1965 Paper II-A

FEATURE ARTICLE

CALCULATION OF USEFUL POROSITY IN SHALY SANDSTONES

A. HOSSIN COMPAGNIE FRANÇAISE DES PÉTROLES (Paris)

ABSTRACT

Porosity determination of a shaly sandstone is bound to be altered by interstitial clay.

Now the effect of that clay is different according to the procedure of measurement employed.

Advantage in take from this « separation » between processes to calculate the useful porosity and, in addition, the clay percentage.

Basic data entering in calculation may be either direct readings from porosity diagrams (induced Neutron radio-activity, velocity or density measurements), or quantities worked out from these readings.

In both cases, calibration of diagrams in terms of porosity with the help of measured porosities on cores and estimation of clay percentages are required.