GB2063966A - Emulsifier system for oil recovery - Google Patents

Abstract

An emulsifier system for use in the tertiary recovery of oil comprises a mixture of a surfactant comprising a neutralized, oxidized solvent extracted oil and a cosurfactant comprising an alcohol having no more than 12 carbon atoms. The cosurfactant alcohol component preferably comprises a mixture of C2 to C8 alcohols. Tertiary recovery of oil is achieved by injecting brine or water, the emulsifier system and a polymer into an injection well and recovering oil from a producing well.

Description

SPECIFICATION Emulsifier system for oil recovery The present invention relates to a new emulsifier system for use in enchanced (tertiary) oil recovery.

Emulsifier systems for use in enhanced oil recovery commonly take the form of a mixture of a surfactant and a cosurfactant. All surfactants currently under development for use in enhanced oil recovery are sodium petroleum sulfonates. While sodium petroleum sulfonates appear to hold the most promise for use as surfactants in enhanced oil recovery, they are disadvantageous for a number of reasons. For example, sodium petroleum sulfonates are produced using large quantities of sulfuric acid or sulfur trioxide, and hence specialized equipment and handling procedures are required. In addition, waste materials, i.e. acid sludges, are produced and these represent a significant waste disposal problem. Furthermore, sodium petroleum sulfonates have not shown good stability over a wide range of brine concentrations. Finally, sodium petroleum sulfonates are relatively expensive.

Various alcohols, primarily t-butanol, are the current choice for the co-surfactant. Unfortunately, current emulsifier systems based on mixtures of sodium petroleum sulfonates and various alcohols such as t-butanol are disadvantageous in a number of respects. For example, such emulsifier systems tend to be useful only over a comparatively narrow salinity range. In addition, the volume of emulsion produced in situ when such emulsifier systems are used is less than desired. Also, such emulsifier systems are comparatively expensive.

The provision of a surfactant for use in enhanced oil recovery which does not suffer from the above disadvantage is a desirable objective. It is an object of the present invention to provide a new surfactant for use in enhanced oil recovery which can be made without using sulfuric acid or sulfur trioxide. It is another object of the present invention to provide a new emulsifier system for use in enhanced oil recovery which is operable over a wider range of salinity and which provides a large volume of emulsion in use than known emulsion systems. It is a further object of the present invention to provide an emulsifier system which is inexpensive and simple to make.

We have found according to the invention that a surfactant ideally suited for use in enhanced oil recovery can be made by air-oxidizing solvent extracted oils, neutralizing the air-oxidized solvent extracted oil with an alkali metal hydroxide to produce a grease-like soap and then combining the grease-like soap with an alcohol, such as t-butanol. The emulsifier so obtained is stable over a wide range of brine concentrations, uses inexpensive starting materials, is simple and inexpensive to make, does not require specialized equipment or produce significant waste. In addition, the emulsifier system has been found to exhibit an extremely low interfacial tension with both brine and hydrocarbon and in addition exhibit high oil recovery in sand pack core tests, thereby making it ideally suited for use as an emulsifier system in enhanced oil recovery.

Thus, the present invention therefore provides a novel emulsifier system for use in enhanced oil recovery comprising an emulsifier system comprising a mixture of a surfactant and an alcohol having no more than 12 carbon atoms, the surfactant comprising a neutralized oxidized solvent extracted oil.

We have further found that the use of a mixture of alcohols rather than a single alcohol as the cosurfactant will provide an emulsifier system effective over a wider salinity range and capable of providing a greater volume of emulsion in use, and the use of a mixture of alcohols is therefore preferred.

In accordance with the present invention there is thus also provided in the known process for the tertiary recovery of oil wherein brine or water, an emulsifier system and a polymer are injected into an injection well and oil recovered from a producing well, the improvement compising using as the emulsifier system a mixture of an alcohol having no more than 12 carbon atoms and a surfactant comprising a neutralized, oxidized solvent extracted oil.

DETAILED DESCRIPTION As indicated above, the inventive emulsifier system comprises the combination of one or more alcohols and a surfactant composed of a neutralized air-oxidized solvent extracted oil.

