Subsea Control Pod Exchange Apparatus for BOP Stack Maintenance
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Solution Overview
Problem
Existing methods for deploying and retrieving subsea control pods, especially in deepwater environments exceeding 5,000 feet, are limited and often require the use of subsea remotely operated vehicles (ROVs) or involve the retrieval of the entire Lower Marine Riser Package (LMRP).
Innovation Solution
The development of systems and methods that enable the retrieval, deployment, and installation of subsea control pods on any part of the BOP stack without relying on conventional guidelines and with minimal use of subsea ROVs. This involves the use of a control pod exchange apparatus and a BOP stack connection assembly that facilitates the alignment and coupling of the exchange device to the BOP stack, allowing for the swapping of control pods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional methods are used to retrieve subsea control pods in deepwater environments, then the entire LMRP must be retrieved or ROVs must be used, but this increases device complexity and operational time
Solution Approach 1:
The system segments the LMRP assembly into separable components: the LMRP itself and the control pods. The control pods are designed as independent, removable units that can be exchanged without retrieving the entire LMRP structure. This segmentation enables selective maintenance of only the faulty control pod rather than the entire assembly.
Solution Approach 2:
A specialized control pod exchange apparatus serves as an intermediary device between the surface vessel and the subsea control pods. This apparatus includes a pod holder and positioning mechanisms that facilitate the transfer and exchange of control pods at depth, eliminating the need for direct ROV manipulation or LMRP retrieval.
2Productivity
If ROVs are used to deploy and retrieve control pods, then pod replacement is possible, but operational time and cost increase significantly
Solution Approach 1:
The system prepares replacement control pods in advance on the surface vessel, ready for immediate deployment. The exchange apparatus is pre-positioned and configured to receive and install pods quickly. This preliminary preparation eliminates the need for complex subsea assembly operations and enables rapid pod exchange.
Solution Approach 2:
The control pod exchange apparatus is designed to enable self-contained pod replacement operations at depth without requiring external ROV assistance during the actual exchange. The apparatus includes integrated positioning, holding, and release mechanisms that allow the control pod to be exchanged autonomously once the apparatus is in position.
3Ease of repair
If control pods are made removable for maintenance, then repair capability is improved, but system reliability may be compromised due to additional connection points
Solution Approach 1:
The control pod is designed as an integrated assembly that combines the control electronics, hydraulic connections, and electrical interfaces into a single removable unit. This merging of functions into a modular pod maintains reliable connections through standardized interfaces while enabling complete pod replacement if any component fails, rather than requiring separate access to individual components.
Solution Approach 2:
The system incorporates redundant control pods that can be pre-positioned and swapped in the event of a failure. This redundancy cushions against potential connection failures or pod malfunctions by providing an immediate backup, maintaining system reliability while preserving repair capability.
Data Source
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Figure 2B
AI summary
A method for replacing a first control pod of a BOP stack includes (a) lowering a control pod exchange device subsea. In addition, the method includes (b) coupling the control pod exchange device to the BOP stack. Further, the method includes (c) transferring the first control pod from the BOP stack to the control pod exchange device after (b). Still further, the method includes (d) lifting the control pod exchange device to the surface after (c).