# US 8,739,869 B2 · Systems and methods for enhanced waterfloods

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- Number: US 8,739,869 B2
- Document ID: US8739869B2
- Status: Granted
- Kind: B2
- Application number: 13/286,901
- Filed: 2011-11-01
- Published: 2012-05-24
- Granted: 2014-06-03
- Earliest claimed: 2010-11-19
- Assignees: ExxonMobil Upstream Research Company
- Applicants: Thomas W Willingham; Robin Gupta; Mauro Lo Cascio; Peter Griffin Smith, Jr.; Jung-gi Jane Shyeh; Robert D. Kaminsky
- Inventors: Thomas W Willingham; Robin Gupta; Mauro Lo Cascio; Peter Griffin Smith, Jr.; Jung-gi Jane Shyeh; Robert D. Kaminsky
- Web page: https://patentgrep.com/patent/US8739869B2

## CPC

- E21B 43/20: Displacing by water
- B01D 61/0022: {Apparatus therefor}
- C09K 8/58: Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
- B01D 61/025: {Reverse osmosis; Hyperfiltration}
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE

## Abstract

Methods for enhanced oil recovery from a subterranean formation including adding a first salt to a first aqueous stream to form a first injection stream with an increased concentration of a first ion. A second salt is added to a second aqueous stream to form a second injection stream with an increased concentration of a second ion. The second injection stream is of different composition than the first injection stream and the first injection stream and the second injection stream have substantially the same interfacial tension with a hydrocarbon and substantially the same kinematic viscosity. The first injection stream is injected into the formation at a first time and the second injection stream is injected into the formation at a second time. The first injection stream and second injection stream contact at least some overlapping portion of the formation. Oil is recovered from the overlapping portion of the formation.

## Claims

### Claim 1

A method for enhancing oil recovery from a subterranean formation, comprising:
adding a first salt to a first aqueous stream to form a first injection stream with an increased concentration of a first ion;
adding a second salt to a second aqueous stream to form a second injection stream with an increased concentration of a second ion, wherein the second injection stream is of substantially different composition than the first injection stream, and wherein the first injection stream and the second injection stream have substantially a same interfacial tension with a hydrocarbon and substantially a same kinematic viscosity;
injecting the first injection stream into the subterranean formation at a first time;
injecting the second injection stream into the subterranean formation at a second time, wherein the first injection stream and the second injection stream contact an overlapping portion of the subterranean formation; and
recovering oil from the overlapping portion of the subterranean formation.

### Claim 2 (depends on 1)

The method of claim 1, wherein adding at least one of the first salt and the second salt comprises:
making a concentrated solution from a solid salt; and
adding the concentrated solution to an aqueous stream.

### Claim 3 (depends on 1)

The method of claim 1, wherein adding at least one of the first salt and the second salt comprises adding a solid salt to an aqueous stream.

### Claim 4 (depends on 1)

The method of claim 1, wherein the kinematic viscosity of the second stream is within about 30% of the kinematic viscosity of the first injection stream at a common temperature and shear rate.

### Claim 5 (depends on 1)

The method of claim 1, wherein the interfacial tension of the second injection stream with the hydrocarbon is within a factor of three of the interfacial tension of the first injection stream as measured at a same temperature.

### Claim 6 (depends on 1)

The method of claim 1, further comprising adjusting a concentration of an ion to be greater than about 2,000 ppm different between the first injection stream and the second injection stream.

### Claim 7 (depends on 1)

The method of claim 1, further comprising selecting a different salt for the first ion and the second ion.

### Claim 8 (depends on 1)

The method of claim 1, further comprising injecting the first injection stream and the second injection stream into the subterranean formation via a single well completed within the subterranean formation.

### Claim 9 (depends on 1)

The method of claim 1, further comprising injecting at least one of the first injection stream and the second injection stream into the subterranean formation via a well completed within a watered out zone of the subterranean formation.

### Claim 10 (depends on 1)

The method of claim 1, further comprising splitting a formation water stream to form the first aqueous stream and the second aqueous stream.

### Claim 11 (depends on 1)

The method of claim 1, further comprising forming an aqueous stream by reducing an ion concentration in another aqueous stream.

### Claim 12 (depends on 1)

The method of claim 1, wherein at least one of the first salt and the second salt comprise at least one of borate, phosphate, silicate, nitrate, carbonate, citrate, acetate and sulfate.

### Claim 13 (depends on 12)

The method of claim 12, wherein the phosphate is added in a concentration that is greater than about 1,000 ppm and less than about 10,000 ppm.

