GB1579167A - Use of alkyl glycidyl ether sulphonates in the recovery of oil from oil-bearing formations - Google Patents

Description

(54) THE USE OF ALKYL GLYCIDYL ETHER SULPHONATES IN THE RECOV ERY OF OIL FROM OIL-BEARING FORMATIONS (71) We, ETHYL CORPORATION, a Corporation organised and existing under the laws of the State of Virginia. United States of America, of 330 South Fourth Street, Richmond, State of Virginia, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the use of surfactants and surfactant compositions to enhance the recovery of oil from oil-bearing formations. In particular, the invention is concerned with the use of surfactant salt compositions which are highly stable against hydrolysis at elevated temperatures and for prolonged periods and are especially suitable for use in systems which contain brine and alkaline earth metal ions.

The art is voluminous and involves the use of one, two, three or more surfactants, individually or in combination. Such art is typified. for example. by U.S. Patent Specifications Nos 3,3()8.()68: 3,5()8.612; 3,527,3()1; 3.714,062; 3.777,81X; 3,782,472, and 3,827,497; and the art cited therein. It is evident from the foregoing typical art that an extremely wide variety of surfactant and auxiliary materials is known, it also being known that the effectiveness and longevity of various materials depend upon numerous factors such as temperature. and the fortuitous or planned presence or absence of salt and of metal ions contributed by the formation. or otherwise.

The compositions disclosed in U.S. Patent Specification No. 3.827,497 have limitations with respect to temperature since they are based on or include the, salts of sulfated oxyalkylated alcohol. Salts which contain the C-O-S linkage are known to be hydrolytically unstable at elevated temperatures. The sultanates of U.S. Patent Specification No.

3,827,497 are ethvl sulfonates which are difficult to produce.

The preparation of alkyl glyceryl sulftnates in general is described in U.S. Patent Specifications Nos 2,989,547 and 3.1)24,273.

In accordance with the teachings of the present invention. salts of sulfated oxyalkylated alcohol are avoided.

The invention provides a method for obtaining oil from a subterranean oil-bearing formation which method comprises contacting the formation with a compound of the formula RO(CH2CH2O),l(CH2CHOHCH2SORM),ll wherein R is alkyl having from 8 to 2() carbon atoms, n is from 2 to 10. m is from 1 to 2 and M is an alkali metal, amine or ammonium cation. and then recovering at least a part of the available oil.

By the use of the alkyl glyceryl ether sulfonate slats of the present invention, based on 2-10 mol ethoxylates of alcohols having from 8 to 20 carbon atoms per molecule, (and typically produced therefrom by reacting from about 1 to about 2 mols of epichlorohydrin per mol of alcohol followed by Streckerization with an alkali metal sulfitc) compositions are provided which are easily produced and which have inherently imporived hydrolytic stability at elevated temperatures especially in comparison to sulfated ethoxylated alcohols.

As a result, the compositions are most resistant to hydrolysis during the prolonged time the oil recovery surfactant compositions are required to be in the ground in contact with brine and alkaline earth metal ions. This property is of particular value in situations where the oil-bearing formations are located comparatively deep within the earth's crust.

Although useful in other ways, the surfactants used in the present invention are especially useful in combination with a polyalkylene glycol alkyl ether or in ternarv combination with polyalkylene glycol alkyl ethers and a surfactant salt of an organic sulfonate. such as those described in U.S. Patent Specification No 3,827,497. On the other hand, the present surfactants are characterized by being useful in aqueous solutions in general.

Compositions for use in the present invention contain alkyl glyceryl ether sulfonate salts of the formula RO(CH2CH2O)n(CH2CHOHCH2SO3M)m, wherein R is alkyl having from 8 to 20 carbon atoms (as determined by the starting alcohol subjected to alkoxylation), n is from 2 to 10 (as determined by the mole ratio of alkylene oxide reacted with the starting alcohol), m is from 1 to 2 (as determined by the ratio of epichlorohydrin reacted with the alkoxylated alcohol), and M is an alkali metal, amine or ammonium cation. Preferably R has from 12 to 16 carbon atoms. Preferably n is from 2 to 6. Preferably M is sodium.

P r e f e r a b l y t h e s a l t c o n s i s t s e s s e n t i a l l y o f C 1 2 - 1 6 H 2 5.

33O(CH2CH2O)3(CH2CHOHCH2SO3Na)1.2.

