Subsea Choke Assembly with Tangential Orifices for Phase Separation
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Solution Overview
Problem
Conventional choke assemblies for controlling fluid flow in subterranean wells suffer from high shear rates, leading to fluid phase mixing and emulsification, and are vulnerable to damage from entrained solids, which hinders fluid separation and requires frequent replacement, especially in subsea installations.
Innovation Solution
A choke assembly with a separation chamber that separates fluid phases before the choke element, using a rotational flow pattern to minimize shear and a plug and cage design with tangentially oriented openings to reduce damage from solids, allowing controlled flow and separation of oil, water, and gas while preventing solids from reaching the choke element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional choke assemblies use perpendicular orifices in the cage, then fluid flow control is achieved, but high shear rates cause fluid phase mixing and emulsification
Solution Approach 1:
The invention changes the orientation of orifices from perpendicular (symmetric) to tangential (asymmetric) relative to the cage axis. This asymmetric orientation allows fluid to enter the cage in a tangential direction, creating a rotational flow pattern that reduces shear rates between fluid phases and prevents emulsification, while still maintaining effective flow control capability.
Solution Approach 2:
The invention modifies the flow parameters by changing the orifice orientation angle from 90 degrees (perpendicular) to approximately 0 degrees (tangential). This parameter change transforms the flow regime from high-shear direct impingement to low-shear rotational flow, enabling phase separation to be maintained while fluid control function is preserved.
2Productivity
If conventional choke assemblies use perpendicular orifices, then flow control is effective, but significant mixing and emulsification of oil and water phases occurs
Solution Approach 1:
By orienting orifices tangentially rather than perpendicularly to the cage axis, the invention creates an asymmetric flow entry configuration. This causes fluid to enter along the tangential direction and follow a rotational path through the cage, significantly reducing turbulent mixing and emulsification of oil and water phases while maintaining flow control effectiveness.
Solution Approach 2:
The invention converts the potentially harmful high-shear direct flow into a beneficial low-shear rotational flow pattern. The tangential orifice orientation transforms what would be destructive mixing forces into gentle rotational movement that maintains phase separation, effectively converting a harmful effect into a beneficial one.
3Productivity
If conventional choke assemblies use an external cage design, then better fluid flowrate control is provided, but the cage is vulnerable to damage from entrained solids
Solution Approach 1:
The invention inverts the conventional approach by placing the separation chamber upstream of the choke element rather than downstream. This reversal allows solids to be separated from the fluid stream before entering the cage, protecting the cage from solid damage while maintaining the external cage design's flow control advantages.
Solution Approach 2:
The invention performs preliminary separation of solids from the fluid stream before the fluid reaches the choke element. By positioning the separation chamber upstream and using centrifugal forces to remove solids first, the cage is protected from solid particle damage before it can occur, while the flow control function remains intact.
4Adaptability or versatility
If conventional choke assemblies operate at subsea installations, then subsea production is enabled, but frequent replacement is required due to solid damage
Solution Approach 1:
The invention performs preliminary solid removal in a separation chamber positioned upstream of the choke element. This preliminary action prevents solids from reaching and damaging the cage and plug components, significantly extending the assembly's service life in harsh subsea environments where replacement is difficult and expensive.
Solution Approach 2:
By inverting the conventional arrangement and placing separation upstream rather than downstream, the invention protects vulnerable components from solid damage in subsea installations, enabling longer operational periods between replacements and improving overall reliability in remote offshore locations.
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 solution effectively reduces fluid shear, enhances phase separation, and minimizes damage to the choke assembly, enabling efficient control of fluid flow and separation, reducing the need for frequent replacements and facilitating subsea operations.
Implementation Method 1
A choke assembly with a separation chamber that separates fluid phases before the choke element, using a rotational flow pattern to minimize shear
Implementation Method 2
a plug and cage design with tangentially oriented openings to reduce damage from solids
Data Source
AI summary
A choke assembly comprises an inlet (48) for a multiphase fluid stream, the stream comprising a first relatively heavy fluid phase and a second relatively light fluid phase; a first fluid outlet (116); a choke element (22) disposed between the inlet and the first fluid outlet operable to control the flow of fluid between the inlet and the first fluid outlet; a separation chamber (40, 114) disposed to provide separation of phases in the fluid stream upstream of the choke element; and a second outlet (118) for removing fluid from the separation cavity. The choke assembly is of particular use in the control of fluid streams produced from a subterranean well, in particular oil and gas produced from a subsea well.