Styrylaryloxy ether sulfonates, a process for their preparation and their use in the recovery of crude oil
DESCRIPTION 
     Styrylaryloxy ether sulfonates, a process for their preparation, and their use in the recovery of crude oil 
     The invention relates to novel styrylaryloxy ether sulfonates, their preparation, and their use as surfactants, in particular for tertiary recovery of crude oil, and also synergistic surfactant combinations. 
     In the recovery of oil from underground reservoirs, it is generally only possible to recover 20-30% of the oil originally present by primary recovery methods. In these, the oil reaches the surface with the aid of the natural reservoir pressure. In secondary recovery, water is forced into the geological formation and the oil is recovered through several production wells. This water flooding as a secondary measure is relatively inexpensive and is therefore used frequently, but in many cases only leads to slightly increased recovery of oil from the reservoir. 
     When the secondary oil recovery measures have been completed, a further economic recovery of oil can only be achieved by introducing mechanical energy. In the heterogeneous pore space, the water, which has a relatively low viscosity, passes the oil, which has a relatively high viscosity, so that virtually only water and no more oil is recovered. If the degree of water invasion at about 98% has exceeded the economic limit, only tertiary oil recovery methods are suitable. These are taken to mean methods in which either the viscosity of the oil is reduced and/or the interfacial tension between water and oil is reduced. 
     Most methods can be classified as thermal oil recovery methods, solution or mixture flooding, or surfactant or polymer flooding, or as combinations of several of the methods mentioned. In thermal recovery methods, steam or hot water is injected into the reservoir or in situ combustion takes place. In solution or mixture methods, a solvent for the crude oil (gas or a liquid) is injected into the reservoir. 
     Surfactant flooding methods are based on a considerable decrease in the interfacial tension between the oil and the flooding water. Depending on the surfactant concentration, a distinction is made between surfactant flooding (low tension flooding), micelle flooding and emulsion flooding. 
     In the monograph by D. O. Shah and R. S. Schechter: Improved Oil Recovery by Surfactant and Polymer Flooding, Academic Press Inc., New York, and in numerous patent specifications, a large number of surfactants are listed which can be used in the surfactant flooding process. Surfactants which are described here are, above all, sulfonates, such as, for examples, synthetic and natural petroleumsulfonates, alkylsulfonates, such as, for example, Na C 13  -C 18  -sec-alkanesulfonate MW 328/350, Na α-olefin-sulfonate and Na (vinylidene)olefinsulfonate, alkylarylsulfonate, such as, for example, Na dodecylbenzenesulfonate, alkyltoluenesulfonates or alkylxylenesulfonates. However, these sulfonates only have a very low tolerance limit for the salt content of the reservoir water. Thus, for example, petroleumsulfonates are soluble only in water having a salt content of 1.5% of NaCl. 
     Sulfonates are also very sensitive, above all, to the alkaline earth metals contained in the reservoir of water. When these surfactants are used at relatively high salt concentrations, precipitation products are formed which can lead to blockage of the porous spaces of the formation. Many reservoirs have relatively high salinity, for example 25% in northern Germany. In order to be able to work with sulfonates in these reservoir systems, combinations with alcohols and/or nonionic surfactants (alkyl or alkylaryl polyglycol ethers) are proposed which are stable at these salt concentrations, but the oil-mobilizing action has usually been worsened. 
     U.S. Pat. No. 3,827,497 proposes the use of salts of sulfated oxyalkylated alcohols. However, it has been shown that salts which contain the COS bond are hydrolytically cleaved at elevated temperatures. U.S. Pat. Nos. 4,018,278, 4,088,189, 4,077,471, 4,120,228, 4,318,816, 4,194,564, 4,318,816 and 3,977,471 describe ether sulfonates (C 12  -C 15  -alkyl- and alkylaryl ether sulfonates) which are stable in reservoir water having a high salt content (200 g/l) and at a reservoir temperature up to 120° C. However, an oil-mobilizing action with the aid of the surfactants can only be determined in selected reservoirs. Similar results have been experienced using the alkyl ether propane sulfonate and alkyl ether glycidyl ether sulfonate products described in German Offenlegungsschrift No. 2,724,442 and German Offenlegungsschrift No. 2,724,490. The use in oil recovery of tributyl phenol ether glycidyl sulfonates and tributyl ether sulfonates is also known (German Offenlegungsschrift No. 3,347,578 and German Offenlegungsschrift No. 3,346,676). 
     Individual reservoirs differ in the temperature, which can be between 20° and 120° C., in the oil composition, which can be paraffinic, naphthenic, aromatic, high-, medium- or low-viscosity, in the salt content and the salt composition, which can be between 3% and 25% of NaCl with various contents of alkaline earth metals, in the reservoir formation, the minerological composition (for example sandstone or limestone), porosity and permeability. The object is therefore to find surfactants or surfactant combinations which are effective under the maximum number of reservoir conditions present (ie. in the temperature range from 20° to 120° C., and a salt content from 30 to 250 g/l) and for the various types of oil. 
     It has now been found that styryl phenol or cresol ether sulfonates are effective when used as surfactants for oil recovery at various reservoir parameters. 
     The invention relates to styrylaryloxy ether sulfonates of the formula ##STR2## in which either R 1  denotes styryl and simultaneously R 2  and R 3  are identical or different and denote hydrogen or styryl, or R 1  and R 2  are nonidentical and each denote methyl or styryl and simultaneously R 3  denotes hydrogen or styryl, x denotes a number from 2 to 20, preferably 2 to 12, and M denotes an ammonium or alkali metal cation. 
     Preference is given to styryl cresol ether sulfonates of the above formula in which R 1  and R 2  are nonidentical and each denote methyl or styryl, and R 3  denotes hydrogen or styryl, and x and M have the abovementioned meanings. The styryl radical is in all cases taken to mean a group of the formula ##STR3## 
     These compounds are prepared according to the following reaction equation: ##STR4## The reaction of the intermediate compound with sodium sulfite takes place at 130° to 190° C., preferably 160°-180° C., in aqueous solution, if appropriate together with cosolvents such as lower alcohols (iso-propanol or butanol), glycols or glycol ethers. In order to increase the yield, it is advantageous to add a small amount of the final product from a previous batch to the reaction batch. It is also possible to use potassium sulfite in place of sodium sulfite. 
     The mono- and di-styrylphenol and -cresol ether sulfonates of the above formula are surfactants which are distinguished by stability in a broad temperature and pH range. Aqueous solutions of these compounds reduce the surface tension at the surfactant solution/air phase interface to values in the order of about 40 mNm -1  (according to Du Nouy) and the oil/surfactant solution interfacial tension to values of about 10 -2  mNm -1  (spinning drop interfacial tensiometer). As a consequence of their activity and stability over a broad pH range, these compounds are suitable for alkaline and acidic metal cleaning agents and fire extinguishing agents. In addition, they are effective emulsifiers for emulsion polymerization and are suitable as stabilizers for latex and other polymer emulsions. Also of particular interest is the use of these compounds in tertiary oil recovery and in well stimulation and formation fracturing of crude oil reservoirs. Use of the compounds of the present invention increases the oil yield in this process. In all cases, the surfactant is generally employed in amounts of 0.01 to 10, preferably 0.05 to 3%. 
     The styrylphenol and -cresol ether sulfonates according to the invention may particularly advantageously be employed in combination with other anionic surfactants, such as, for example, olefinsulfonates, alkanesulfonates, α-olefinsulfonates, internal olefinsulfonates, alkylarylsulfonates, dodecylbenzenesulfonates, petroleumsulfonates, alkylxylenesulfonates, alkyltoluenesulfonates and nonionic surfactants of alkyl- or alkylphenyl polyglycol ethers. Of particular interest here are mixtures of the mono- or di-styrylcresol ether sulfonates according to the invention and alkanesulfonates or olefinsulfonates and/or petroleumsulfonates in the mixing ratio 4:1 to 1:4. Further suitable additives are alcohols, glycol ethers, alkylglycol ethers and dialkylglycol ethers. In addition, the viscosity of flooding water can be increased by polymers such as, for example, hydroxyethylcellulose, polyacrylamides, copolymers based on acrylamide, or polysaccharides. 
    
