Compact Integral Forged Underwater Valves in Engineering Projects
Aug 18, 2024
As China's offshore oil and gas resource development deepens, underwater production systems have become a primary development model due to their good reliability and minimal impact on natural disasters. The layout strategy of underwater production systems, including drilling design, underwater manifold location selection, connection system layout, and offshore installation and operation, has long been a focus for scholars and engineering projects. Common layout methods include single-well tiebacks, pipe strings, cluster manifolds, and underwater base plates. Among these, modular manifolds offer significant advantages in size, weight, cost, and manufacturing time due to their compact structural design. These advantages have gradually become the mainstream development direction.
As core components of the subsea manifold, the layout of valves and logistics pipelines is crucial to its structure. To meet compact design requirements, optimizing the connection form of valves and logistics pipelines is necessary, such as adopting the concept of a "compact integral forged underwater valve group." This design concept was proposed as early as 1937 and has been further applied and developed in recent years. For example, a "Y-shaped branch module" design was adopted in an offshore oil and gas project to maximize structural commonality. Recent technical research has also proposed a compact, integrally forged underwater valve group with a "diamond-shaped" flow channel structure. A comparative study of different valve combination forms found that the double-valve combination has more flexibility, simple design, and lower manufacturing cost. It also has less impact on the operation of underwater remotely controlled robots.
Although the development status of compact integrally forged underwater valves has been discussed in the literature, the discussion on logistics flow channel design, processing technology reliability, and offshore installation operations remains relatively limited. This article examines traditional cluster manifolds and compact integrally forged underwater valve groups, comparatively analyzing their advantages and key technologies. Additionally, using a domestic oil field development project as an example, this article conducts an in-depth discussion on compact integrally forged underwater valves, including practical applications of these valve groups. These studies provide important references and ideas for the design of modular manifolds during the engineering stage.
A CNOOC oil field is located in the Pearl River Mouth Basin of the South China Sea, with an average water depth of approximately 400 meters. As shown in Figure 3, this area contains eight production wells, and the logistics of each well are connected to the underwater manifold through the inflow and outflow pipelines of the jumper pipe.
Figure 3 The structure of the compact integral forged underwater valve assembly manifold
Two compact, integrally forged underwater valve sets are installed at the center of the underwater manifold. Each valve set gathers the logistics of four production wells. Similar to the description in Section 1, the flow from each well enters between the two valves. The production pipeline outlets are located at both ends of the valve set. The flow enters directly into the dual production main pipes of the manifold; the test pipeline outlet is located at the center of the valve set. The test pipelines from both valve sets merge into a test main pipe, allowing single-well measurement through an underwater multiphase flowmeter, and finally connect to the dual production main pipes of the manifold.
To more intuitively demonstrate the advantages of the compact integrally forged underwater valve group over the traditional cluster underwater manifold, Figure 4 compares the traditional cluster underwater manifold with the compact integrally forged underwater manifold designed for this project. This figure illustrates the subsea valve group manifold structure. As shown in Figure 4(a), the traditional cluster underwater manifold also adopts the approach where the flow from each production well enters between two valves and then proceeds to the production and test pipelines. However, the large number of pipelines increases the distance between adjacent valves and between the dual production main pipes of the manifold. Additionally, to avoid interference between the manifold production supervisor and the jumper incoming pipeline, the height of the jumper incoming pipeline must be raised, and it should access the manifold through an elbow. To ensure the structural stability of the manifold, the design of multiple pipeline support devices must be considered, and detailed calculations and mechanical strength analyses should be conducted. Finally, the increase in the types and number of pipelines results in a significant amount of subsequent welding work. The reliability and duration of the welding process will impact the processing quality and manufacturing cycle of the manifold.
Figure 4(b) illustrates a compact integrally forged underwater valve group manifold structure. Since the valve group adopts a modular design, the distance between the dual production main pipes of the manifold is significantly reduced. As shown in Figure 4(a), the production pipeline and test pipeline are designed inside the valve body of the compact integrally forged underwater valve group, greatly reducing the number of pipelines and pipeline-related design and welding work. The external interface of the valve group is also simpler and clearer. It should also be noted that although the compact integrally forged underwater valve group manifold encounters the issue of interference between the jumper inlet pipeline and the manifold production supervisor, it is necessary to increase the longitudinal height of the jumper inlet pipeline. However, the jumper pipeline can be directly connected to the valve body of the valve group without the need for an elbow. Therefore, using compact integrally forged underwater valve groups can significantly reduce the difficulty of manifold design and subsequent processing and manufacturing, facilitating the rapid advancement of manifold development and optimizing the overall project schedule. It is understood that, compared to traditional cluster-type underwater manifolds, the compact integrally forged underwater valve manifold reduces weight by 30%, size by 50%, and supply period by 30%. In the future development of offshore oil and gas fields, especially in deeper waters, it is expected to be more widely used in the development of lower integrated oil and gas fields.
