A Simplified Pore Size Distribution Apparatus

Abstract

Introduction In the intensive analysis of core samples from oil reservoirs, there is a recognized need for pore size distribution data. Such data, if collected with adequate precision and in sufficient quantity, should contribute to a better interpretation of fluid flow phenomena than is now possible from a knowledge of permeability and porosity data alone. It is hoped, for instance, that pore size distribution data may eventually provide a useful aid for predicting whether a water flood, or other secondary recovery methods, will be successful in a given reservoir. Apparatus for measuring pore size distribution by mercury injection at pressures ranging from 0 to 2,000 psi have been described in the literature. All of these apparatus are somewhat complex and fairly expensive. Furthermore, the calibration of some of the apparatus is not always easy. Great difficulty, for instance, was experienced in obtaining reproducible pressure-volume correction data for the mercury pump shown in one of the references. An apparatus was therefore developed which was less complicated and less expensive than those of previously described designs. This apparatus is, in some respects, an improved version of a previously described low pressure apparatus (maximum pressure 150 psi) which did not employ a mercury pump but instead used a precision bore glass tube for measuring the injected volumes. Tests were performed with the apparatus from vacuum to 2,000 psi and it was observed that the apparatus furnished reproducible pressure-volume correction data. In addition, it was noted that the maximum correction was small, precision of measurement was high, and operation of the entire apparatus was relatively easy. Although the apparatus was designed exclusively for samples of 1 in. diameter and 1 in. length or smaller, it could be modified without much difficulty for larger samples, if desired.