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Title: Self-potential observations during hydraulic fracturing

Abstract

The self-potential (SP) response during hydraulic fracturing of intact Sierra granite was investigated in the laboratory. Excellent correlation of pressure drop and SP suggests that the SP response is created primarily by electrokinetic coupling. For low pressures, the variation of SP with pressure drop is linear, indicating a constant coupling coefficient (Cc) of -200 mV/MPa. However for pressure drops >2 MPa, the magnitude of the Cc increases by 80% in an exponential trend. This increasing Cc is related to increasing permeability at high pore pressures caused by dilatancy of micro-cracks, and is explained by a decrease in the hydraulic tortuosity. Resistivity measurements reveal a decrease of 2% prior to hydraulic fracturing and a decrease of {approx}35% after fracturing. An asymmetric spatial SP response created by injectate diffusion into dilatant zones is observed prior to hydraulic fracturing, and in most cases this SP variation revealed the impending crack geometry seconds before failure. At rupture, injectate rushes into the new fracture area where the zeta potential is different than in the rock porosity, and an anomalous SP spike is observed. After fracturing, the spatial SP distribution reveals the direction of fracture propagation. Finally, during tensile cracking in a point load device withmore » no water flow, a SP spike is observed that is caused by contact electrification. However, the time constant of this event is much less than that for transients observed during hydraulic fracturing, suggesting that SP created solely from material fracture does not contribute to the SP response during hydraulic fracturing.« less

Authors:
;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
929494
Report Number(s):
LBNL-63455
Journal ID: ISSN 0148-0227; JGREA2; R&D Project: 0; BnR: YN0100000; TRN: US200813%%216
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research
Additional Journal Information:
Journal Volume: 112; Related Information: Journal Publication Date: 2007; Journal ID: ISSN 0148-0227
Country of Publication:
United States
Language:
English
Subject:
54; DIFFUSION; DILATANCY; DISTRIBUTION; ELECTRODYNAMICS; FRACTURES; FRACTURING; GEOMETRY; GRANITES; HYDRAULIC FRACTURING; HYDRAULICS; PERMEABILITY; PORE PRESSURE; POROSITY; PRESSURE DROP; TRANSIENTS; WATER

Citation Formats

Moore, Jeffrey R, and Glaser, Steven D. Self-potential observations during hydraulic fracturing. United States: N. p., 2007. Web. doi:10.1029/2006JB004373.
Moore, Jeffrey R, & Glaser, Steven D. Self-potential observations during hydraulic fracturing. United States. https://doi.org/10.1029/2006JB004373
Moore, Jeffrey R, and Glaser, Steven D. 2007. "Self-potential observations during hydraulic fracturing". United States. https://doi.org/10.1029/2006JB004373. https://www.osti.gov/servlets/purl/929494.
@article{osti_929494,
title = {Self-potential observations during hydraulic fracturing},
author = {Moore, Jeffrey R and Glaser, Steven D},
abstractNote = {The self-potential (SP) response during hydraulic fracturing of intact Sierra granite was investigated in the laboratory. Excellent correlation of pressure drop and SP suggests that the SP response is created primarily by electrokinetic coupling. For low pressures, the variation of SP with pressure drop is linear, indicating a constant coupling coefficient (Cc) of -200 mV/MPa. However for pressure drops >2 MPa, the magnitude of the Cc increases by 80% in an exponential trend. This increasing Cc is related to increasing permeability at high pore pressures caused by dilatancy of micro-cracks, and is explained by a decrease in the hydraulic tortuosity. Resistivity measurements reveal a decrease of 2% prior to hydraulic fracturing and a decrease of {approx}35% after fracturing. An asymmetric spatial SP response created by injectate diffusion into dilatant zones is observed prior to hydraulic fracturing, and in most cases this SP variation revealed the impending crack geometry seconds before failure. At rupture, injectate rushes into the new fracture area where the zeta potential is different than in the rock porosity, and an anomalous SP spike is observed. After fracturing, the spatial SP distribution reveals the direction of fracture propagation. Finally, during tensile cracking in a point load device with no water flow, a SP spike is observed that is caused by contact electrification. However, the time constant of this event is much less than that for transients observed during hydraulic fracturing, suggesting that SP created solely from material fracture does not contribute to the SP response during hydraulic fracturing.},
doi = {10.1029/2006JB004373},
url = {https://www.osti.gov/biblio/929494}, journal = {Journal of Geophysical Research},
issn = {0148-0227},
number = ,
volume = 112,
place = {United States},
year = {Thu Sep 13 00:00:00 EDT 2007},
month = {Thu Sep 13 00:00:00 EDT 2007}
}