Surfactant The surfactant of the emulsifier system of the present invention is produced by the nuetralization of an air-oxidized solvent extracted oil. Solvent extracted oils are conventional petroleum refinery streams produced by extracting aromatics from various streams taken off the vacuum distillation tower of a refinery with solvents such as furfural and phenol. They are commonly referred to as either solvent extracted neutral oils or bright stocks, and normally contain no more than about 12, perferably 5% aromatics. In accordance with the present invention, any solvent extracted oil having a viscosity ranging from 50 SUS (Saybolt Universal Seconds) at 1000 (380C) to 250 SUS at 2100F (990C) can be used.

Preferred solvent extracted oils are those having a viscosity between 100 SUS at 1 000F (380C) and 120 SUS at 21O0F (990C).

The most preferred solvent extracted oil is SEN--300. It is also desirable that the solvent extracted oils be subjected to dewaxing and clay contacting before use in the present invention, although this is not essential.

In making the surfactant of the inventive emulsifier system, the solvent extracted oil is subjected to air oxidation. Air oxidation of hydrocarbons is well known, and a description of many air oxidation techniques can be found in the literature. In the present invention, air oxidation is conveniently accomplished by heating the solvent extracted oil to elevated temperature while contacting the oil with a suitable amount of air. Normally a catalyst is included in the solvent extracted oil to enhance the reaction rate.

In accordance with the present invention, the catalyst used in this air oxidation is normally a mixture of an oil soluble metal compound and a salt of a strong base and a weak acid. Oil soluble metal compounds are well known catalysts for the oxidation of hydrocarbons. Examples of such compounds are manganese stearate, iron naphthenate, iron stearate, copper naphthenate, copper stearate and the like. Mixtures of such compounds can be used. Compounds containing manganese and/or iron are especially preferred.

As the second component of the catalyst, any salt of a strong base and a weak acid can be used.

For example, alkali metal carbonates and acetates are useful. Alkali metal carbonates are preferred and sodium carbonate is most preferred.

The catalyst system can be added to the oil incrementally, although it is preferred to add the entire catalyst charge to the oil before oxidation begins. Moreover, it is convenient to add the oil soluble metal compound in the form of a solution in a light hydrocarbon such as a light distillate or diesel oil.

The amount of catalyst system added to the oil can vary widely. When the oil soluble metal compound is used in the form of a solution in a light hydrocarbon, the amount added to the oil should be between about 0.05 to 5cc of the oil soluble metal compound solution containing 6% metal per 100 grams of oil. The preferred amount of oil soluble metal compound is 0.1 to 2.0 cc per 100 grams of oil and most preferred is 1 cc per 100 grams oil. The amount of the second component of the catalyst system, i.e. the salt of a strong base and weak acid, is normally about 0.05 to 2 grams per 100 grams of oil. The preferred amount is 0.1 to 1.0 grams per 100 grams of oil and the most preferred amount is about 0.2 grams per 100 grams of oil.

Oxidation is accomplished by contacting air with the oil/catalyst mixture while heating the mixture to elevated temperature. Normally, air is introduced at a rate of about 1 to 4 SCF (0.028 to 0.112 cubic metre) per 100 grams of oil per hour, although any amount is operable. About 2.8 SCF (0.078 cubic metre) per 100 grams of oil per hour is preferred. The reaction temperature is normally about 2500F (121 0C) to 35O0F (1 770C) with 2850F (1 4O0C) being preferred. As the oil/catalyst mixture is heated from ambient, an exothermic reaction occurs beginning at a temperature of about 2500F (121 OC) to 2750F (1350C).The reaction temperature is increased by about 2O0F (11 OC) to 5O0F (280C) when the exothermic reaction occurs. After this initial exothermic reaction, heat must be supplied to keep the oxidation going. It has been observed that in some instances the reaction is killed at the higher end of the above temperature range and in any event higher temperatures do not make the reaction go faster.

Therefore it is preferable to operate at the lower end of the above temperature range.

The oxidation reaction is continued until the oil exhibits an acid number of about 10 to 40, preferably about 1 5 to 35, most preferably about 30 to 35 mg KOH/gram sample. As a practical matter, acid numbers higher that about 40 should be avoided since this means that too much of the oil is forming dibasic acids which are ineffective as surfactants. On the other hand, acid numbers of at least about 10 and preferably 1 5 are necessary to give significant surfactant effect.

Usually, the air oxidation will take from about 1 to 12 hours or more, depending upon the reaction conditions, the oil being used and the acidity desired in the final product. It has been found, for example, that using SEN--300 as the oil and operating at the most preferred conditions specified above, the oxidation time of about 5 to 8 hours, most preferably about 8 hours, gives a suitable oxidation product.

