.
F during prefabrication, both ends of pipe sections can be equipped with universal mechanical flanges to realize convenient and reliable mechanical connection between pipe sections or with steel pipe sections.
G. recycling can be realized.
(2) Application field and effect of flexible hose.
Flexible hoses are used in offshore oilfield development projects in China, but the number and scope are not large. Because of the high cost of hose materials, most of them are selected and applied in some special parts or specific environments to give full play to the special advantages of flexible hoses. After practical testing, the quality is generally stable and reliable, and the effect is good under the harsh marine environment and complex dynamic action. There are two applications of flexible hoses in offshore oil development projects in China. One is the jumper or power riser between floating production system and single-point mooring or underwater production system, and the other is the submarine oil pipeline system. This paper focuses on the application of the latter.
A. 1 In September, 1989, China Offshore Oil Corporation laid a 6 "hose submarine oil pipeline between platform W 10-3A and platform W13b in Beibu Gulf (a drilling and production dual-purpose platform modified from" Nanhai1"), which The length of the hose is about 1800m, which is made by French company Coflexip, and China is responsible for the design, laying and installation of the pipeline. This submarine hose was laid by a tugboat named Nanhai 2 1 1. The ship was refitted. A fixed roller device was installed in the middle of the ship to fix the hose reel, and a hose launching tail slot was installed at the stern. The hose is connected to both ends of the platform by sleeving the hose in the J-shaped steel pipe and fixing the J-shaped steel pipe on the sheath. It only takes one day to lay this kind of hose, which greatly saves time and pipeline laying cost compared with laying steel pipes.
B1991July, during the construction of Wei 10-3 northern oilfield development project, China Offshore Oil Corporation successfully laid and installed the second submarine oil pipeline with hose in Beibu Gulf. The internal diameter of the pipeline is 6 "(152 mm) and the length is about 4.25km, from platform W 10-3C (a fixed drilling and oil production platform modified from" Bohai No.6 "jack-up drilling platform) to platform W 10-3A. The length of this flexible hose submarine oil pipeline is the longest in China sea area at present. The French company Coflexip is responsible for the design of hose structure and pipe laying (including the modification design of "Nanhai 2 10" and "Nanhai 2 1 1"), and is responsible for the manufacture and supply of hoses. The modification construction of pipe-laying vessels ("Nanhai 2 10" and "Nanhai 2 1 1") and the offshore installation of hoses are all completed by CNOOC. See Figure 15-23 for the general layout of two flexible hose submarine oil pipelines in W 10-3 Oilfield in Beibu Gulf.
Figure 15-23 The hose submarine oil pipeline laid in W 10-3 oil field in Beibu Gulf.
C1993 Lufeng 13- 1 Oilfield jointly developed by the Pearl River Estuary has laid and put into operation a 6 "submarine flexible oil hose. The water depth of this oilfield is140 ~150m. The oil hose is a floating oil storage device from the wellhead oil production platform to Nanhai Shengkai, with a total length of about 1.85km, as shown in Figure 15.24.
D.65438+1March, 1996, contracted French Coflixip Company to lay three flexible submarine pipelines in Liu Hua11oil field in the Pearl River Estuary. One of these three hoses is a 6 "testing and metering pipeline, and the other two are subsea production and injection pipelines. One end of the pipeline is connected to the single-point mooring system of Nanhai Shengli floating production and storage unit, and the other end is connected to the underwater base of Nanhai Challenge semi-submersible drilling and production auxiliary platform, with a total length of about 2.5km. See Figure 15-25 for the arrangement of three hoses. Liu Hua 1 1- 1 Oilfield is jointly developed by China Amoco Oriental Oil Company and Comac Oil Company of the United States, and the water depth of the oilfield is 300 ~ 350 meters. ..
Figure 15-24 Lufeng 13- 1 Oil Pipeline in Oilfield
Figure 15-25 Liu Hua 1 1- 1 Layout of Three Hoses in the Oilfield
E. 1993 in the submarine pipeline system of Suizhong 36- 1 oilfield test area development project in Liaodong Bay, three sections of flexible hoses were used to replace some steel risers and expansion elbows. At that time, the life power platform of this oilfield needed to erect six platform risers of submarine pipelines, and the upper module of the platform had been installed. When installing submarine pipelines and risers, it is impossible to adopt the usual method of integral hoisting of risers, expansion elbows and flat pipes. In order to solve this problem, a scheme of replacing some steel risers and expansion elbows with flexible hoses is put forward, and the practice proves that the expected effect has been achieved. One section of the three-section hose is used for natural gas transportation with an inner diameter of 88.9mm, one section is used for water injection with an inner diameter of 152.4mm, and the other section is used for oil transportation with an inner diameter of 203.2 mm. The lengths of the three-section hose are all 60m. Suizhong 36- 1 Oilfield test area is 30m deep.
