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Distributed Acoustic Sensing (DAS) of Strain at Earth Tide Frequencies: Laboratory Tests

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The solid Earth strains in response to the gravitational pull from the Moon, Sun, and other planetary bodies. Measuring the flexure of geologic material in response to these Earth tides provides information about the geomechanical properties of rock and sediment. Such measurements are particularly useful for understanding dilation of faults and fractures in competent rock. A new approach to measuring earth tides using fiber optic distributed acoustic sensing (DAS) is presented here. DAS was originally designed to record acoustic vibration through the measurement of dynamic strain on a fiber optic cable. Here, laboratory experiments demonstrate that oscillating strain can be measured with DAS in the microHertz frequency range, corresponding to half-day (M2) lunar tidal cycles. Although the magnitude of strain measured in the laboratory is larger than what would be expected due to earth tides, a clear signal at half-day period was extracted from the data. With the increased signal-to-noise expected from quiet field applications and improvements to DAS using engineered fiber, earth tides could potentially be measured in deep boreholes with DAS. Because of the distributed nature of the sensor (0.25 m measurement interval over kilometers), fractures could be simultaneously located and evaluated. Such measurements would provide valuable information regarding the placement and stiffness of open fractures in bedrock. Characterization of bedrock fractures is an important goal for multiple subsurface operations such as petroleum extraction, geothermal energy recovery, and geologic carbon sequestration.

Citation Formats

California State University. (2018). Distributed Acoustic Sensing (DAS) of Strain at Earth Tide Frequencies: Laboratory Tests [data set]. Retrieved from https://dx.doi.org/10.15121/1512085.
Export Citation to RIS
Coleman, Thomas, Becker, Matthew W. Distributed Acoustic Sensing (DAS) of Strain at Earth Tide Frequencies: Laboratory Tests. United States: N.p., 24 Jan, 2018. Web. doi: 10.15121/1512085.
Coleman, Thomas, Becker, Matthew W. Distributed Acoustic Sensing (DAS) of Strain at Earth Tide Frequencies: Laboratory Tests. United States. https://dx.doi.org/10.15121/1512085
Coleman, Thomas, Becker, Matthew W. 2018. "Distributed Acoustic Sensing (DAS) of Strain at Earth Tide Frequencies: Laboratory Tests". United States. https://dx.doi.org/10.15121/1512085. https://gdr.openei.org/submissions/1129.
@div{oedi_3785, title = {Distributed Acoustic Sensing (DAS) of Strain at Earth Tide Frequencies: Laboratory Tests}, author = {Coleman, Thomas, Becker, Matthew W.}, abstractNote = {The solid Earth strains in response to the gravitational pull from the Moon, Sun, and other planetary bodies. Measuring the flexure of geologic material in response to these Earth tides provides information about the geomechanical properties of rock and sediment. Such measurements are particularly useful for understanding dilation of faults and fractures in competent rock. A new approach to measuring earth tides using fiber optic distributed acoustic sensing (DAS) is presented here. DAS was originally designed to record acoustic vibration through the measurement of dynamic strain on a fiber optic cable. Here, laboratory experiments demonstrate that oscillating strain can be measured with DAS in the microHertz frequency range, corresponding to half-day (M2) lunar tidal cycles. Although the magnitude of strain measured in the laboratory is larger than what would be expected due to earth tides, a clear signal at half-day period was extracted from the data. With the increased signal-to-noise expected from quiet field applications and improvements to DAS using engineered fiber, earth tides could potentially be measured in deep boreholes with DAS. Because of the distributed nature of the sensor (0.25 m measurement interval over kilometers), fractures could be simultaneously located and evaluated. Such measurements would provide valuable information regarding the placement and stiffness of open fractures in bedrock. Characterization of bedrock fractures is an important goal for multiple subsurface operations such as petroleum extraction, geothermal energy recovery, and geologic carbon sequestration.
}, doi = {10.15121/1512085}, url = {https://gdr.openei.org/submissions/1129}, journal = {}, number = , volume = , place = {United States}, year = {2018}, month = {01}}
https://dx.doi.org/10.15121/1512085

Details

Data from Jan 24, 2018

Last updated May 13, 2019

Submitted Apr 26, 2019

Organization

California State University

Contact

Matthew W Becker

562.985.8983

Authors

Thomas Coleman

Silixa LLC

Matthew W. Becker

Department of Geological Sciences California State University ...

Research Areas

DOE Project Details

Project Name Phase I Project: Fiber Optic Distributed Acoustic Sensing for Periodic Hydraulic Tests

Project Lead William Vandermeer

Project Number EE0006763

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