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What is the significance of pore pressure in a saturated shale layer?
Author(s) -
Gonçalvès J.,
RousseauGueutin P.,
de Marsily G.,
Cosenza P.,
Violette S.
Publication year - 2010
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2009wr008090
Subject(s) - disjoining pressure , oil shale , swelling , pore water pressure , diffusion , volume (thermodynamics) , porosity , mineralogy , geotechnical engineering , geology , clay minerals , porosimetry , porous medium , materials science , composite material , thermodynamics , wetting , paleontology , physics
Electrostatic interactions, associated with negatively charged surfaces of clay minerals, produce a so‐called “disjoining pressure” when diffuse layers overlap, i.e., at low porosity. Disjoining pressure is the pressure difference between the water in the clay pore space and that in a bulk solution at the same depth. Another widely used concept in clay‐rocks is the “swelling pressure.” It corresponds in fact to the macroscopic average of the disjoining pressure. This study proposes to determine the value of the swelling pressure of a natural material by a simple volume‐averaging approach of the disjoining pressure, calculated for each clay mineral present in the material. The swelling pressure, which is dependent on the salinity of the pore fluid, is introduced into a hydrochemomechanical coupling, yielding a more general pressure diffusion equation. The results are compared to swelling pressure measurements for natural shale samples. The implications of this swelling pressure for water pressure measurements in natural formations are also discussed.