skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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

Abstract

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 informationmore » 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.« less

Authors:
;
Publication Date:
Research Org.:
DOE Geothermal Data Repository; California State University
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Geothermal Technologies Program (EE-2C)
Contributing Org.:
California State University
OSTI Identifier:
1512085
Report Number(s):
1129
DOE Contract Number:  
EE0006763
Resource Type:
Data
Country of Publication:
United States
Availability:
GDRHelp@ee.doe.gov
Language:
English
Subject:
15 Geothermal Energy; geothermal; energy; earth tide; DAS; distributed acoustic sensing; fiber optics sensors; low frequency strain; geomechanics; measurement; Matlab; EGS; Lab Tests; fracture; characterization; hydraulic; stimulation strain

Citation Formats

Coleman, Thomas, and Becker, Matthew W. Distributed Acoustic Sensing (DAS) of Strain at Earth Tide Frequencies: Laboratory Tests. United States: N. p., 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. doi:10.15121/1512085.
Coleman, Thomas, and Becker, Matthew W. Wed . "Distributed Acoustic Sensing (DAS) of Strain at Earth Tide Frequencies: Laboratory Tests". United States. doi:10.15121/1512085. https://www.osti.gov/servlets/purl/1512085.
@article{osti_1512085,
title = {Distributed Acoustic Sensing (DAS) of Strain at Earth Tide Frequencies: Laboratory Tests},
author = {Coleman, Thomas and 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},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {1}
}

Dataset:

Save / Share: