Wellbore Choke Device for Accurate Cement Placement
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Solution Overview
Problem
Inadequate bottom hole pressure often prevents a standing column of high specific gravity liquid from reaching the top of a wellbore during plugging operations, leading to inaccurate cement placement and potential over- or under-displacement of perforations, which can result in incomplete plugging or blockage of unwanted areas.
Innovation Solution
A choke device is installed in the wellbore to control the volume and pressure of the settable medium, allowing precise injection of cement into the desired perforations by calculating the volume of the wellbore tubulars and perforations, and using a pump out valve to maintain positive pressure until the settable medium reaches the desired location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standing column of high specific gravity liquid is used to reach the top of the wellbore, then accurate cement placement can be achieved, but insufficient bottom hole pressure prevents the liquid column from reaching the top
Solution Approach 1:
A choke device is installed in the wellbore to act as an intermediary mechanism. The choke creates artificial backpressure that compensates for insufficient bottom hole pressure, enabling the high specific gravity liquid column to reach and maintain position at the top of the wellbore for accurate cement placement.
Solution Approach 2:
The choke device changes the pressure parameter profile in the wellbore by creating a pressure differential. By restricting flow through the choke, the system transforms the insufficient bottom hole pressure into adequate column support pressure, allowing the liquid to reach the desired elevation.
2Measurement precision
If positive pressure is maintained at the surface to support the liquid column, then accurate monitoring of cement location is possible, but liquid free falls down the wellbore when bottom hole pressure is insufficient
Solution Approach 1:
The choke device serves as a mediator between surface pressure and bottom hole pressure. It allows positive pressure to be maintained at the surface for monitoring purposes while preventing the liquid from free falling by creating the necessary pressure differential to support the column.
3Reliability
If cement volume is increased to ensure complete plugging, then perforations are more likely to be sealed, but over-displacement occurs blocking unintended areas
Solution Approach 1:
The choke device enables feedback control of cement placement. By monitoring pressure changes as cement passes through the choke, the operator can determine when the desired volume has been injected, preventing over-displacement and blockage of unintended areas while ensuring complete plugging of target perforations.
Solution Approach 2:
The choke allows precise control of the volume parameter by creating a measurable pressure differential. This enables injection of the exact required cement volume to seal perforations without exceeding the amount that would block unintended areas.
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
Ensures accurate placement of the settable medium, preventing over- or under-displacement, and maintaining positive pressure to effectively plug the wellbore without blocking unintended areas, even when bottom hole pressure is insufficient to support a standing column of liquid.
Implementation Method 1
a pump out valve which blocks the through bore until a predetermined pressure level is applied to the valve
Implementation Method 2
injecting a settable medium into the wellbore... which may then form a permanent barrier to flow across the perforations and out of the well
Data Source
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AI summary
A process for plugging a wellbore, e.g. an oil or gas well, comprises installing a choke device into the wellbore in order to increase the back pressure to allow better control when introducing cement to plug the wellbore. The device has a cylindrical shape with a central through bore. On the external profile is a shoulder which, when the device is installed in a wellbore, comes to rest against a nipple in the wellbore. The device may free fall for all or part of the way down but would normally be pumped down at least for the last part of its delivery. In the bore is a pump out ball which blocks the through bore until the device reaches the nipple and stops, at which point pressure increases and the ball is ejected. Cement and other liquid may then be pumped through the choke device to the distal region of the well.