### Claim 14 (depends on 12)

The method of claim 12, wherein the borate is added in a concentration that is greater than about 5,000 ppm and less than about 22,500 ppm.

### Claim 15 (depends on 12)

The method of claim 12, wherein the borate is added in a concentration that is greater than about 5,000 ppm and less than about 13,500 ppm.

### Claim 16 (depends on 1)

The method of claim 1, further comprising reducing a concentration of another ion in the first aqueous stream.

### Claim 17 (depends on 1)

The method of claim 1, further comprising setting a pH of the first aqueous stream to at least 1 pH point difference from the second aqueous stream.

### Claim 18 (depends on 1)

The method of claim 1, further comprising setting a concentration of the first ion in the first injection stream at least 1000 ppm higher than a concentration of a same ion in the second injection stream.

### Claim 19 (depends on 1)

The method of claim 1, further comprising setting a concentration of the second ion in the second injection stream at least 1000 ppm higher than a concentration of a same ion in the first injection stream.

### Claim 20 (depends on 1)

The method of claim 1, further comprising treating at least one of an aqueous stream and an injection stream to remove at least a portion of at least one of dissolved calcium ions and dissolved magnesium ions.

### Claim 21 (depends on 1)

The method of claim 1, further comprising:
injecting the first injection stream through a first wellbore; and
injecting the second injection stream through a second wellbore.

### Claim 22 (depends on 1)

The method of claim 1, further comprising adjusting a concentration of a selected ion to at least 1 gram of ion per kg of aqueous solution.

### Claim 23 (depends on 1)

The method of claim 1, further comprising:
adding a third salt to a third aqueous stream to form a third injection stream;
injecting the third injection stream into the subterranean formation at a third time subsequent to the first time and the second time.

### Claim 24 (depends on 23)

The method of claim 23, wherein the third salt is the same as the first salt.

### Claim 25 (depends on 23)

The method of claim 23, wherein a composition of the first injection stream is the same as a composition of the third injection stream.

### Claim 26

A system for enhancing oil recovery from a subterranean formation, comprising:
a first injection solution comprising a first salt added to a first aqueous stream;
a second injection solution comprising a second salt added to a second aqueous stream, wherein the first injection solution and the second injection solution have substantially a same interfacial tension with a hydrocarbon and substantially a same kinematic viscosity;
an injection well to the subterranean formation;
an injection system configured to inject the first injection solution and the second injection solution into the subterranean formation so that the first injection solution and the second injection solution contact a common portion of the subterranean formation;
a production well configured to produce fluids from the common portion of the subterranean formation; and
a separation system configured to separate the fluids into an aqueous stream and a hydrocarbon stream.

### Claim 27 (depends on 26)

The system of claim 26, wherein the kinematic viscosity of the second injection solution is within about 30% of the kinematic viscosity of the first injection solution as measured at a common temperature and shear rate.

### Claim 28 (depends on 26)

The system of claim 26, wherein the interfacial tension of the second injection solution is within a factor of three of the interfacial tension of the first injection solution as measured against a hydrocarbon at a same temperature.

### Claim 29 (depends on 26)

The system of claim 26, wherein a concentration of an ion is at least 2,000 ppm different between the first injection solution and the second injection solution.

### Claim 30 (depends on 26)

The system of claim 26, wherein the first salt comprises at least one of borate, phosphate, silicate, nitrate, carbonate, citrate, acetate and sulfate.

### Claim 31 (depends on 26)

The system of claim 26, wherein the second salt comprises at least one of borate, phosphate, silicate, nitrate, carbonate, citrate, acetate and sulfate.

### Claim 32 (depends on 26)

The system of claim 26, wherein the first salt and the second salt comprise a same ion and a concentration of the same ion in the second injection solution is higher than a concentration of the same ion in the first injection solution.

### Claim 33 (depends on 26)

The system of claim 26, further comprising separate injection wells for the first injection solution and the second injection solution.

### Claim 34 (depends on 26)

The system of claim 26, wherein a pH of an injection solution is less than about 8.

### Claim 35 (depends on 26)

The system of claim 26, wherein the second injection solution has a total salinity of less than about 33% of the first injection solution.

### Claim 36 (depends on 26)

The system of claim 26, wherein the second injection solution has a total salinity of greater than about 10,000 ppm.

### Claim 37 (depends on 26)

The system of claim 26, wherein an average subterranean formation temperature of the subterranean formation is greater than about 130° F. (54° C.).

### Claim 38 (depends on 26)

The system of claim 26, further comprising a single well bore for both injection and production.