Subsea Equipment Retrieval Using Pressure-Compensating Accumulators
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Solution Overview
Problem
The retrieval and replacement of subsea oil and gas equipment pose challenges due to high pressure, hydraulic locking of flanged connections, and the formation of hydrates and damaging constituents, leading to potential equipment fouling and material damage, which complicates maintenance and repair.
Innovation Solution
A system incorporating an accumulator device that acts as a pulsation dampener, pressure compensator, and pressure relief device, positioned in fluid communication with subsea equipment, to manage pressure changes, prevent hydraulic locking, and vent expanding gases, while also storing and injecting equipment protection fluids to mitigate hydrate formation and material damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If subsea equipment is operated at high pressure in deep water, then production efficiency is improved, but equipment retrieval becomes difficult due to hydraulic locking of flanged connections
Solution Approach 1:
The system divides the equipment retrieval process into distinct phases: normal operation phase, shutdown phase, and retrieval phase. During retrieval, the system segments the pressure management by isolating the equipment from the high-pressure production environment using isolation valves, allowing the equipment to be depressurized and retrieved without affecting ongoing production operations.
Solution Approach 2:
The patent introduces intermediary components including isolation valves, accumulators, and venting systems that mediate between the high-pressure production system and the equipment to be retrieved. These intermediaries allow pressure equalization and hydraulic lock prevention without requiring complete system shutdown or exposure to high pressures during retrieval.
2Ease of repair
If equipment is isolated for retrieval, then maintenance can be performed, but hydrates and precipitates form causing equipment fouling
Solution Approach 1:
The system performs preliminary actions before equipment isolation by injecting hydrate inhibitors and flow assurance chemicals into the equipment while it is still under pressure and flowing. This preliminary chemical treatment prevents hydrate and precipitate formation during the subsequent isolation and retrieval period, eliminating the need for equipment cleaning after retrieval.
Solution Approach 2:
The patent maintains continuous protection against hydrate formation by keeping chemical injection systems active throughout the isolation period. Accumulators store additional chemical supplies that are automatically injected if pressure or temperature conditions indicate hydrate formation risk, ensuring continuous protection even when the equipment is shut in for retrieval.
3Ease of operation
If flow is stopped for equipment shutdown, then retrieval can be initiated, but damaging constituents accumulate causing material damage
Solution Approach 1:
The system employs self-service mechanisms where automatic monitoring sensors detect the accumulation of damaging constituents such as CO2 and H2S during equipment shutdown. When thresholds are exceeded, the system automatically triggers chemical injection from accumulators to neutralize these constituents, without requiring external intervention or equipment retrieval to address the problem.
Solution Approach 2:
The patent uses pneumatic and hydraulic systems to circulate protective chemicals through the equipment during shutdown periods. Compressed gas or pressurized fluid systems deliver chemical treatments that react with and neutralize damaging constituents like CO2 and H2S, preventing material damage while the equipment remains isolated for retrieval.
4Ease of operation
If vented couplers are used to facilitate disassembly, then flanged connections can be separated, but seawater leaks into equipment and hydrocarbons leak to environment
Solution Approach 1:
The patent introduces sealed coupler designs that incorporate intermediary sealing elements and controlled venting pathways. These intermediaries allow pressure equalization during disassembly to prevent hydraulic locking, while maintaining seals that prevent seawater ingress and hydrocarbon egress throughout the disassembly process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates safe handling and transportation of subsea equipment by reducing pressure, preventing hydraulic locking and hydrate formation, and protecting equipment from damaging constituents, thereby simplifying retrieval and maintenance processes.
Implementation Method 1
an accumulator device that is in fluid communication with the subsea equipment, wherein a pressure boundary of the accumulator device is adapted to move in response to a pressure change on the subsea equipment as the subsea equipment is raised from the subsea environment
Implementation Method 2
A system incorporating an accumulator device that acts as a pulsation dampener, pressure compensator, and pressure relief device
Implementation Method 3
the presence of seawater completely surrounding the flanged joint may hydraulically 'lock' the flanges together
Implementation Method 4
when flow through the subsea equipment is stopped, hydrates and/or other undesirable hydrocarbon precipitates can sometimes form inside of the equipment
Data Source
Figure 1A
Figure 1B~1D
Figure 1E~1G
AI summary
Generally, the present disclosure is directed to systems that may be used to facilitate the retrieval and/or replacement of production and/or processing equipment that may be used for subsea oil and gas operations. In one illustrative embodiment, a system is disclosed that includes, among other things, subsea equipment (100) that is adapted to contain a first fluid while operating in a subsea environment (160), and an accumulator device (120a, 120b, 120c, 120d, 120e) that is in fluid communication with the subsea equipment (100), wherein a pressure boundary of the accumulator device (120a, 120b, 120c, 120d, 120e) is adapted to move in response to a pressure change on the subsea equipment (100) as the subsea equipment (100) is raised from the subsea environment (160).