Frequency Slope Analysis for Gas Reservoir Detection
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Solution Overview
Problem
Current seismic methods for gas detection rely on analyzing reflection amplitude, which is affected by various geological variables, making it difficult and unreliable to accurately determine gas or fluid content.
Innovation Solution
The method involves using frequency slope analysis of seismic data to detect high-frequency attenuation indicative of gas deposits, by generating a frequency spectrum and calculating slopes between the peak and maximum frequencies, and constructing a frequency-slope map to visually indicate gas presence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If reflection amplitude analysis is used for gas detection, then the detection method is simple to implement, but the detection reliability is low due to multiple affecting variables
Solution Approach 1:
The patent changes the detection parameter from reflection amplitude to frequency slope. By analyzing the slope of frequency spectra obtained through spectral decomposition, the method identifies gas reservoirs based on frequency attenuation characteristics rather than amplitude variations, thereby improving detection reliability while maintaining operational simplicity
Solution Approach 2:
The patent replaces the traditional amplitude-based detection mechanism with a frequency-based analysis mechanism. Through spectral decomposition and frequency slope calculation, the system substitutes the mechanical interpretation of amplitude data with a more robust frequency domain analysis that is less sensitive to lithology and porosity variations
2Measurement precision
If frequency spectrum analysis is performed to improve gas detection accuracy, then the measurement precision is improved, but the computational complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the frequency spectrum into multiple discrete frequency bins through spectral decomposition. The frequency slope is calculated for each bin separately, allowing precise identification of frequency attenuation patterns while organizing the computational task into manageable segments that can be processed systematically
Solution Approach 2:
The patent introduces frequency slope as an intermediary parameter between the raw frequency spectrum and the final gas detection result. By calculating the slope of the frequency spectrum and using it as the primary indicator for gas reservoir identification, the method simplifies the interpretation process while maintaining high measurement precision
Data Source
AI summary
The present disclosure describes methods and systems, including computer-implemented methods, computer program products, and computer systems for direct gas reservoir detection using frequency slope. One computer-implemented method includes receiving seismic data corresponding to a target formation. Further, the method includes based on a time-frequency analysis of the seismic data, generating a representation of a time-variant frequency response of the seismic data. Yet further, the method includes generating a frequency spectrum for each of one or more locations within the target formation using the representation of the time-variant frequency response. Additionally, the method includes calculating one or more frequency slopes between a peak frequency and a maximum frequency of each frequency spectrum. The method also includes based on the one or more frequency slopes, determining for each location whether gas are present.