Recovery of Oil from Reservoirs (Patent No: 894605)

Inventor: Amoco Canada Petroleum Company

Location: Calgary

Comments: N/A

Description: THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of recovering crude oil from a subterranean oil reservoir through a producing well which comprises the steps of; injecting a fluid solvent into said reservoir through an injection well, said solvent having a substantial degree of miscibility with said crude oil, being liquefiable at the temperature of said reservoir and being injected in an amount equal to between about 3% and about 10% of the reservoir pore volume to produce within said reservoir in the neighborhood of said injection well an oil solvent transition zone, a front or bank of crude oil, and a second bank contiguous to said transition zone consisting essentially of pure solvent; maintaining a pressure within said reservoir during injection of said solvent to establish said bank of said solvent as a liquid; thereafter injecting into said reservoir through the injection well, at a pressure and in an amount sufficient to maintain and drive said liquid bank toward said producing well, a fluid drive agent which is substantially miscible with and forms a second transition zone with said solvent and substantially immiscible with said crude oil under said temperature and pressure conditions in the reservoir; and withdrawing said crude oil from said producing well.

2. A method as claimed in claim 1 wherein the fluid drive agent is normally liquid.

3. A method as claimed in claim 2 wherein the solvent is miscible with water and the fluid drive agent is water.

4. A method as claimed in claim 3 wherein the solvent is acetone, isopropyl alcohol, n-propyl alcohol, allyl alcohol, diacetone alcohol, 2-butoxyethanol, 2-(2-butoxyethoxy) ethanol, dioxane, or ethyl alcohol.

5. A method as claimed in claim 4 wherein the injection of water is continued until substantially all of the crude oil and of said solvent is recovered from the reservoir.

6. A method as claimed in claim 3, 4 or 5 wherein the reservoir is a porous subsurface formation containing a non-wetting phase which is resistant to direct displacement by water flow and which substantially restricts the flow of water through the formation.

7. In the method of producing oil from a subterranean oil reservoir wherein the reservoir oil is replaced by an ultimate displacing fluid which is immiscible with said oil at reservoir temperature and pressure, said reservoir having in communication therewith at least one injection well and one production well, the steps of injecting into said reservoir through said at least one injection well, in an amount equal to between 3% and 10% of the reservoir pore volume, a slug of a first solvent fluid which is substantially miscible with the reservoir oil and miscible with said ultimate displacing fluid at said temperature and pressure, thereafter injecting into said reservoir through said injection well said ultimate· displacing fluid whereby to force said first solvent fluid through said reservoir in contact with the reservoir oil and withdrawing reservoir oil from said reservoir through said production well.

8. In the method of producing oil from a subterranean oil reservoir wherein the reservoir oil is replaced by an ultimate displacing fluid which is immiscible with said oil at reservoir temperature and pressure, said reservoir having in communication therewith at least one injection well and one production well, the steps of injecting into said reservoir through said at least one injection well, in an amount equal to between 3% and 10% of the reservoir pore volume, a slug of a first solvent fluid which is substantially miscible with the reservoir oil and is also miscible with said ultimate displacing fluid at reservoir temperature and pressure, thereafter injecting into said reservoir through said injection well said ultimate displacing fluid whereby to force said first solvent fluid through said reservoir in contact with the reservoir oil, simultaneously with the injecting steps maintaining pressure on the reservoir sufficiently high to insure miscibility between the first solvent fluid and the reservoir oil and between the first solvent fluid and the ultimate displacing fluid, and withdrawing reservoir oil from said reservoir through said production well.

9. In the method of producing oil from a subterranean oil reservoir wherein the reservoir oil is ultimately replaced by a gas comprising principally methane which is immiscible with said oil at reservoir temperature and pressure, said reservoir having in communication therewith at least one injection well and one production well the steps of injecting into said reservoir through said at least one injection well in an amount equal to between 3% and 10% of the reservoir pore volume, a slug of a first solvent fluid which is miscible with the reservoir oil and also is miscible with said gas at reservoir temperature and pressure thereafter injecting into said reservoir through said injection well said gas whereby to force said first solvent fluid through said reservoir in contact with the reservoir oil, simultaneously with said injecting steps maintaining pressure on the reservoir sufficiently high to insure miscibility between the first solvent fluid and the reservoir oil and between the first solvent fluid and the ultimate displacing fluid and withdrawing reservoir oil from said reservoir through said production well.

