# US 2021/0333191 A1 · Methods of determining cation exchange sites in rock core samples > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0333191 A1 - Document ID: US20210333191A1 - Status: Published application - Kind: A1 - Application number: 16/859,035 - Filed: 2020-04-27 - Published: 2021-10-28 - Earliest claimed: 2020-04-27 - Assignees: Saudi Arabian Oil Company - Applicants: Saudi Arabian Oil Company - Inventors: Quan Chen - Web page: https://patentgrep.com/patent/US20210333191A1 ## CPC - G01N 15/082: {Investigating permeability by forcing a fluid through a sample} - E21B 49/02: by mechanically taking samples of the soil - G01N 33/241: {for hydrocarbon content} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract A method for determining properties of different cation exchange sites in a rock core sample may include providing a rock core sample that is in either a preserved state or a non-preserved state, wherein a preserved form of the rock core sample 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 and the one or more fluids in at least two separate coreflooding steps to render the rock core sample clean of indigenous exchangeable cations; and determining an amount of indigenous exchangeable cations adsorbed onto the cation exchange sites. ## Claims ### Claim 1 A method for determining properties of different cation exchange sites in a rock core sample, the method comprising: providing a rock core sample, wherein a preserved form of the rock core sample 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 and the one or more fluids in at least two separate coreflooding steps to render the rock core sample clean of indigenous exchangeable cations; and determining an amount of indigenous exchangeable cations adsorbed onto the cation exchange sites. ### Claim 2 (depends on 1) The method of claim 1, wherein the provided rock core sample is in a preserved state. ### Claim 3 (depends on 1) The method of claim 1, wherein the provided rock core sample is in a non-preserved state and wherein the method further comprises: displacing all native components out of the pore space of the rock core sample; subjecting the rock core sample clean of native components to a coreflooding steps to inject formation brine into the rock core sample; injecting a reservoir crude oil into the rock core sample until reaching irreducible water saturation and equilibrium between formation brine, the reservoir crude oil, and the cation exchange sites, such that rock core sample 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. ### Claim 4 (depends on 1) The method of claim 1, wherein the amount of indigenous exchangeable cations is quantified from an extract of an injection fluid upon completion of extraction by an analytical method. ### Claim 5 (depends on 1) The method of claim 1, wherein the subjecting the rock core sample to a plurality of coreflooding steps comprises: displacing the crude oil in the rock core sample with a formation brine until oil ceases production; displacing an excess of cations present in a plurality of interstitial pore spaces of the rock core sample by using a first organic solvent; and displacing the plurality of indigenous exchangeable cations from the cation exchange sites of the rock core sample with a first injection fluid until completion of extraction. ### Claim 6 (depends on 5) The method of claim 5, wherein the amount of indigenous exchangeable cations is quantified from an extract of the first injection fluid upon completion of extraction by an analytical method. ### Claim 7 (depends on 1) The method of claim 1, further comprising: determining a pore volume of the rock core sample. ### Claim 8 (depends on 4) The method of claim 4, wherein the injection fluid is an ammonium acetate solution. ### Claim 9 (depends on 4) The method of claim 4, wherein the first organic solvent is ethanol. ### Claim 10 (depends on 3) The method of claim 3, wherein displacing all native components out of the pore space of the rock core sample comprises: alternately injecting a second organic solvent and a third organic solvent, wherein the third organic solvent is the last injected to render the pore space of the rock core sample clean of native components. ### Claim 11 (depends on 10) The method of claim 10, wherein the second organic solvent is toluene and the third organic solvent is methanol. ### Claim 12 A method for determining an amount of indigenous exchangeable cations adsorbed onto cation exchange sites in a rock core sample, at a preserved state of the rock core sample, the method comprising: providing a rock core sample that includes at least a plurality of indigenous exchangeable cations adsorbed onto the cation exchange sites and a plurality of cation exchange sites occupied by a crude oil; displacing the crude oil in the rock core sample with a formation brine until oil ceases production; displacing an excess of cations present in a plurality of interstitial pore spaces of the rock core sample by using a first organic solvent; displacing the plurality of indigenous exchangeable cations from the cation exchange sites of the rock core sample with an injection fluid until completion of extraction; and calculating an amount of indigenous exchangeable cations adsorbed onto the cation exchange sites. ### Claim 13 (depends on 12) The method of claim 12, wherein the amount of indigenous exchangeable cations is quantified from extracts of the injection fluid upon completion of extraction by analytical methods. ### Claim 14 (depends on 12) The method of claim 12, further comprising: determining a pore volume of the rock core sample. ### Claim 15 A method for determining an amount of indigenous exchangeable cations adsorbed onto cation exchange sites in a rock core sample, at a non-preserved state of the rock core sample, the method comprising: providing a rock core sample in a non-preserved state; displacing all native components out of the pore space of the rock core sample by alternately injecting a first organic solvent and a second organic solvent, wherein the second organic solvent is the last injected; displacing the second organic solvent with a formation brine to adsorb a plurality of exchangeable cations onto the different cation exchange sites of the rock core sample; injecting a reservoir crude oil into the rock core sample until reaching irreducible water saturation and equilibrium between formation brine, the reservoir crude oil, and the cation exchange sites, such that rock core sample 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; displacing the reservoir crude oil in the rock core sample with formation brine until oil ceases production; displacing an excess of cations present in a plurality of interstitial pore spaces of the rock core sample by using a third organic solvent; displacing the plurality of indigenous cations adsorbed onto the cation exchange sites of the rock core sample with a second injection fluid until completion of extraction; and calculating an amount of indigenous exchangeable cations adsorbed onto the cation exchange sites. ### Claim 16 (depends on 15) The method of claim 15, wherein the amount of indigenous exchangeable cations is quantified from extracts of the injection fluid upon completion of extraction by analytical methods. ### Claim 17 (depends on 15) The method of claim 15, further comprising: determining a pore volume of the rock core sample.