Downhole Tool Control Using Asynchronous Drill String Pulses
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Solution Overview
Problem
Controlling downhole tools in harsh underground environments is challenging due to difficulties in precise rotational speed control and pressure measurement, and existing communication protocols are inefficient and prone to errors from stick-slip and latency.
Innovation Solution
A control method using asynchronous communication that modulates the drill string's operational parameters, such as rotational speed or pressure, to convey control commands through pulses within a flexible time window, independent of precise measurements, and utilizes a controller to interpret these pulses for tool activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wired or wireless communication techniques are used to control downhole tools, then control capability is provided, but reliability is reduced due to harsh downhole environment and depth
Solution Approach 1:
The patent replaces electrical/wireless communication systems with a mechanical communication system that uses drill string rotation as the transmission medium. Control commands are encoded in rotational speed variations that propagate mechanically through the drill string to the downhole tool, eliminating vulnerability to harsh environmental conditions and depth-related signal degradation.
Solution Approach 2:
The drill string itself serves as an intermediary medium for transmitting control commands. Instead of direct electrical or wireless communication, the system uses the drill string's mechanical rotation as a carrier wave, with control information encoded in rotational speed modulations that travel through the drill string to activate the downhole tool.
2Ease of operation
If ball or dart objects are dropped into the bore to block it and actuate mechanical mechanisms, then tool activation is achieved, but the bore becomes unavailable for other operations
Solution Approach 1:
The patent replaces the ball/dart blocking mechanism with a rotational speed-based control system. Instead of physically blocking the bore to activate tools, the system modulates drill string rotational speed to encode control commands, allowing the bore to remain open and available for continuous drilling operations while still enabling tool activation.
Solution Approach 2:
The control system uses periodic variations in rotational speed to encode control commands. By modulating the rotation speed in specific patterns (acceleration/deceleration cycles), the system transmits control information without requiring physical obstruction of the bore, enabling continuous operational availability.
3Productivity
If multiple tools are run on a single drill string to minimize trips, then operational efficiency is improved, but control complexity increases when tools share the same actuation principle
Solution Approach 1:
The patent segments the control space by assigning different modulation frequencies to different downhole tools. Each tool is assigned a unique frequency signature, allowing multiple tools to be controlled simultaneously on the same drill string without interference. The control system can independently address each tool by modulating rotation at its specific frequency.
Solution Approach 2:
The system uses dynamic frequency assignment where different tools respond to different rotational speed modulation frequencies. By varying the frequency of rotational speed modulations, the system can selectively activate different tools along the drill string, enabling complex multi-tool operations without increasing overall control complexity.
4Ease of operation
If communication protocols rely on fixed predetermined time slots with precise rotational speed control, then structured communication is achieved, but measurement errors increase due to stick-slip and latency
Solution Approach 1:
The patent incorporates feedback mechanisms where the downhole tool detects rotational speed modulations and sends acknowledgment signals back up the drill string. This feedback loop allows the surface system to verify successful command reception and adjust modulation parameters accordingly, compensating for variations caused by stick-slip and latency without requiring ultra-precise timing.
Solution Approach 2:
The system uses changes in rotational speed parameters (frequency, amplitude, duration) to encode control commands rather than relying on precise timing within fixed slots. By making the communication robust to parameter variations, the system tolerates measurement errors from stick-slip phenomena and system latency while maintaining reliable control.
Data Source
AI summary
A method, apparatus and machine readable instructions for controlling a downhole tool are provided. An operational parameter of a drill string associated with the downhole tool is sensed to detect a number of pulses of the operational parameter within a time window having a predetermined duration. The pulses correspond to a period during which the operational parameter deviates from a baseline value and the detection of the number of pulses accommodates at least one of a variable pulse duration and a variable pulse magnitudes within the time window. A control command to control the downhole tool is executed depending on the detected number of pulses of the operational parameter.