Subsurface Formation Imaging Alignment via Window and Edge Correlation
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Solution Overview
Problem
High-resolution imaging tools face inaccuracies due to non-uniform tool motion during borehole logging, particularly from stick-and-slip phenomena, which conventional methods fail to correct effectively, leading to misaligned images and reduced measurement precision.
Innovation Solution
The implementation of a system that aligns images using global, window-based and edge-based alignment methods independent of accelerometer data, where sub-images are divided into windows and aligned based on relative shifts, and edge associations are used to correct for severe tool movement irregularities, enhancing image accuracy and reducing misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If images are acquired across multiple electrodes during borehole logging, then borehole coverage is improved, but image alignment accuracy deteriorates due to non-uniform tool motion
Solution Approach 1:
The patent divides the image alignment problem into two levels: global alignment using window-based correlation across the entire image, and local alignment using edge-based correlation in specific regions. This segmentation allows different alignment strategies to be applied at different scales, improving overall alignment accuracy while maintaining comprehensive borehole coverage from multiple electrodes
Solution Approach 2:
The patent applies different alignment quality requirements to different regions of the image. Edge-based alignment is applied locally at boundaries between electrode sets where misalignment is most critical, while window-based correlation provides global context. This local quality approach ensures high precision at critical interfaces without compromising overall coverage
2Reliability
If conventional accelerometer-based correction methods are used, then tool motion compensation is provided, but measurement precision deteriorates due to stick-and-slip phenomena
Solution Approach 1:
The patent introduces image features (edges and window patterns) as intermediaries between the raw sensor data and the final aligned image. Instead of directly using accelerometer data to correct positions, the system uses correlation of image features to determine alignment offsets, which inherently filters out the stick-and-slip noise that plagues direct accelerometer-based correction methods
Solution Approach 2:
The patent replaces the mechanical/physical correction approach (accelerometer-based position tracking) with an image processing-based approach (correlation of image features). This substitution eliminates the fundamental limitation of accelerometer data during stick-and-slip events, as the alignment is derived from the actual image content rather than motion sensors
Data Source
AI summary
A method includes generating a set of sub-images of a subsurface formation based on measurement values acquired by a plurality of sensors corresponding to one or more signals that have propagated through the subsurface formation, wherein each of the set of sub-images correspond to one of the plurality of sensors. The plurality of sensors are on a tool in a borehole, wherein each of the plurality of sensors are at different spatial positions with respect to each other. The method also includes generating a combined image by aligning the set of sub-images based on the measurement values, wherein the aligning of the set of sub-images is independent of acceleration of the tool during tool motion.