Eccentricity Correction Algorithm for Borehole Shape Computation
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Solution Overview
Problem
Traditional borehole shape computation algorithms, particularly in logging while drilling (LWD) ultrasonic borehole imaging, face challenges in accurately correcting tool eccentricity and determining the borehole shape when the borehole wall is irregular, leading to inaccurate images due to the limitations of methods like least-square circle fitting or elliptical fitting.
Innovation Solution
An eccentricity correction algorithm that employs comprehensive assumptions and criteria, such as the presence of a partial intact borehole and stacking of adjacent transducer firings, to compute borehole shape with high accuracy, applicable to various types of calipers including ultrasonic, mechanical, and wireline calipers, minimizing points outside the fitted curve and error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional least-square circle fitting or elliptical fitting methods are used to compute borehole shape, then the computation process is simple, but the measurement precision and manufacturing precision of borehole shape are inaccurate
Solution Approach 1:
The patent segments the borehole shape computation into multiple depth intervals, processing each interval independently with the eccentricity correction algorithm. This segmentation allows complex computations to be managed in manageable portions while maintaining overall accuracy across the entire borehole profile.
Solution Approach 2:
The patent applies preliminary eccentricity correction to the caliper data before computing the borehole shape. By pre-correcting for tool eccentricity and using assumptions about intact borehole sections, the algorithm prepares the data to eliminate systematic errors before the main shape computation, significantly improving measurement precision.
2Productivity
If individual processing is performed for each transducer firing, then the measurement precision is high, but the productivity and processing time increase
Solution Approach 1:
The patent merges adjacent transducer firings into stacked groups, processing multiple firings simultaneously rather than individually. This combining approach maintains measurement precision by using all available data while significantly improving productivity through parallel processing of multiple firings within the same computational framework.
Solution Approach 2:
The eccentricity correction algorithm is designed to handle multiple transducer firings universally, applying the same correction principles across all firings regardless of their specific characteristics. This multi-functional approach allows the system to process diverse firing data through a unified algorithm, improving efficiency without sacrificing accuracy.
3Measurement precision
If comprehensive eccentricity correction is applied to all data, then the measurement precision improves, but the loss of time and processing resources increase
Solution Approach 1:
The patent applies local quality by treating different portions of the borehole data differently. It identifies and corrects eccentricity in sections where intact borehole geometry is detected, while leaving already-processed or irrelevant sections unchanged. This selective approach maintains precision where needed while reducing unnecessary processing time elsewhere.
Solution Approach 2:
The algorithm applies partial correction by using assumptions about intact borehole sections to infer eccentricity corrections without requiring comprehensive processing of all possible data points. This partial action approach achieves sufficient precision for most applications while significantly reducing processing time and computational resources required.
Data Source
AI summary
The subject disclosure provides for a method of eccentricity correction of a borehole shape computation. The method includes deploying a caliper tool into a borehole penetrating a subterranean formation and acquiring field measurements with the deployed caliper tool. The method includes applying, in a processor circuit, an eccentricity correction algorithm to one or more standoff samples from the obtained field measurements, wherein the eccentricity correction algorithm produces a shape fitted curve that represents a measured borehole with a least number of points outside of the shape fitted curve and a least amount of error. The method includes determining eccentricity-corrected borehole coordinates with the applied eccentricity correction algorithm and determining a borehole shape from the eccentricity-corrected borehole coordinates. The method includes determining tool location coordinates relative to the borehole with the determined borehole shape.