Under these conditions, the acid number of the resulting product as determined by ASTM D-974, is about 35 mg KOG/g sample. This is equal to 0.624 meg KOH/g sample. Under the same conditions, lower viscosity oils will have a higher acid number and higher viscosity oils will have a lower acid number.

To produce the surfactant of the emulsifier used according to the invention the oxidized oil described above is reacted with an aqueous solution of an inorganic base, preferably an alkali metal hydroxide. Sodium hydroxide is preferred although the other alkali metal hydroxides can be employed.

The amount of aqueous hydroxide solution reacted with the oxidized oil can vary widely. Normally the amount of base used is about 1 to 4.5 or more times the milliequivalents indicated by the acid number.

A range of 2 to 2.75 times the milliequivalents indicated by the acid number is preferred.

The reaction can be carried out at any temperature, although temperatures between about room temperature and 25O0F (11 20C) are most practical. The reaction system, of course, should be stirred from time to time to ensure complete reaction.

The time for the reaction to be completed varies primarily upon reaction temperature with higher temperatures causing faster reaction times. In any event, the product produced by this procedure, i.e.

the surfactant used according to the invention, is in the form of a semi-solid grease-like material which may or may not contain water. Thus the reaction should be continued until oxidized solvent extracted oil described above, which is a viscous fluid somewhat more viscous than that solvent extracted oil starting material, changes into a semi-solid grease-like material. This material is preferably completely neutralized although it need not be, i.e. partially neutralized materials are also effective. When the reaction is carried out at room temperature, neutralization may take up to 2 days or even longer. When the reaction is carried out at higher temperature, e.g. 2500F (121 C), the reaction may proceed to conclusion in as little as a half an hour or even shorter times.

Production of neutralized, oxidized solvent extracted oils is shown described in U.S. Patent 2,653,909, (Frazier) the disclosure of which is incorporated herein by reference.

Cosurfactant To make the emulsifier system of the present invention the surfactant described above is admixed with an alcohol. Any alcohol containing 12 carbon atoms or less can be employed. If single alcohols are used, those having from 3 to 6 carbon atoms are preferred. Of these, t-butanol is the most preferred alcohol.

In most preferred embodiment of the invention, the alcohol comprises a mixture of alcohols having less than 12 carbon atoms. More preferred mixtures are those containing alcohols having 2 to 8 carbon atoms. Of such mixtures, those which contain no more than 70%, preferably 55% by weight, of any one particular alcohol are even more preferred. Still more preferred alcohols are those having an alcohol distribution set forth in the following Table Table I C2 0.025%, preferably 425% C3 0.125%, preferably 925% C4 0.570%, preferably 4070% Q 0.1-12% Cs 0.1-10% C, 0.1-10% the percents being based on the weight of the total amount of alcohols in the mixture having 2 or more carbon atoms.Of such mixtures, those which are composed almost completely of iso-alcohols and normal alcohols with the iso/normal ratio being about 0.7/2 are especially preferred. Also, compositions which contain essentially no methanol and no ethanol are also especially preferred.

Alcohol mixtures for use in the present invention can be produced by any technique. Preferably, however, they are produced by contacting synthesis gas with a novel copper/thorium alkali metal oxide catalyst. Synthesis gas is composed primarily of carbon monoxide and hydrogen, and it has been found that when synthesis gas is contacted with this unique catalyst a mixed alcohol composition is produced having a C2 to C5 distribution in accordance with the preferred embodiments of the invention as described above in Table I. The alcohol mixtures produced by this technique also normally contain a significant amount of methanol, and thus is is desirable to distill off or otherwise remove the methanol from the alcohol composition before use in this invention.Also, if it is desirable to use an essentially ethanol-free alcohol mixture in this invention, the ethanol produced in accordance with the above technique can also be distilled off before use. Normally, the alcohol mixtures produced by this procedure are composed predominantly of primary alcohols.

The technique for making alcohol mixture of the type described above and a more detailed description of these mixtures is described in European Patent Publication Number 0 005 492 filed May 7, 1 979 the disclosure of which is incorporated herein by reference.

The alcohol mixtures can be also used together with any conventional surfactant. For example, sodium petroleum sulfonates can be used as the surfactant. Preferably, however, neutralized oxidized solvent extracted oils are combined with the mixture of alcohols described above to produce the preferred embodiment of this invention.

