# US 4,393,936 A · Method for the enhanced recovery of oil and natural gas > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,393,936 A - Document ID: US4393936A - Status: Granted - Kind: A - Application number: 06/303,957 - Filed: 1981-09-21 - Granted: 1983-07-19 - Earliest claimed: 1981-09-21 - Assignees: Union Oil Company of California - Inventors: Virgil A. Josendal - Web page: https://patentgrep.com/patent/US4393936A ## CPC - E21B 43/16: Enhanced recovery methods for obtaining hydrocarbons - C09K 8/594: Compositions used in combination with injected gas {, e.g. CO2 orcarbonated gas}(C09K8/592 takes precedence) - E21B 43/164: {Injecting CO2 or carbonated water (in combination with organic material C09K8/594)} - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE ## Abstract A method for the enhanced recovery of both natural gas and liquid petroleum from hydrocarbon-containing subterranean formations, particularly dipping subterranean formations, by the consecutive steps of introducing a gaseous displacement fluid to recover natural gas and thereafter introducing an oil-miscible displacement fluid to recover undrained oil and/or other liquid petroleum. ## Claims ### Claim 1 A method for the recovery of hydrocarbons from a subterranean formation containing both natural gas and liquid petroleum, said formation having an upper first zone containing said natural gas, said method comprising the steps of: (a) introducing a gaseous displacement fluid through a first well communicating with said first zone so as to displace at least a portion of said natural gas from said first zone to a second well and recovering said portion of natural gas through said second well; and (b) thereafter introducing an oil-miscible displacement fluid into said formation at a selected pressure so as to displace at least a portion of said liquid petroleum to a recovery well, and recovering said portion of liquid petroleum through said recovery well. ### Claim 2 (depends on 1) The method defined in claim 1 wherein said gaseous displacement fluid is nitrogen or a nitrgen-containing gas. ### Claim 3 (depends on 1) The method defined in claim 1 wherein said oil-miscible displacement fluid is selected from the group consisting of carbon dioxide, nitrous oxide and sulfur oxides. ### Claim 4 (depends on 1) The method defined in claim 1 wherein said second well communicates with said first zone at a position which is at a higher elevation than the position at which said first well communicates with said first zone. ### Claim 5 (depends on 4) The method as defined in claim 4 wherein, at the conditions prevailing in said first zone during step (a), said gaseous displacement fluid has a density greater than or equal to the density of said natural gas. ### Claim 6 (depends on 4) The method defined in claim 4 wherein said first well is in fluid communication with said formation at about the interface between said first zone and an underlying second zone containing liquid petroleum. ### Claim 7 (depends on 1) The method defined in claim 1 wherein said first well communicates with said first zone at a position which is at a higher elevation than the position at which said second well communicates with said first zone. ### Claim 8 (depends on 7) The method defined in claim 7 wherein, at the conditions prevailing in said first zone during step (a), said gaseous displacement fluid has a density less than or equal to the density of said natural gas. ### Claim 9 (depends on 7) The method defined in claim 7 wherein said second well is in fluid communication with said formation at about the interface between said first zone and an underlying second zone containing liquid petroleum. ### Claim 10 (depends on 1) The method defined in claim 1 wherein said subterranean formation has a second zone containing liquid petroleum underlying said first zone and wherein said portion of liquid petroleum recovered during said step (b) includes at least some liquid petroleum from said second zone. ### Claim 11 (depends on 10) The method defined in claim 10 wherein during step (b) said oil-miscible displacement fluid is injected into said second well so as to form a miscible transition fluid with at least a portion of said liquid petroleum. ### Claim 12 (depends on 11) The method defined in claim 11 wherein said method further comprises the step of (c) thereafter injecting a drive fluid through said second well so as to displace at least a portion of said miscible transition fluid to said recovery well. ### Claim 13 (depends on 12) A method as defined in claim 12 wherein said drive fluid comprises at least a portion of said gaseous displacement fluid which has been recovered from said first zone for recycle. ### Claim 14 (depends on 1) The method defined in claim 1 wherein said liquid petroleum comprises undrained oil contained in said first zone and wherein said portion of liquid petroleum recovered during said step (b) includes at least some of said undrained oil. ### Claim 15 (depends on 14) The method as defined in claim 14 wherein during step (b) said oil-miscible displacement fluid is injected into said second well to displace said portion of said undrained oil for recovery through a well which communicates with said formation at a position which is at a lower elevation than the position at which said second well communicates with said formation. ### Claim 16 (depends on 14) The method defined in claim 14 wherein during step (b) said oil-miscible displacement fluid is injected into said second well so as to form a miscible transition fluid with at least a portion of said undrained oil. ### Claim 17 (depends on 16) The method defined in claim 16 wherein said method further comprises the step of (c) thereafter injecting a drive fluid through said second well so as to displace at least a portion of said miscible transition fluid to said recovery well. ### Claim 18 (depends on 14) A method as defined in claim 14 wherein said drive fluid comprises at least a portion of said gaseous displacement fluid which has been recovered from said first zone for recycle. ### Claim 19 A method for the recovery of natural gas, undrained oil, and liquid petroleum from a dipping subterranean hydrocarbon-containing formation having an