Back Pressure Valve for Dense Phase CO2 Injection
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Solution Overview
Problem
Carbon capture and storage systems face challenges in maintaining fluid pressure during CO2 injection, which can lead to undesirable phase transitions causing temperature drops and equipment failures due to the lack of effective pressure regulation in well completions.
Innovation Solution
A back pressure valve system with a housing, piston, power spring, and reference pressure port is used to maintain fluid pressure above the liquid to gas transition level, allowing for controlled injection and preventing phase transitions by regulating pressure and flow through a variable choke mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CO2 is injected at high pressure to maintain dense phase, then injection capacity is improved, but phase transition to gas occurs causing temperature drops and equipment failures
Solution Approach 1:
The back pressure valve incorporates a reference pressure port that provides feedback from the annulus pressure to the valve mechanism. This feedback loop allows the valve to automatically sense pressure changes and adjust the choke opening accordingly, maintaining stable back pressure that prevents CO2 phase transition while enabling high injection rates without causing equipment failures from temperature drops
Solution Approach 2:
The valve is configured to be self-regulating through the differential pressure mechanism between injection side and reference side. The valve automatically adjusts its own opening based on the pressure differential, eliminating the need for external control systems or manual intervention to maintain proper back pressure and prevent phase transitions
2Temperature
If back pressure is increased to prevent phase transition, then temperature stability is improved, but injection pressure requirement increases
Solution Approach 1:
The variable choke mechanism dynamically adjusts the flow area parameter to optimize the balance between back pressure and injection pressure requirements. By changing the choke opening size, the system can maintain temperature stability through adequate back pressure while minimizing the injection pressure requirement to the extent possible
3Device complexity
If a fixed choke is used to regulate flow, then device complexity is reduced, but ability to adapt to varying injection rates is worsened
Solution Approach 1:
The valve employs a dynamic choke mechanism where the stem can move axially to vary the flow area. This dynamic adjustment capability, driven by the differential pressure between injection and reference sides, allows the valve to automatically adapt to varying injection rates while maintaining proper back pressure, achieving versatility without requiring complex external control systems
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 maintains CO2 in a dense phase, preventing detrimental cooling and equipment failures by regulating pressure and flow, facilitating high-capacity CO2 injection while avoiding phase transitions and ensuring stable well operations.
Implementation Method 1
a power spring disposed in the housing and operably coupled to the piston... The power spring is configured to bias the piston against the internal sealing surface
Implementation Method 2
The reference pressure port extends from an opening in an external wall of the housing to a chamber on an uphole end of the piston such that a reference pressure acts on the uphole end of the piston
Implementation Method 3
maintain fluid pressure above the liquid to gas transition level, allowing for controlled injection and preventing phase transitions by regulating pressure and flow
Implementation Method 4
In the open position, the stem and internal seat function as a variable choke. As an operating injection pressure increases, the stem moves farther away from the internal seat, increasing a flow area through the central bore
Data Source
AI summary
Systems and methods for injection fluid into a well or aquifer while regulating pressure. The systems and methods include a back pressure valve biased to a closed position. The back pressure opens when an injection pressure of the fluid exceeds a reference pressure. The back pressure valve controls pressure of the injection fluid above the back pressure valve to maintain the injection fluid in a dense state.