Passive Seismic Exploration Using Ambient Noise Frequency Bands
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Solution Overview
Problem
Existing passive seismic techniques for exploring subsurface regions face challenges due to high amplitude noise from human activities and insufficient spatial resolution, limiting their effectiveness in detecting hydrocarbon reservoirs.
Innovation Solution
A method utilizing a plurality of sensors sensitive to three orthogonal components of seismic interface waves in the frequency range of 0-1 Hz, allowing for recording and processing of ambient seismic data to measure energy in specific frequency bands, which enhances spatial resolution and reduces noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive seismic techniques are used to detect weak tremor signals, then energy consumption is reduced and environmental impact is minimized, but the detection precision deteriorates due to high amplitude noise from human activities
Solution Approach 1:
The patent changes the frequency parameter by focusing on very low frequency bands (0.01-1 Hz) where anthropogenic noise is minimal compared to traditional seismic frequencies. This parameter shift allows passive detection to maintain precision by targeting frequency ranges less contaminated by human activity noise
Solution Approach 2:
The patent replaces traditional mechanical seismic sources with natural ambient seismic noise as the probing signal. This substitution eliminates the need for active energy sources while enabling detection through sophisticated processing of environmental vibrations, thereby reducing environmental impact without sacrificing detection capability
2Device complexity
If conventional seismometers are spaced hundreds of kilometers apart for ambient noise tomography, then the device complexity is reduced, but the spatial resolution deteriorates to continental scale only
Solution Approach 1:
The patent changes the frequency parameter to very low frequencies (0.01-1 Hz) which have longer wavelengths and can propagate over shorter distances with less attenuation. This enables high spatial resolution imaging at local scales (kilometers rather than continental scales) while maintaining relatively simple sensor deployment
Solution Approach 2:
The patent utilizes the frequency dimension more effectively by operating in the very low frequency band, which provides additional information content that enables high-resolution imaging without requiring dense spatial sampling. This frequency-dimensional approach complements the spatial dimension to achieve high resolution with simpler arrays
3Measurement precision
If sensors record ambient noise in the frequency range below 0.5 Hz for long periods, then the measurement precision improves for continental scale imaging, but the productivity deteriorates due to extremely long recording durations
Solution Approach 1:
The patent shifts the frequency parameter to the very low frequency band (0.01-1 Hz), which contains sufficient information for high-resolution imaging at local scales. This parameter change reduces the required recording duration from years to hours or days, thereby improving productivity while maintaining imaging precision
Solution Approach 2:
The patent applies partial action by recording for shorter durations than traditional ambient noise tomography requires. By focusing on the very low frequency band and using sophisticated signal processing, the method achieves adequate signal-to-noise ratio and imaging quality without requiring extremely long recording periods, thus improving efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables effective exploration of subsurface regions with improved spatial resolution and reduced noise interference, making it suitable for detecting hydrocarbon reservoirs and applicable in various environments, including onshore and offshore locations.
Implementation Method 1
using a plurality of sensors at a plurality of locations to obtain seismic data by recording ambient seismic interface waves in a frequency range whose lower limit is greater than or equal to 0 Hz and whose upper limit is less than or equal to substantially 1 Hz
Data Source
AI summary
A passive method for exploring a region below the surface of the earth. The method comprises using a plurality of sensors to obtain seismic data obtained by recording ambient seismic interface waves in a frequency range whose lower limit is greater than 0 Hz, and whose upper limit is less than or equal to substantially 1 Hz. The sensors may be sensitive to three orthogonal components. Recordings may be made simultaneously by all sensors and normalization of data is unnecessary. The sensors may be moved and clean data may be selected. Local dispersion curves may be determined to improve vertical resolution. The data are processed so as to obtain a measure of the energy in a frequency band within the frequency range. The energy measure may be calculated by integrating the spectrum in the frequency domain over a desired frequency range. The resulting calculated energy provides information about the region of the earth being explored.