Hybrid Seismic Sensor Network for Microseismic Monitoring
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Solution Overview
Problem
Current microseismic monitoring systems are limited in their ability to accurately record and characterize seismic events with lower frequencies and larger magnitudes, such as those occurring during hydraulic fracturing, due to spectral bandwidth and time window limitations, which can lead to inaccurate magnitude estimates and risk assessments.
Innovation Solution
A hybrid seismic network comprising a combination of high-frequency and lower-frequency seismic sensors, including force-balanced accelerometers and geophones, deployed both at the surface and downhole, to enhance frequency range and recording capabilities, allowing for more accurate characterization of microseismic events across a broader magnitude range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional high-frequency geophones are used for microseismic monitoring, then location accuracy is improved, but frequency range and magnitude estimation accuracy for larger events deteriorate
Solution Approach 1:
The monitoring system is segmented into multiple sensor types with different frequency responses. High-frequency geophones (e.g., 4.5 Hz, 15 Hz) are deployed for precise location of small microseismic events, while low-frequency accelerometers (e.g., 0.5 Hz, 1 Hz) are deployed for accurate magnitude estimation of larger events. This segmentation allows each sensor type to optimize its performance for specific event magnitudes and frequency ranges.
Solution Approach 2:
The monitoring system achieves multi-functionality by integrating both high-frequency geophones and low-frequency accelerometers into a single network. This universal system can simultaneously monitor and characterize both small microseismic events (requiring high-frequency sensors for location accuracy) and larger magnitude events (requiring low-frequency sensors for accurate magnitude estimation), eliminating the need for separate monitoring systems.
2Measurement precision
If high-frequency sensors are deployed, then spectral characterization of small events is improved, but recording capability for low-frequency signals deteriorates
Solution Approach 1:
The sensor network is segmented by frequency response characteristics. High-frequency geophones (4.5 Hz, 15 Hz) provide excellent spectral characterization for small microseismic events with frequencies above 1 Hz, while low-frequency accelerometers (0.5 Hz, 1 Hz) reliably capture and characterize low-frequency signals from larger magnitude events, ensuring accurate magnitude estimation across the full spectrum of seismic activity.
Solution Approach 2:
The system changes the frequency response parameter of the sensors deployed in the network. By selecting sensors with different natural frequencies and bandwidths, the system adapts its sensitivity to different frequency ranges. High-frequency geophones are optimized for events with corner frequencies above 1 Hz, while low-frequency accelerometers are optimized for events with corner frequencies below 1 Hz, allowing reliable magnitude estimation across different event sizes.
3Device complexity
If a single sensor type is used, then system complexity is reduced, but measurement accuracy across different event magnitudes deteriorates
Solution Approach 1:
The sensor network is segmented into distinct functional groups: high-frequency geophone arrays for location determination and low-frequency accelerometer arrays for magnitude estimation. This segmentation allows each group to be optimized for its specific measurement task, improving overall measurement precision without requiring an overly complex integrated sensor design.
Solution Approach 2:
The hybrid sensor network achieves universality by being capable of accurately measuring both small microseismic events and larger magnitude events with a single integrated system. The network processes data from multiple sensor types to provide comprehensive characterization of all seismic events, maintaining measurement precision across the full magnitude range while managing system complexity through standardized data processing protocols.
Data Source
AI summary
A system for monitoring seismicity during fluid injection at or near a hydrocarbon reservoir comprising: a first set of seismic sensors for deployment at a site for collecting seismic data; a second set of seismic sensors for sub-surface deployment at the site at a depth lower than the first set of seismic sensors for collecting seismic data, the first set of seismic sensors having a lower frequency response than that of the second set of seismic sensors; and a data collection system in communication with the first and second set of sensors.