Recovery of oil using microemulsions

Claim 1

A METHOD OF RECOVERING CRUDE OIL FROM A SUBTERRANEAN FORMATION HAVING ONE OR MORE INJECTION MEANS IN FLUID COMNUNICATION WITH ONE OR MORE PRODUCTION MEANS WHICH COMPRISES INJECTING INTO SAID FORMATION THROUGH SAID INJECTION MEANS A FIRST LIQUID SLUG, THEN INJECTING INTO SAID FORMATION THROUGH SAID INJECTION MEANS A SECOND LIQUID SLUG, SAID SLUGS BEING MUTUALLY IMMISCIBLE AND AT LEAST ONE OF SAID SLUGS BEING A MICROEMULSION, TO DISPLACE CRUDE OIL IN SAID FORMATION TOWARD SAID PRODUCTION MEANS; DRIVING SAID SLUGS THROUGH SAID FORMATION BY INJECTION OF A DRIVING FLUID; AND RECOVERING CRUDEOIL THROUGH SAID PRODUCTION MEANS.

Claim 2

A METHOD OF RECOVERING CRUDE OIL FROM A SUBTERRANEAN FORMATION HAVING ONE OR MORE INJECTION MEANS IN FLUID COMNUNICATION WITH ONE OR MORE PRODUCTION MEANS WHICH COMPRISES INJECTING INTO SAID FORMATION THROUGH SAID INJECTION MEANS A FIRST LIQUID SLUG, THEN INJECTING INTO SAID FORMATION THROUGH SAID INJECTION MEANS A SECOND LIQUID SLUG, SAID SLUGS BEING MUTUALLY IMMISCIBLE AND AT LEAST ONE OF SAID SLUGS BEING A MICROEMULSION, TO DISPLACE CRUDE OIL IN SAID FORMATION TOWARD SAID PRODUCTION MEANS; DRIVING SAID SLUGS THROUGH SAID FORMATION BY INJECTION OF A DRIVING FLUID; AND RECOVERING CRUDEOIL THROUGH SAID PRODUCTION MEANS.

Claim 10

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises injecting into said formation through said injections means a microemulsion comprising an aqueous medium, an oil and a surfactant, said microemulsion being immiscible under the conditions of injection with a composition consisting essentially of said oil contained in said microemulsion; driving said microemulsion through said injection means; and recovering crude oil through said production means.

Claim 11

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises injecting into said formation through said injections means a microemulsion comprising an aqueous medium, an oil and a surfactant, said microemulsion being immiscible under the conditions of injection with a composition consisting essentially of said oil contained in said microemulsion; driving said microemulsion through said injection means; and recovering crude oil through said production means.

Claim 16

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into mutually immiscible microemulsions in equilibrium, one more dense than the other; c. injecting into said subterranean formation through said injection means the less dense microemulsions; d. injecting into said subterranean formation through said injection means the more dense microemulsion, step (c) and (d) being carried out concurrently or in the order of (c) to (d); e. injecting into said subterranean formation a driving fluid to drive said less dense microemulsion and more dense microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; an d f. recovering crude oil through said production means.

Claim 17

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into mutually immiscible microemulsions in equilibrium, one more dense than the other; c. injecting into said subterranean formation through said injection means the less dense microemulsions; d. injecting into said subterranean formation through said injection means the more dense microemulsion, step (c) and (d) being carried out concurrently or in the order of (c) to (d); e. injecting into said subterranean formation a driving fluid to drive said less dense microemulsion and more dense microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; an d f. recovering crude oil through said production means.

Claim 23

A mEthod of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, said oil having physical and chemical characteristics substantially the same as the physical and chemical characteristics of the crude oil in said formation and said aqueous medium having physical and chemical characteristics substantially the same as the physical and chemical characteristics of the formation water: b. allowing said composition formed in step (a) to separate into multiphases at least one phase being a microemulsion and one phase being an oil phase in equilibrium with said microemulsion, the oil in said oil phase having physical and chemical properties substantially the same as the physical and chemical properties of the crude oil in said formation; c. separating said microemulsion from said oil phase; d. injecting into said subterranean formation through said injection means said microemulsion; e. injecting into said subterranean formation through said injection means a driving fluid to drive said microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; and f. recovering crude oil through said production means.

Claim 24

A mEthod of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, said oil having physical and chemical characteristics substantially the same as the physical and chemical characteristics of the crude oil in said formation and said aqueous medium having physical and chemical characteristics substantially the same as the physical and chemical characteristics of the formation water: b. allowing said composition formed in step (a) to separate into multiphases at least one phase being a microemulsion and one phase being an oil phase in equilibrium with said microemulsion, the oil in said oil phase having physical and chemical properties substantially the same as the physical and chemical properties of the crude oil in said formation; c. separating said microemulsion from said oil phase; d. injecting into said subterranean formation through said injection means said microemulsion; e. injecting into said subterranean formation through said injection means a driving fluid to drive said microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; and f. recovering crude oil through said production means.