    
     EXAMPLE 1 
     Na monostyryl-o-cresol(6 EO)-sulfonate 
     (Na α-phenylethyl-o-cresol(6 EO)-sulfonate) 
     120 g (0.245 mol) of the chloride (7.25% of organically bound chlorine) prepared from α-phenylethyl-o-cresol(6 EO)-polyglycol ether by OH/Cl substitution by means of thionyl chloride, are transferred into a 0.7 liter stirred autoclave with 37 g of sodium sulfite, 230 g of water, 5 g of isopropanol, 50 g of sulfonate solution from a previous batch and, if appropriate, NaOH to pH 9-10, and the mixture is stirred for 6 hours at 175° C. The product obtained contains 27.9% of sulfonate, which corresponds to a yield of 80.0% (relative to the chloride employed) and a sulfonate molecular weight of 558. 
     EXAMPLE 2 
     Na monostyryl-p-cresol(8 EO)-sulfonate 
     140 g (0.25 mol) of the chloride (6.35% of organically bound chlorine) prepared from α-phenylethyl-p-cresol(8 EO)-polyglycol ether by OH/Cl substitution by means of thionyl chloride are transferred into a 0.7 liter stirred autoclave with 36 g of sodium sulfite, 260 g of water, 5 g of isopropanol, 50 g of a sulfonate solution from a previous batch and, if appropriate, NaOH to pH 9-10, and the mixture is stirred for 6 hours at 175° C. The product obtained contains 28.0% of sulfonate, which corresponds to a yield of 79% (relative to the chloride employed) and a sulfonate molecular weight of 627. 
     EXAMPLE 3 
     Na distyryl-o-cresol(13 EO)-sulfonate 
     (Na di-α-phenylethyl-o-cresol(13 EO) sulfonate) 
     140 g (0.155 mol) of di-α-phenyl-o-cresol(13 EO) chloride (3.9% of organically bound chlorine) are transferred into a 0.7 liter stirred autoclave with 24 g of sodium sulfite, 280 g of water, 5 g of isopropanol, 50 g of sulfonate solution from a previous batch and, if appropriate, NaOH to pH 9-10, and the mixture is stirred for 6 hours at 175° C. The product obtained contains 27.6% of sulfonate, this corresponds to a yield of 81.6% (relative to the chloride employed) and a sulfonate molecular weight of 974. 
     EXAMPLE 4 
     Na distyryl-p-cresol(17 EO)-sulfonate 
     (Na α-phenylethyl-p-cresol(17 EO)-sulfonate) 
     120 g (0.1 mol) of di-α-phenylethyl-p-cresol(17 EO) chloride (3.3% of organically bound chlorine) are transferred into a 0.7 liter stirred autoclave with 17 g of sodium sulfite, 200 g of water, 5 g of isopropanol, 50 g of sulfonate solution from a previous batch and, if appropriate, NaOH to pH 9-10, and the mixture is stirred for 6 hours at 175° C. The product obtained contains 28.8% of sulfonate, which corresponds to a yield of 77.8% (relative to the chloride employed) and a sulfonate molecular weight of 1150. 
     In order to determine the effectiveness of the compounds according to the invention and of the synergistic surfactant combination, the microcapillary oil removal method described in U.S. Pat. No. 4,008,165, determination of the interfacial tension by the spinning drop interfacial tensiometer method, the phase behavior in accordance with Winsor and Laboratory flooding experiments in glass tubes filled with sand are employed. 
     In microcapillary oil removal, glass microcapillaries from Drummond Scientific Co./USA which have a volume of 5 μl, a length of 30 mm and a diameter of 0.45 mm are used as a model of the pore space in the reservoir. 
     The microcapillaries are sealed at one end by melting, evacuated in a desiccator and filled with crude oil. The capillaries are introduced vertically, with the opening facing up, into surfactant solutions (test tubes) whose temperatures are controlled in a waterbath, and the displacement of oil is recorded visually as a function of time. 
     With the aid of the following assessment table, the effectiveness of the surfactants can be determined as a function of their concentration, the salt concentration, pH, temperature and oil composition. 
     Value 
     9 empty (30 mm) after 10 minutes 
     8 empty after 1 hour 
     7 empty after 3 hours 
     6 empty after 20 hours 
     5 16-25 mm emptying after 20 hours 
     4 9-15 mm emptying after 20 hours 
     3 4-8 mm emptying after 20 hours 
     2 1-3 mm emptying after 20 hours 
     1 trace emptying after 20 hours 
     0 unchanged after 20 hours 
