Bottom-Hole Assembly Torque Generator for Directional Drilling
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Solution Overview
Problem
Directional drilling methods often result in 'stick-slip' issues, accumulation of drill cuttings, and tool face instability due to the inability to rotate the drill string without sacrificing directional control, especially in boreholes with multiple nonlinear segments or long horizontal segments.
Innovation Solution
A bottom-hole assembly equipped with a torque generator that allows the drill string to rotate independently of the drill bit, using a modified positive displacement motor and bearing section to counterbalance reactive torque, enabling controlled rotation for both linear and nonlinear bore segment drilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the drill string is stopped to maintain directional control during nonlinear bore segment drilling, then directional accuracy is improved, but drill string stability deteriorates causing stick-slip issues
Solution Approach 1:
The drill string system is segmented into two independent rotational components: the drill string itself and the bottom-hole assembly. The drill string can rotate independently to maintain stability and prevent stick-slip, while the BHA rotates independently to control the drill bit orientation for directional accuracy. This segmentation allows both functions to operate simultaneously without interference.
Solution Approach 2:
A bearing section acts as an intermediary between the drill string and the bottom-hole assembly, allowing independent rotation of each component. The bearing section enables the drill string to rotate without directly rotating the BHA, and vice versa, providing the mechanical decoupling needed to resolve the contradiction between maintaining directional control and preventing stick-slip instability.
2Measurement precision
If the drill string is stopped for directional drilling, then tool face orientation control is improved, but borehole cleaning deteriorates due to drill cutting accumulation
Solution Approach 1:
The rotational function is segmented between the drill string and the bottom-hole assembly. The drill string rotates continuously at a slower speed to maintain borehole cleaning and prevent drill cutting accumulation, while the BHA rotates independently at controlled speeds to maintain precise tool face orientation. This segmentation allows both cleaning and directional control functions to operate simultaneously.
Solution Approach 2:
The drill string maintains continuous rotation throughout the drilling process, even during nonlinear bore segment drilling, to ensure continuous borehole cleaning and prevent drill cutting accumulation. The independent rotation capability of the BHA allows this continuous drill string rotation to occur without compromising tool face orientation control, thus maintaining the continuity of the useful cleaning action.
3Productivity
If the drill string is rotated during directional drilling, then borehole cleaning is improved, but directional control deteriorates due to reactive torque
Solution Approach 1:
The rotational motion is segmented into two independent components: drill string rotation for borehole cleaning and BHA rotation for directional control. The bearing section mechanically decouples these two rotational functions, allowing the drill string to rotate at higher speeds for improved cleaning efficiency while the BHA rotates independently at controlled speeds to maintain precise directional control despite reactive torque.
Solution Approach 2:
The bearing section serves as an intermediary that allows the drill string to rotate independently of the BHA. This intermediary mechanism enables the drill string to provide borehole cleaning through continuous rotation while the BHA maintains directional control by rotating independently, effectively isolating the reactive torque effects to the BHA component only.
4Stability of the object's composition
If the drill string is stopped to prevent stick-slip, then drill bit engagement stability is improved, but drilling speed deteriorates
Solution Approach 1:
The rotational function is segmented between the drill string and the bottom-hole assembly. The drill string rotates continuously at a slower speed to maintain drill bit engagement stability and prevent stick-slip, while the BHA rotates independently to control the drilling direction. This segmentation allows the system to maintain both stability and productivity simultaneously by distributing the rotational functions across two independent components.
Solution Approach 2:
The drill string maintains continuous rotation throughout the drilling process to ensure continuous drill bit engagement stability and prevent stick-slip issues. The independent rotation capability of the BHA allows this continuous drill string rotation to occur without compromising drilling direction control, thus maintaining the continuity of the useful drilling action and improving overall drilling speed.
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
This solution eliminates 'stick-slip' issues, ensures consistent weight on the drill bit, enhances borehole cleaning, and maintains directional control by allowing continuous rotation of the drill string, improving the rate of penetration and reducing the risk of drill motor stalling.
Implementation Method 1
a torque generator to generate a torque that counterbalances a reactive torque generated by rotation of a drill bit
Implementation Method 2
a modified positive displacement motor having a drive shaft adapted to be connected to the drill string
Implementation Method 3
a bearing section that surrounds the drive shaft and is connected to a top of the bottom-hole assembly to permit the bottom-hole assembly to rotate independently of the drive shaft and the drill string
Implementation Method 4
rotation of the drill string at a static drive speed induces the torque generator to generate a torque that counterbalances a reactive torque
Data Source
AI summary
A bottom-hole assembly for directional drilling incorporates a torque generator with a drive shaft connected to a drill string. The torque generator generates a torque that counters a reactive torque when a drill bit of the bottom-hole assembly is driven. When the drill string is rotated at a static drive speed, a drill tool face of the bottom-hole assembly is stabilized to drill a nonlinear bore segment. When the drill string is rotated at a rotational speed other than the static drive speed the bottom-hole assembly is rotated to drill a linear bore segment.