Passive Accumulator Annulus Pressure Control
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Solution Overview
Problem
Well annulus pressure management is challenging due to thermal expansion and contraction, leading to potential casing collapse or rupture, as existing manual bleeding methods fail to maintain pressure within an acceptable range during thermal cycling.
Innovation Solution
A pressure maintenance system utilizing a passive accumulator with a gas pressure system and a pressure controller to maintain a set pressure range, incorporating a nitrogen plant and storage tanks, and a method involving fluid addition and replacement to stabilize pressure levels during temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If manual bleeding methods are used to release excess pressure, then pressure can be reduced temporarily, but pressure cannot be maintained within an acceptable range during thermal cycling
Solution Approach 1:
A passive accumulator is introduced as an intermediary device between the annulus and the surface equipment. The accumulator contains a compressible gas charge that acts as a mediator to absorb pressure fluctuations automatically, maintaining pressure within an acceptable range without requiring manual intervention or complex active control systems.
Solution Approach 2:
The passive accumulator operates autonomously using the compressibility of its gas charge to automatically absorb expansion forces and maintain pressure. The system self-regulates pressure fluctuations during thermal cycling without requiring external power, control systems, or manual operation, thereby improving reliability through self-service operation.
2Reliability
If a passive accumulator with gas pressure system is used to maintain pressure, then pressure stability is improved, but device complexity increases
Solution Approach 1:
The active control elements (pumps, valves, sensors, and control systems) are extracted from the pressure maintenance system. Only the passive accumulator with its pre-charged compressible gas is retained, which automatically maintains pressure through its inherent physical properties. This extraction of active components significantly reduces system complexity while maintaining pressure stability.
Solution Approach 2:
The system utilizes changes in the physical state of the gas charge (compression and expansion) in response to temperature variations. As temperature increases, the gas expands to absorb excess pressure; as temperature decreases, the gas contracts to maintain pressure. This parameter-based approach simplifies the system by relying on fundamental thermodynamic principles rather than complex mechanical or electronic controls.
3Stability of the object's composition
If fluids are allowed to expand and contract freely in the annulus, then thermal cycling is accommodated, but pressure control is lost leading to casing collapse or rupture
Solution Approach 1:
The compressible gas charge in the passive accumulator acts as a counterbalancing force against the thermal expansion and contraction of the annulus fluid. When the fluid expands due to heating, the gas compresses to absorb the excess volume and maintain pressure. When the fluid contracts due to cooling, the gas expands to replace the withdrawn volume and maintain pressure. This counterbalancing mechanism simultaneously accommodates volume changes and maintains pressure control.
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 pressure within a preset range throughout thermal cycles, reducing the risk of casing collapse and ensuring stable operation by automatically adjusting fluid volumes and gas addition/venting to compensate for thermal expansion and contraction.
Implementation Method 1
Over time, fluids in outer annuli are heated by the production fluids and expand
Implementation Method 2
after a well is shut in, or temporarily closed off from production, the casing at higher levels in the well drops in temperature. This lowers the pressure in the casing
Implementation Method 3
A gas pressure system is included to maintain a gas in a headspace over the fluid in the passive accumulator
Data Source
AI summary
A system and methods for maintaining pressure on an annulus in a well are provided. An example of a pressure maintenance system for an annulus on a well, included a passive accumulator coupled to the annulus to accept fluid expanding in the annulus or to supply fluid to replace fluid contracting in the annulus. A gas pressure system is included to maintain a gas in a headspace over the fluid in the passive accumulator, and a pressure controller maintains pressure in the headspace within a set range.