Concentrations The improved emulsifier system of the present invention is made by admixing the surfactant as described above with the alcohol mixture. The surfactant/alcohol ratio can vary widely and is normally between about 0.5 to 12 parts by weight surfactant per part alcohols. Preferably, 1 to 4 parts surfactant per part alcohol are used. Most preferably, 2 parts surfactant to 1 part alcohol are used.

The following Examples illustrate the invention: Introduction Preparation of Emulsifier System 900 g of 300 SEN using 9 cc (1 cc/1 00 g) manganese naphthenate solution and 1.8 g (0.2 g/l 00 g) sodium carbonate catalyst, was air oxidized using an air rate of 25 ft3/hr (0.7m3/hr) corresponding to 2.8 ft3/hr/1 00 g) (0.08m3/hr/1 00 g) for 8 hours at 2850F (1 400C). The acid number of the resulting product was 35. The yield of product was about 97 weight percent 200 g of this product was neutralized with 19.968 g of 50 weight percent sodium hydroxide for 5 days at room temperature. The mixture was stirred with a spatula at least twice a day. The resulting surfactant produce was grease-like and appeared to be homogeneous.The actual amount (9.984 g) of sodium hydroxide used for neutralization was equal to 2 times the value indicated by acid number. 509 of t-butanol was dissolved in 100 g of the surfactant described above to produce an emulsifier system of the present invention.

Testing of Emulsifier System To learn more about how the emulsifier system of the present invention behaves when in contact with both hydrocarbon and a brine solution, the following runs were done. In each run, 8 ml of the emulsifier system was dissolved in 46 ml of normal octane (hydrocarbon phase). This was then added to 46 ml of a brine solution in 100 ml graduated cylinder. The phases were mixed by inverting the cylinder several times. The cyclinder was then allowed to stand for 2 weeks to allow the phases to separate and equilibrate. The volume of each phase was then determined. Fourteen runs were accomplished with the brine concentration ranging from 0.5 to 8.0% NaCI. The results are reported in the following Table II.

TABLE II Example 1 Phase behaviour of Emulsifier System Brine ml Wt% ml Middle ml Run NaCI Brine Phase Oil 1 0.50 54.0 0.0 46.0 2 0.75 54.2 0.0 45.8 3 1.00 54.9 0.0 45.1 4 1.50 56.9 0.0 43.1 5 1.75 37.0 20.1 42.9 6 2.00 41.0 15.8 43.2 7 2.50 43.2 15.0 41.8 8 3.00 43.8 13.3 42.9 9 3.50 s 44.8 13.4 41.8 10 4.00 46.3 11.4 42.3 11 5.00 45.7 12.8 41.5 12 6.00 46.0 7.0 47.0 13 7.00 46.5 3.5 50.0 14 8.00 47.0 0.0 53.0 As will be noted in Table il, from a brine concentration of 0.5 to 1.5 weight percent, all the emulsifier is in the brine phase. At 1.75% sodium chloride, a third middle phase is formed and the volume of this phase is much greater than the 8 ml of emulsifier added to the system. Comparing the volumes of the hydrocarbon and brine phases, it is clear that some of the hydrocarbon (3.5 ml) and more of the brine (9 ml) has been incorporated in the middle phase. The middle phase is larger than the amount of emulsifier system added to a brine concentration of 5%. At this level, 0.3 ml of brine and 4.5 ml of hydrocarbon are in the middle phase. Even at a brine concentration of 7% the third phase is formed, although in less amounts than the amount of emulsifier system added since some of the emulsifier has transferred to the hydrocarbon phase. At 8% brine the system reverts back to two phases, the bulk of the emulsifier system being in the hydrocarbon phase.

These results indicate that the emulsifier system according to the invention is stable over a very wide range of brine concentration that might be encountered in an oil field. The effective range with this emulsifier system is much broader than for petroleum sulfonate which means that the emulsifier system according to the invention should operate in a superior manner in the field.

Interfacial Tension Measurements To be of value in enhanced oil recovery, the emulsifier system of the present invention must exhibit an extremely low interfacial tension with both hydrocarbon and brine phases. To determine these interfacial tensions when using the emulsifier system of Example, 8 ml of this emulsifier system was dissolved in 46 ml of normal octane. The mixture obtained was then mixed with 46 ml of a 2% NaCI aqueous solution and allowed to equilibrate. 15 volume percent of a middle phase was obtained.The interfacial tension was measured with a spinning drop tensiometer developed by the University of Texas and it was found that the interfacial tension between the middle phase and the hydrocarbon phase was 1.35 x 10-4 dynes/cm and the interfacial tension between the middle phase and the aqueous phase was 3.1 x 10-3 dynes/cm.

