Scale limits to fluid pressure diffusion during rapid self-sealing deformation and fluid flow

Ian Main, Bryne Ngwenya, Stephen Elphick, Brian Smart, Brian Crawford, Christelle Poux

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract / Description of output

We investigate the effects of chemical fluid-rock disequilibrium and true triaxial stress states on axial permeability at confining pressures of the order 35 MPa at temperatures below 80C. Two suites of experiments are described, the first involving anelastic compaction and eventual failure at a constant strain rate. The decay in inferred hydraulic diffusivity here is found to be exponential, with a rate constant which depends both on stress state and the fluid chemistry, and which may change during deformation. In particular strain hardening deformation is found to be associated with more rapid sealing above a critical strain of the order 1% or so. Predicted asymptotic diffusion lengths are of the order a few metres for such deformation. In a separate suite of experiments, designed to monitor the continuous flow of fluids through stressed rock, a similar exponential decay was observed using a synthetic brine. These changes were associated with detectable changes in pore fluid chemistry. Fine particles (clays and detrital fragments) present in the natural core sample produced rapid sealing with predicted asymptotic diffusion lengths of the order a few hundred m to a few km, depending on the initial fluid-rock equilibrium conditions.

Original languageEnglish
Title of host publication2nd North American Rock Mechanics Symposium, NARM 1996
Editors Hassani, Mitri, Aubertin
PublisherAmerican Rock Mechanics Association (ARMA)
Pages1161-1168
Number of pages8
ISBN (Print)905410838X, 9789054108382
Publication statusPublished - 1 Jan 1996
Event2nd North American Rock Mechanics Symposium, NARM 1996 - Montreal, Canada
Duration: 19 Jun 199621 Jun 1996

Publication series

Name2nd North American Rock Mechanics Symposium, NARM 1996

Conference

Conference2nd North American Rock Mechanics Symposium, NARM 1996
Country/TerritoryCanada
CityMontreal
Period19/06/9621/06/96

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