Polyol for improving sweep efficiency in oil reservoirs

Abstract

The proposed method is an improved chemical flooding of an oil reservoir, especially one containing heavy oil or bitumen, that is cheaper than traditional chemical flooding techniques. This is obtained by viscosifying the displacing phase with a polyol, such as glycerol and/or its derivatives. Glycerol and its derivatives are an excellent additive because they are cheaper than the more commonly used chemicals, work only as a viscosifying agent, do not alter the reservoir properties, and have a wide range of viscosity facilitating the displacement of a wider range of heavy oils. This improved chemical flooding can be used with any other enhanced oil recovery technique, including thermal means, solvent assisted and polymer floodings.

Claims

1. A method of improving oil recovery, comprising: a) measuring the viscosity of oil in a reservoir; b) selecting a fluid consisting essentially of a polyol and yielding a mobility ratio (M) of less than; c) injecting said fluid into at least one injection well in a reservoir, said injection well being in fluid communication with at least one producing well; d) displacing the oil in said reservoir using said fluid; and e) producing said oil and said fluid in said at least one producing well.

2. The method of claim 1, wherein said polyol consists of glycerol, polyglycerol, or a derivative thereof.

3. The method of claim 2, wherein said polyol is chosen from the following group: glycerol, diglycerol, polyglycerol-3, polyglycerol-4, or derivatives or mixtures thereof.

4. The method of claim 1, wherein said polyol is up to a 100% wt glycerol, diglycerol, polyglycerol-3, or polyglycerol-4.

5. A process for displacing oil within an oil bearing formation penetrated by at least one injection well in fluid communication with at least one producing well, comprising measuring the viscosity of oil in a reservoir, selecting a fluid consisting essentially of a polyol and yielding a mobility ratio (M) of less than 1, and injecting from about up to 1.0 pore volume of said fluid into said formation through said at least one injection well to move said oil to at least one production well.

6. The process of claim 5, wherein said polyol is chosen from the following group: glycerol, diglycerol, polyglycerol-3, polyglycerol-4, derivatives or mixtures thereof.

7. A method for recovering oil from a subterranean reservoir, said reservoir being penetrated by at least one injection well and by at least one production well, both wells being in fluid communication with at least a portion of the subterranean reservoir, comprising: a) measuring the viscosity of oil in a reservoir; b) selecting a fluid consisting essentially of a polyol and yielding a mobility ratio (M) of less than 1, said polyol selected from glycerol, diglycerol, polyglycerol-3, polyglycerol-4, derivatives or mixtures thereof; c) injecting said fluid into the reservoir via said injection well; and d) recovering oil displaced by said fluid.

8. A method of improving oil recovery from a reservoir, said reservoir being penetrated by at least one injection well and by at least one production well, both wells being in fluid communication with each other and at least a portion of the subterranean reservoir, comprising: a) measuring the viscosity of oil in a reservoir; b) performing a thermal enhanced oil recovery technique on said reservoir; c) measuring the viscosity of oil in a reservoir after said thermal enhanced oil recovery technique; d) selecting a fluid consisting essentially of a polyol and yielding a mobility ratio (M) of less than 1, said polyol selected from glycerol, diglycerol, polyglycerol-3, polyglycerol-4, or derivatives thereof; e) injecting said fluid into said reservoir, via said injection well; and f) recovering oil displaced by said fluid.

9. The method of claim 8, wherein said thermal enhanced oil recovery technique is SAGD, CSS, steam flood, VAPEX, ES-SAGD/SAP, SLAG or a combination thereof.

10. A method of improving sweep efficiency of a reservoir, wherein a sweep fluid is injected into a reservoir to drive oil towards a production well, the improvement comprising measuring the viscosity of oil in a reservoir, selecting a polyol that yields a mobility ratio (M) of less than 1 in said reservoir, said polyol consisting essentially of glycerol, diglycerol, polyglycerol or mixtures thereof as the sweep fluid, wherein said sweep fluid consists essentially of said polyol.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1. Schematic of a polyol-based chemical flood using a five-spot aerial pattern.

(2) FIG. 2 Showing a SAGD technique that can be combined with a polyol sweep, wherein gravity drainage can be improved by sweeping the reservoir with a polyol as described with the methods of the invention.

(3) FIG. 3. Reference SAGD method.

DETAILED DESCRIPTION

(4) The present invention describes a novel method of enhancing heavy oil recovery. In particular, the viscosity of the displacing phased used to flooding the reservoir is increased through the use of a polyol. Polyols, especially glycerol based polyols, increase the viscosity by a greater amount than other compounds commonly used and are much cheaper.

(5) A method of improving oil recovery is provided, comprising injecting an aqueous solution comprising a polyol into at least one injection well in a reservoir, said injection well being in fluid communication with at least one producing well; displacing the oil in said reservoir using said aqueous solution; and producing said oil and aqueous solution in said at least one producing well.

(6) Preferably, the aqueous solution contains water and a polyol, such as 10-100% polyol and 0-90% water. The water can be produced brine, seawater, fresh water, or mixtures thereof, but any convenient source of water can be used.