     This method has the advantage that, with the low diameter of the microcapillaries, the viscosity and the density of the oils do not greatly influence the oil removal action and it is possible to work with reservoir oil and reservoir water. 
     According to Taber, J. Petr. Techn. 3 (1969), pp. 3-12, surfactants are suitable for tertiary oil recovery only if the interfacial tension at the oil/salt water phase interface is reduced to values of less than 10 -2  mNm -1 . For determining the interfacial tension at the oil/water phase interface, the spinning drop interfacial tensiometer developed by Wade and Burkowsky is used. (M. Burkowsky and C. Marx: Uber den Mechanismus des Tensidflutens in hochsalinaren Systemen [On the Mechanism of Surfactant Flooding in High-Saline Systems]; Erd/oL-Erdgas-Zeitschrift 95 (1979), pp. 17-25). 
     The method is based on the fact that an oil drop which is introduced into a capillary rotating about the horizontal axis and which contains a liquid (salt water and surfactant) of relatively high density is deformed. The drop is extended until equilibrium of the deforming forces and the interfacial tension is reached. 
     The interfacial tension is calculated according to Vonnegut (B. Vonnegut, Rev. Sci. Instruments 13 (1942), pp. 6-9) from the measured oil drop diameter R, the rotation speed W and the density difference Δd, according to the following formula: ##EQU1## According to the current explanation of the mechanism of oil removal in surfactant flooding, the formation of a 3rd phase (middle phase) of a microemulsion is the prerequisite for an optimum surfactant flooding result [Rieckmann, M., &#34;Tertiare Erdolgewinnung&#34; [Tertiary Oil Recovery], Erdol und Kohle-Erdgas-Petrochemie, 36 (1983) 281-282, Healy, R. N. and Reed, R. L., Soc. Petr. Eng. J. 10 (1979) 492-501, Obah, B. and Neumann, J. H. &#34;uber die Bildung von Mikroemulsionen&#34; [On the Formation of Microemulsions], Tenside Detergents 20 (1983) 145-151]. This desired third phase arises in the system when the interfacial tension at the oil/salt water phase interface is greatly reduced. 
     When determining the middle phases, 5 ml of surfactant solution (with salt water) and 5 ml of oil (reservoir oil or model oil) are introduced into a test tube, the test tube is sealed by melting, shaken vigorously and stored in a drying cabinet at constant temperature. After a storage time of one hour, the test tubes are again shaken vigorously and then stored without further mixing. After a storage time of 1 and 7 days, the formation of the phases (middle phase) is determined. 
     A further important selection criterion is the oil-mobilizing action of the styryl ether sulfonates which is investigated in laboratory flooding experiments. Suitable experimental conditions are flooding experiments using artificial sand, sandstone or limestone beds which are introduced into glass tubes. When carrying out the experiments, quartz sand of certain grain sizes are shaken into Quickfit glass tubes (length: 15 cm, internal diameter: 2.6 cm) with the aid of a vibrator. The sand-filled flooding tube is provided with a frit, seal and cover plate and tested for leaks. The tubes are filled with degassed formation water, the physical data, porosity and permeability are determined according to Darcy&#39;s Law and subsequently soaked in oil. The tubes are heated, and injection water can be injected after calibrating the pressure gauge and checking the feed rates of the injection pumps. Surfactant or polymer flooding commences when the oil yield remains constant over a relatively long period of time (about 1.5 to 2.0 PV). After the chemical slog, the amount of which depends on the concentration, the viscosity, economic efficiency etc., flooding water is again injected. The flooding experiment is complete when no oil or only very little oil is flooded out. The amounts of water and oil brought out (recovered) are determined volumetrically and plotted against the pore volume (oil recovery curve). 
     The values measured using these methods are collated in the tables below. In all cases, 1% strength aqueous solutions of the surfactants were employed. (Exceptions are given). In all examples, &#34;EO&#34; denotes ethylene oxide. In all cases, the alkanesulfonate used in the examples has a molecular weight of 328, and the alkylxylenesulfonate has a molecular weight of 390. 
     