(a) Traditional cluster manifold structure
(b) Compact integrally forged underwater valve group manifold structure
Figure 4 Comparison of traditional cluster manifold and compact integrally forged underwater valve manifold in engineering projects
This article presents a comparative analysis of traditional cluster-type underwater manifold valves and compact integrally forged underwater valve groups from the perspectives of overall design, offshore installation operations, and future application potential. Based on this analysis, the key design technologies of the compact integrally forged underwater valve group were identified and discussed, and the application advantages were further elaborated upon through actual engineering projects.
Compared to traditional cluster-type subsea manifolds, the compact integrally forged subsea valve manifold structure incorporates production and test pipelines within the valve manifold body. It is small and light, which significantly reduces the design effort required for the manifold. The reduced difficulty in structural strength analysis at this stage improves the reliability of the welding process during the processing and manufacturing stage. Additionally, the optimization of ship resources and underwater ROV operation paths during offshore installation helps shorten the project development cycle and reduce costs.
Given that the compact integrally forged subsea valve group is designed for multiple wellheads, particularly for the integrated oil and gas field logistics collection function, the flow channel design of the production and test pipelines within the valve body is crucial. Valves should be installed before the wellhead logistics enter the production and test supervisors. The production and test pipelines should be designed to avoid interference with each other. Based on the principle of maintaining the independence of each valve actuator, and considering the processing technology and testing difficulties of the multi-valve group, the optimal matching solution should be determined for the number of wellheads and the flow channel design of each valve group.
The manufacturing and delivery process of the compact integrally forged underwater valve group, following the design stage, involves elements such as raw material heat treatment, valve body surfacing, flow channel machining and grinding, and assembly testing. Given that the single underwater valve has successfully achieved localized demonstration applications, we should continue optimizing future underwater production systems toward compactness and modularization, and advance the processing of compact integrally forged underwater valve groups. Iterative updates to manufacturing and testing techniques and equipment will promote the further maturity of underwater base-plate development plans, creating favorable conditions for the economic development of integrated underwater oil and gas fields.
As core components of the subsea manifold, the layout of valves and logistics pipelines is crucial to its structure. To meet compact design requirements, optimizing the connection form of valves and logistics pipelines is necessary, such as adopting the concept of a "compact integral forged underwater valve group." This design concept was proposed as early as 1937 and has been further applied and developed in recent years. For example, a "Y-shaped branch module" design was adopted in an offshore oil and gas project to maximize structural commonality. Recent technical research has also proposed a compact, integrally forged underwater valve group with a "diamond-shaped" flow channel structure. A comparative study of different valve combination forms found that the double-valve combination has more flexibility, simple design, and lower manufacturing cost. It also has less impact on the operation of underwater remotely controlled robots.
Although the development status of compact integrally forged underwater valves has been discussed in the literature, the discussion on logistics flow channel design, processing technology reliability, and offshore installation operations remains relatively limited. This article examines traditional cluster manifolds and compact integrally forged underwater valve groups, comparatively analyzing their advantages and key technologies. Additionally, using a domestic oil field development project as an example, this article conducts an in-depth discussion on compact integrally forged underwater valves, including practical applications of these valve groups. These studies provide important references and ideas for the design of modular manifolds during the engineering stage.
A CNOOC oil field is located in the Pearl River Mouth Basin of the South China Sea, with an average water depth of approximately 400 meters. As shown in Figure 3, this area contains eight production wells, and the logistics of each well are connected to the underwater manifold through the inflow and outflow pipelines of the jumper pipe.
Figure 3 The structure of the compact integral forged underwater valve assembly manifold
Two compact, integrally forged underwater valve sets are installed at the center of the underwater manifold. Each valve set gathers the logistics of four production wells. Similar to the description in Section 1, the flow from each well enters between the two valves. The production pipeline outlets are located at both ends of the valve set. The flow enters directly into the dual production main pipes of the manifold; the test pipeline outlet is located at the center of the valve set. The test pipelines from both valve sets merge into a test main pipe, allowing single-well measurement through an underwater multiphase flowmeter, and finally connect to the dual production main pipes of the manifold.
