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Elastic‐wave velocities in sandstones with non‐load‐bearing clay
Author(s) -
Gal Doron,
Dvorkin Jack,
Nur Amos
Publication year - 1999
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1999gl900106
Subject(s) - porosity , geology , bearing (navigation) , geotechnical engineering , quartz , elastic modulus , stiffness , mineralogy , materials science , composite material , paleontology , cartography , geography
The elastic moduli (and acoustic velocities) of shaley sandstones strongly depend on the amount of clay as well as on its position among sand grains. In many cases clay may fill pores without noticeably affecting the stiffness of the rock. Such clays are non‐load‐bearing. Here, the stiffness of the rock is determined primarily by the load‐bearing quartz frame. We examine several data sets and show that in this case a simple unique relation exists between the acoustic velocity and the porosity of the load‐bearing frame of the rock. This porosity can be calculated as the sum of the effective porosity (total porosity minus microporosity inside clay) and the volumetric fraction of clay in the rock. Also, it is the sum of the total porosity and the volumetric fraction of solid clay particles in the rock.