Matched-Actuator Drilling Choke for Precise Backpressure Control
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Solution Overview
Problem
There is a need for a compact, high-pressure, large-bore choke that can be mounted directly on the outlet of a rotating control device in drilling operations, capable of withstanding pressures up to 5000 psi, and functioning independently without complex computer systems, while maintaining controllability and incorporating a novel calibration method for optimal performance.
Innovation Solution
A plug design choke with a matched actuator, featuring a calibration method that includes connecting an electronic controller, flowmeter, and pressure sensor to determine optimal proportional and integral gains for a PID controller, allowing for precise control of backpressure using gain scheduling and a calibrated choke system that can be installed in the return line of a drilling system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact choke design is used to mount directly on rotating control device outlet, then space utilization and portability are improved, but withstanding high pressure (up to 5000 psi) becomes more difficult
Solution Approach 1:
The choke system is divided into distinct functional components: a compact choke body for flow control, a separate actuator assembly for plug actuation, and a mounting interface for the rotating control device. This segmentation allows each component to be optimized independently - the choke body remains compact while the actuator provides sufficient force for high-pressure operation.
Solution Approach 2:
The choke plug is pre-positioned in a controlled manner using the actuator mechanism before high-pressure conditions occur. The actuator assembly includes pre-loaded springs and positioning mechanisms that ensure the plug is correctly seated and ready to withstand pressure loads, preventing premature failure under high pressure.
2Measurement precision
If a matched actuator with calibration curve is used for precise control, then backpressure control precision is improved, but device complexity increases
Solution Approach 1:
The actuator is pre-calibrated during manufacturing to establish a known relationship between actuator position and choke opening. This preliminary calibration creates a reference curve that simplifies field operation, as the actuator can be directly positioned without requiring complex real-time calculations or adjustments during drilling operations.
Solution Approach 2:
The system incorporates position feedback mechanisms that monitor actuator location and correlate it with choke opening status. This feedback loop allows the control system to verify the actual choke position matches the commanded position, maintaining precision while using a relatively simple actuator design without requiring complex computer systems.
3Reliability
If independent operation without complex computer systems is achieved, then system reliability is improved, but control capability over multiple parameters deteriorates
Solution Approach 1:
The choke system is designed to be self-regulating through inherent mechanical characteristics of the plug and seat geometry. The choke plug's tapered design creates a natural flow-closing action that reduces the need for complex electronic control, allowing the system to maintain reliability through independent mechanical operation while still providing adequate control for single-parameter adjustment.
Solution Approach 2:
The actuator mechanism is designed to perform multiple functions: it controls choke opening, provides positioning feedback, and can be manually overridden if needed. This multi-functionality allows a single relatively simple component to handle various control scenarios without requiring complex computer systems, maintaining both reliability and adaptability.
Data Source
AI summary
A method of calibrating a choke system includes connecting to the positioner an electronic controller which is programmed to output a control signal representing the desired position of the plug, connecting to the electronic controller a flowmeter which is configured to provide a flow signal representing the rate of flow of fluid from the pump to the inlet and a pressure sensor which is configured to provide a pressure signal representing the fluid pressure at the inlet, connecting the inlet to a reservoir of fluid via a pump which is operable to pump fluid from the reservoir into the inlet at varying flow rates, and using gain scheduling to determine optimum values of proportional gain and integral gain required for control of the choke using a proportional differential and integral controller at a plurality of different rates of flow of fluid along the central flow passage.