Subsea Wellhead Barrier Relocation for Tree Retrieval
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Solution Overview
Problem
The process of setting additional barriers in the wellhead system before retrieving a subsea tree is time-consuming and expensive, as it requires installing temporary barriers and replacing full-bore isolation valves, which complicates the wellhead installation and servicing operations.
Innovation Solution
The solution involves locating all primary well barriers within the tubing hanger and production tubing string, eliminating the need for these barriers in the subsea tree, thereby simplifying the construction, installation, and servicing of the wellhead system by transforming the subsea tree into a flowline connection body with reduced size, weight, and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temporary barriers and full-bore isolation valves are installed in the wellhead system before retrieving the subsea tree, then well control and safety are improved, but installation time and operational complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-installing barriers within the tubing hanger and production tubing string during the initial wellhead assembly, before the subsea tree is installed. This allows the barriers to be in place beforehand, eliminating the need for time-consuming installation of temporary barriers and full-bore isolation valves when the subsea tree needs to be retrieved. The barriers are positioned and configured in advance to provide well control without requiring additional intervention later.
Solution Approach 2:
The patent extracts the barrier function from the subsea tree and relocates it to the tubing hanger and production tubing string. By taking out the barrier requirement from the subsea tree assembly, the patent eliminates the need to install additional barriers when retrieving the subsea tree. The barriers are integrated into the production tubing string, which remains in place during subsea tree retrieval operations.
2Reliability
If multiple barriers are installed in the wellhead system, then safety and well control are improved, but device complexity and installation cost increase
Solution Approach 1:
The patent merges the barrier function with the production tubing string and tubing hanger assembly. Instead of having separate barriers and separate subsea tree components, the barriers are integrated into the production tubing string, combining multiple functions into a single unified system. This reduces device complexity by eliminating redundant components and simplifying the overall wellhead system architecture.
Solution Approach 2:
The patent applies multi-functionality by designing the production tubing string to serve multiple purposes: it acts as both the production conduit and the barrier system. The tubing hanger and production tubing string are configured to provide well control functionality in addition to their primary production function, eliminating the need for separate dedicated barrier devices and reducing overall system complexity.
3Reliability
If barriers are located in the subsea tree, then well control is provided, but the subsea tree size, weight, and cost increase
Solution Approach 1:
The patent extracts the barrier function from the subsea tree and relocates it to the production tubing string and tubing hanger. By removing the barrier requirement from the subsea tree, the subsea tree can be designed as a lighter, simpler flowline connection body without the weight and cost burden of incorporating multiple barrier components.
Solution Approach 2:
The patent segments the well control function from the subsea tree and assigns it to the production tubing string system. This segmentation allows the subsea tree to be optimized for its primary function as a flowline connection, reducing its size and weight, while the barrier function is provided by the separately optimized production tubing string and tubing hanger assembly.
Data Source
AI summary
A subsea wellhead assembly having an arrangement of primary well barriers provided in equipment that is located within the well and/or the wellhead housing is provided. The subsea wellhead assembly may include a tubing hanger positioned in or below a wellhead housing coupled to a subsea well, a tree cap fluidly coupled to the tubing hanger and disposed atop the wellhead housing, and a pair of master production valves configured to be selectively actuated from an open position to a closed position to shut in the subsea well, each of the pair of master production valves located within or below the wellhead housing.