Example 2 Another emulsifier system of the present invention was prepared. In this preparation, Example 1 was repeated except that four parts surfactant were added tq one part t-butanol.

6 ml of the emulsifier system so obtained was dissolved in 47 ml of dodecane. The mixture obtained was then mixed with 47 ml of a 3% NaCI aqueous solution and allowed to equilibrate. 1 5 volume percent of a middle phase was obtained. The interfacial tensions were again measured and it was found that the interfacial tension between the middle phase and the hydrocarbon phase was 1.27 x 10-4 dynes/cm and the interfacial tension between the middle phase and the aqueous phase was 3.3 x l0-3dynes/cm.

From the interfacial tension measurements in both Examples 1 and 2, it can be seen that extremely low interfacial tensions are obtained. Thus, the emulsifier systems according to the invention should be ideally suited for use in enhanced oil recovery where low interfacial tensions are required.

Example 3 In order to test the emulsifier systems of the invention in the tertiary recovery of oil, a tertiary oil recovery test was accomplished using the emulsifier system of Example 1. In this test, a glass cylinder 1 inch (2.54 cm) in diameter and 12 inches (0.3 meters) long was packed with sand to form a sand pack having a permeability of 4.4 Darcies. The sand pack was then flushed with carbon dioxide and then flushed with a 2% aqueous NaCI solution as brine. Next, the sand pack was flushed with 50 cc of normal octane as the hydrocarbon and the sand pack was then again flushed with the brine solution. A solution of 8 ml of the emulsifier system of Example 1 in 46 ml of n-octane was prepared. At the conclusion of the second brine flush, a 7% pore volume emulsifier system slug was injected into the sand pack at a rate of 6 ml per hour.This was followed by a 1 pore volume slug of a polymer solution consisting of 1,000 parts per million Dow P-700 (a partially hydrolyzed polyacrylamide) dissolved in a 2% NaCI aqueous solution. The effluent from the sand pack was recovered and it was found that the amount of tertiary oil recovered was 75%.

Example 4 Example 3 was repeated except that the emulsifier system of Example 2 was used, dodecane was used as the hydrocarbon, the brine solution was 3% NaCI, the polymer solution contained 2,000 ppm Dow P-700, the emulsifier solution contained 6 ml emulsifier and 47 ml of dodecane and a 5% pore volume slug of the emulsifier system was injected at a rate of 6 ml per hour. The amount of tertiary oil recovered in this example was 84%.

Example 5 In order to compare the phase behaviour of a mixture of alcohols with t-butanol as cosurfactants, three different emulsifier systems were prepared, two of the emulsifier systems using alcohol mixtures in accordance with the present invention and the third emulsifier system using t-butanol in accordance with the prior art. The surfactant in each of the emulsifier systems was composed of a neutralized oxidized oil prepared by air-oxidizing SEN-300 to form a product having an acid number of 37.9 and then neutralizing the product at room temperature with 2.75 equivalents of NaOH. The emulsifier systems were formed by combining 8 parts of this surfactant with 1 part of the alcohol. One of the alcohol mixtures contained alcohols having from 2 to 8 carbon atoms and the other alcohol mixture contained alcohols having from 3 to 8 carbon atoms.The compositions of these alcohol mixtures are set forth in the following Table Ill.

TABLE III Parts by Weight C2-C8 C3-C8 Ethanol 8.80 Acetone 2.00 Isopropanol 2.50 2.80 Normal Propanol 11.01 12.34 Secondary Butanol 3.70 4.15 Isobutanol 42.96 48.16 Normal Butanol 7.31 8.20 Normal Pentanol 8.21 9.20 Normal Hexanol 7.21 8.20 Octanol 6.20 6.95 In order to test the surfactants, a series of emulsions was produced, each emulsion comprising 47.5 ml kerosene, 5.0 ml emulsifier and 47.5 ml of brine. For each emulsifier system, five different emulsions were produced having salt contents varying from 1% to 9%. In a similar fashion, five different emulsions were prepared using the emulsifier containing t-butanol as the alcohol.

