Downhole Velocity Correction via Joint Inversion
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Solution Overview
Problem
Traditional methods for calculating depths in borehole logging using the double integral of accelerations accumulate significant errors over time, leading to misalignment of images and inaccurate formation readings.
Innovation Solution
The system employs an independent 'mismatch distance' measurement as an external reference to jointly invert accelerometer readings and calculate velocities, thereby estimating depths more accurately and avoiding error accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the double integral of acceleration measurements is used to calculate depth, then the depth can be estimated from available sensor data, but significant errors accumulate over time leading to poor measurement precision
Solution Approach 1:
The patent introduces an independent reference measurement (mismatch distance between sensors or conveyance velocity) as an intermediary to correct the depth calculation. This mediator provides an external reference that breaks the error accumulation chain of the double integral method, allowing depth to be calculated with significantly reduced errors (within 1 foot accuracy).
Solution Approach 2:
The patent implements feedback by using the independent reference measurement to continuously correct the depth estimation. The mismatch distance or velocity measurements provide feedback signals that are used to adjust and correct the depth calculations, preventing error accumulation and maintaining high precision over extended logging operations.
2Manufacturing precision
If traditional double integral method is used for depth calculation, then the system remains simple, but image alignment and formation reading accuracy deteriorate
Solution Approach 1:
The independent reference measurement acts as a mediator that corrects depth calculations without requiring complete system redesign. By introducing this additional measurement channel (mismatch distance or velocity), the system achieves proper image alignment and formation reading accuracy while adding only moderate complexity compared to the traditional method.
3Reliability
If accelerometer data alone is used for depth calculation, then the measurement system remains simple, but reliability of depth estimation deteriorates due to error accumulation
Solution Approach 1:
The patent merges multiple independent measurement methods (accelerometer data and either mismatch distance or velocity measurements) into a unified depth calculation system. This combination of measurement channels increases reliability by providing redundant information and cross-validation, reducing the impact of errors in any single measurement method.
Solution Approach 2:
The independent reference measurement (mismatch distance or velocity) serves as a mediator that validates and corrects the accelerometer-based depth calculations. This intermediary measurement channel provides an independent check on the primary measurement method, significantly improving the reliability of depth estimation over the logging duration.
Data Source
AI summary
A method and system for performing a velocity correction downhole. A method may include disposing a downhole tool into a borehole, taking one or more measurements of the borehole with one or more pads disposed on the downhole tool, creating one or more images from the one or more measurements to form an image log at a depth within the borehole, identifying a mismatch distance between the one or more images in the image log, and correcting the one or more images at the depth within the borehole based at least in part on the mismatch distance.