The foregoing salts are in general used in aqueous media so that preferred compositions for use in the present invention are aqueous solutions of the foregoing alkyl glyceryl ether sulfonite salts.

In preferred aspect, the present invention includes a method of recovering oil from a subterranean oil-bearing formation which comprises: A) injecting into the formation a saline solution containing a mixture of (a) from 0.5 to 15 percent by weight based on said solution of a surfactant salt of an organic sulfonate. (b) from 0.25 to 10 percent by weight based on said solution of a polyalkylene glycol alkyl ether, and (c) from 0.25 to 10 percent by weight based on said solution of alkyl glyceryl ether salt of the formula RO(CH2CH2O)nCH2CHOHCH2SO3M)m wherein R is alkyl having from 8 to 20 carbon atoms, n is from 2 to 10, m is from 1 to 2, and M is an alkali metal, amine or cation; and B flooding the formation with a saline solution to effect oil recovery therefrom. Preferably. Component (a) is an alkali metal salt of a petroleum sulfonate. Component(b) is diethylene glycol hexyl ether and Component (c) is an alkali metal salt. Preferably, the amounts of Components (a), (b) and (c) are, respectively, 2-10 percent, 1-8 percent and 1-8 percent by weight.

Preferably, the saline solution in Step B) contains a polymer to improve the mobility thereof, such polymer preferably being a polysaccharide.

The compositions can be used in combination with sulfonated oxyalkylated alcohol such as that described in U.S. Patent Specifiation No. 3,827,497 as an extender in situations where the utmost stability against hydrolysis is not required for the entire period of water flooding operation. Thus, in some instances it may be desired to include sulfated or sulfonated oxyalkylated alcohol salt in the present compositions with the expectation that. as the surfactant salt containing system progresses through the formation, normally becoming more dilute due to combination with water or brine present in the formation itself, a progressive timewise deterioration of the less stable salt of sulfated or sulfonated oxyalkylated alcohol can result in a preferred overall process, especially in the presence of certain alkali metal ions such as calcium or magnesium ions.

It is noteworthyl that these salts contain only C-C linkages, C-O-C linkages and C-S-O linkages in the fundamental skeleton thereof. Notably absent from these compositions are the unstable ester linkage C) C-O-C and the C-O-S linkage of sulfated oxyalkylated alcohol. The salts of the present invention are characterized by the absence of linkages which are hydrolytically unstable at elevated temperatures and by the presence in the molecule of the glyceryl sulfonate group -CH2CHOHCH2SO3M. An outstanding advantage of such structures is that they are readily prepared by reaction of an oxyalkylated alcohol with epichlorohydrin followed by sulfonation with alkali metal sulfite.

In general, the salts are used in aqueous solution so as to facilitate the introduction thereof into oil-bearing formations in the earth. Typical solutions contain from about 0.005 wt. percent to about a saturation amount of the preferred salt in water: however, these concentrations may vary depending upon the method chosen for making the solutions and introducing them into the formation. Solutions may be introduced into the formation separately for each individual solute or in combinations such as with surfactant salts of organic sulfonates and of polyalkylene glycol alkyl ethers, such ternary systems in water frequently being especially preferred for injection. Such systems can be used with more or less pure water or with water which contains alkali metal halides such as sodium chloride in solution; viz, brine, as well as with water containing alkaline earth metal ions, either with or without the alkali metal halide of the brine.

A preferred process in accordance with the present invention involves the recovery of oil from a subterrancan oil-bearing formation by injecting into the formation a saline solution containing the alkyl glyceryl ether sulfonate salt of the present invention, a surfactant salt of an organic sulfonate and a polyalkylene glycol alkyl ether and then flooding the formation with an aqueous medium to effect oil recovery therefrom. Preferred flooding aqueous medium is frequently a brine or saline solution to minimize costs inherent in obtaining non-saline aqueous solutions in the field.

