Differential Phase Semblance for Acoustic Logging
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Solution Overview
Problem
Current acoustic logging methods face challenges in achieving high resolution and accuracy for formation slowness and porosity measurements due to destructive interference and incoherent noise, which are not effectively addressed by existing phase semblance processing techniques.
Innovation Solution
The use of differential phase values between array signals in both time and frequency domains to create coherence semblance images, excluding destructive interference and reducing noise through waveform stacking by shifting signal reference points, provides a more accurate estimate of formation slowness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase semblance processing techniques are used, then formation slownest measurements can be obtained, but destructive interference and incoherent noise reduce measurement precision and resolution
Solution Approach 1:
The patent extracts and removes destructive interference components from the acoustic signals through differential phase processing. By calculating phase differences between multiple receiver signals and applying semblance processing, the method isolates and eliminates incoherent noise and destructive interference patterns, retaining only the coherent formation response signals for accurate slowness measurement.
Solution Approach 2:
The patent converts the harmful effect of destructive interference into a useful indicator. By analyzing the phase relationships and coherence of signals across multiple receivers, the method identifies regions where destructive interference occurs and uses this information to enhance the contrast and resolution of the final slowness image, turning noise into a diagnostic tool.
2Measurement precision
If array-based acoustic data processing is used, then subsurface information can be extracted, but resolution and accuracy are limited by conventional processing methods
Solution Approach 1:
The patent transitions from conventional single-dimension processing to multi-dimensional analysis by incorporating signals from multiple receivers arranged in arrays. The method processes data in both time and frequency domains simultaneously, creating a two-dimensional semblance domain that preserves more information about formation properties and enables higher resolution imaging through coherent signal stacking.
Solution Approach 2:
The patent merges signals from multiple receivers through coherent stacking in the semblance domain. By combining phase information from all receiver elements and applying differential phase processing, the method consolidates weak individual signals into a strong coherent response, enhancing the signal-to-noise ratio and recovering high-resolution subsurface information that would be lost in conventional processing.
3Productivity
If conventional semblance processing is applied, then processing can be completed, but incoherent noise reduces the quality of formation characterisation
Solution Approach 1:
The patent applies preliminary differential phase processing and coherence analysis before final slowness calculation. By pre-processing the signals to remove incoherent components and enhance coherent signals through phase differencing and stacking, the method prepares cleaner input data for the final measurement, improving reliability without significantly increasing overall processing time.
Data Source
AI summary
In some embodiments, apparatus and systems, as well as methods, may operate to shift signal data associated with a set of receivers, in time or phase with respect to signal data associated with a receiver reference point, to transform the signal data into shifted data, wherein the signal data corresponds to energy waves propagated through a geological formation before being received by the set of receivers; to multiply the shifted data by a complex conjugate of the signal data associated with the receiver reference point to provide differential phase values; to sum and average the differential phase values to provide differential phase semblance values; and to publish the differential phase semblance values, or information derived from the differential phase semblance values to one of a storage medium, a hardcopy printout, or a display. Additional apparatus, systems, and methods are disclosed.