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Example 1                                                                 
Surface tension according to Du Nouy (mNm.sup.-1)                         
(25° C./40° C.)                                             
          Dist. water  50 g/l of NaCl                                     
          (72.6/70.0 mNm.sup.-1)                                          
                       (76/74 mNm.sup.-1)                                 
          0.5%         0.5%                                               
          25° C.                                                   
                 40° C.                                            
                           25° C.                                  
                                   40° C.                          
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Na monostyryl-o-                                                          
            43.4     44.8      41.9  43.2                                 
cresol(6 EO) ether                                                        
sulfonate                                                                 
Na monostryl-o-                                                           
            45.8     45.8      43.3  43.8                                 
cresol(8 EO) ether                                                        
sulfonate                                                                 
Na distyryl-o-                                                            
            46.4     46.2      43.7  44.2                                 
cresol(15 EO) ether                                                       
sulfonate                                                                 
Na monostyryl-p-                                                          
            43.5     43.1      41.0  42.2                                 
cresol(8 EO) ether                                                        
sulfonate                                                                 
Na distyryl-p-                                                            
            48.0     45.0      44.7  43.9                                 
cresol(17 EO) ether                                                       
sulfonate                                                                 
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Example 2                                                                 
Interfacial tension according to Du Nouy (mNm.sup.-1)                     
at room temperature (RT), pH = 6.5, content of                            
active substance (A.sub.S) = 0.5%                                         
                       50 g/l of                                          
          Dist. water/n-octane                                            
                       NaCl/n-octane                                      
          (50.8/51.1 mNm.sup.-1)                                          
                       (43.6 mNm.sup.-1)                                  
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Na monostyryl-o-                                                          
            9.0            5.5                                            
cresol(6 EO) ether                                                        
sulfonate                                                                 
Na monostyryl-o-                                                          
            9.0            6.0                                            
cresol(8 EO) ether                                                        
sulfonate                                                                 
Na distyryl-o-                                                            
            8.4            6.3                                            
cresol(15 EO) ether                                                       
sulfonate                                                                 
Na monostyryl-p-                                                          
            9.0            6.0                                            
cresol(8 EO) ether                                                        
sulfonate                                                                 
Na distyryl-p-                                                            
            10.6           7.0                                            
cresol(17 EO) ether                                                       
sulfonate                                                                 
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Example 3                                                                 
Interfacial tension according to Du Nouy (mNm.sup.-1)                     
at RT, pH 6.5, AS = 0.5%                                                  
                      50 g/l of                                           
          Dist. water/toluene                                             
                      NaCl/toluene                                        
          (34.0/34.8 mNm.sup.-1)                                          
                      (33.3/33.5 mNm.sup.-1)                              
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Na monostyryl-o-                                                          
            4.9           1.5                                             
cresol(6 EO) ether                                                        
sulfonate                                                                 
Na monostyryl-o-                                                          
            4.6           1.9                                             
cresol(8 EO) ether                                                        
sulfonate                                                                 
Na distyryl-o-                                                            
            4.5           2.5                                             
cresol(15 EO) ether                                                       
sulfonate                                                                 
Na monostyryl-p-                                                          
            4.5           1.6                                             
cresol(8 EO) ether                                                        
sulfonate                                                                 
Na distyryl-p-                                                            
            5.0           2.4                                             
cresol(17 EO) ether                                                       
sulfonate                                                                 
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Example 4                                                                 
Interfacial tension according to Du Nouy (mNm.sup.-1)                     
at 40° C., pH 6.5, AS = 0.5%                                       
                      50 g/l of                                           
          Dist. water/toluene                                             
                      NaCl/toluene                                        
          (32.5 mNm.sup.-1)                                               
                      (30.5 mNm.sup.-1)                                   
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Na monostyryl-p-                                                          
            4.0           1.2                                             
cresol(8 EO) ether                                                        
sulfonate                                                                 
Na distyryl-p-                                                            
            4.1           1.7                                             
cresol(17 EO) ether                                                       
sulfonate                                                                 
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Example 5                                                                 
Interfacial tension according to Du Nouy (mNm.sup.-1)                     
at 40° C., pH 6.5, AS = 0.5%                                       
                       50 g/l of                                          
          Dist. water/n-octane                                            
                       NaCl/n-octane                                      
          (29.8/40.4 mNm.sup.-1)                                          
                       (32.8 mNm.sup.-1)                                  
Na monostyryl-p-                                                          
            8.9            6.0                                            
cresol(8 EO)                                                              
ether sulfonate                                                           
Na distyryl-p-                                                            
            9.9            6.7                                            
cresol(17 EO) ether                                                       
sulfonate                                                                 
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Example 6                                                                 
Na mono-/di-styrylcresol ether sulfonate                                  
                               Interfacial      Phase behavior            
            NaCl/CaCl.sub.2    tension  Microcapillary                    
                                                (middle phase             
            (g/l)  Temperature                                            
                          Solubility                                      
                               spinning drop                              
                                        oil removal                       
                                                formation)                
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Na distyryl-o-                                                            
             140/60                                                       
                   25° C.                                          
                          +    ca. 10.sup.-2 mNm.sup.-1                   
                                        9       +                         
cresol(6 EO) sulfonate                                                    
            150/0  40° C.                                          
                          +    ca. 10.sup.-2 mNm.sup.-1                   
                                        9       +                         
Na distyryl-o-                                                            
             180/20                                                       
                   40° C.                                          
                          +    ca. 10.sup.-2 mNm.sup.-1                   
                                        9       +                         
cresol(13 EO) sulfonate                                                   
Na distyryl-o-                                                            
             140/60                                                       
                   60° C.                                          
                          +    ca. 10.sup.-2 mNm.sup.-1                   
                                        8       +                         
cresol(8 EO) sulfonate                                                    
Na distyryl-o-                                                            
            150/0  60° C.                                          
                          +    ca. 10.sup.-2 mNm.sup.-1                   
                                        9       +                         
cresol(19 EO) sulfonate                                                   
Paraffin oil                                                              
            150/0  25° C.                                          
                          +    ca. 10.sup.-2 mNm.sup.-1                   
                                        8       +                         
Na distyryl-p-                                                            
cresol(6 EO) sulfonate                                                    
K oil       150/0  25° C.                                          
                          +    ca. 10.sup.-2 mNm.sup.-1                   
                                        6       +                         
Na distyrylphenol-                                                        
(15 EO) suflonate                                                         
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Example 7                                                                 
Na distyryl-                                                              
o-cresol(8                                                                
        Na dodecyl-                                                       
                 Interfacial tension (spinning drop) mNm.sup.-1           
EO) sulfon-                                                               
        benzene- reservoir oil K, 35/15 g/l of NaCl/CaCl.sub.2            
ate     sulfonate                                                         
                 25° C.                                            
                          40° C.                                   
                                 60° C.                            
                                        80° C.                     
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  0.5%    0.5%   1 · 10.sup.-2                                   
                          1 · 10.sup.-2                          
                                 3 · 10.sup.-2                   
                                        4 · 10.sup.-2            
0%      1%       *--      --     --     --                                
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 *Solutions not measurable or not effective                               
 