The organic sulfonate components useful in connection with the present invention include those described in U.S. Patent Specification No. 3,827,497. Preferably, sulfonates are used which are readily available commercially such as "Bryton Chemical F467", "Witco Chemical TRS-t0". (Bryton and Witco are Registered Trade Marks.) Suitable sulfonates are usually and preferably metal salts of alkaryl sulfonates, preferably alkali metal salts and alkyl beazene 'sulfonates containing 12 to 30 carbon atoms. Suitable sulfonates also can be aliphatic sulfonates, alkylated naphthalene sulfonates and the like, the essential requirements being that they have surfactant properties and avoid the unstable structures if utmost hydrolytic stability is desired. The cationic portion of such sulfonates can be ammonium or amine as well as alkali metal but is usually and preferably sodium. The molecular weight of the organic sulfonate surfactant is usually from 300-600, preferably from 350-525. These materials can be prepared by well known procedures such as those described in U.S. Patent Specification No 3,3()8,068. They can be prepared synthetically or can be prepared from petroleum and are commonly known as petroleum sulfonates.

The polyalkylene glycol monoalkyl ethers are widely available commercially. The alkylene group is usually ethylene but can be propylene or others up to five carbon atoms. It can repeat itself up to about to times (i.e. the "poly" can be up to about 10) but usually repeats itself 2-6 times, more usually twice, e.g. diethylene. It should be understood that in the formula RO(CH2CH20),l(CH2-CHOHCH2SO3M)m for any specified polyalkylene, the number of alkylene units (n) is either exactly as specified or varies but the average is as specified. This same principle also applies to the alkyl group. Preferably the glycol portion is diethylene glycol. The alkyl group will normally contain 2-12 carbon atoms, preferably 4-10. In general the more alkylene units or the longer the alkylene unit, the longer the alkyl group should be. The preferred component is diethylene glycol hexyl ether. These materials are available commercially or can be made by known procedures.

As indicated already the preferred compositions are those characterized by an alkyl glyceryl ether sulfonate structure based on a preferred ethoxylated alcohol structure. Such materials typically are readily prepared by the reaction of ethoxylated alcohols with epichlorohydrin followed by a reaction with alkali metal sulfite. This introduces the glyceryl sulfonate structure readily and at good yields. The ethoxylated alcohol is suitably produced by reacting an alcohol ROIl with ethylene oxide. The alcohol so reacted is preferably an aliphatic alcohol having from 12 to 16 carbon atoms. Preferably, the alcohol used is predominantly a primary alkanol, more preferably a synthetic primary alcohol mixture containing up to about 50 percent of branched primary alcohols.

The present compositions. in addition to the salts of the invention and the optional organic sulfonate salt and polyalkylene glycol alkyl ether, may also contain sulfated or sulfonated oxyalkylated alcohols or salts thereof.

The invention will now be further described and illustrated with reference to the accompanying drawings and the following Examples.

The various Figures of the drawings show stability characteristics for various compositions embodying the features of the present invention as well as for comparative compositions to show the superiority of the present compositions over the prior art.

Figure 1 shows the stability characteristics of compositions utilizing the salt C12,16H25, 330(CH2CH20)3 (CH2CHOHCH2S03Na)l 2 at 75OF; Figure 2 shows the stability properties of the salt of Figure 1 at a temperature of 15()OF; Figure 3 shows the unsatisfactory stability properties of the comparative salt C12-lhH25- XlO(CH2CHOHCH,SORNa)l, at 75"F; Figure 4 shows the unsatisfactory stability properties of the composition of Figure 3 at 150OF.

Figure 5-10 show the stability properties of the salt of Figure 1 at 75"F and 15()OF with three additional petroleum sulfonates; and Figures 11 and 12 show the stability properties of the crude salt of Figure 1 with Petrostep 450 at 75 F and 150 F, respectively.

Alkyl glyceryl ether sulfonates prepared as described in the following Examples and comparative samples were tested using the following procedure.

To a 4-ounce bottle was added 2.5 grams of petroleum sulfonate (Petronate L of Witco Chemical Company) which is a petroleum sulfonate of 415 to 430 equivalent weight range.

Then l gram of hexanol ethoxylate averaging two ethoxy groups per molecule was added.

Next, 1.5 grams (active basis) of candidate alkyl glyceryl ether sulfonate composition or comparative material was added preferably as an aqueous solution of 10-40 percent concentration or as lot)() percent active material.

Next the appropriate amount of sodium chloride was added preferably as a 10 percent aqueous solution to give the desired final concentration of salt (brine).

Similarly, the appropriate amount of calcium ion was added preferably as a 1 percent solution of calcium ion prepared as calcium chloride.

