A New Parameter to Assess Hydromechanical Effect in Single-hole Hydraulic Testing and Grouting

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Grouting or filling of the open voids in fractured rock is done by introducing a fluid, a grout, through boreholes under pressure. The grout may be either a Newtonian fluid or a Bingham fluid. The penetration of the grout and the resulting pressure profile may give rise to hydromechanical effects, which depends on factors such as the fracture aperture, pressure at the borehole and the rheological properties of the grout. In this paper, we postulate that a new parameter, {angstrom}, which is the integral of the fluid pressure change in the fracture plane, is an appropriate measure to describe the ... continued below

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Rutqvist, Jonny; Fransson, A.; Tsang, C.-F.; Rutqvist, J. & Gustafson, G. September 1, 2007.

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Grouting or filling of the open voids in fractured rock is done by introducing a fluid, a grout, through boreholes under pressure. The grout may be either a Newtonian fluid or a Bingham fluid. The penetration of the grout and the resulting pressure profile may give rise to hydromechanical effects, which depends on factors such as the fracture aperture, pressure at the borehole and the rheological properties of the grout. In this paper, we postulate that a new parameter, {angstrom}, which is the integral of the fluid pressure change in the fracture plane, is an appropriate measure to describe the change in fracture aperture volume due to a change in effective stress. In many cases, analytic expressions are available to calculate pressure profiles for relevant input data and the {angstrom} parameter. The approach is verified against a fully coupled hydromechanical simulator for the case of a Newtonian fluid. Results of the verification exercise show that the new approach is reasonable and that the {angstrom}-parameter is a good measure for the fracture volume change: i.e., the larger the {angstrom}-parameter, the larger the fracture volume change, in an almost linear fashion. To demonstrate the application of the approach, short duration hydraulic tests and constant pressure grouting are studied. Concluded is that using analytic expressions for penetration lengths and pressure profiles to calculate the {angstrom} parameter provides a possibility to describe a complex situation and compare, discuss and weigh the impact of hydromechanical couplings for different alternatives. Further, the analyses identify an effect of high-pressure grouting, where uncontrolled grouting of larger fractures and insufficient (or less-than-expected) sealing of finer fractures is a potential result.

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  • Journal Name: Journal of Rock Mechanics and Mineral Science; Journal Volume: 44; Related Information: Journal Publication Date: 2007

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  • Report No.: LBNL-801E
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 936252
  • Archival Resource Key: ark:/67531/metadc901754

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  • September 1, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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  • Sept. 30, 2016, 6:48 p.m.

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Rutqvist, Jonny; Fransson, A.; Tsang, C.-F.; Rutqvist, J. & Gustafson, G. A New Parameter to Assess Hydromechanical Effect in Single-hole Hydraulic Testing and Grouting, article, September 1, 2007; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc901754/: accessed August 18, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.