Phase Velocity Processing for Acoustic First Break Identification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Identifying the first break of acoustic signals in subterranean formations is challenging due to ambient noise that often equals or exceeds the signal magnitude, leading to false signal detection.
Innovation Solution
A method involving the creation of semblance and phase separation plots, combined with a tool line, to accurately identify the first break and determine wave slowness and arrival time by analyzing acoustic data from multiple receivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ambient noise filtering is not applied, then signal detection sensitivity is maintained, but false first break detection increases
Solution Approach 1:
The patent transforms the 1D waveform amplitude data into a 2D semblance plot domain (time-slowness space), adding a dimensional transformation that enables separation of true signals from noise through geometric patterns. The semblance calculation creates a new representation where coherent signals form distinct linear patterns while random noise remains scattered, allowing visual and algorithmic discrimination.
Solution Approach 2:
The patent introduces semblance as an intermediary computational process between raw waveform data and first break identification. This intermediary transformation computes the coherence of signals across multiple receivers, creating a semblance value that acts as a mediator to distinguish true first breaks from noise based on their coherence properties rather than raw amplitude.
2Productivity
If simple amplitude thresholding is used, then processing speed is maintained, but measurement precision of first break deteriorates
Solution Approach 1:
The patent performs preliminary semblance calculation across a range of slowness values and time picks before final first break identification. This preliminary action pre-processes the data into a semblance domain where true signals are enhanced, allowing subsequent faster identification algorithms to work with pre-filtered information rather than raw noisy waveforms.
Solution Approach 2:
By transforming waveform data into semblance plots in time-slowness space, the patent enables visualization and identification of first breaks as intersection points of tool lines with semblance contours. This dimensional transformation allows geometric intersection methods to replace complex amplitude-based picking, improving both speed and precision.
3Measurement precision
If multiple processing methods (semblance and phase separation) are combined, then first break identification accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges semblance processing and phase separation processing into a unified workflow where both methods operate on the same input data and their results are combined through tool line intersections. This merging allows the system to leverage the complementary strengths of both methods: semblance for coherence-based identification and phase separation for velocity-based identification, achieving higher accuracy than either method alone.
Solution Approach 2:
The patent creates a multi-functional processing system where the same data pipeline supports both semblance calculations and phase separation calculations. The tool line concept serves as a universal framework that can be applied to interpret results from either method, providing a unified interpretation mechanism that reduces operational complexity despite the multiple processing paths.
Data Source
AI summary
A method and apparatus for processing acoustic data recorded by a subterranean receiver array. The method includes emitting an acoustic signal into a formation, receiving the signal after it passes through the array, and processing the data with semblance and phase velocity processing. Semblance and phase velocity plots are generated and combined into a single plot. The phase velocity processing creates phase separation lines, the phase separation line that crosses the closest contour of the semblance plot is identified. The point where the intersecting phase separation line crosses an associated tool line marks the slowness and travel time that provides maximum coherence.