Subsea Pipeline Locking Member Onshore Welding
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Solution Overview
Problem
The existing methods for laying subsea pipelines, particularly the reel-laying method, face delays and safety concerns due to the need for offshore welding of abandonment heads, which can be flawed and difficult to test under critical conditions.
Innovation Solution
Incorporating an in-line first locking member within the pipeline that can be coupled with a complementary second locking member, allowing for secure attachment and lowering without the need for offshore welding, enabling the pipeline to be prepared and tested onshore before laying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If offshore welding of abandonment heads is performed during the laying process, then the pipeline can be attached to the A&R wire for lowering into the water, but the process experiences delays and the welding quality cannot be adequately tested under critical conditions
Solution Approach 1:
The abandonment head is welded to the pipeline onshore before the pipeline is reeled onto the reel and deployed offshore. This preliminary welding action allows the attachment to be performed in a controlled environment where testing can be conducted, eliminating the need for time-consuming offshore welding during the critical laying process while ensuring adequate welding quality through pre-deployment testing
2Strength
If the pipeline is clamped and cut above the clamp during the laying process, then the abandonment head can be welded offshore, but the welding must be sufficiently strong to take all the weight of the pipeline extending from the vessel to the sea floor
Solution Approach 1:
The abandonment head is welded to the pipeline onshore before deployment, allowing the welding operation to be performed in a controlled environment where proper welding procedures, equipment, and testing facilities are available. This eliminates the difficulties of offshore welding while ensuring the attachment has sufficient strength to support the pipeline weight, as the welding can be properly executed and tested before the pipeline is deployed into service
3Reliability
If conventional abandonment methods are used with offshore welding, then the pipeline can be abandoned, but detailed testing of the abandonment head attachment is difficult to achieve in the timing and situation of an ongoing pipe-laying operation
Solution Approach 1:
The abandonment head attachment is completed and tested onshore before the pipeline is deployed offshore. This timing allows for comprehensive testing of the attachment under controlled conditions, including load testing and inspection, to verify its reliability. The testing is performed as part of the pre-deployment preparation rather than during the critical pipe-laying operation, eliminating the constraints of timing and situation that make testing difficult in conventional offshore methods
Data Source
AI summary
A method of laying a subsea pipeline from a reel, the pipeline having an in-line first locking member, the method having at least the steps of: (a) laying the pipeline under the water from the reel; (b) cutting the pipeline above the first locking member; (c) coupling the first locking member with a complementary second locking member; and (d) lowering the first and second locking members under the water. In this way, the pipeline already has located within it a suitable locking member for the abandoning operation, avoiding the need for a separate off-shore welding operation.