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ESTIMATION OF IRREDUCIBLE WATER SATURATION AND EFFECTIVE PORE SIZE OF MUDSTONES
Author(s) -
Honda Hiromi,
Magara Kinji
Publication year - 1982
Publication title -
journal of petroleum geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.725
H-Index - 42
eISSN - 1747-5457
pISSN - 0141-6421
DOI - 10.1111/j.1747-5457.1982.tb00551.x
Subject(s) - saturation (graph theory) , water saturation , porosity , geology , lithology , mineralogy , hydrocarbon , soil science , geotechnical engineering , petrology , chemistry , organic chemistry , mathematics , combinatorics
A theoretical consideration of immobile water saturation in mudstone is made by means of a capillary model of a porous medium using the air and water absolute permeabilities of a sample. The calculated values of immobile water saturation of the Tertiary mudstones from Japan tend to support a generally‐accepted concept; virtually all the water in mudstones is irreducible. Immobile or irreducible water saturation increases gradually with decrease of porosity of mudstones; 15% porosity is a critical value beyond which mudstones contain 100% immobile water in the pores. Pore sizes of the mudstones estimated by the same model are considerably greater than those estimated by Welte (1972), and are more comparable with Momper's (1978) atypical pore size range of mudstone. The result of analysis indicates that radius of principal pores of the mudstones, which are effective on fluid flow, ranges from about 0.1–0.5 μm. The result thus suggests that even relatively large hydrocarbon molecules can effectively pass through the rock.