# US 12,595,725 B2 · Oil displacement method for an ultra-high water-cut reservoir > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,595,725 B2 - Document ID: US12595725B2 - Status: Granted - Kind: B2 - Application number: 18/897,603 - Filed: 2024-09-26 - Published: 2026-01-15 - Granted: 2026-04-07 - Earliest claimed: 2024-07-12 - Assignees: China University of Petroleum-Beijing - Applicants: China University of Petroleum-Beijing - Inventors: Kaoping Song; Bingyu Ji; Hongtao Fu; Zhaojie Song - Web page: https://patentgrep.com/patent/US12595725B2 ## CPC - E21B 43/164: {Injecting CO2 or carbonated water (in combination with organic material C09K8/594)} - E21B 43/20: Displacing by water - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract An oil displacement method for an ultra-high water-cut reservoir, including the following steps: injecting water into the reservoir to carry out a water flooding until water cut of the reservoir is greater than 90%; injecting a polymer solution and a supercritical carbon dioxide oil displacement agent, respectively; injecting water to carry out water flooding after injection of the polymer solution or the supercritical carbon dioxide oil displacement agent is completed; where injection amounts of both the polymer solution and the supercritical carbon dioxide oil displacement agent are not less than 0.1 PV, and a total injection amount of the polymer solution and the supercritical carbon dioxide oil displacement agent is 0.3-1.2 PV; and a viscosity ratio of the polymer solution to a crude oil in the reservoir is 1:(0.8-10), and a viscosity ratio of the supercritical carbon dioxide oil displacement agent to the crude oil in the reservoir is 1:(10-800). ## Claims ### Claim 1 An oil displacement method for an ultra-high water-cut reservoir having a water cut greater than 90%, comprising the following steps: (1) injecting water into the reservoir to carry out a water flooding until water cut of the reservoir is greater than 90%; (2) injecting a polymer solution and a supercritical carbon dioxide oil displacement agent, respectively; (3) injecting water to carry out water flooding, after injection of the polymer solution or the supercritical carbon dioxide oil displacement agent is completed; wherein injection amounts of both the polymer solution and the supercritical carbon dioxide oil displacement agent are not less than 0.1 PV, and a total injection amount of the polymer solution and the supercritical carbon dioxide oil displacement agent is 0.3-1.2 PV; and a viscosity ratio of the polymer solution to crude oil in the reservoir is 1:(0.8-10), and a viscosity ratio of the supercritical carbon dioxide oil displacement agent to the crude oil in the reservoir is 1:(10-800). ### Claim 2 (depends on 1) The oil displacement method for an ultra-high water-cut reservoir according to claim 1, wherein a viscosity of the polymer solution is not less than 1 mPa·s; and/or, a viscosity of the supercritical carbon dioxide oil displacement agent is greater than a viscosity of pure supercritical carbon dioxide and less than a viscosity of the crude oil in the reservoir. ### Claim 3 (depends on 2) The oil displacement method for an ultra-high water-cut reservoir according to claim 2, wherein the injection amount of the polymer solution is 0.1-0.6PV, and/or the injection amount of the supercritical carbon dioxide oil displacement agent is 0.1-0.6PV. ### Claim 4 (depends on 3) The oil displacement method for an ultra-high water-cut reservoir according to claim 3, wherein step (2) is performed in multiple cycles; the injection amount of the polymer solution is 0.05-0.2PV, and the injection amount of the supercritical carbon dioxide oil displacement agent is 0.05-0.2PV. ### Claim 5 (depends on 2) The oil displacement method for an ultra-high water-cut reservoir according to claim 2, wherein step (2) is performed in multiple cycles; the injection amount of the polymer solution is 0.05-0.2PV, and the injection amount of the supercritical carbon dioxide oil displacement agent is 0.05-0.2PV. ### Claim 6 (depends on 2) The oil displacement method for an ultra-high water-cut reservoir according to claim 2, wherein an internal pressure of the reservoir is less than a miscible pressure of the supercritical carbon dioxide oil displacement agent and the crude oil. ### Claim 7 (depends on 2) The oil displacement method for an ultra-high water-cut reservoir according to claim 2, wherein the polymer solution comprises a polymer and water; and the polymer comprises at least one of xanthan gum, crosslinked polymer, hydrophobic associated polymer, comb polymer, and star polymer. ### Claim 8 (depends on 2) The oil displacement method for an ultra-high water-cut reservoir according to claim 2, wherein the polymer solution further comprises a surfactant and a basic compound; the surfactant comprises at least one of non-ionic surfactant, anionic surfactant and zwitterionic surfactant; and the basic compound comprises at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, and ammonium hydroxide. ### Claim 9 (depends on 8) The oil displacement method for an ultra-high water-cut reservoir according to claim 8, wherein an average molecular weight of the polymer is 3 million to 21 million. ### Claim 10 (depends on 2) The oil displacement method