Methods of determining cation exchange sites occupied by crude oil and the wettability of cation exchange sites in rock core samples in a preserved state

Abstract

A method for determining properties of different cation exchange sites in a rock core sample, at a preserved state of the rock core sample may include providing a rock core sample that includes a plurality of indigenous exchangeable cations adsorbed onto the cation exchange sites, a plurality of cation exchange sites occupied by a crude oil, and one or more fluids occupying pore spaces in the rock core sample; subjecting the rock core sample to a plurality of coreflooding steps, the plurality of coreflooding step displacing the plurality of indigenous exchangeable cations, the crude oil, and the one or more fluids in at least three separate coreflooding steps to render the rock core sample clean of native components; determining an amount of indigenous exchangeable cations adsorbed onto the cation exchange sites; subjecting the rock core sample clean of native components to a plurality of coreflooding steps to determine a total amount of exchangeable cations adsorbed onto the cation exchange sites when the rock core sample is clean of native components; and determining at least one property of different cation exchange sites in the rock core sample at the preserved state based on the amount of indigenous exchangeable cations and the total amount of exchangeable cations.