To more intuitively demonstrate the advantages of the compact integrally forged underwater valve group over the traditional cluster underwater manifold, Figure 4 compares the traditional cluster underwater manifold with the compact integrally forged underwater manifold designed for this project. This figure illustrates the subsea valve group manifold structure. As shown in Figure 4(a), the traditional cluster underwater manifold also adopts the approach where the flow from each production well enters between two valves and then proceeds to the production and test pipelines. However, the large number of pipelines increases the distance between adjacent valves and between the dual production main pipes of the manifold. Additionally, to avoid interference between the manifold production supervisor and the jumper incoming pipeline, the height of the jumper incoming pipeline must be raised, and it should access the manifold through an elbow. To ensure the structural stability of the manifold, the design of multiple pipeline support devices must be considered, and detailed calculations and mechanical strength analyses should be conducted. Finally, the increase in the types and number of pipelines results in a significant amount of subsequent welding work. The reliability and duration of the welding process will impact the processing quality and manufacturing cycle of the manifold.
Figure 4(b) illustrates a compact integrally forged underwater valve group manifold structure. Since the valve group adopts a modular design, the distance between the dual production main pipes of the manifold is significantly reduced. As shown in Figure 4(a), the production pipeline and test pipeline are designed inside the valve body of the compact integrally forged underwater valve group, greatly reducing the number of pipelines and pipeline-related design and welding work. The external interface of the valve group is also simpler and clearer. It should also be noted that although the compact integrally forged underwater valve group manifold encounters the issue of interference between the jumper inlet pipeline and the manifold production supervisor, it is necessary to increase the longitudinal height of the jumper inlet pipeline. However, the jumper pipeline can be directly connected to the valve body of the valve group without the need for an elbow. Therefore, using compact integrally forged underwater valve groups can significantly reduce the difficulty of manifold design and subsequent processing and manufacturing, facilitating the rapid advancement of manifold development and optimizing the overall project schedule. It is understood that, compared to traditional cluster-type underwater manifolds, the compact integrally forged underwater valve manifold reduces weight by 30%, size by 50%, and supply period by 30%. In the future development of offshore oil and gas fields, especially in deeper waters, it is expected to be more widely used in the development of lower integrated oil and gas fields.
(a) Traditional cluster manifold structure
(b) Compact integrally forged underwater valve group manifold structure
Figure 4 Comparison of traditional cluster manifold and compact integrally forged underwater valve manifold in engineering projects
This article presents a comparative analysis of traditional cluster-type underwater manifold valves and compact integrally forged underwater valve groups from the perspectives of overall design, offshore installation operations, and future application potential. Based on this analysis, the key design technologies of the compact integrally forged underwater valve group were identified and discussed, and the application advantages were further elaborated upon through actual engineering projects.
Compared to traditional cluster-type subsea manifolds, the compact integrally forged subsea valve manifold structure incorporates production and test pipelines within the valve manifold body. It is small and light, which significantly reduces the design effort required for the manifold. The reduced difficulty in structural strength analysis at this stage improves the reliability of the welding process during the processing and manufacturing stage. Additionally, the optimization of ship resources and underwater ROV operation paths during offshore installation helps shorten the project development cycle and reduce costs.
Given that the compact integrally forged subsea valve group is designed for multiple wellheads, particularly for the integrated oil and gas field logistics collection function, the flow channel design of the production and test pipelines within the valve body is crucial. Valves should be installed before the wellhead logistics enter the production and test supervisors. The production and test pipelines should be designed to avoid interference with each other. Based on the principle of maintaining the independence of each valve actuator, and considering the processing technology and testing difficulties of the multi-valve group, the optimal matching solution should be determined for the number of wellheads and the flow channel design of each valve group.
The manufacturing and delivery process of the compact integrally forged underwater valve group, following the design stage, involves elements such as raw material heat treatment, valve body surfacing, flow channel machining and grinding, and assembly testing. Given that the single underwater valve has successfully achieved localized demonstration applications, we should continue optimizing future underwater production systems toward compactness and modularization, and advance the processing of compact integrally forged underwater valve groups. Iterative updates to manufacturing and testing techniques and equipment will promote the further maturity of underwater base-plate development plans, creating favorable conditions for the economic development of integrated underwater oil and gas fields.
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