US4125156A — Aqueous surfactant systems for in situ multiphase…

Claim 1

Independent Claim 173 words

A process for preparing an optimized aqueous surfactant system comprising: (a) preparing a series of aqueous surfactant systems at different brine concentrations, the surfactant of said series of surfactant systems having a relatively small hydrophobic portion; mixing each surfactant system separately with a series of pure hydrocarbons from a homologous series and allowing the mixtures to equilibrate; (b) determining the relative volume of the phases in the resulting equilibrated mixtures in (a) and preparing a phase volume diagram for each hydrocarbon; (c) mixing oil from a formation to be produced with at least one surfactant-brine composition of the type used in (a), allowing the resulting mixture to equilibrate and comparing it with the phase volume diagrams of (b); and (d) using said comparison of (c) in conjunction with the relationship that increasing electrolyte concentration is equivalent to increasing the hydrophobic portion of said surfactant to prepare a new aqueous surfactant system thus adjusted so as to yield upon contact with said oil of said formation, three phases over a narrow range of salinity.

Claim 2

Dependent Claim 173 words

A process for preparing an optimized aqueous surfactant system comprising: (a) preparing a series of aqueous surfactant systems at different brine concentrations, the surfactant of said series of surfactant systems having a relatively small hydrophobic portion; mixing each surfactant system separately with a series of pure hydrocarbons from a homologous series and allowing the mixtures to equilibrate; (b) determining the relative volume of the phases in the resulting equilibrated mixtures in (a) and preparing a phase volume diagram for each hydrocarbon; (c) mixing oil from a formation to be produced with at least one surfactant-brine composition of the type used in (a), allowing the resulting mixture to equilibrate and comparing it with the phase volume diagrams of (b); and (d) using said comparison of (c) in conjunction with the relationship that increasing electrolyte concentration is equivalent to increasing the hydrophobic portion of said surfactant to prepare a new aqueous surfactant system thus adjusted so as to yield upon contact with said oil of said formation, three phases over a narrow range of salinity.

Claim 3

Dependent Claim 161 words

A method according to claim 1 wherein said each surfactant system of said series of surfactant systems contains a cosurfactant and wherein said new surfactant system is a surfactant-cosurfactant-brine prepared using (1) a surfactant having a greater hydrophobic portion and/or a less water-soluble cosurfactant than those of said series of surfactant systems, and (2) a concentration of salt in the brine of said surfactant-cosurfactant-brine corresponding to that wherein three phases form or to that just adjacent to where three phases form on said contact with said oil corresponding to said formation oil, the concentration of said surfactant in said series of aqueous surfactant systems being within the range of 1 to 7 weight percent based on the weight of water and said cosurfactant being present in said series of surfactant systems in an amount such that a cosurfactant/surfactant ratio is within the range of 0.25:1 to 1.5:1, and wherein substantially equal volumes of said surfactant system and said oil are mixed.

Claim 4

Dependent Claim 65 words

A method according to claim 2 wherein said surfactant is a petroleum sulfonate and wherein sid hydrophobic portion is increased by using a sulfonate having an equivalent weight sufficiently greater than that of (a) to decrease the range of salinity over which three phases form to less than about 1 percentage point but no more greater than the minimum amount necessary to effect this decrease.

Claim 5

Dependent Claim 44 words

A method according to claim 3 wherein said surfactant of (a) is a petroleum sulfonate toward the lower end of a 375-500 average equivalent weight range and said higher equivalent weight sulfonate is toward the upper end of said 375-500 average equivalent weight range.

Claim 6

Dependent Claim 27 words

A method according to claim 3 wherein said surfactant of (a) is a petroleum sulfonate with an average equivalent weight within the range of 400 to 200.

Claim 7

Dependent Claim 58 words

A method according to claim 3 wherein said cosurfactant of said series of surfactant systems has a solubility toward the intermediate portion of a 0.5 to 20 grams per 100 grams of water range and said less soluble cosurfactant has a solubility toward the lower end of said 0.5 to 20 grams per 100 grams of water range.

Claim 8

Dependent Claim 18 words

A method according to claim 3 wherein said cosurfactant of said series of surfactant systems is isobutyl alcohol.

