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Changes in geophysical properties caused by fluid injection into porous rocks: analytical models
Author(s) -
Pride Steven R.,
Berryman James G.,
Commer Michael,
Nakagawa Seiji,
Newman Gregory A.,
Vasco Donald W.
Publication year - 2017
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/1365-2478.12435
Subject(s) - permeability (electromagnetism) , geology , anisotropy , population , isotropy , porosity , porous medium , electrical resistivity and conductivity , conductivity , petrophysics , materials science , geotechnical engineering , elasticity (physics) , mineralogy , mechanics , composite material , physics , chemistry , optics , biochemistry , demography , quantum mechanics , membrane , sociology
Analytical models are provided that describe how the elastic compliance, electrical conductivity, and fluid‐flow permeability of rocks depend on stress and fluid pressure. In order to explain published laboratory data on how seismic velocities and electrical conductivity vary in sandstones and granites, the models require a population of cracks to be present in a possibly porous host phase. The central objective is to obtain a consistent mean‐field analytical model that shows how each modeled rock property depends on the nature of the crack population. The crack populations are described by a crack density, a probability distribution for the crack apertures and radii, and the averaged orientation of the cracks. The possibly anisotropic nature of the elasticity, conductivity, and permeability tensors is allowed for; however, only the isotropic limit is used when comparing to laboratory data. For the transport properties of conductivity and permeability, the percolation effect of the crack population linking up to form a connected path across a sample is modeled. However, this effect is important only in crystalline rock where the host phase has very small conductivity and permeability. In general, the importance of the crack population to the transport properties increases as the host phase becomes less conductive and less permeable.