F1In April, 1998, four flexible hoses produced by Wel 1-stream Company of the United States were installed in the submarine pipeline system of Jinzhou 9-3 Oilfield Development Project in Bohai Sea. The installation site is near the caisson foundation platform in the east/west area, and the flexible hose is used as an expansion elbow connecting the vertical pipe in the caisson and the steel flat pipe outside the caisson foundation. It is mainly considered that the scouring depth near the caisson foundation is1.5m. When the riser passes through the caisson wall and is connected with the flat pipe, the distance from the point passing through the caisson wall to the seabed is1.5m. Therefore, there will be an expansion elbow section suspended from the seabed between the riser and the flat pipe. If steel pipes are used, there will be the risk of fatigue damage caused by eddy current excitation. Therefore, the flexible hose with better fluid resistance is designed and selected. Specifications are 2-section 12 "oil pipeline and 2-section 65/8" high-pressure water injection pipe. The length of hose at caisson end in the west area is 50m, and that in the east area is 70m. It has been used for five years since it was put into production, and there has been no problem.
(3) Technical development and application prospect of flexible hose.
Flexible hose was first developed by French Petroleum Research Institute after nearly ten years' research. It is a patented product suitable for oil and gas industry, and then Coflexip Company was established to specialize in production. At that time, the world was dominant, in a monopoly position, and the price was relatively expensive. However, because it has many obvious advantages over steel pipe, it is especially favored in the field of offshore oil industry, and its application scope is expanding. In recent years, the United States, Japan and some European countries have successively produced this kind of hose, among which "Wellstream" company in the United States has become a strong competitor of Coflexip company. With the development of technology and the competition in the market, the price of this kind of products has been declining, and the application field and scale have been further expanded.
Second, the application of the "main pipe" pipeline structure and related technologies
(A) "sub-mother pipe" pipeline structure engineering example
Figure 15-26 Structural Piping Diagram of "Mother Pipe and Child Pipe"
China Offshore Oil Corporation designed, laid and installed a submarine pipeline with a length of about 10km and an outer diameter of 2.375 "for conveying ethylene glycol antifreeze in the first phase of Jinzhou 20-2 condensate gas field exploration and development in Liaodong Bay of Bohai Sea. The "main pipeline" has an outer diameter of 8.625 inches and is used to transport natural gas produced at the wellhead. This pipeline is the gathering and transportation pipeline of condensate gas field, which is used to transport the natural gas produced by Nangao Platform to Beigao Platform and then to the onshore processing terminal. In order to prevent hydrate formation in Nanping-Zhongbeiping 10km submarine natural gas pipeline, ethylene glycol antifreeze was injected from the pipeline entrance. In order to reduce the production cost and realize the reuse of antifreeze, we put forward the process scheme of separating and recovering antifreeze in the north platform, and then pumping the recovered ethylene glycol back to the south platform with a 2 "small tube, thus realizing the reuse of antifreeze. In order to realize this technical scheme, several pipeline structural schemes are compared, such as adopting flexible collection hose or laying two steel pipes respectively. However, after technical and economic analysis and comparison, it is finally decided to adopt the steel pipe pipeline with "sub-mother pipe" structure, which is considered technically feasible. It is obviously the most reasonable way to install the existing pipe-laying ship and lay two steel pipes together and bury them in the same ditch, so that the project cost is the lowest. The seabed of the pipeline route is flat soft soil, and the water depth is about 18m.
Figure 15-26 shows the main parameters of the pipeline with "sub-main pipe" structure.
(B) "sub-mother pipe" pipeline structure related technologies
This kind of submarine pipeline is used for the first time in China, and it is rare in the world.
First of all, the design of this kind of pipeline can not find specific and clear guiding provisions in the general international standards, nor can it find methods and principles that can be used as the basis for design. In the pipeline design, according to the specific conditions of the project, consider taking the 2 "small pipe as the additional load of the 8" main pipe, control the structural strength of the 8 "main pipe, and ensure that the two pipes will not be separated during installation. Although it can be said from the design concept, it has not been designed, experienced and grasped. Finally, American Gulf Engineering Company was invited to cooperate to complete the design of submarine pipeline with "sub-mother pipe" structure.
According to the design requirements, a 2-inch pipe laying line is added outside the existing pipe laying line by using the "Binhai 109" pipe laying ship. Using the flexibility of the 2 "pipe, after the 8" main pipe finishes the finger pouring of the on-site node horse body, connect the 2 "pipe to the sewer line of the main pipe, tie and fix the pipe on the main pipe according to the design requirements, and then launch and lay it on the seabed together. During the laying process, the applied tensile force is all on the 8 "main pipe, and the 2" small pipe is only fixed on the main pipe as an additional load, and the stress control is not carried out by using stress components during installation.
(3) The application prospect of "secondary trunk" pipeline structure
Practice has proved that the design, laying and installation of this kind of submarine pipeline with "sub-mother pipe" structure is very successful, and the expected purpose has been achieved, which has accumulated valuable experience for the design and laying of this special submarine pipeline in China. The application prospect of "sub-main pipe" pipeline structure is broad.