Claim 9

Dependent Claim 58 words

A method according to claim 3 wherein said new surfactant system is injected into a reservoir through at least one injection well where it contacts oil in said reservoir to form in situ a microemulsion, thereafter a mobility buffer fluid is injected, and thereafter a drive fluid is injected, forcing oil from said reservoir toward a recovery well.

Claim 10

Dependent Claim 30 words

A method according to claim 8 wherein said injection of said new surfactant system is preceded by a preflush having a salinity similar to that of said new surfactant system.

Claim 11

Dependent Claim 19 words

A method according to claim 1 wherein said aqueous surfactant composition contains a water-soluble polymer as a viscosifying agent.

Claim 12

Dependent Claim 57 words

A method according to claim 1 wherein said new surfactant system on equilibration with a substantially equal volume of oil from said reservoir forms three phases and wherein V o /V w in the microemulsion phase is in the range of 0.1 to 10 and V s /V o in the microemulsion phase is less than 1.

Claim 13

Dependent Claim 67 words

A method according to claim 1 wherein said new surfactant system on equilibration with a substantially equal volume of oil from said reservoir forms two phases, a brine-rich microemulsion phase and an oil phase and wherein V o /V w in the microemulsion phase is greater than 0.05 and V s /V o is less than 1.5, and wherein said two-phase region is near the three-phase region.

Claim 14

Dependent Claim 71 words

A method according to claim 1 wherein said new surfactant system on equilibration with a substantially equal volume of oil from said reservoir forms two phases, an aqueous phase and an oil-rich microemulsion phase, and wherein V w /V o in the microemulsion phase is greater than 0.05 and V s /V w in the microemulsion phase is less than 1.5, and wherein said two-phase region is near the three-phase region.

Claim 15

Dependent Claim 162 words

A process for recovering oil from a subterranean oil-bearing reservoir comprising the steps of (a) injecting into said reservoir through at least one injection well, an aqueous surfactant system comprising water, electrolyte, surfactant and cosurfactant which surfactant system corresponds in surfactant and cosurfactant composition to a system which on contact with oil corresponding to that in said reservoir forms three phases, a predominantly oil phase, an immiscible microemulsion phase, and a predominantly aqueous phase over a range of electrolyte concentration of less than 1 percentage point by weight based on the weight of said water, the injected surfactant system having a concentration of said electrolyte in said water within a 1 percentage point range beginning at about the point said formation of three phases starts and encompassing the three-phase region; (b) contacting said surfactant system with said oil in said reservoir; (c) thereafter injecting a drive fluid thus forcing said oil toward at least one recovery well; and (d) recovering said oil.

Claim 16

Dependent Claim 162 words

A process for recovering oil from a subterranean oil-bearing reservoir comprising the steps of (a) injecting into said reservoir through at least one injection well, an aqueous surfactant system comprising water, electrolyte, surfactant and cosurfactant which surfactant system corresponds in surfactant and cosurfactant composition to a system which on contact with oil corresponding to that in said reservoir forms three phases, a predominantly oil phase, an immiscible microemulsion phase, and a predominantly aqueous phase over a range of electrolyte concentration of less than 1 percentage point by weight based on the weight of said water, the injected surfactant system having a concentration of said electrolyte in said water within a 1 percentage point range beginning at about the point said formation of three phases starts and encompassing the three-phase region; (b) contacting said surfactant system with said oil in said reservoir; (c) thereafter injecting a drive fluid thus forcing said oil toward at least one recovery well; and (d) recovering said oil.

Claim 17

Dependent Claim 129 words

A method according to claim 14 wherein said electrolyte is present in a concentration within the range of 5,000 to 25,000 parts by weight per million parts by weight of water; said surfactant system which is injected into said reservoir contains said surfactant in a concentration within the range of 1-7 weight percent based on the weight of said water and contains said cosurfactant in a concentration within the range of 1-7 weight percent based on the weight of said water; said surfactant is a petroleum sulfonate having an average equivalent weight within the range of 375-500; and said cosurfactant has a solubility in water within the range of 0.5 to 20 grams per 100 grams of water; and wherein said drive fluid is preceded by a mobility buffer.

Claim 18

Dependent Claim 38 words

A method according to claim 15 wherein said formation of three phases occurs over a range of electrolyte concentration of less than 0.5 of a percentage point and said cosurfactant is a C 4 or C 5 alcohol.

Claim 19

Dependent Claim 28 words

A method according to claim 15 wherein said electrolyte is predominantly sodium chloride, said injected surfactant system is essentially free of oil and is preceded by a preflush.

