Downhole Tool Depth Correction for Stick-Slip Artifacts
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Solution Overview
Problem
High resolution imaging data from logging-while-drilling (LWD) tools is affected by stick-slip, leading to gaps in measurement data that require correction techniques like interpolation, resulting in image artifacts and distortions due to variations in rotational rate of the logging tools.
Innovation Solution
A method and system that corrects the original depth of measurement data by calculating a new depth as a function of time using a relationship between tool rotation data and measured depth, incorporating high resolution RPM data from downhole sensors and surface ROP measurements to generate a high resolution ROP data curve, which removes stick sections and corrects remaining data for depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If interpolation techniques are used to correct gaps in measurement data, then continuity of measurement data is improved, but image artifacts and distortions are introduced
Solution Approach 1:
The patent replaces traditional interpolation methods with a physics-based correction approach using downhole RPM measurements and rate of penetration (ROP) calculations. Instead of mathematically estimating missing data points through interpolation, the system uses actual sensor data from the downhole environment to calculate corrected depth values, thereby avoiding the artifacts and distortions that interpolation introduces while still achieving continuous measurement data.
2Measurement precision
If high resolution imaging is performed during variable rotational rate drilling, then imaging detail is improved, but measurement accuracy deteriorates due to stick-slip effects
Solution Approach 1:
The patent implements a feedback mechanism by using downhole RPM measurements to continuously monitor and correct for stick-slip effects. The system measures the actual rotational rate of the logging tool, compares it to expected values, and uses this feedback to calculate corrected depth measurements. This closed-loop approach maintains high imaging resolution while compensating for accuracy degradation caused by variable rotational rates during drilling.
Solution Approach 2:
The patent introduces RPM measurements and ROP calculations as intermediary parameters that bridge the gap between imaging data and depth information. These intermediaries serve as mediators that translate the effects of variable rotational rate into correctable depth adjustments, allowing the system to maintain both high imaging resolution and measurement accuracy simultaneously.
3Device complexity
If traditional depth correction methods are used, then processing simplicity is maintained, but depth accuracy deteriorates due to stick-slip effects
Solution Approach 1:
The patent enables the measurement system to self-correct for stick-slip effects by incorporating downhole RPM sensors that provide self-generated correction data. The system uses its own operational parameters (rotational rate measurements) to automatically adjust depth measurements without requiring external intervention or complex post-processing, thereby improving depth accuracy while maintaining relatively simple processing requirements.
Data Source
AI summary
A method of processing downhole measurement data includes: receiving formation measurement data generated by a downhole tool during a logging-while drilling operation over a selected time period; receiving a measured depth corresponding to the selected time period based on data taken at a surface location; receiving tool rotation data generated by measurements of a rotational rate of the downhole tool taken by a downhole sensor during the selected time period; calculating a new depth of the tool as a function of time over the selected time period based on a relationship between the tool rotation data and the measured depth; and correcting an original depth of the measurement data with the new depth.