    
     
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Example 8                                                                 
Na                                                                        
distryl-                                                                  
        Na sec-                                                           
o-cresol (8                                                               
        alkane-  Interfacial tension (spinning drop) mNm.sup.-1           
EO) sulfon-                                                               
        sulfonate                                                         
                 reservoir oil K, 70/30 g/l of NaCl/CaCl.sub.2            
ate     MW 328   25° C.                                            
                          40° C.                                   
                                 60° C.                            
                                        80° C.                     
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  0.5%    0.5%   5 · 10.sup.-2                                   
                          2 · 10.sup.-2                          
                                 2 · 10.sup.-2                   
                                        4 · 10.sup.-2            
0%      1%       *--      --     --     --                                
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 *Solutions not measurable or not effective                               
 
    
     
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Example 9                                                                 
Na      Na                                                                
distyryl-o-                                                               
        dodecyl- Interfacial tension (spinning drop) mNm.sup.-1           
cresol(8 EO)                                                              
        benzene- reservoir oil K, 90/10 g/l of NaCl/CaCl.sub.2            
sulfonate                                                                 
        sulfonate                                                         
                 40° C. 60° C.                              
                                      80° C.                       
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  0.5%    0.5%   3 · 10.sup.-2                                   
                          2 · 10.sup.-2                          
                                 2 · 10.sup.-2                   
                                        5 · 10.sup.-2            
0%      1%       *--      --     --     --                                
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 *Solutions not measurable or not effective                               
 
    
     
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Example 10                                                                
Na                                                                        
distyryl-                                                                 
       Na                                                                 
o-cresol                                                                  
       dodecyl- Interfacial tension (spinning drop) mNm.sup.-1            
(8 EO) benzene- reservoir oil K, 100 g/l of NaCl, pH 6.5                  
sulfonate                                                                 
       sulfonate                                                          
                25° C.                                             
                         40° C.                                    
                                60° C.                             
                                       80° C.                      
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  0.5%   0.5%   1 · 10.sup.-2                                    
                         4 · 10.sup.-2                           
                                3 · 10.sup.-2                    
                                        3 · 10.sup.-2            
0%     1%       *--      --     --      --                                
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 *Solutions not measurable or not effective                               
 
    
     
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Example 11                                                                
                  Interfacial tension (spinning drop) mNm.sup.-1          
Na distryl-o-     reservoir                                               
cresol(13 EO)                                                             
        Na dodecylbenzene-                                                
                  oil K, 90/10 g/l of NaCl/CaCl.sub.2                     
sulfonate                                                                 
        sulfonate 25° C.                                           
                       40° C.                                      
                             60° C.                                
                                  80° C.                           
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0.5%    0.5%      4 · 10.sup.-2                                  
                       9 · 10.sup.-3                             
                             2 · 10.sup.-2                       
                                  7 · 10.sup.-2                  
  0%      1%      *--  --    --   --                                      
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 *Solutions not measurable or not effective                               
 
    
     
