Managed Pressure Drilling Choke with Variable-Rate Transmission
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Solution Overview
Problem
Existing drilling choke control systems face challenges in achieving precise pressure control within a limited range of motion, requiring extensive calibration and high precision components, leading to increased man-hours and frequent recalibration due to time-related deteriorations.
Innovation Solution
Implementing a non-linear transfer mechanism between the actuator and the drilling choke, allowing for a variable relationship between actuation and position, which enhances control by making motion quicker near full opening and slower near full closure, thereby expanding the effective control range and reducing precision requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a direct linear transfer mechanism is used between actuator and drilling choke, then the system structure is simple, but the control precision is insufficient and requires extensive calibration
Solution Approach 1:
The patent applies a non-linear transfer mechanism that dynamically adjusts the relationship between actuator position and choke opening based on the desired pressure control curve. This allows the system to achieve precise pressure control without requiring high-precision mechanical components, as the non-linear transformation compensates for imperfections in the actuator positioning.
2Measurement precision
If high precision components are used to achieve accurate pressure control, then the control accuracy is improved, but the calibration time and man-hours increase
Solution Approach 1:
The patent transforms the control problem from requiring high-precision mechanical components to using a non-linear parameter transformation. By changing the transfer function between actuator position and choke opening, the system achieves accurate pressure control with standard components, significantly reducing calibration time and eliminating the need for frequent recalibration.
3Adaptability or versatility
If the choke motion speed is constant throughout the range, then the actuator operation is simple, but the control range is limited and requires frequent recalibration
Solution Approach 1:
The non-linear transfer mechanism creates a variable speed relationship where the choke motion speed changes according to the desired pressure control characteristics. This allows the system to cover a broader pressure control range and reduces the frequency of recalibration, while the complexity is managed through the use of standard actuator components.
Data Source
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Figure 2A
AI summary
An apparatus can include a choke with a flow restrictor member having at least two positions, a flow coefficient Cv of the choke with the flow restrictor member in one position being less than with the flow restrictor member in the other position, and an operational device that displaces the flow restrictor member at a variable actuation rate, the actuation rate with the flow restrictor member in one position being less than with the flow restrictor in the other position. A method can include displacing a flow restrictor member, thereby decreasing a flow coefficient Cv of a choke, and decreasing a rate of change of the flow coefficient Cv in response to decreasing the flow coefficient Cv. A drilling system can include a choke with a flow restrictor member, and a continuously variable transmission which causes an actuation rate to vary based on a position of the flow restrictor member.