Claim 29

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilibrium, one of said phases being a predominantly oil phase; c. separating from said mutually immiscible phases at least one microemulsion phase immiscible with said predominantly oil phase; d. injecting into said formation through said injection means at least one microemulsion phase separated in step (c) from said predominantly oil phase; e. injecting into said formation a drive fluid to drive said injected phases through said formation toward said production means to displace crude oil toward said production means; and f. recovering crude oil through said production means.

Claim 30

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilibrium, one of said phases being a predominantly oil phase; c. separating from said mutually immiscible phases at least one microemulsion phase immiscible with said predominantly oil phase; d. injecting into said formation through said injection means at least one microemulsion phase separated in step (c) from said predominantly oil phase; e. injecting into said formation a drive fluid to drive said injected phases through said formation toward said production means to displace crude oil toward said production means; and f. recovering crude oil through said production means.

Claim 36

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means, which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling withiN the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation; b. allowing said composition formed in step (a) to separate into multitphases, at least two phases comprising microemulsions, one more dense than the other, said microemulsions being mutually immiscible and in equilibrium; c. analyzing the more dense microemulsion and less dense microemulsion to determine the percentage of oil, aqueous medium and surfactant therein; d. separately preparing a microemulsion of substantially the same composition as said more dense microemulsion analyzed in step (c) and separately preparing a microemulsion of substantially the same composition of said less dense microemulsion analyzed in step (c); e. injecting into said subterranean formation said less dense microemulsion formed in step (d) in a volume effective to displace oil in said formation; f. injecting into said subterranean formation said more dense microemulsion formed in step (d) in a volume effective to displace oil in said formation, step (e) and (f) being carried out concurrently or in the order of (e) to (f); g. injecting into said formation a drive fluid to drive said less dense microemulsion and more dense microemulsion through said formation toward said production means; and h. recovering crude oil through said production means.

Claim 37

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means, which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling withiN the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation; b. allowing said composition formed in step (a) to separate into multitphases, at least two phases comprising microemulsions, one more dense than the other, said microemulsions being mutually immiscible and in equilibrium; c. analyzing the more dense microemulsion and less dense microemulsion to determine the percentage of oil, aqueous medium and surfactant therein; d. separately preparing a microemulsion of substantially the same composition as said more dense microemulsion analyzed in step (c) and separately preparing a microemulsion of substantially the same composition of said less dense microemulsion analyzed in step (c); e. injecting into said subterranean formation said less dense microemulsion formed in step (d) in a volume effective to displace oil in said formation; f. injecting into said subterranean formation said more dense microemulsion formed in step (d) in a volume effective to displace oil in said formation, step (e) and (f) being carried out concurrently or in the order of (e) to (f); g. injecting into said formation a drive fluid to drive said less dense microemulsion and more dense microemulsion through said formation toward said production means; and h. recovering crude oil through said production means.

Claim 43

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportion such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation. b. allowing said composition formed in step (a) to separate into multiphases at least one phase being a microemulsion and one phase being a predominantly oil phase in equilibrium with said microemulsion; c. analyzing said microemulsion to determine the percentage of oil, aqueous medium, and surfactant therein; d. separately preparing a microemulsion of substantially the same composition as said microemulsion analyzed in step (c); e. injecting into said subterranean formation said microemullsion formed in step (d) in a volume effective to displace oil in said formation; f. injecting into said formation a drive fluid to drive said microemulsion through said formation toward said production means; and g. recovering crude oil through said production means.

Claim 44

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportion such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation. b. allowing said composition formed in step (a) to separate into multiphases at least one phase being a microemulsion and one phase being a predominantly oil phase in equilibrium with said microemulsion; c. analyzing said microemulsion to determine the percentage of oil, aqueous medium, and surfactant therein; d. separately preparing a microemulsion of substantially the same composition as said microemulsion analyzed in step (c); e. injecting into said subterranean formation said microemullsion formed in step (d) in a volume effective to displace oil in said formation; f. injecting into said formation a drive fluid to drive said microemulsion through said formation toward said production means; and g. recovering crude oil through said production means.

Claim 50

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phase in equilibrium, one of said phases being a predominantly oil phase; c. separating from said mutually immiscible phases at lease one microemulsion phase immiscible with said predominantly oil phase; d. analyzing said at least one microemulsion phase immiscible with said oil phase separated in step (c) to determine the percentage of oil, aqueous medium, and surfactant; e. separately preparing a composition of substantially the same composition as said at least one microemulsion phase immiscible with said oil phase analyzed in step (d); f. injecting into said subterranean formation said composition prepared in step (e); g. injecting into said formation a drive fluid to drive said injected at least one phase through said formation toward said production means; and h. recovering crude oil through said production means.