After preparation, each of the emulsions was allowed to stand until separation occurred. At this time, the volumes of the different phases produced were measured, and the results are set forth in the following Table IV.

TABLE IV Comparison of Phase Behavior of Emulsifiers Containing Mixed Alcohols and t-Butanol Surfactant: Oxidized 300 SEN; Acid No.37.9 Neutralized at Room Temperature with 2.75 equivalents NaOH Surfactant to Alcohol Ratio 8:1 Hydrocarbon: (Kerosine) 47.5 ml Emulsifier: 5.0 ml Brine: 47.5 ml ml Hydrocarbon Phase Middle Phase Brine Phase Mixed Alcohols Mixed Alcohols Mixed Alcohols % NaCl in t-butyl t-butyl t-butyl Brine C2-C8 C3-C8 Alcohol C2-C8 C3-C8 Alcohol C2-C8 C3-C8 Alcohol 1 44.3 47.1 46.3 0.0 0.0 0.0 55.7 52.9 53.7 3 39.7 38.8 41.7 32.2 30.6 0.0 28.1 30.6 58.3 5 39.3 37.7 38.8 23.0 23.0 23.2 37.7 39.3 38.0 7 37.3 38.6 38.8 22.0 22.1 19.9 40.7 39.3 41.3 9 36.9 36.0 34.7 20.5 18.9 20.7 42.6 45.1 44.6 As will be noted from Table IV, at 1% brine level, essentially all of the emulsifier is in the brine phase, regardless of the alcohol used. However, at 3% brine a third phase forms when alcohol mixtures are used as the cosurfactant whereas no third phase form when t-butanol is the cosurfactant. At 5%, 7% and 9% brine, all three emulsifiers produce three phases.The formation of the third phase, i.e. the emulsifier phase, implies that the emulsifiers will result in low interfacial tensions required for enhanced oil recovery. Most importantly, the mixture of alcohols produce the all important third phase over wider range of brine concentration. Thus they can be used successfully in a wider range of field concentrations.

Example 6 A neutralized oxidized solvent extracted oil surfactant was prepared by air-oxidizing SEN-300 to a saponification number of 147.9 and neutralizing the product at 1 050C to 1 320C with an amount of NaOH equivalent to the saponification number. Two emulsifier systems were prepared with this surfactant, the C3-C8 alcohol mixture described in Example 5 being used as the cosurfactant in one emulsifier system and t-butanol being used as the cosurfactant in the other system. In both systems, the surfactant/alcohol ratio was 2:1.

A series of emulsions was prepared with each emulsifier system, each emulsion containing 6 ml of emulsifier, 47 ml dodecane and 47 ml of a brine whose salt concentration varied from 1 to 12%. After preparation, the emulsions were allowed to separate and the amounts of the various phases formed were measured. The results obtained are set forth in the following Table V.

TABLE V Comparison of Phase Behaviour of Emulsifiers Containing Mixed Alcohols and t-Butanol Surfactant: Oxidized 300 SEN; Saponification No.: 147.9 Neutralized at 1 050C to 1 320C with NaOH equivalent to saponification number.

Surfactant to Alcohol Ratio 2:1 Hydrocarbon: (Dodecane) 47.0 ml Emulsifier: 6:0 ml Brine: 47.0 ml S/oNaCI Hydrocarbon Phase Middle Phase Brine Phase in C3-C8 t-butyl C3-C8 t-butyl C3-C8 t-butyl Brine Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol 1 48.0 46.0 0.0 0.0 52.0 54.0 2 46.0 45.7 0.0 0.0 54.0 54.3 3 46.7 45.3 8.0 0.0 45.3 54.7 4 46.0 45.3 9.0 3.4 45.0 51.3 5 45.3 45.6 8.0 2.7 46.7 51.7 6 45.4 45.7 7.3 5.0 47.3 49.3 7 44.7 45.7 7.3 6.3 48.0 48.0 8 44.7 45.7 7.0 5.6 ' 48.3 48.7 9 44.7 45.7 7.3 5.6 48.0 48.7 10 46.4 45.3 7.3 6.0 46.3 48.7 11 45.4 45.3 7.3 6.0 47.3 48.7 12 44.7 45.3 7.3 5.7 48.0 49.0 As will be noted from Table V, the emulsifier system formed with a mixture of alcohols produced a third phase that is stable over a broader range of brine concentration than t-butanol. Equally important, the emulsifier produced using the mixed alcohols produces a greater volume of the third phase. This indicates that it is more effective in solubilizing both hydrocarbon and brine. This is another indication that an emulsifier made with mixed alcohols will result in lower interfacial tensions.

