1962 Paper C

AN ANALYSIS OF THE FORMATION RESISTIVITY FACTOR-POROSITY RELATIONSHIP OF SOME ASSUMED PORE GEOMETRIES

Guy Towle - Welex a Division of Halliburton

ABSTRACT

Numerous investigations have been made of the relationship between formation resistivity factor and porosity of reservoir rocks. One of the most widely used expressions of this relationship is the familiar Archie equation,

F=Ø-m

whereby "m" is adjusted to make the expression fit measured data.

The purpose of this paper is to analyze a system of rock particles with consideration given to pore geometry as well as tortuosity. The pore systems considered are:

(1) mutually perpendicular intersecting tubes
(2) mutually perpendicular intersecting planes
(3) vugs
(4) tubes and vugs
(5) planes and vugs

The study indicates that for these systems, pore geometry exerts a large influence on the F-Ø relationship. The cementation factor, m, of a pore system is related to the vugginess of the system as well as to the tortuosity.

Some of the characteristics of natural rocks can be explained with the synthetic pore systems developed in this paper.