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Title: Hydromechanical modeling of pulse tests that measure both fluidpressure and fracture-normal displacement of the Coaraze Laboratory site,France

Abstract

In situ fracture mechanical deformation and fluid flowinteractions are investigated through a series of hydraulic pulseinjection tests, using specialized borehole equipment that cansimultaneously measure fluid pressure and fracture displacements. Thetests were conducted in two horizontal boreholes spaced one meter apartvertically and intersecting a near-vertical highly permeable faultlocated within a shallow fractured carbonate rock. The field data wereevaluated by conducting a series of coupled hydromechanical numericalanalyses, using both distinct-element and finite-element modelingtechniques and both two- and three-dimensional model representations thatcan incorporate various complexities in fracture network geometry. Oneunique feature of these pulse injection experiments is that the entiretest cycle, both the initial pressure increase and subsequent pressurefall-off, is carefully monitored and used for the evaluation of the insitu hydromechanical behavior. Field test data are evaluated by plottingfracture normal displacement as a function of fluid pressure, measured atthe same borehole. The resulting normal displacement-versus-pressurecurves show a characteristic loop, in which the paths for loading(pressure increase) and unloading (pressure decrease) are different. Bymatching this characteristic loop behavior, the fracture normal stiffnessand an equivalent stiffness (Young's modulus) of the surrounding rockmass can be back-calculated. Evaluation of the field tests by couplednumerical hydromechanical modeling shows that initial fracture hydraulicaperture and normal stiffness vary by amore » factor of 2 to 3 for the twomonitoring points within the same fracture plane. Moreover, the analysesshow that hydraulic aperture and the normal stiffness of the pulse-testedfracture, the stiffness of surrounding rock matrix, and the propertiesand geometry of the surrounding fracture network significantly affectcoupled hydromechanical responses during the pulse injection test. Morespecifically, the pressure-increase path of the normaldisplacement-versus-pressure curve is highly dependent on thehydromechanical parameters of the tested fracture and the stiffness ofthe matrix near the injection point, whereas the pressure-decrease pathis highly influenced by mechanical processes within a larger portion ofthe surrounding fractured rock.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Director. Office of Science. Office of AdvancedScientific Computing Research. Office of Basic Energy Sciences. ChemicalSciences Geosciences and Biosciences Division
OSTI Identifier:
910586
Report Number(s):
LBNL-60442
Journal ID: ISSN 1365-1609; IJRMA2; R&D Project: G3Y81; TRN: US200724%%259
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
International Journal of Rock Mechanics&MiningSciences
Additional Journal Information:
Journal Volume: 43; Journal Issue: 7; Related Information: Journal Publication Date: 10/2006; Journal ID: ISSN 1365-1609
Country of Publication:
United States
Language:
English
Subject:
54; APERTURES; BOREHOLES; CARBONATE ROCKS; DEFORMATION; EVALUATION; FIELD TESTS; FLUID FLOW; FRACTURES; GEOMETRY; HYDRAULICS; MONITORING; SIMULATION; UNLOADING; numerical modeling pulse tests fractures networkhydromechanical coupling simultaneous pressure and fracture-normaldisplacement measurements distinct element method finite elementmethod

Citation Formats

Cappa, F, Guglielmi, Y, Rutqvist, J, Tsang, C-F, and Thoraval, A. Hydromechanical modeling of pulse tests that measure both fluidpressure and fracture-normal displacement of the Coaraze Laboratory site,France. United States: N. p., 2006. Web. doi:10.1016/j.ijrmms.2006.03.006.
Cappa, F, Guglielmi, Y, Rutqvist, J, Tsang, C-F, & Thoraval, A. Hydromechanical modeling of pulse tests that measure both fluidpressure and fracture-normal displacement of the Coaraze Laboratory site,France. United States. https://doi.org/10.1016/j.ijrmms.2006.03.006
Cappa, F, Guglielmi, Y, Rutqvist, J, Tsang, C-F, and Thoraval, A. 2006. "Hydromechanical modeling of pulse tests that measure both fluidpressure and fracture-normal displacement of the Coaraze Laboratory site,France". United States. https://doi.org/10.1016/j.ijrmms.2006.03.006. https://www.osti.gov/servlets/purl/910586.
@article{osti_910586,
title = {Hydromechanical modeling of pulse tests that measure both fluidpressure and fracture-normal displacement of the Coaraze Laboratory site,France},
author = {Cappa, F and Guglielmi, Y and Rutqvist, J and Tsang, C-F and Thoraval, A},
abstractNote = {In situ fracture mechanical deformation and fluid flowinteractions are investigated through a series of hydraulic pulseinjection tests, using specialized borehole equipment that cansimultaneously measure fluid pressure and fracture displacements. Thetests were conducted in two horizontal boreholes spaced one meter apartvertically and intersecting a near-vertical highly permeable faultlocated within a shallow fractured carbonate rock. The field data wereevaluated by conducting a series of coupled hydromechanical numericalanalyses, using both distinct-element and finite-element modelingtechniques and both two- and three-dimensional model representations thatcan incorporate various complexities in fracture network geometry. Oneunique feature of these pulse injection experiments is that the entiretest cycle, both the initial pressure increase and subsequent pressurefall-off, is carefully monitored and used for the evaluation of the insitu hydromechanical behavior. Field test data are evaluated by plottingfracture normal displacement as a function of fluid pressure, measured atthe same borehole. The resulting normal displacement-versus-pressurecurves show a characteristic loop, in which the paths for loading(pressure increase) and unloading (pressure decrease) are different. Bymatching this characteristic loop behavior, the fracture normal stiffnessand an equivalent stiffness (Young's modulus) of the surrounding rockmass can be back-calculated. Evaluation of the field tests by couplednumerical hydromechanical modeling shows that initial fracture hydraulicaperture and normal stiffness vary by a factor of 2 to 3 for the twomonitoring points within the same fracture plane. Moreover, the analysesshow that hydraulic aperture and the normal stiffness of the pulse-testedfracture, the stiffness of surrounding rock matrix, and the propertiesand geometry of the surrounding fracture network significantly affectcoupled hydromechanical responses during the pulse injection test. Morespecifically, the pressure-increase path of the normaldisplacement-versus-pressure curve is highly dependent on thehydromechanical parameters of the tested fracture and the stiffness ofthe matrix near the injection point, whereas the pressure-decrease pathis highly influenced by mechanical processes within a larger portion ofthe surrounding fractured rock.},
doi = {10.1016/j.ijrmms.2006.03.006},
url = {https://www.osti.gov/biblio/910586}, journal = {International Journal of Rock Mechanics&MiningSciences},
issn = {1365-1609},
number = 7,
volume = 43,
place = {United States},
year = {2006},
month = {4}
}