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Example 12                                                                
Na distryl-p-     Interfacial tension (spinning drop) mNm.sup.-1          
cresol (6 EO)                                                             
        Na dodecylbenzene-                                                
                  reservoir oil I, 200 g/l of NaCl                        
sulfonate                                                                 
        sulfonate 25° C.                                           
                       40° C.                                      
                             60° C.                                
                                  80° C.                           
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0.5%    0.5%      1 · 10.sup.-2                                  
                       6 · 10.sup.-2                             
                             7 · 10.sup.-2                       
                                  2 · 10.sup.-2                  
                  (+)  (+)   (+)  (+)                                     
  0%      1%      *--  --    --   --                                      
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 (+) denotes formation of a middle phase                                  
 *Solutions not measurable or not effective                               
 
    
     
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Example 13                                                                
Na distyryl-o-    Interfacial tension (spinning drop) mNm.sup.-1          
cresol (6 EO)                                                             
        Na dodecylbenzene-                                                
                  reservoir oil K, 140/60 g/l of NaCl/CaCl.sub.2          
sulfonate                                                                 
        sulfonate 25° C.                                           
                       40° C.                                      
                             60° C.                                
                                  80° C.                           
__________________________________________________________________________
0.5%    0.5%      ca. 10.sup.-2                                           
                       ca. 10.sup.-2                                      
                             ca. 10.sup.-2                                
                                  ca. 10.sup.-2                           
  0%      1%      *--  --    --   --                                      
__________________________________________________________________________
 *Solutions not measurable or not effective                               
 
    
     
         __________________________________________________________________________
Example 14                                                                
Na distyryl-o-    Interfacial tension (spinning drop) mNm.sup.-1          
cresol (13 EO)                                                            
        Na dodecylbenzene-                                                
                  reservoir oil K, 70/30 g/l of NaCl/CaCl.sub.2           
sulfonate                                                                 
        sulfonate 25° C.                                           
                       40° C.                                      
                             60° C.                                
                                  80° C.                           
__________________________________________________________________________
0.5%    0.5%      1 · 10.sup.-2                                  
                       1 · 10 .sup.-2                            
                             3 · 10.sup.-2                       
                                  8 · 10.sup.-2                  
  0%      1%      *--  --    --   --                                      
__________________________________________________________________________
 *Solutions not measurable or not effective                               
 
    
     
         __________________________________________________________________________
Example 15                                                                
Na distyryl-o-   Interfacial tension (spinning drop) mNm.sup.-1           
cresol (6 EO)                                                             
         Na sec-alkane-                                                   
                 reservoir oil K, 200 g/l of NaCl/l                       
sulfonate                                                                 
         sulfonate                                                        
                 25° C.                                            
                      40° C.                                       
                            60° C.                                 
                                 80° C.                            
__________________________________________________________________________
0.5%     0.5%    1 · 10.sup.-2                                   
                      3 · 10.sup.-2                              
                            1 · 10.sup.-2                        
                                 2 · 10.sup.-2                   
  0%       1%    *--  --    --   --                                       
__________________________________________________________________________
 *Solutions not measurable or not effective                               
 
    
     
         __________________________________________________________________________
Example 16                                                                
Na distyryl-o-    Interfacial tension (spinning drop) mNm.sup.-1          
cresol (6 EO)                                                             
        Na dodecylbenzene-                                                
                  reservoir oil II, 150 g of NaCl/l                       
sulfonate                                                                 
        sulfonate 25° C.                                           
                       40° C.                                      
                             60° C.                                
                                  80° C.                           
__________________________________________________________________________
0.5%    0.5%      2 · 10.sup.-2                                  
                       3 · 10.sup.-                              
                             2 · 10.sup.-2                       
                                  3 ·10.sup.-3                   
                  (6/+)                                                   
                       (6/+) (6/+)                                        
                                  (9/+)                                   
  0%      1%      *--  --    --   --                                      
__________________________________________________________________________
 The numbers 6 and 9 indicate the values measured in microcapillary oil   
 removal; (+) denotes formation of a middle phase                         
 *Solutions not measurable or not effective                               
 
    
     
         __________________________________________________________________________
Example 17                                                                
Na distyryl-p-  Interfacial tension (spinning drop) mNm.sup.-1            
cresol (18 EO)                                                            
        Na sec-alkane-                                                    
                reservoir oil I, 60° C.                            
sulfonate                                                                 
        sulfonate                                                         
                180/20 g/l of NaCl/CaCl.sub.2                             
                             140/60 g/l of NaCl/CaCl.sub.2                
__________________________________________________________________________
0.5%    0.5%    6 · 10.sup.-2                                    
                             4 · 10.sup.-2                       
  0%      1%    *--          --                                           
__________________________________________________________________________
 *Solutions not measurable or not effective                               
 
    
     
         __________________________________________________________________________
Example 18                                                                
Na distyryl-o-   Interfacial tension (spinning drop) mNm.sup.-1           
cresol (6 EO)                                                             
         Na sec-alkane-                                                   
                 reservoir oil II, 135/15 g/l of NaCl/CaCl.sub.2          
sulfonate                                                                 
         sulfonate                                                        
                 25° C.                                            
                      40° C.                                       
                            60° C.                                 
                                 80° C.                            
__________________________________________________________________________
0.5%     0.5%    1 · 10.sup.-2                                   
                      2 · 10.sup.-1                              
                            5 · 10.sup.-2                        
                                 3 · 10.sup.-3                   
                 (2/-)                                                    
                      (0/+) (9/+)                                         
  0%       1%    *--  --    --   --                                       
__________________________________________________________________________
 The numbers 0.2 or 9 indicate the values measured in microcapillary oil  
 removal; (+) or (-) denotes that a middle phase has formed or has not    
 formed.                                                                  
 *Solutions not measurable or not effective                               
 