Claim 20

Dependent Claim 19 words

A method according to claim 14 wherein said aqueous surfactant composition contains a water-soluble polymer as a viscosifying agent.

Claim 21

Dependent Claim 136 words

A process for recovering oil from a subterranean oil-bearing reservoir comprising: injecting into said reservoir through at least one injection well a substantially oil-free aqueous surfactant system comprising a surfactant and brine, said surfactant system characterized in that on contact with a substantially equal volume of formation crude oil, said surfactant system takes up said oil and forms three phases, a predominantly oil phase, a predominantly aqueous phase, and a surfactant-rich microemulsion phase, wherein said microemulsion phase has a V o /V w of 0.1 to 10, and a V s /V w of less than 1.0, said phases having interfacial tensions less than about 0.1 dynes/cm, said thus formed microemulsion being immiscible with said predominantly oil phase and with said aqueous phase; forcing said oil toward at least one recovery well; and recovering said oil.

Claim 22

Dependent Claim 136 words

A process for recovering oil from a subterranean oil-bearing reservoir comprising: injecting into said reservoir through at least one injection well a substantially oil-free aqueous surfactant system comprising a surfactant and brine, said surfactant system characterized in that on contact with a substantially equal volume of formation crude oil, said surfactant system takes up said oil and forms three phases, a predominantly oil phase, a predominantly aqueous phase, and a surfactant-rich microemulsion phase, wherein said microemulsion phase has a V o /V w of 0.1 to 10, and a V s /V w of less than 1.0, said phases having interfacial tensions less than about 0.1 dynes/cm, said thus formed microemulsion being immiscible with said predominantly oil phase and with said aqueous phase; forcing said oil toward at least one recovery well; and recovering said oil.

Claim 23

Dependent Claim 25 words

A process according to claim 19 wherein said V o /V w is near unity, and said V s /V w is less than 0.5.

Claim 24

Dependent Claim 17 words

A method according to claim 19 wherein said brine substantially corresponds to formation brine in said reservoir.

Claim 25

Dependent Claim 48 words

A method according to claim 19 wherein said surfactant composition is prepared using a brine differing in salinity from that of the formation brine and wherein said surfactant composition is preceded by a preflush having a salinity substantially corresponding to that of said brine of said surfactant system.

Claim 26

Dependent Claim 56 words

A method according to claim 19 wherein said surfactant is a petroleum sulfonate having an equivalent weight within the range of 375 to 500, said brine has an electrolyte concentration within the range of 5,000 to 25,000 parts by weight per million parts by weight water, and wherein said surfactant system contains in addition a cosurfactant.

Claim 27

Dependent Claim 17 words

A method according to claim 23 wherein said cosurfactant is a C 4 or C 5 alcohol.

Claim 28

Dependent Claim 42 words

A method according to claim 23 wherein said V w /V o in the microemulsion phase is greater than 0.2 and said V s /V w in the microemulsion phase is less than 0.5 and said interfacial tension is less than 0.01.

Claim 29

Dependent Claim 19 words

A method according to claim 19 wherein said aqueous surfactant composition contains a water-soluble polymer as a viscosifying agent.

Claim 30

Dependent Claim 127 words

A process for recovering oil from a subterranean oil-bearing reservoir comprising: injecting into said reservoir through at least one injection well, a substantially oil-free aqueous surfactant system comprising a surfactant and a brine, said surfactant system characterized in that on contact with a substantially equal volume of said formation oil said surfactant system takes up said oil to form two phases, a predominantly aqueous phase and an oil-rich surfactant-rich microemulsion phase, said microemulsion phase having a V w /V o greater than 0.05 and V s /V w less than 1.5, said phases having an interfacial tension of less than 0.1 dynes/cm, said thus formed microemulsion phase being immiscible with said predominantly aqueous phase; forcing said oil toward at least one recovery well; and recovering said oil.

Claim 31

Dependent Claim 127 words

A process for recovering oil from a subterranean oil-bearing reservoir comprising: injecting into said reservoir through at least one injection well, a substantially oil-free aqueous surfactant system comprising a surfactant and a brine, said surfactant system characterized in that on contact with a substantially equal volume of said formation oil said surfactant system takes up said oil to form two phases, a predominantly aqueous phase and an oil-rich surfactant-rich microemulsion phase, said microemulsion phase having a V w /V o greater than 0.05 and V s /V w less than 1.5, said phases having an interfacial tension of less than 0.1 dynes/cm, said thus formed microemulsion phase being immiscible with said predominantly aqueous phase; forcing said oil toward at least one recovery well; and recovering said oil.

