Subsea Gas Dehydration Using Modular Co-Current Contactors
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Solution Overview
Problem
Conventional subsea dehydration systems are large and heavy, making them impractical for offshore and subsea oil and gas production due to high external pressures, and chemical inhibitors add to operating costs, while physical separation alone fails to remove water vapor effectively.
Innovation Solution
A subsea system using compact co-current contacting systems in series to dehydrate natural gas streams, where a lean solvent stream is divided and sequentially contacted with the gas stream to form a dry natural gas stream, with the rich solvent returned to the surface for regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional counter-current contactors are used for dehydration, then dehydration effectiveness is improved, but equipment size and weight increase significantly
Solution Approach 1:
The patent divides the dehydration function into multiple co-current contactors (typically 3-5 units) arranged in series, where each contactor performs partial dehydration. This segmentation allows each individual unit to be compact and lightweight while collectively achieving the required dehydration effectiveness that would otherwise require a single large counter-current contactor.
Solution Approach 2:
The patent utilizes the pressure differential between the gas stream and liquid solvent to drive co-current flow through the contactors without requiring mechanical pumps or complex mechanical structures. This hydraulic approach eliminates heavy mechanical drive systems while maintaining effective contact between phases.
2Object-affected harmful factors
If chemical inhibitors are injected to prevent hydrate formation and corrosion, then protection effectiveness is improved, but operating costs increase
Solution Approach 1:
The patent converts the harmful presence of water vapor into a beneficial process target by using it as the driving force for co-current flow and mass transfer. By removing water vapor through physical absorption in co-current contactors, the system prevents hydrate formation and corrosion without requiring chemical inhibitors, thereby eliminating ongoing chemical procurement and injection costs.
Solution Approach 2:
The system uses the natural pressure differential and flow characteristics of the gas and liquid streams to achieve dehydration without external energy input or chemical additives. The process is self-sustaining, relying on inherent thermodynamic and hydrodynamic properties rather than costly external interventions.
3Device complexity
If physical separation alone is used, then equipment simplicity is improved, but water vapor removal effectiveness deteriorates
Solution Approach 1:
The patent introduces a liquid solvent as an intermediary substance that facilitates water vapor removal from the gas stream. The solvent acts as a mediator that absorbs water vapor through mass transfer in co-current contactors, achieving effective dehydration while maintaining relative system simplicity compared to complex mechanical separation equipment.
Solution Approach 2:
The patent changes the phase and concentration parameters of water in the gas stream by using liquid absorption. Water vapor in the gas phase is converted to liquid phase in the solvent, with the solvent concentration progressively increasing as it moves through the series of contactors, achieving thorough dehydration.
4Productivity
If subsea placement is implemented, then production efficiency is improved, but equipment design complexity increases due to high external pressures
Solution Approach 1:
By dividing the dehydration system into multiple small co-current contactors rather than one large pressure vessel, each individual unit can be designed to withstand subsea pressures more easily. The segmented approach allows for modular construction and deployment, reducing the overall design complexity compared to a single large counter-current contactor rated for subsea conditions.
Solution Approach 2:
The co-current flow system utilizes pressure differentials to drive fluid movement without requiring complex mechanical pumps or actuators that would need to be rated for subsea environments. This hydraulic approach simplifies the mechanical design requirements for subsea deployment.
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
The system effectively reduces hydrate formation and corrosion by removing water vapor, lowering operating costs and enabling modular, retrievable equipment design suitable for subsea applications.
Implementation Method 1
each of the co-current contacting systems is configured to contact the lean solvent stream with the wet natural gas stream to absorb at least a portion of water from the natural gas stream
Data Source
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AI summary
Systems and methods for subsea dehydrating a natural gas stream are provided herein. The system includes a lean solvent feed system, including a line from a topsides facility, wherein the line is configured to divide a lean solvent stream to feed lean solvent to each of a number of co-current contacting systems in parallel. The co-current contacting systems are placed in series along a wet natural gas stream, wherein each of the co-current contacting systems is configured to contact the lean solvent stream with the wet natural gas stream to adsorb at least a portion of the water from the wet natural gas stream to form a dry natural gas stream. A rich solvent return system includes a line to combine rich solvent from each of the plurality of co-current contacting systems and return a rich solvent stream to the topsides facility.