Claim 51

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phase in equilibrium, one of said phases being a predominantly oil phase; c. separating from said mutually immiscible phases at lease one microemulsion phase immiscible with said predominantly oil phase; d. analyzing said at least one microemulsion phase immiscible with said oil phase separated in step (c) to determine the percentage of oil, aqueous medium, and surfactant; e. separately preparing a composition of substantially the same composition as said at least one microemulsion phase immiscible with said oil phase analyzed in step (d); f. injecting into said subterranean formation said composition prepared in step (e); g. injecting into said formation a drive fluid to drive said injected at least one phase through said formation toward said production means; and h. recovering crude oil through said production means.

Claim 52

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the muliphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilibrium; c. injecting into said formation at least one microemulsion phase of said mutually immiscible phases; d. injecting a drive fluid into said formation to drive said mutually immiscible phases through said formation toward said production means to displace crude oil toward said production means; and e. recovering crude oil through said production means.

Claim 53

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the muliphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilibrium; c. injecting into said formation at least one microemulsion phase of said mutually immiscible phases; d. injecting a drive fluid into said formation to drive said mutually immiscible phases through said formation toward said production means to displace crude oil toward said production means; and e. recovering crude oil through said production means.

Claim 54

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilbrium; c. injecting into said formation one microemulsion composition having substantially the same chemical composition as one of said mutually immiscible phases; d. injecting a drive fluid into said formation to drive said composition through said formation toward said production means to displace crude oil toward said production means; and e. recovering crude oil through said production means.

Claim 55

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilbrium; c. injecting into said formation one microemulsion composition having substantially the same chemical composition as one of said mutually immiscible phases; d. injecting a drive fluid into said formation to drive said composition through said formation toward said production means to displace crude oil toward said production means; and e. recovering crude oil through said production means.

Claim 56

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said cOmposition formed in step (a) to separate into three mutually immiscible phases in equilibrium, one of said phases being a predominantly oil phase, one of said phases being a predominantly aqueous phase and one of said phases being a microemulsion; c. separating said microemulsion from the remaining of said three phases formed in step (b); d. injecting into said subterranean formation through said injection means said microemulsion; e. injecting into said subterranean formation through said injection means a driving fluid to drive said microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; and f. recovering crude oil through said production means.

Claim 57

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said cOmposition formed in step (a) to separate into three mutually immiscible phases in equilibrium, one of said phases being a predominantly oil phase, one of said phases being a predominantly aqueous phase and one of said phases being a microemulsion; c. separating said microemulsion from the remaining of said three phases formed in step (b); d. injecting into said subterranean formation through said injection means said microemulsion; e. injecting into said subterranean formation through said injection means a driving fluid to drive said microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; and f. recovering crude oil through said production means.

Claim 58

The method of claiam 46 wherein said microemulsion is injected as a 0.02 to 2 PV slug.

Claim 59

The method of claiam 46 wherein said microemulsion is injected as a 0.02 to 2 PV slug.

Claim 63

A method of recovering crude oil for a subterrranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, said oil having physical and chemical characteristics substantially the same as the physical and chemical characteristics of the crude oil in said formation and said aqueous medium having physical and chemical characteristics subtantially the same as the physical and chemical characteristics of the formation water; b. allowing said composition formed in step (a) to separate into three mutually immiscible phases in equilibrium, one of said phases being a predominantly oil phase, one of said phases being a predominantly aqueous phase and one of said phases being a microemulsion; c. separating said microemulsion from the remaining of said three phases formed in step (b); d. injecting into said subterranean formation through said injection means said microemulsion; e. injecting into said subterranean formation through said injection means a driving fluid to drive said microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; and f. recovering crude oil through said production means.

Claim 64

A method of recovering crude oil for a subterrranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, said oil having physical and chemical characteristics substantially the same as the physical and chemical characteristics of the crude oil in said formation and said aqueous medium having physical and chemical characteristics subtantially the same as the physical and chemical characteristics of the formation water; b. allowing said composition formed in step (a) to separate into three mutually immiscible phases in equilibrium, one of said phases being a predominantly oil phase, one of said phases being a predominantly aqueous phase and one of said phases being a microemulsion; c. separating said microemulsion from the remaining of said three phases formed in step (b); d. injecting into said subterranean formation through said injection means said microemulsion; e. injecting into said subterranean formation through said injection means a driving fluid to drive said microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; and f. recovering crude oil through said production means.