The sample was then adjusted to 1()() grams to provide the desired concentration of the ingredients. The sample was then heated and stirred vigorously in a sealed system to prevent evaporation of any of the components and when dispersion or dissolution was complete the samplcs were placed in an environment of the desired temperature and observed after 24 hours or more. Obscrvations were made as to the stability or instability of the system. Instability in general is a definite and easily visible phase separation so that a curd of water insoluble material separates either at the bottom or the top depending on the brine concentrations. Generally, all solutions are opaque. Satisfactory conditions are stable dispersions. Rarcly, clear systems are obtained and indicated by "C". Those which showed good rcsults were tested further by dilution with the appropriate sodium chloride and calcium ion solutions at proportions of 1:1. 1:2, 1:5 and 1:10, and reexamined at the indicited temperatures for stability or instability. Samples were tested with 1, 2, 3, 4 and 5 percent by weight of sodium chloride and with 20(), 500, 1000 and 2000 parts per million of calcium ion. Data are shown on the Figures for the various contents of sodium chloride, calcium ion and for the various dilutions of 0, 1:1 with brine and calcium ion solution, 1:2 with brine and calcium ion solution, etc.

In the following Examplcs. Example II is given for comparative purposes.

Example I C12-16H25-33O(CH2CH2O)3(CH2CHOHCH2SO3Na)1.2 The alkyl glyccryl ether sulfonate composition was prepared using the following procedure. Separate three mol ethoxylates (average) of dodecanol. tetradecanol and hexadecanol were combined in approximately 65/25/10 weight ratios.

139.1 grams of diodecanol 52.5 grams of tetradecanol 21.4 grains of hexadecanol The mixture was heated to 90 C, then 4 grams of tin tetrachloride was added. Then 72.1 grams of epichlorohydrin was added. The mol ratio of epichlorohydrin to alkoxylated alcohol was 1.2:1. The mixture was placed in a separatory funnel and about 5 percent by volume of deionized water was added to destroy the catalyst activity.

2()() Grimes (().45 mol) of the Addict was placed in a 2-liter autoclave. 1()3 Grams of Na2SO3 (().X17 mol) was added. 2() Grams of a 50 wt. percent solution of NaOH was added.

677 Grams of water was added. The autoclave was closed, heated to 200 C, agitated for 1 hour, then cooled to room temperature.

The resulting active alkyl glyceryl ether sulfonate was recovered and tested as described.

Data obtained are presented in Figures 1 and 2 for 75 F and 150 F, respectively.

The recovery procedure employcd was the following. The cooled crude product from the autoclave was dc-oilcd hy mixing with aqueous ethanol (1:1 by volume of ethanol and water) in such proportions to provide a 5-10 wt. percent of sulfonate in the mixture and then extracting 4 times with 2()-25 percent by volume of petroleum ether. The methanol was then removed by boiling and isopropanol added to restore the original alcohol-water-crude sulfonate volume. The de-oiled mixture was then hcated to about 45 C and enough sodium carbonate added to provide a system supersaturated in sodium carbonate. The system was agitated and allowed to cool to room temperature. The upper (isopropanol) phase containing the active sulfonate was separated and the alcohol removed by evaporation. The sulfonate was then diicd for approximately 3 hours in a vacuum oven at 100 C and less than 5() mm Hg absolute pressure Example 11 (Comparitive) C12-16H25-33O(CH2CHOHCH2SO3Na)1.2 This alkyl glyceryl sulfonate comparative sample was prepared using the procedure of Example I: however. alcohol wis used that had not been previously ethoxylated. The comparative rcsults of Figures 3 and 4 show the superiority of the alkoxylated composition of the present invention.

Examples III-VI C12-16H25-33O(CH2CH2O)3(CH2CHOHCH2SO3Na)1.2 The above alkyl glyceryl ether sulfonate as prepared in Example I was tested with different petroleum sulfonate with different proportions In Example VI. the candidate alkyl glyceryl sulfonate was used directly from the reaction with sodium sulfite and NaOH without recovery.

For each of the following examples, instead of 2.5 grams of the petroleum sulfonate, 3.0 grams was used. As before, one gram of the hexanol ethoxylate averaging two ethoxy groups per molecule was used. Instead of 1.5 grams (active basis) of candidate alkyl glyceryl ether sulfonate, 1.0 grams was used. Otherwise the procedure described previously was followed at 1, 3 and 5 percent by weight of sodium chloride and with 200, 500, 1000 and 2000 parts per million of calcium ion, the testing for the non-diluted sample of Example IV being extended to include 6,8, 10 and 12 percent by weight of sodium chloride and 5000 and 10,000 parts per million of calcium ion to show how far stability extended beyond the ranges of usual interest.