Example 7 A series of emulsions was produced using the two emulsifier systems of Example 6. A series of emulsions was formed using dodecane as the hydrocarbon and an equal amount of a sodium chloride brine as the aqueous phase. In those emulsions in which the emulsifier was formulated with t-butanol, the brine was 7% in NaCI while in those emulsions prepared using an emulsifier formulated with the mixed alcohols the brine was 5% in NaCI. After formulation, the emulsions were allowed to stand and the amounts of the different phases produced were determined. The results obtained are set forth in the following Table VI.

TABLE VI Effect of Emulsifier Concentration on the Phase Behaviour of Emulsifiers Containing Mixed Alcohols and t-Butanol Surfactant: Oxidized 300 SEN; Saponification No.: 147.9 Neutralized at 1050Cto 1320with NaOH equivalent to saponification number.

Surfactant to Alcohol Ratio 2:1 Brine Con.: 7% for emulsifier with t-butanol 5% for emulsifier with mixed alcohol Hydrocarbon: Dodecane ml Hydrocarbon Phase Middle Phase Brine Phase Emulsifier C3-C8 t-butyl C3-C8 t-butyl C3-C8 t-butyl Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol 6 45.3 45.7 8.0 6.3 46.7 48.0 8 45.0 45.3 12.3 8.0 42.7 46.7 10 43.4 44.4 13.3 10.3 43.3 45.3 12 42.0 45.7 16.3 12.0 41.7 42.3 14 41.4 45.7 19.3 12.6 39.3 41.7 As will be noted from the above table, the amount of emulsifier phase formed using t-butanol is essentially equivalent to the amount of emulsifier added. However, when the emulsifier is formulated with a mixture of alcohols, the amount of third phase formed is 30% greater.This is still another indication of the superiority of the mixture of alcohols as cosurfactants.

Example 8 Example 6 was repeated except that the surfactant was produced by air oxidizing SEN-300 to a saponification number of 128.9 and neutralizing with NaOH at 1000C to 1 270C. The results obtained are set forth in the following Table VII.

TABLE VII Comparison of Phase Behaviour of Emulsifiers Containing Mixed Alcohols and t-Butanol Surfactant: Oxidized 300 SEN; Saponification No.: 128.9 Neutralized at 11 O0C to 1 270C with NaOH equivalent to saponification number.

Surfactant to Alcohol Ratio 2:1 Hydrocarbon: (Dodecane) 47.0 ml Emulsifier: 6.0 ml Brine: 47.0 ml ml % NaCI Hydrocarbon Phase Middle Phase Brine Phase in C3-C8 t-butyl C3-C8 t-butyl C3-C8 t-butyl Brine Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol 1 46.7 47.0 0.0 0.0 53.3 53.0 2 45.7 46.7 0.0 0.0 54.3 53.3 3 45.6 46.7 9.7 0.0 44.7 53.3 4 45.0 47.0 9.0 1.3 46.0 51.7 5 44.6 46.3 7.7 5.0 47.7 48.7 6 43.7 46.3 8.0 5.7 48.3 48.0 Again it can be seen that the third phase produced in the emulsions is stable over a wider range of brine concentrations when the emulsifier system is formulated using mixed alcohols as the cosurfactant.

Moreover, the third phase is also larger when mixed alcohols are used.

Example 9 Example 7 was repeated except that the surfactant was the surfactant described in Example 8 and the brine concentration was 8% for the emulsifier formulated with t-butanol and 4% for the emulsifier formulated with the mixed alcohol. The results obtained are set forth in the following Table VII I.

TABLE VIII Effect of Emulsifier Concentration on the Phase Behaviour of Emulsifiers Containing Mixed Alcohols and t-Butanol Surfactant: Oxidized 300 SEN; Saponification No.: 147.9 Neutralized at 110 C to 1 270C with NaOH equivalent to saponification number.