for an ultra-high water-cut reservoir according to claim 2, wherein the supercritical carbon dioxide oil displacement agent comprises supercritical carbon dioxide and a base solution dissolved in the supercritical carbon dioxide, and the base solution comprises a thickening agent, a cosolvent and water; in the base solution, a mass percentage content of the thickening agent is 0.05-3 wt %, a mass percentage content of the cosolvent is 0.05-6 wt %, and a balance is water; and the cosolvent comprises at least one of kerosene, ether, and n-decane. ### Claim 11 (depends on 10) The oil displacement method for an ultra-high water-cut reservoir according to claim 10, wherein the thickening agent comprises at least one of siloxane-based thickening agent and hydrocarbon-based thickening agent; the siloxane-based thickening agent comprises at least one of a compound represented by Formula 1, a compound represented by Formula 2, and a compound represented by Formula 3, in Formula 1, x and y are each independently selected from a positive integer; in Formula 2, i, j, and k are each independently selected from a positive integer; and in Formula 3, h is selected from a positive integer; and the hydrocarbon-based thickening agent comprises at least one of a compound represented by Formula 4, a compound represented by Formula 5, and a compound represented by Formula 6, in Formula 4, a, b, and c are each independently selected from a positive integer; in Formula 5, n is selected from a positive integer; and in Formula 6, m is selected from a positive integer. ### Claim 12 (depends on 1) The oil displacement method for an ultra-high water-cut reservoir according to claim 1, wherein the injection amount of the polymer solution is 0.1-0.6PV, and/or the injection amount of the supercritical carbon dioxide oil displacement agent is 0.1-0.6PV. ### Claim 13 (depends on 12) The oil displacement method for an ultra-high water-cut reservoir according to claim 12, wherein step (2) is performed in multiple cycles, the injection amount of the polymer solution is 0.05-0.2PV, and the injection amount of the supercritical carbon dioxide oil displacement agent is 0.05-0.2PV. ### Claim 14 (depends on 1) The oil displacement method for an ultra-high water-cut reservoir according to claim 1, wherein step (2) is performed in multiple cycles; the injection amount of the polymer solution is 0.05-0.2PV, and the injection amount of the supercritical carbon dioxide oil displacement agent is 0.05-0.2PV. ### Claim 15 (depends on 1) The oil displacement method for an ultra-high water-cut reservoir according to claim 1, wherein an internal pressure of the reservoir is less than a miscible pressure of the supercritical carbon dioxide oil displacement agent and the crude oil. ### Claim 16 (depends on 1) The oil displacement method for an ultra-high water-cut reservoir according to claim 1, wherein the polymer solution comprises a polymer and water, and the polymer comprises at least one of xanthan gum, crosslinked polymer, hydrophobic associated polymer, comb polymer, and star polymer. ### Claim 17 (depends on 1) The oil displacement method for an ultra-high water-cut reservoir according to claim 1, wherein the polymer solution further comprises a surfactant and a basic compound; the surfactant comprises at least one of non-ionic surfactant, anionic surfactant and zwitterionic surfactant; and the basic compound comprises at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, and ammonium hydroxide. ### Claim 18 (depends on 17) The oil displacement method for an ultra-high water-cut reservoir according to claim 17, wherein an average molecular weight of the polymer is 3 million to 21 million. ### Claim 19 (depends on 1) The oil displacement method for an ultra-high water-cut reservoir according to claim 1, wherein the supercritical carbon dioxide oil displacement agent comprises supercritical carbon dioxide and a base solution dissolved in the supercritical carbon dioxide, and the base solution comprises a thickening agent, a cosolvent and water; in the base solution, a mass percentage content of the thickening agent is 0.05-3 wt %, a mass percentage content of the cosolvent is 0.05-6 wt %, and a balance is water; and the cosolvent comprises at least one of kerosene, ether, and n-decane. ### Claim 20 (depends on 19) The oil displacement method for an ultra-high water-cut reservoir according to claim 19, wherein the thickening agent comprises at least one of siloxane-based thickening agent and hydrocarbon-based thickening agent; the siloxane-based thickening agent comprises at least one of a compound represented by Formula 1, a compound represented by Formula 2, and a compound represented by Formula 3, in Formula 1, x and y are each independently selected from a positive integer; in Formula 2, i, j, and k are each independently selected from a positive integer; and in Formula 3, h is selected from a positive integer; and the hydrocarbon-based thickening agent comprises at least one of a compound represented by Formula 4, a compound represented by Formula 5, and a compound represented by Formula 6, in Formula 4, a, b, and c are each independently selected from a positive integer; in Formula 5, n is selected from a positive integer; and in Formula 6, m is selected from a positive integer.