Vertical Tree (subsea)

The Vertical Tree: A Modern Design for Subsea Production

Introduction:

In the demanding environment of subsea oil and gas production, efficiency and reliability are paramount. The subsea tree, a critical piece of equipment, plays a crucial role in controlling the flow of hydrocarbons from the wellhead to the surface. Among the various subsea tree designs, the vertical tree has emerged as a popular choice, particularly for deepwater applications.

Vertical Tree: Key Features and Advantages

The defining feature of a vertical tree is its master valve location above the tubing hanger. This seemingly simple design choice offers several significant advantages:

Enhanced Flow Efficiency: The vertical configuration allows for a more direct flow path from the wellbore to the production manifold, minimizing pressure drop and increasing flow efficiency.
Simplified Installation: With the master valve situated above the tubing hanger, the installation process is less complex and time-consuming. This can be particularly beneficial in deepwater environments where installation challenges are amplified.
Accessibility and Maintenance: The top-mounted master valve provides easier access for inspection, maintenance, and intervention, reducing downtime and improving operational efficiency.
Optimized Flow Control: The vertical design offers greater control over flow rates and allows for easier integration with flow control devices.

Hold: The Importance of a Master Valve above the Tubing Hanger

The positioning of the master valve above the tubing hanger is crucial for maintaining hold – the ability to isolate the wellbore from the production system in case of an emergency. In a vertical tree design, the master valve effectively seals the wellbore, preventing uncontrolled flow even in the event of a tubing hanger failure. This ensures safety and prevents potential environmental damage.

Applications of Vertical Trees:

Vertical trees are well-suited for a wide range of subsea applications, including:

Deepwater Production: The inherent advantages of a vertical tree, especially its improved flow efficiency and ease of installation, make it an ideal choice for deepwater production.
High-Pressure/High-Temperature Wells: The robust design and efficient flow control of vertical trees make them suitable for handling challenging well conditions.
Subsea Tie-Backs: The streamlined design and accessibility of vertical trees facilitate seamless integration with subsea tie-back systems.

Conclusion:

The vertical tree design with its master valve above the tubing hanger represents a modern approach to subsea production. It offers enhanced efficiency, simplified installation, improved accessibility, and greater flow control, all while ensuring critical hold capabilities. As the subsea industry continues to push boundaries, the vertical tree will likely play an even greater role in enabling safe and efficient oil and gas production in the world's deepwater resources.

Test Your Knowledge

Quiz: The Vertical Tree

Instructions: Choose the best answer for each question.

1. What is the defining characteristic of a vertical subsea tree?

a) It has a horizontal flow path. b) It is designed for shallow water applications. c) The master valve is located above the tubing hanger. d) It lacks a tubing hanger.

Answer

c) The master valve is located above the tubing hanger.

2. What is the main benefit of the vertical tree design in terms of flow?

a) Reduced flow rate. b) Increased flow efficiency. c) Increased pressure drop. d) No change in flow efficiency.

Answer

b) Increased flow efficiency.

3. Why is the vertical tree design advantageous for deepwater applications?

a) Simplified installation and less time-consuming. b) Increased risk of tubing hanger failure. c) Difficult access for maintenance. d) Reduced flow control.

Answer

a) Simplified installation and less time-consuming.

4. What is the main benefit of the master valve being above the tubing hanger?

a) It allows for easier access to the production manifold. b) It reduces the need for flow control devices. c) It ensures "hold" capability in case of an emergency. d) It increases the risk of environmental damage.

Answer

c) It ensures "hold" capability in case of an emergency.

5. Which of the following is NOT an application of vertical subsea trees?

a) Deepwater production. b) High-pressure/high-temperature wells. c) Onshore oil and gas production. d) Subsea tie-backs.

Answer

c) Onshore oil and gas production.

Exercise:

Scenario: You are an engineer working on a deepwater oil and gas production project. Your team is considering using a vertical subsea tree for the project.

Task:

List three key advantages of using a vertical subsea tree for this specific scenario (deepwater).
Explain how the vertical tree's "hold" capability is crucial for safety and environmental protection in deepwater operations.

Exercise Correction

1. Advantages of a vertical tree in deepwater:

Simplified installation: The vertical design simplifies installation, which is especially beneficial in deepwater due to the challenging environment and increased costs.
Improved flow efficiency: The direct flow path reduces pressure drop, maximizing production in deepwater where flow rates are often affected by depth and pressure.
Enhanced accessibility: The top-mounted master valve allows for easier maintenance and intervention, reducing downtime and operational costs in remote deepwater locations.

2. "Hold" capability in deepwater:

The ability of the vertical tree to effectively isolate the wellbore from the production system in case of an emergency (through the master valve above the tubing hanger) is essential in deepwater. In case of a tubing hanger failure or other unforeseen event, the "hold" prevents uncontrolled flow of hydrocarbons, potentially leading to an oil spill and environmental damage. This is especially important in deepwater, where a spill would be difficult and costly to contain and could cause significant ecological harm.

Books

Subsea Engineering Handbook by M.J. Brown, et al. - Provides a comprehensive overview of subsea engineering, including various subsea tree designs and applications.
Subsea Production Systems by R.B. Andersen - A detailed resource on subsea production systems, covering components, design principles, and operational aspects.
The Subsea Well by A.B. Fjelde and B. T. Kjelland - Focuses on the technical aspects of subsea well completion, including wellhead equipment, tree designs, and control systems.

Articles

Vertical Subsea Trees: A New Approach to Subsea Production by J.P. Smith and R. K. Jones - An article discussing the advantages of vertical trees and their suitability for deepwater production.
The Importance of Hold in Subsea Tree Design by A. D. Miller - A technical article highlighting the importance of hold functionality in subsea tree design, particularly for vertical configurations.
Subsea Tree Design: A Comparison of Vertical and Horizontal Configurations by S. K. Lee - An article comparing the advantages and disadvantages of vertical and horizontal subsea trees for different applications.

Online Resources

OneSubsea (SLB): Provides information on their subsea equipment and technologies, including various tree designs.
TechnipFMC: Another leading provider of subsea equipment, with information on their subsea tree designs and capabilities.
Subsea World News: A news portal for the subsea industry, covering recent developments, projects, and technologies, including updates on vertical trees.

Search Tips

"Vertical subsea tree" + "design" OR "advantages" OR "applications" - This query will return relevant articles and resources on the design, benefits, and uses of vertical trees.
"Subsea tree" + "master valve location" OR "hold capability" - This query will help you find information on the positioning of the master valve in subsea trees and its significance for well control.
"Deepwater subsea production" + "tree designs" - This search will lead you to articles and resources focusing on subsea tree designs specifically for deepwater production.