Surfactant to Alcohol Ratio 2:1 Brine Con.: 8% for emulsifier with t-butanol 4% for emulsifier with mixed alcohol Hydrocarbon: Dodecane ml Hydrocarbon Phase Middle Phase Brine Phase Emulsifier C3-C8 t-butyl C3-C8 t-butyl C3-C8 t-butyl Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol 6 45.0 45.3 9.0 6.0 46.0 48.7 8 44.0 45.3 12.0 8.0 44.0 46.7 10 43.0 45.3 15.0 8.7 42.0 46.7 12 41.3 45.0 16.7 11.0 42.0 44.0 14 40.0 44.6 20.0 12.7 40.0 42.7 Again it can be seen that the volume of the middle phase is equal to or less than the amount of emulsifier in the system when the emulsifier is formulated with t-butanol but when the emulsifier is formulated with a mixed alcohol the amount of middle phase is about 1.5 times the amount of emulsifier.This again is clear indication of the superiority of the emulsifier using the mixture of alcohols as surfactant.

EXAMPLE 10 The interfacial tensions of the two emulsifier systems of Example 7 and the two emulsifier systems of Example 9 in the respective emulsions exhibiting optimal salinity were determined. The results are set forth in the following Table IX.

TABLE IX Effect of Alcohol on Interfacial Tension Surfactant: Oxidized 300 SEN Neutralized hot with NaOH equivalent to saponification number Surfactant: Alcohol ratio 2.1 Hydrocarbon: Dodecane Optimal Oxidized Salinity % Oil Alcohol % NaCI Emulsifier Sap. No.

t-butanol 7 10 147.1 C3-C8 5 14 147.1 t-butanol 8 14 128.9 C3-C8 4 14 128.9 Interfacial Tension dynes/cm Alcohol yMW pOM yOW t-butanol 0.0573 too dark C3-C8 0.0238 too dark 0.0425 t-butanol 0.1212 0.0432 C3-C8 0.0179 0.0025 0.0253 As can be seen, although the emulsifiers formulated with alcohol mixtures exhibit a lower optimal salinity, they also result in a lower interfacial tension. In the emulsifier system using the surfactant produced from SEN--300 oxidized to a saponification number of 147.9, the interfacial tension between the middle and aqueous phases was cut in half by using the alcohol mixture. A measurement could not be made by using the middle and hydrocarbon phase because the system was too dark. With the emulsifier produced using a surfactant made from SEN-300 oxidized to a saponification number of 128.9, the interfacial tensions (both middle phase-water and middle phase-hydrocarbon) are an order of magnitude lower than the corresponding t-butanol emulsifier system. This demonstrates very conclusively the superiority of mixtures of alcohols as the cosurfactants.

Claims (14)

1. An emulsifier system comprising a mixture of a surfactant and an alcohol cosurfactant having no more than 12 carbon atoms, said surfactant comprising a neutralized oxidized solvent extracted oil.

2. An emulsifier system as claimed in claim 1 which comprises 0.5 to 12 parts surfactant to 1 part alcohol.

3. An emulsifier system as claimed in claim 1 or claim 2 in which the solvent extracted oil subjected to oxidation has a viscosity between 50 SUS at 1000F and 250 SUS at 210 F.

4. An emulsifier system as claimed in claim 3 in which the oxidized solvent extracted oil has an acid number of 10 to 40 before neutralization.

5. An emulsifier system as claimed in claim 4 in which the oxidized solvent extracted oil has an acid number of about 30 to 35 and further wherein said alcohol is t-butanol.

6. An emulsifier system as claimed in any of claims 1 to 4 in which the alcohol cosurfactant comprises a mixture of alcohols having no more than 12 carbon atoms.

7. An emulsifier system as claimed in claim 6 in which the alcohols are primary alcohols.

8. An emulsifier system as claimed in claim 6 or claim 7 in which the alcohols have from 2 to 8 carbon atoms.

9. An emulsifier system as claimed in any of claims 6 to 8 in which the mixture contains no more than 55% of any one alcohol.

10. An emulsifier system as claimed in claim 9 in which the mixture has the following alcohol distribution: C2 025% C3 0.125% C4 0.570% C5 0.1-12% C6 0.1-10% C7 0.1-10%

11. An emulsifier system as claimed in claim 9 in which the alcohol mixture is made by contacting synthesis gas with a copper/thorium/alkali metal oxide catalyst, optionally with removal of methanol and/or ethanol.

12. An emulsifier system substantially as herein described with reference to the Examples.

13. A process for the tertiary recovery of oil in which brine or water, an emulsifier system and polymer are injected into an injection well and oil recovered from a producing well.

14. A process as claimed in claim 13 substantially as herein described.