    
     
         ______________________________________                                    
Example 19                                                                
               Interfacial tension (spinning                              
               drop) mNm.sup.-1                                           
Na distyryl-p-       reservoir                                            
cresol(11 EO)                                                             
         Na sec-alkane-                                                   
                     oil       I, 200 g/l of NaCl                         
sulfonate                                                                 
         sulfonate   40° C.                                        
                               60° C.                              
                                      80° C.                       
______________________________________                                    
0.5%     0.5%        5 · 10.sup.-2                               
                               1 · 10.sup.-2                     
                                      6 · 10.sup.-2              
                     (8/+)     (9/+)  (8/+)                               
0%       1%          *--       --     --                                  
______________________________________                                    
 The numbers 8 and 9 indicate the values measured in microcapillary oil   
 removal; (+) denotes formation of a middle phase.                        
 Solutions not measurable or not effective                                
 
    
     
         ______________________________________                                    
Example 20                                                                
               Interfacial tension (spinning                              
               drop) mNm.sup.-1                                           
Na distyryl-o-       reservoir                                            
                             I,105/45 g/l of                              
cresol(6 EO)                                                              
         Na sec-alkane-                                                   
                     oil     NaCl/CaCl.sub.2                              
sulfonate                                                                 
         sulfonate   25° C.                                        
                             40° C.                                
                                   60° C.                          
                                         80° C.                    
______________________________________                                    
0.5%     0.5%        10.sup.-1                                            
                             10.sup.-1                                    
                                   10.sup.-2                              
                                         10.sup.-2                        
                     (0/-)   (0/-) (8/+) (6/+)                            
0%       1.0%        *--     --    --    --                               
______________________________________                                    
 The numbers 0.6 and 8 indicate the values measured in microcapillary oil 
 removal; (+) or (-) denotes that a middle phase has formed or has not    
 formed.                                                                  
 Solutions not measurable or not effective                                
 
    
     
         ______________________________________                                    
Example 21                                                                
                 Interfacial tension (spinning                            
                 drop) mNm.sup.-1                                         
Na monostyryl-p-       reservoir I, 105/45 g/l of                         
cresol(8 EO)                                                              
           Na sec-alkane-                                                 
                       oil       NaCl/CaCl.sub.2                          
sulfonate  sulfonate   60° C.                                      
                                 80° C.                            
______________________________________                                    
0.5%       0.5%        4 · 10.sup.-2                             
                                 6.10.sup.-2                              
0%         1%          *--       --                                       
______________________________________                                    
  *Solutions not measurable or not effective                              
 
    
     
         ______________________________________                                    
Example 22                                                                
            Interfacial tension (spinning                                 
            drop) mNm.sup.-1                                              
Na distyryl-p-                                                            
         Na sec-  reservoir                                               
cresol(8 EO)                                                              
         alkane-  oil      I, 200 g of NaCl/l                             
sulfonate                                                                 
         sulfonate                                                        
                  25° C.                                           
                           40° C.                                  
                                 60° C.                            
                                        80° C.                     
______________________________________                                    
0.5%     0.5%     10.sup.-2                                               
                           10.sup.-2                                      
                                 1 · 10.sup.-2                   
                                        3 · 10.sup.-2            
                                 (8/+)  (9/+)                             
0%       1%       *--      --    --     --                                
______________________________________                                    
 The numbers 8 and 9 indicate the values measured in microcapillary oil   
 removal; (+) denotes formation of a middle phase.                        
 *Solutions not measurable or not effective                               
 
    
     
         __________________________________________________________________________
Example 23                                                                
                      Synergistic surfactant combinations                 
                      70/30 g/l of NaCl/CaCl.sub.2, reservoir oil I,      
Na distyryl-o-                                                            
        Na dodecyl-                                                       
              Na petroleum-                                               
                      pH 6.5 (interfacial tension/microcapillary          
cresol (13 EO)                                                            
        benzene-                                                          
              sulfonate                                                   
                      oil removal/solubility/phase behavior)              
sulfonate                                                                 
        sulfonate                                                         
              (MW 420)                                                    
                      25° C.                                       
                           40° C.                                  
                                60° C.                             
                                     80° C.                        
__________________________________________________________________________
 0.7%   0.25% 0.05%   sol. (-)                                            
                           sol. (-)                                       
                                sol. (-)                                  
                                     sol. (-)                             
0.55%   0.40% 0.05%   5 · 10.sup.-2                              
                           4 · 10.sup.-2                         
                                6 · 10.sup.-2                    
                                     4 · 10.sup.-2               
                      (6/+)                                               
                           (8/+)                                          
                                (9/+)                                     
                                     (9/+)                                
0.50%   0.25% 0.25%   sol. (-)                                            
                           sol. (-)                                       
                                sol. (-)                                  
                                     sol. (-)                             
0.40%   0.45% 0.15%   3 · 10.sup.-2                              
                           4 · 10.sup.-2                         
                                4 · 10.sup.-2                    
                                     6 · 10.sup.-2               
                      (6/+)                                               
                           (9/+)                                          
                                (9/+)                                     
                                     (9/+)                                
0.30%   0.05% 0.05%   7 · 10.sup.-3                              
                           4 · 10.sup.-2                         
                                4 · 10.sup.-2                    
                                     5 · 10.sup.-2               
                      (6/+)                                               
                           (9/+)                                          
                                (9/+)                                     
                                     (9/+)                                
__________________________________________________________________________
 The numbers 6, 8 and 9 indicate the values measured in microcapillary oil
 removal; (+) or (-) indicate that a middle phase has formed or has not   
 formed.                                                                  
 
