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Electrokinetic coupling in hydraulic...

University of California, Berkeley., Earth & Planetary Science.

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Electrokinetic coupling in hydraulic fracture propagation.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Electrokinetic coupling in hydraulic fracture propagation./
作者:	Cuevas, Nestor Herman.
面頁冊數:	127 p.
附註:	Adviser: James W. Rector, III.
Contained By:	Dissertation Abstracts International70-08B.
標題:	Geophysics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3369047
ISBN:	9781109308433

Electrokinetic coupling in hydraulic fracture propagation.
Cuevas, Nestor Herman.

Electrokinetic coupling in hydraulic fracture propagation. - 127 p.

Adviser: James W. Rector, III.

Thesis (Ph.D.)--University of California, Berkeley, 2009.

Electrokinetic coupling is the most popular mechanism proposed to explain observed electromagnetic signals associated with the hydraulic fracturing of rocks. Measurements in both controlled laboratory and in situ conditions show clear evidence of the phenomenon. However there have been no reports on the description of the source mechanism, its relationship to a propagating crack, nor the electromagnetic field distribution due to such a source advancing through an electrically conductive medium. In this work it is shown that a surface electric current density arising on the walls of a fluid driven propagating crack can explain the measurements of electric streaming potential recorded during hydraulic fracturing experiments.

ISBN: 9781109308433Subjects--Topical Terms:

535228
Geophysics.

Electrokinetic coupling in hydraulic fracture propagation.
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100 1 $a Cuevas, Nestor Herman. $3 1035734
245 1 0 $a Electrokinetic coupling in hydraulic fracture propagation.
300 $a 127 p.
500 $a Adviser: James W. Rector, III.
500 $a Source: Dissertation Abstracts International, Volume: 70-08, Section: B, page: .
502 $a Thesis (Ph.D.)--University of California, Berkeley, 2009.
520 $a Electrokinetic coupling is the most popular mechanism proposed to explain observed electromagnetic signals associated with the hydraulic fracturing of rocks. Measurements in both controlled laboratory and in situ conditions show clear evidence of the phenomenon. However there have been no reports on the description of the source mechanism, its relationship to a propagating crack, nor the electromagnetic field distribution due to such a source advancing through an electrically conductive medium. In this work it is shown that a surface electric current density arising on the walls of a fluid driven propagating crack can explain the measurements of electric streaming potential recorded during hydraulic fracturing experiments.
520 $a The properties of the streaming current source are studied at the microscopic scale in light of the electrokinetic coupling expected at the outermost grains of the crack's surface. Expressions are derived for the average macroscopic transport equations describing the coupled fluid, and electrical current flow, at the interface between a fluid continuum and a homogeneous porous medium, where a Darcy flow regime (porous medium) competes with a rather Poiseuille type (fracture channels). The properties of the electrokinetic boundary sources are analyzed in light of the average electrical current density arising on the interface, as the fluid electrolyte flows in both the porous media and the adjacent fluid continuum. It is found that two coupling coefficients are required to describe the streaming current density. Indeed the flow is driven by both, a tangential pressure gradient, as well as by forward momentum transfer across the permeable boundary. The coupling coefficients are obtained from the spatial average of the tangential stress exerted on the pore surfaces, and they are found to be position dependent, as the tangential stress transitions from that on the porous conduits, to that on the surface of the outer most grains. Furthermore each coefficient gives rise to both a volumetric current density, due to the flow along the pore conduits, as well as a surface current density, due to the flow along the outer most surface. The latter contribution is found to dominate, as the tangential stress scales with the macroscopic characteristic length of the system.
520 $a From a macroscopic stand point a source space-time function is established for the average current density prescribed by the pressure profile expected at the walls of a crack, which propagates under mobile equilibrium, in the context of linear elasticity theory. Expressions for the electromagnetic fields due to such a source are derived for a crack propagating with a constant velocity, in a homogeneous isotropic conducting medium. It is found that the spatial and temporal behavior of the fields reasonably agree with measurements performed under controlled laboratory experiments. In situ measurements are only studied qualitatively. Nevertheless, despite the obvious fact that a homogeneous whole-space medium does not appropriately describe a realistic earth model, the magnitude of the fields and the temporal behavior of the signals can be well reproduced using typical parameters of a hydraulic fracturing procedure.
520 $a Electrokinetic coupling has also been proposed in the context of earthquake precursory signals, due to dilatant crack growth at depth. Several ideas have been discussed in the literature in order to justify experimental measurements of electromagnetic field which presumably appear before the onset of an earthquake. The source mechanism described in the present report, occurring at depth ranges of earthquake slip zones, yields electromagnetic signal levels which are 3 orders of magnitude smaller than the noise floor of currently available commercial instrumentation. This suggests that observing this type of phenomenon as an earthquake precursor would then be very challenging.
590 $a School code: 0028.
650 4 $a Geophysics. $3 535228
690 $a 0373
710 2 $a University of California, Berkeley. $b Earth & Planetary Science. $3 1035733
773 0 $t Dissertation Abstracts International $g 70-08B.
790 $a 0028
790 1 0 $a Glaser, Steven D. $e committee member
790 1 0 $a Morrison, Huntley F. $e committee member
790 1 0 $a Pride, Steven R. $e committee member
790 1 0 $a Rector, James W., III, $e advisor
791 $a Ph.D.
792 $a 2009
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3369047