Surface Joint Castellation Sealing for Surface BOP Completion
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Solution Overview
Problem
The existing methods for completing subsea wells using a surface blowout preventer (BOP) are complex and inefficient, as they require pipe rams or variable-bore rams on the mudline closure device (MCD) to seal around the slip joint, increasing complexity and diminishing the advantages of using a surface BOP over a subsea BOP.
Innovation Solution
A surface joint with castellations that can be sealingly engaged by variable-bore rams of the surface BOP, allowing for a simplified design that eliminates the need for additional rams on the MCD and enables precise sealing and alignment of the landing string, even with imprecise stack-up lengths and formation depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pipe rams or variable-bore rams are provided on the mudline closure device to seal around the slip joint, then sealing capability is improved, but device complexity increases
Solution Approach 1:
The sealing function is extracted from the MCD by providing the sealing surface on the surface joint instead. The MCD no longer needs pipe rams or VBRs for sealing, as the surface joint's castellations provide the sealing interface with the surface BOP rams.
Solution Approach 2:
The surface joint acts as an intermediary component between the landing string and the surface BOP. It provides the sealing interface that allows the surface BOP rams to seal around the landing string without requiring complex sealing mechanisms on the MCD.
2Reliability
If pipe rams or variable-bore rams are provided on the mudline closure device, then sealing around slip joint is improved, but the advantage of using surface BOP over subsea BOP is diminished
Solution Approach 1:
The sealing function is extracted from the MCD and relocated to the surface joint, enabling the use of a simpler surface BOP configuration without pipe rams or VBRs on the MCD, thus preserving the advantages of surface BOP over subsea BOP.
3Reliability
If castellations are provided on the surface joint, then sealing interface reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The sealing surface is segmented into multiple castellations rather than requiring a single complex sealing mechanism. This segmentation allows for simpler manufacturing of individual castellation elements while providing multiple potential sealing locations.
Solution Approach 2:
The casting process parameters can be optimized to create the castellation geometry. By using casting techniques, the complex-looking castellation structure can be manufactured relatively simply as a single integrated component.
Data Source
AI summary
A surface joint provides a sealing interface between pipe rams or variable-bore rams of a surface blowout preventer and a landing string. The surface joint may be used in a system including the surface blowout preventer, a subsea mudline closure device having a conventional configuration without additional pipe rams or variable-bore rams used to close on a slip joint, and a high-pressure riser.