Example 111 The petroleum sulfonate used was Petrostep 420 of Stepan Chemical Company which is a 60 percent active material having 21 percent free oil, 17.5 percent water, 1.5 percent inorganic salts and an approximate equivalent weight of 420. Data are shown for 75"F and 150 F by Figures 5 and 6, respectively.

Example IV The petroleum sulfonate used was Petrostep 450 of Stepan Chemical Company which is a 60 percent active material having 13.5 percent free oil, 24.5 percent water, 2.() percent inorganic salts and an approximate equivalent weight of 450. Data are shown for 75"F and 150 F by Figures 7 and 8, respectively.

Example V The petroleum sulfonate used was Petrostep 465 of Stepan Chemical Company which is a 60 percent active material having 13.1 percent free oil, 23.5 percent water, 3.6 percent inorganic salts and an approximate equivalent weight of 465. Data are shown for 75"F and 150 F by Figures 9 and 10. respectively.

Example VI Example lV was repeated at 1, 3, and 5 wt. percent NaCI and 200. 5(10, 1000, and 200() parts per million of calcium ion using the crude alkyl glyceryl ether sulfonate as prepared in Example I but without using the recovery procedure described in Example I. The amount of crude was used on a basis of the active content. Data are shown for 75 F and 150 F by Figures 11 and 12, respectively.

From the foregoing, it is evident that the features of the present invention may be employed in various ways. Although the C12-16 salt composition is a preferred mixture, individual salts such as those wherein the alkyl group has 8, 10, 12, 14, 16, 18 or 20 carbon atoms may be used.

Claims (17)

WHAT WE CLAIM IS:

1. A method for obtaining oil from a subterranean oil-bearing formation which method comprises contacting the formation with a compound of the formula RO(CH2CH2O),l- (CH,CHOHCH,SOqM),l" , wherein R is alkyl having from 8 to 20 carbon atoms, n is from 2 to 10, m is from 1 to 2 and M is an alkali metal, amine or ammonium cation, and then recovering at least a part of of the available oil.

2. A method as claimed in claim 1, wherein R has from 12 to 16 carbon atoms.

3. A method as claimed in claim 1 or claim 2, wherein n is from 2 to 6.

4. A method as claimed in any one of claims 1 to 3, wherein M is sodium.

5. A method as claimed in claim 1 wherein said compound is C12.16H25.3O(CH2CH2O)3(CHCHOHCH2SO3Na)1 2

6. A method wherein the said compound is contacted with the oil-bearing formation in the form of a composition containing water.

7. A method as claimed in claim 6, wherein the composition also contains sodium chloride.

8. A method as claimed in claim 6 or claim 7, wherein the composition also contains a polyalkylene glycol alkyl ether.

9. A method as claimed in claim 8, wherein the polyalkylene glycol alkyl ether is diethylene glycol hexyl ether.

1U. A method as claimed in any one of claims 6 to 9. wherein the composition also contains a surfactant salt of an organic sulfonate.

11. A method as claimed in claim 1(). wherein the surfactant salt of an organic sulfonate is an alkali metal salt of a petroleum sulfonate.

12. A method as claimed in claim 6. wherein the composition is a saline solution containing a mixture of the following components: a. 0.5-15 percent by weight based on said solution of a surfactant salt of an organic sulfonate. b. 0.25-10 percent by weight based on said solution of a polyalkylene glycol alkyl ether and c. 0.25-10 percent by weight based on said solution of a compound of the formula RO(CH2CH2O),,(CH2CHOHCH2SOXM),l, wherein R, m, M, and n are as defined in claim 1.

13. Method as claimed in any preceding claim, wherein oil recovery is effected by flooding the formation with a saline solution.

14. A method as claimed in claim 13, wherein the saline solution contains a polymer to improve the nobility thereof.

15. A method as claimed in claim 14, wherein the polymer is a polysaccharide.

16. A method as claimed in claim 1 substantially as hereinbefore described.

17. Oil or an oil-containing material which has been obtained from a subterranean oil-bearine formation by a method as claimed in any one of claims 1 to 16.