Downhole Tractor for Logging Tool Stick-Slip Reduction
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Solution Overview
Problem
Non-uniform tool motion caused by stick-slip affects the accuracy of logging data acquisition in boreholes, leading to challenges in depth control and data quality due to variations in force and friction during the conveyance of logging tools.
Innovation Solution
Employing a downhole tractor connected to the logging tool to absorb changes in conveyance force and maintain steady motion, reducing the impact of stick-slip by using a combination of tractor conveyance and wireline in gravity-conveyed sections of boreholes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a logging tool is conveyed through a borehole using gravity and wireline, then the logging data can be obtained during conveyance, but non-uniform tool motion caused by stick-slip occurs leading to poor depth control and reduced data quality
Solution Approach 1:
A downhole tractor is introduced as an intermediary device between the logging tool and the wireline conveyance system. The tractor engages with the borehole wall to provide additional propulsion and stabilize tool motion, acting as a mediator that eliminates stick-slip effects while maintaining the gravity-conveyed operation mode.
Solution Approach 2:
The system transitions from static wireline-pulled conveyance to dynamic hybrid conveyance where the downhole tractor actively adjusts its engagement with the borehole wall to maintain uniform tool motion. The tractor's drive mechanism dynamically compensates for variations in friction and gravity forces throughout the borehole.
2Force
If wireline tension increases to move the logging tool through high-friction sections, then the tool can overcome friction, but the wireline stretches causing tool stoppage and stick-slip motion
Solution Approach 1:
The downhole tractor serves as a mechanical intermediary that transfers force directly to the tool through contact with the borehole wall, bypassing the wireline's elastic limitation. This allows high conveyance force to be applied without wireline stretching, maintaining steady tool speed.
Solution Approach 2:
The system replaces the wireline's mechanical force transmission mechanism with a downhole tractor's direct mechanical propulsion. The tractor's engagement with the borehole wall substitudes the wireline's tensile force application, eliminating the stretch-speed coupling problem.
3Measurement precision
If the logging tool is raised through the borehole, then logging data can be obtained during ascent, but stick-slip motion occurs making accurate depth control challenging
Solution Approach 1:
The downhole tractor acts as a mediator during tool ascent, providing continuous engagement with the borehole wall to maintain uniform upward motion. This eliminates the stick-slip cycles that normally occur during wireline-pulled ascent, enabling accurate depth control throughout the logging process.
Solution Approach 2:
The downhole tractor ensures continuous, uninterrupted tool conveyance by maintaining constant engagement with the borehole wall during ascent. This continuous action prevents the periodic stoppage and sudden movement characteristic of stick-slip motion, ensuring steady data acquisition at uniform 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 approach improves the quality of logging data by ensuring consistent tool motion, reducing data loss and blurring, and synchronizing measurement points with depth measurements, thereby enhancing the accuracy of logging data acquisition.
Implementation Method 1
Employing a downhole tractor connected to the logging tool to absorb changes in conveyance force and maintain steady motion, reducing the impact of stick-slip by using a combination of tractor conveyance and wireline in gravity-conveyed sections of boreholes
Data Source
AI summary
The disclosure provides a method of obtaining logging data of subterranean formations and a logging system for doing the same. One example method includes: (1) conveying a logging tool and downhole tractor through a gravity-conveyed section of a borehole, and (2) obtaining logging data from the logging tool during the conveying, wherein the downhole tractor is employed for at least a portion of the obtaining of the logging data. Another example method includes: (1) lowering a logging tool and an open-hole tractor through a gravity conveyed section of an open borehole, (2) raising the logging tool and the open-hole tractor through the gravity conveyed section, (3) obtaining, from the logging tool during the raising, logging data associated with the gravity conveyed section of the open borehole, and (4) employing the open-hole tractor for at least a portion of the raising of the logging tool during the obtaining.