DETERMINATION OF FREE VOLUME OF A ROCK SAMPLE USING HIGH PRESSURE ADSORPTION DATA

摘要

A method of characterizing free volume of a rock sample includes test operations that measure pressure decay data from stepwise pressurization of the rock sample with a test gas. An initial free volume of the rock sample is calculated as a function of the pressure decay data. An initial maximum storage capacity of the rock sample is derived as a function of the initial free volume of the rock sample. A volume of test gas adsorbed as a liquid is calculated based on the maximum storage capacity of the rock sample. An updated free volume of the rock sample is calculated based on the initial free volume and the volume of the test gas adsorbed as a liquid. An updated maximum storage capacity of the rock sample is derived as a function of the updated free volume. Calculations of the volume of test gas adsorbed as a liquid, the updated free volume and the updated maximum capacity of the rock sample can be repeated until the updated maximum storage capacity and the updated free volume converge respectively to give the maximum storage capacity and free volume of the rock sample.

主权项

1. A method of characterizing free volume of a rock sample including:
a) measuring pressure decay data from stepwise pressurization of the rock sample with a test gas; b) calculating an initial free volume of the rock sample as a function of the pressure decay data of a); c) deriving an initial maximum storage capacity of the rock sample as a function of the initial free volume of the rock sample calculated in b); d) calculating a volume of test gas adsorbed as a liquid based on the initial maximum storage capacity determined in c); e) calculating an updated free volume of the rock sample based on the initial free volume calculated in b) and the volume of the test gas adsorbed as a liquid calculated in d); f) deriving an updated maximum storage capacity of the rock sample as a function of the updated free volume calculated in e); g) processing the updated maximum storage capacity of the rock sample derived in f) in order to determine whether convergence of maximum storage capacity of the rock sample has been reached; h) in the event that convergence of the maximum storage capacity of the rock sample has not been reached, calculating a volume of test gas adsorbed as a liquid based on the updated maximum storage capacity determined in f) and iteratively repeating the operations of e) to g) based on the volume of test gas adsorbed as a liquid derived from the last updated maximum storage capacity until convergence of the maximum storage capacity of the rock sample has been reached; and i) in the event that convergence of the maximum storage capacity of the rock sample has been reached, equating the updated free volume of the rock sample from which the converged maximum storage capacity of the rock sample was determined to the free volume of the sample.