10. In the method of producing oil from a subterranean oil reservoir wherein the reservoir oil is ultimately replaced by a gas comprising principally ethane which is immiscible with said oil at reservoir temperature and pressure, said reservoir having in communication therewith at least one injection well and one production well, the steps of injecting into said reservoir through said at least one injection well, in an amount equal to between 3% and 10% of the reservoir pore volume, a slug of a first solvent fluid, comprising principally hydrocarbons higher than methane and lower than pentane. which is miscible with the reservoir oil and also is miscible with said gas at reservoir temperature and pressure, thereafter injecting into said reservoir through said injection well said gas whereby to force said first solvent fluid through said reservoir in contact with the reservoir oil, simultaneously with said injecting steps maintaining pressure on the reservoir sufficiently high to insure miscibility between the first solvent fluid and the reservoir oil and between the first solvent fluid and the ultimate displacing fluid, and withdrawing reservoir oil from said reservoir through said production well.

11. In the method of producing oil from a subterranean oil reservoir wherein the reservoir oil is ultimately replaced by a gas comprising principally methane which is immiscible with said oil at reservoir temperature and pressure, said reservoir having in communication therewith at least one injection well and one production well, the steps of injecting into said reservoir through said at least one injection well, in an amount equal to between 3% and 10% of the reservoir pore volume, a slug of a first solvent fluid comprising propane, thereafter injecting into said reservoir through said injection well said gas whereby to force said first solvent fluid through said reservoir in contact with the reservoir oil, simultaneously with said injecting steps maintaining pressure on the reservoir sufficiently high to insure miscibility between the first solvent fluid and the reservoir oil and between the first solvent fluid and the ultimate displacing fluid, and withdrawing reservoir oil from said reservoir through said production well.

12. In the method of producing oil from a subterranean oil reservoir wherein the reservoir oil is ultimately replaced by water, which is immiscible with said oil at reservoir temperature and pressure, said reservoir having in communication therewith at least one injection well and one production well, the steps of injecting into said reservoir through said at least one injection well, in an amount equal to between 3% and 10% of the reservoir pore volume, a slug of a first fluid which is miscible with the reservoir oil and also is miscible with said water at reservoir temperature and pressure, thereafter injecting into said reservoir through said injection well said water whereby to force said first fluid through said reservoir in contact with the reservoir oil and withdrawing reservoir oil from said reservoir through said production well.

13. In the method of producing oil from a subterranean oil reservoir wherein the reservoir oil is ultimately replaced by water, which is immiscible with said oil at reservoir temperature and pressure, said reservoir having in communication therewith at least one injection well and one production well, the steps of injecting into said reservoir through said at least one injection well, in an amount equal to between 3% and 10% of the reservoir pore volume, a slug of a first fluid, comprising an oil-and-water-soluble alcohol, which is miscible with the reservoir oil and also is miscible with said water at reservoir temperature and pressure, thereafter injecting into said reservoir through said injection well said water whereby to force said first fluid through said reservoir in contact with the reservoir oil, and withdrawing reservoir oil from said reservoir through said production well.

14. In the method of producing oil from a subterranean oil reservoir wherein the reservoir oil is ultimately replaced by water, which is immiscible with said oil at reservoir temperature and pressure, said reservoir having in communication therewith at least one injection well and one production well, the steps of injecting into said reservoir through said at least one injection well, in an amount equal to between 3% and 10% of the reservoir pore volume, a slug of a first fluid, comprising normal propyl alcohol, which is miscible with the reservoir oil and also is miscible with said water at reservoir temperature and pressure, thereafter injecting into said reservoir through said injection well said water whereby to force said first fluid through said reservoir in contact with the reservoir oil, and withdrawing reservoir oil from said reservoir through said production well.

15. In the method of producing oil from a subterranean oil reservoir wherein the reservoir oil is ultimately replaced by water, which is immiscible with said oil at reservoir temperature and pressure, said reservoir having in communication therewith at least one injection well and one production well, the steps of injecting into said reservoir through said at least one injection well, in an amount equal to between 3% and 10% of the reservoir pore volume, a slug of a first fluid, comprising isopropyl alcohol which is miscible with the reservoir oil and also is miscible with said water at reservoir temperature and pressure, thereafter injecting into said reservoir through said injection well said water whereby to force said first fluid through said reservoir in contact with the reservoir oil, and withdrawing reservoir oil from said reservoir through said production well.

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE

16. A method as claimed in Claim 1 wherein a mixture of the drive agent and the solvent is withdrawn from the second transition zone through a producing well located in the reservoir in the second transition zone, whereby the length of the second transition zone is substantially reduced.

17. A method as claimed in Claim 16 in which at least a part of the solvent is separated from said mixture and injected into said bank of substantially pure solvent by injecting said solvent into a well located in said reservoir within the bank of substantially pure solvent.

18. A method as claimed in Claim 16 or 17 in which at least a part of the drive agent is separated from the mixture and injected into the zone containing the drive agent by injecting said drive agent into a well located in said reservoir within said zone containing substantially pure drive agent.

19. A method as claimed in Claim 16 or 17 in which the solvent is L.P.G . and the drive agent is a predominantly hydrocarbon gas.