updip first zone containing natural gas and undrained oil overlying a second zone containing liquid petroleum, said method comprising the steps of: (a) injecting a gaseous displacement fluid through a first well into said first zone so as to displace at least a portion of said natural gas from said first zone to an updip second well and recovering said portion of natural gas through said second well, said gaseous displacement fluid being selected from the group consisting of nitrogen and nitrogen-containing gases and having a density which is greater than or equal to the density of said natural gas under the conditions prevailing in said first zone; and (b) thereafter injecting an oil-miscible displacement fluid into said first zone at a selected pressure so as to displace at least a portion of said undrained oil from said first zone and at least a portion of said liquid petroleum from said second zone to a downdip third well and recovering said portions of undrained oil and liquid petroleum through said third well, said oil-miscible displacement fluid being selected from the group consisting of carbon dioxide, nitrous oxide, and sulfur oxides. ### Claim 20 A method for the recovery of natural gas, undrained oil and liquid petroleum from a dipping subterranean hydrocarbon-containing formation having an updip first zone containing natural gas and undrained oil overlying a second zone containing liquid petroleum, said method comprising the steps of: (a) injecting a gaseous displacement fluid through a second well into said first zone so as to displace at least a portion of said natural gas from said first zone to a downdip first well and recovering said portion of natural gas through said first well, said gaseous displacement fluid being selected from the group consisting of nitrogen and nitrogen-containing gases and having a density which is less than or equal to the density of said natural gas under the conditions prevailing in said first zone; and (b) thereafter injecting an oil-miscible displacement fluid into said first zone at a selected pressure so as to displace at least a portion of said undrained oil from said first zone and at least a portion of said liquid petroleum from said second zone to a downdip third well and recovering said portions of undrained oil and liquid petroleum through said third well, said oil-miscible displacement fluid being selected from the group consisting of carbon dioxide, nitrous oxide, and sulfur oxides. ### Claim 21 (depends on 19, 20) The method defined in claim 19 or 20 wherein during step (b) said oil-miscible displacement fluid is injected through said second well so as to form a miscible transition fluid comprised of said undrained oil and said oil-miscible displacement fluid. ### Claim 22 (depends on 21) The method defined in claim 21 wherein following formation of said miscible transition fluid a gaseous drive fluid is introduced through said second well so as to displace said miscible transition fluid through said first zone and at least a portion of said second zone to said third well for recovery. ### Claim 23 (depends on 22) The method defined in claim 22 wherein said gaseous drive fluid comprises at least a portion of said gaseous displacement fluid which had been recovered from said first zone for recycle. ### Claim 24 (depends on 19, 20) The method defined in claim 19 or 20 wherein said first well is in fluid communication with said petroleum at about the interface of said first and second zones. ### Claim 25 (depends on 1, 19, 20) The method defined in claim 1, 19 or 20 wherein said selected pressure is between about the miscible displacement pressure in the absence of the gaseous displacement fluid and the miscible displacement pressure of the gaseous displacement fluid. ### Claim 26 A method for the recovery of natural gas, undrained oil, and liquid petroleum from a dipping subterranean hydrocarbon-containing formation having an updip first zone containing natural gas and undrained oil overlying a second zone containing liquid petroleum, said method comprising the steps of: (a) treating air so as to generate (1) a gaseous displacement fluid consisting essentially of nitrogen and (2) an oxidizing fluid consisting essentially of oxygen; (b) reacting said oxidizing fluid with carbonaceous matter to generate an oil-miscible displacement fluid comprising carbon dioxide; (c) injecting said gaseous displacement fluid into said first zone through a first well communicating with said first zone near the interface of said first and second zones so as to displace at least a portion of said natural gas from said first zone to an updip second well, and recovering said portion of natural gas through said second well, said gaseous displacement fluid having a density greater than or equal to the density of said natural gas under the conditions prevailing in said first zone; (d) thereafter injecting at least a portion of said oil-miscible displacement fluid into said first zone at a selected pressure so as to form a miscible transition fluid with at least a portion of said undrained oil, said selected pressure being between about the miscible displacement pressure in the absence of said gaseous displacement fluid and about the miscible displacement pressure of said gaseous displacement fluid; (e) thereafter injecting a drive fluid into said first zone so as to displace at least a portion of said miscible transition fluid and at least a portion of said liquid petroleum from said second zone to a downdip third well and recovering said portions of liquid petroleum and undrained oil through said third well. ### Claim 27 (depends on 1, 19, 20, 26) The method defined in claim 1, 19, 20 or 26 wherein said selected pressure is between about 0.8 times the miscible displacement pressure of said gaseous displacement fluid and about 1.05 times the miscible displacement pressure in the absence of said gaseous displacement fluid. ### Claim 28 (depends on 1, 19, 20, 26) The method defined in claim 1, 19, 20 or 26 wherein said selected pressure is between about 0.5 times the miscible displacement pressure of said gaseous displacement fluid and about 1.1 times the miscible displacement pressure in the absence of said gaseous displacement fluid.