(7) Preferable polyols are glycerol, diglycerol, polyglycerol-3, polyglycerol-4, or derivatives or mixtures thereof, and especially glycerol based polyols. The aqueous polyol can also contain other conventional additives, or other inexpensive polymers, such as a polyacrylamide or polysaccharide polymer.

(8) A process for displacing oil within an oil bearing formation penetrated by at least one injection well in fluid communication with at least one producing well is also provided. The method comprises injecting from about up to 1.0 pore volume of aqueous fluid into said formation through said at least one injection well to move said oil to at least one production well, in said volume of aqueous fluid containing a polyol.

(9) Another embodiment provides a method for recovering oil from a subterranean reservoir, said reservoir being penetrated by at least one injection well and by at least one production well, both wells being in fluid communication with at least a portion of the subterranean reservoir, comprising: injecting into the reservoir via said injection well, an aqueous polyol containing fluid, said polyol comprising glycerol, diglycerol, polyglycerol-3, polyglycerol-4 or a mixture thereof; and recovering oil displaced by said aqueous polyol containing fluid.

(10) Another embodiment provides a method of improving oil recovery from a reservoir, said reservoir being penetrated by at least one injection well and by at least one production well, both wells being in fluid communication with at least a portion of the subterranean reservoir, comprising: performing a thermal enhanced oil recovery technique on said reservoir; injecting into said reservoir, via said injection well, an aqueous polyol containing fluid, said polyol comprising glycerol, diglycerol, polyglycerol-3, polyglycerol-4 or a mixture thereof; and recovering oil displaced by said aqueous polyol containing fluid.

(11) The thermal enhanced oil recovery technique, can be any known or to be developed, and includes SAGD, CSS, steam flood, VAPEX, ES-SAGD/SAP, SLAG or other thermal recovery methods.

(12) In yet another embodiment a method, of improving bitumen recovery from a reservoir is provided where the reservoir is penetrated by at least one injection well and by at least one production well, both wells being in fluid communication with at least a portion of the subterranean reservoir, comprising: a) inject crude oil diluents via said injection well, to decrease the viscosity of said bitumen; b) injecting into said reservoir via said injection well, an aqueous polyol containing fluid, said polyol comprising glycerol, diglycerol, polyglycerol-3, polyglycerol-4 or some mixture thereof; and c) recovering said bitumen displaced by said aqueous polyol containing fluid.

(13) The crude oil diluents can be any convenient and inexpensive diluent, including n-alkanes, kerosene, acetophenone, cumene, xylene, toluene, benzene, cyclohexanone, N-methylpyrrolidinone, alpha-methlynapthalene (AMN), and mixtures of thereof. Natural gas and CO.sub.2 can also be used.

(14) In yet another embodiment, is provided a method of improving sweep efficiency of a reservoir, wherein a sweep fluid is injected into a reservoir to drive oil towards a production well, the improvement comprising using aqueous glycerol, diglycerol, or polyglycerol, or derivatives and mixtures thereof as the sweep fluid.

(15) All of the references cited herein are expressly incorporated by reference for all purposes. The discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication data after the priority date of this application. Incorporated references are listed again here for convenience: 1. U.S. Pat. No. 2,431,500, Penick, “Alkylation Process,” Socony Vacuum Oil Co., (1947). 2. U.S. Pat. No. 2,771,138, Beeson, “Waterflooding Method of Secondary Recovery,” Exxon Res. Eng. Co. (1956). 3. U.S. Pat. No. 2,775,557, Morgan, “Drilling Muds Containing Acidacrylamide Copolymer Salts,” American Cyanamid Co. (1956). 4. U.S. Pat. No. 2,842,492, Von Engelhardt, et al., “Process for Increasing the Yield of Oil upon the Flooding with Water of Oil Deposits,” Roehm & Haas GMBH. (1958). 5. U.S. Pat. No. 3,002,960, Kolodny, “Polyacrylamide Preparation,” American Cyanamid Co. (1961). 6. U.S. Pat. No. 3,039,529, McKennon, “Secondary Recovery of Petroleum,” Dow Chemical Co. (1962). 7. U.S. Pat. No. 3,282,337, Pye, “Water Flooding Process for the Recovery of Petroleum,” Dow Chemical Co. (1966). 8. U.S. Pat. No. 3,468,377, Dunlap & Foster, “Waterflooding Employing Surfactant Solution,” Mobil Oil Corp. (1969) 9. U.S. Pat. No. 3,553,130, Stratton, “Oil Recovery,” Phillips Petroleum Co. (1971). 10. U.S. Pat. No. 3,581,824, Hurd, “Oil Recovery Process Using an Ionic Polysaccharide Thickening Agent,” Mobil Oil Corp. (1971). 11. U.S. Pat. No. 3,841,401, Restaino, “Process for Recovering Hydrocarbon Using Polymer Obtained by Radiation Polymerization,” ICI America Inc. (1974). 12. U.S. Pat. No. 4,470,899, Miller & Hupka, “Bitumen Recovery from Tar Sands,” Univ. Utah (1984).