Claim 32

Dependent Claim 22 words

A method according to claim 27 wherein formation brine in said reservoir is substantially identical to said brine of said surfactant system.

Claim 33

Dependent Claim 44 words

A method according to claim 27 wherein formation brine in said reservoir is substantially different in composition from said brine of said surfactant system and said surfactant system is preceded by a preflush using a brine substantially corresponding to that of said surfactant system.

Claim 34

Dependent Claim 42 words

A method according to claim 29 wherein said V o /V w in the microemulsion phase is greater than 0.2, said V s /V o in the microemulsion phase is less than 0.5, and said interfacial tension is less than 0.01 dynes/cm.

Claim 35

Dependent Claim 20 words

A composition according to claim 29 wherein said brine of said surfactant system substantially corresponds to brine in said formation.

Claim 36

Dependent Claim 43 words

A method according to claim 29 wherein brine in said formation differs in composition from said brine of said surfactant system and wherein said surfactant system is preceded by a preflush having a brine content substantially corresponding to that of said surfactant system.

Claim 37

Dependent Claim 56 words

A method according to claim 29 wherein said surfactant is a petroleum sulfonate having an equivalent weight within the range of 375 to 500, said brine has an electrolyte concentration within the range of 5,000 to 25,000 parts by weight per million parts by weight water, and wherein said surfactant system contains in addition a cosurfactant.

Claim 38

Dependent Claim 17 words

A method according to claim 33 wherein said cosurfactant is a C 4 or C 5 alcohol.

Claim 39

Dependent Claim 56 words

A method according to claim 27 wherein said surfactant is a petroleum sulfonate having an equivalent weight within the range of 375 to 500, said brine has an electrolyte concentration within the range of 5,000 to 25,000 parts by weight per million parts by weight water, and wherein said surfactant system contains in addition a cosurfactant.

Claim 40

Dependent Claim 17 words

A method according to claim 35 wherein said cosurfactant is a C 4 or C 5 alcohol.

Claim 41

Dependent Claim 19 words

A method according to claim 27 wherein said aqueous surfactant composition contains a water-soluble polymer as a viscosifying agent.

Claim 42

Dependent Claim 125 words

A process for recovering oil from a subterranean oil-bearing reservoir comprising: injecting into said reservoir through at least one injection well a substantially oil-free aqueous surfactant system comprising a surfactant and a brine characterized in that on contact with a substantially equal volume of said oil in said reservoir, said surfactant system takes up said oil to form two phases, a predominantly oil phase and a predominantly water-rich, surfactant-rich microemulsion phase, said microemulsion phase having a V o /V w greater than 0.05, a V s /V o less than 1.5, said phases having interfacial tension of less than 0.1 dynes/cm, said microemulsion thus formed being immiscible with said predominantly oil phase; forcing said oil toward at least one recovery well; and recovering said oil.

Claim 43

Dependent Claim 125 words

A process for recovering oil from a subterranean oil-bearing reservoir comprising: injecting into said reservoir through at least one injection well a substantially oil-free aqueous surfactant system comprising a surfactant and a brine characterized in that on contact with a substantially equal volume of said oil in said reservoir, said surfactant system takes up said oil to form two phases, a predominantly oil phase and a predominantly water-rich, surfactant-rich microemulsion phase, said microemulsion phase having a V o /V w greater than 0.05, a V s /V o less than 1.5, said phases having interfacial tension of less than 0.1 dynes/cm, said microemulsion thus formed being immiscible with said predominantly oil phase; forcing said oil toward at least one recovery well; and recovering said oil.

Claim 44

Dependent Claim 19 words

A method according to claim 38 wherein said aqueous surfactant composition contains a water-soluble polymer as a viscosifying agent.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1981-11-13	1982-05-15	1982-11-14	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1985-11-13	1986-05-15	1986-11-14	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1989-11-13	1990-05-15	1990-11-14	$7700.00	Window Closed / Lapsed

Aqueous surfactant systems for in situ multiphase microemulsion formation

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