    
     
         __________________________________________________________________________
Example 24                                                                
                       Synergistic surfactant combinations                
                       200 g/l of NaCl, reservoir oil I,                  
Na distyryl-p-         pH 6.5 (interfacial tension/microcapillary         
cresol(11 EO)                                                             
        Na sec-alkane                                                     
               Na petroleum-                                              
                       oil removal/solubility/phase behavior)             
sulfonate                                                                 
        sulfonate                                                         
               sulfonate                                                  
                       40° C.                                      
__________________________________________________________________________
0.7%    0.25%  0.05%   8.10.sup.-2 (3)                                    
 0.45%  0.45%  0.1%    8.10.sup.-3 (6)                                    
0.3%    0.65%  0.05%   4.10.sup.-2 (3)                                    
__________________________________________________________________________
 The numbers 3 and 6 indicate the values measured in microcapillary oil   
 removal.                                                                 
 
    
     
         __________________________________________________________________________
Example 25                                                                
                        Synergistic surfactant combinations               
                        200 g/l of NaCl, reservoir oil I,                 
Na distyryl-p-          pH 6.5 (interfacial tension/microcapillary        
cresol(11 EO)                                                             
        Na sec-alkane-                                                    
                Na alkylxylene-                                           
                        oil removal/solubility/phase behavior             
sulfonate                                                                 
        sulfonate                                                         
                sulfonate                                                 
                        °C.                                        
                             40° C.                                
                                  60° C.                           
                                       80° C.                      
__________________________________________________________________________
0.4%    0.4%    0.2%    1.10.sup.-2                                       
                             9.10.sup.-3                                  
                                  9.10.sup.-3                             
                                       1.10.sup.-2                        
                        (6)  (6)  (6)  (6)                                
                        7.10.sup.-3                                       
                             8.10.sup.-3                                  
                                  1.10.sup.-2                             
                                       1.10.sup.-2                        
                        (8)  (8)  (6)  (6)                                
__________________________________________________________________________
 The numbers 6 and 8 indicate the values measured in microcapillary oil   
 removal.                                                                 
 
    
     
         ______________________________________                                    
Example 26                                                                
                    Synergistic surfactant combinations                   
                    70/30 g/l of NaCl/CaCl.sub.2, reservoir               
                    oil I (interfacial tension/micro-                     
Na distyryl-o-                                                            
         Na C.sub.14 -C.sub.16 --                                         
                    capillary oil removal/solubility/                     
cresol(13 EO)                                                             
         olefin-    phase behavior)                                       
sulfonate                                                                 
         sulfonate  40° C.                                         
______________________________________                                    
0.5%     0.5%       2 · 10.sup.-2 mNm.sup.-1 (6/+)               
______________________________________                                    
 The number 6 indicates the value measured in microcapillary oil removal; 
 (+) indicates formation of a middle phase                                
 
    
     The effectiveness of the compounds according to the invention was confirmed by laboratory flooding experiments with sand packs. 
     
         ______________________________________                                    
Sand pack data:                                                           
Sand: grain size  0.03-0.15 mm                                            
Length            15 cm                                                   
Diameter          3 cm                                                    
Pore volume       41 cm.sup.3                                             
Porosity          48%                                                     
Permeability      800 mDasy                                               
Adhering water    18%                                                     
Oil in place      33.6 cm.sup.3                                           
Surfactant slug   20.5 cm.sup.3 ; 2% of AS                                
Synthetic formation water:                                                
Experiment 1 + 2  70 g of NaCl/l + 30 g of                                
                  CaC1.sub.2 /l                                           
Experiment 3 + 4  200 g of NaCl/l                                         
Temperature:      80° C.                                           
______________________________________                                    
 
    
     Oil removal after water flooding using about four times the amount of the pore volume is about 70%. The oil remaining is set as residual oil saturation S r  =100%. 
     The increased oil removal is reproduced in the table below. 
     
         ______________________________________                                    
Surfactant systems          S.sub.R %                                     
______________________________________                                    
(1)    1.20% of Na distyryl-o-cresol(8 EO)-                               
                                19.2                                      
       sulfonate/0.8% of Na sec-alkanesulfonate                           
(2)    0.8% of Na distyryl-o-cresol(13 EO)-                               
                                45.3                                      
       sulfonate/1.1% of Na sec-alkane sulfonate/                         
       0.1% of Na petroleumsulfonate/1% of sec-                           
       butanol                                                            
(3)    1.20% of Na distyryl-p-cresol(11 EO)-                              
                                21.0                                      
       sulfonate/0.8% of Na sec-alkanesulfonate                           
(4)    1.07% of Na distyryl-p-cresol(11 EO)-                              
                                31.6                                      
       sulfonate/0.74% of Na sec-alkanesulfonate/                         
       0.19% of Na petroleumsulfonate                                     
______________________________________