Claim 65

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation; b. allowing said composition formed in step (a) to separate into three mutually immiscible phases in equilibrium, one of said phases being a precominantly oil phase, one of said phases being a predominantly aqueous phase and one of said phases being a microemulsion; c. analyzing said microemulsion to determinne the percentage of oil, aqueous medium and surfactant therein; d. separately preparing a microemulsion of substantially the same composition as said microemulsion analyzed in step (c); e. injecting into said subterranean formation through said injection means said microemulsion prepared in step (d); f. injecting into said subterranean formation through said injection means a driving fluid to drive said microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; and g. recovering crude oil through said production means.

Claim 66

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation; b. allowing said composition formed in step (a) to separate into three mutually immiscible phases in equilibrium, one of said phases being a precominantly oil phase, one of said phases being a predominantly aqueous phase and one of said phases being a microemulsion; c. analyzing said microemulsion to determinne the percentage of oil, aqueous medium and surfactant therein; d. separately preparing a microemulsion of substantially the same composition as said microemulsion analyzed in step (c); e. injecting into said subterranean formation through said injection means said microemulsion prepared in step (d); f. injecting into said subterranean formation through said injection means a driving fluid to drive said microemulsion through said formation toward said production means to displace crude oil in said formation toward said production means; and g. recovering crude oil through said production means.

Claim 68

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilibrium, one of said phases being a predominantly aqueous phase; c. separating from said mutually immiscible phases at least one microemulsion phase immiscible with said predominantly aqueous phase; d. injecting into said subterranean formation a microemulsion phase having substantially the same composition as said microemulsion phase separated in step (c); e. injecting into said formation a drive fluid to drive said injected at least one microemulsion phase through said formation toward said production means; and f. recovering crude oil through said production means.

Claim 69

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilibrium, one of said phases being a predominantly aqueous phase; c. separating from said mutually immiscible phases at least one microemulsion phase immiscible with said predominantly aqueous phase; d. injecting into said subterranean formation a microemulsion phase having substantially the same composition as said microemulsion phase separated in step (c); e. injecting into said formation a drive fluid to drive said injected at least one microemulsion phase through said formation toward said production means; and f. recovering crude oil through said production means.

Claim 71

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilibrium, one of said phases being a predominantly aqueous phase possibly containing minor amounts of surfactant; c. separating from said mutually immiscible phases at least one microemulsion phase immiscible with said predominantely aqueous phase; d. analyzing said at least one microemulsion phase immiscible with said aqueous phase separated in step (c) to determine the percentages of oil, aqueous medium, and surfactant; e. separately preparing a composition of substantially the same composition as said at least one microemulsion phase immiscible with said aqueous phase analyzed in step (d); f. injecting into said subterranean formation said composition prepared in step (e); g. injecting into said formation a drive fluid to drive said injected at least one phase through said formation toward said production means; an h. recovering crude oil through said production means.

Claim 72

A method of recovering crude oil from a subterranean formation having at least one injection means in fluid communication with at least one production means which comprises: a. mixing an oil, aqueous medium, and surfactant in proportions such that a composition falling within the multiphase region of an oil-water-surfactant ternary diagram is formed, the amounts of said oil, aqueous medium, and surfactant being less than the amounts to be injected into said formation; b. allowing said composition formed in step (a) to separate into a multiplicity of mutually immiscible phases in equilibrium, one of said phases being a predominantly aqueous phase possibly containing minor amounts of surfactant; c. separating from said mutually immiscible phases at least one microemulsion phase immiscible with said predominantely aqueous phase; d. analyzing said at least one microemulsion phase immiscible with said aqueous phase separated in step (c) to determine the percentages of oil, aqueous medium, and surfactant; e. separately preparing a composition of substantially the same composition as said at least one microemulsion phase immiscible with said aqueous phase analyzed in step (d); f. injecting into said subterranean formation said composition prepared in step (e); g. injecting into said formation a drive fluid to drive said injected at least one phase through said formation toward said production means; an h. recovering crude oil through said production means.

Claim 74

A method of recovering crude oil from a subterranean formation which comprises injecting into said formation a microemulsion system comprising an aqueous medium, a hydrocarbon, and a surfactant, said microemulsion system being approximately on a binodal curve separating a multiphase region and a single phase region in a ternary phase diagram of said microemulsion system, displacing said microemulsion system through said formation, and recovering cruDe oil from said formation.

Claim 75

A method of recovering crude oil from a subterranean formation which comprises injecting into said formation a microemulsion system comprising an aqueous medium, a hydrocarbon, and a surfactant, said microemulsion system being approximately on a binodal curve separating a multiphase region and a single phase region in a ternary phase diagram of said microemulsion system, displacing said microemulsion system through said formation, and recovering cruDe oil from said formation.