this invention is applicable to a secondary - type recovery process wherein a subterranean formation is flooded with a displacing fluid containing a semi - polar compound and / or an electrolyte . the displacing fluid can be any fluid which will effectively displace crude petroleum from the subterranean formation . examples of such fluids include miscible - type fluids such as water - external and oil - external emulsions , and water - external and oil - external micellar dispersions . the term &# 34 ; micellar system &# 34 ; is meant to include &# 34 ; micellar solutions &# 34 ; and &# 34 ; micellar dispersions &# 34 ;. the intermediate micellar systems of the invention are composed essentially of a hydrocarbon , an aqueous medium , and a surfactant . examples of hydrocarbon include crude oil , crude column overheads , straight - run gasoline and liquefied petroleum gases . useful surfactants include cationic , nonionic and anionic surface active compounds . a particularly useful surfactant is an alkyl aryl sulfonate containing a monovalent cation ( e . g ., potassium , sodium , ammonium , and alkanol - substituted ammonium ), more commonly known as petroleum sulfonates or as alkyl aryl naphthenic sulfonates . examples of useful surfactants are disclosed in u . s . pat . no . 3 , 275 , 075 . semi - polar compounds , also known as co - surfactants and co - solubilizers , useful with the displacing fluids , especially the micellar dispersions , include alcohols , amines , ethers , esters , aldehydes , and ketones containing one up to about 20 or more carbon atoms . preferably , the semi - polar compound is an alcohol , e . g ., ethanol , isopropanol , n - and isobutanol , the amyl alcohols , ethoxylated alcohols , 1 - and 2 - hexanol , 1 - and 2 - octanol , the decyl alcohols , alkyl aryl alcohols such as p - nonyl phenol and alcoholic liquors such as fusel oil . preferably , the electrolytes are inorganic bases , inorganic acids and inorganic salts , e . g ., ammonium hydroxide , ammonium sulfate , sodium hydroxide , sodium chloride , sodium sulfate , hydrochloric acid , and sulfuric acid . other useful electrolytes can be found in u . s . pat . no . 3 , 330 , 343 . also , the salts contained in brackish or brine water are to be included as water electrolytes . preferred micellar systems will comprise from about 2 to about 20 percent surfactant ( more preferably from about 5 to about 15 percent surfactant ); from about 30 to about 90 percent water ( more preferably from about 50 to about 80 percent water ); from about 2 to about 60 percent hydrocarbon ( more preferably from about 5 to about 40 percent hydrocarbon ); from 0 to about 10 weight percent cosurfactant ( more preferably from about 0 . 1 to about 2 percent cosurfactant ) and from about 0 to about 10 percent electrolyte ( more preferably from about 1 to about 5 weight percent electrolyte ). formation fluids tend to &# 34 ; leach &# 34 ; or &# 34 ; sorb &# 34 ; the surfactant , semi - polar compound and / or electrolyte from the displacing fluid . as a result , the operational characteristics of the displacing fluid in the formation are adversely affected . substantial immiscibility reduces this loss . crude oil sulfonate is prepared by treatment of sweet illinois crude oil with sulfur trioxide diluted with nitrogen in the presence of ethylene dichloride solvent at a temperature which ranges from about 10 ° to about 15 ° c and at atmospheric pressure . crude reaction mixture is neutralized with ammonium hydroxide and the reaction solvent , ethylene dichloride , is removed by vacuum distillation and water is added to cause separation into two distinct liquid phases . the upper phase comprises principally unreacted hydrocarbons and is decanted off . the lower phase comprises petroleum sulfonates , water and electrolyte ( largely ammonium sulfate ) together with some unreacted hydrocarbon . the lower , crude oil sulfonate phase is used to formulate a micellar system slug containing 3 . 5 weight percent -- so 3 nh 4 groups , 60 percent h 2 o and 2 . 0 percent ( nh 4 ) 2 so 4 , the remainder comprising the hydrocarbon portion of the sulfonate molecule and sweet illinois crude oil . hexanol ( 1 . 25 lb / 100 lb alcohol - free micellar system ) is added to the above composition . the above micellar system is shown to be intermediate by the droplet , dilution , and conductivity tests as described below : one drop of solution of the micellar system is dropped in a beaker containing distilled water and its behavior observed . a water - external solution will dissipate in the water in less than a second , an oil - external droplet will maintain its integrity for at least about a second . the droplet of the above micellar system maintains its integrity longer than one second , indicating that the micellar system is not water - external . the micellar system is therefore either oil - external or intermediate . a volume of the above micellar system is tested by placing in a transparent container , e . g ., a graduated cylinder and adding approximately 10 percent by weight of either water or decane . the mixture is inverted once or twice to insure mixing and then allowed to stand . a water - external solution will be miscible with water but not with hydrocarbon as evidenced by the formation of a transparent hydrocarbon layer above the micellar system . an oil - external solution will be miscible with hydrocarbon but not with water , as evidenced by a transparent aqueous phase below the micellar system . the above micellar system on dilution with decane forms a hydrocarbon layer above the micellar system , indicating that the micellar system is not oil - external . since the droplet test showed the micellar system was not water - external , the micellar system is intermediate . in this test the resistivity of the micellar system to be tested is measured in a standard conductivity cell . a water - external micellar system will exhibit a resistivity ( approximately that of the brine it contains ) of less than about 25 ohm - cm , which corresponds to a conductivity of greater than about 0 . 04 ohm . sup . - 1 cm . sup . - 1 . an oil - external solution will exhibit a resistivity greater than about 1 , 000 , 000 ohm - cm , which corresponds to a conductivity of less than about 10 . sup . - 6 ohm . sup . - 1 cm . sup . - 1 . the above micellar system exhibits a conductivity of about 0 . 02 ohm . sup . - 1 cm . sup . - 1 , confirming that the micellar system is an &# 34 ; intermediate micellar system &# 34 ;. the above micellar system is utilized to displace oil from a clean , fired berea sandstone core 22 inches long by 3 inches in diameter . the core is subjected to a vacuum , saturated with connate water obtained from the henry lease in illinois ( hereinafter identified as henry plant water and containing about 18 , 000 ppm of dissolved salts ), flooded to irreducible water saturation with crude oil obtained from the henry lease in illinois ( a sweet black illinois crude having a viscosity of about 7 cp at 22 ° c , hereinafter identified as henry crude oil ) and then flooded with henry plant water to residual oil saturation . the berea core so prepared is flooded with 0 . 03 pv of a slug of the above intermediate micellar system driven through the core by subsequent injection of a solution of polyacrylamide mobility control agent dissolved in substantially fresh water . frontal velocity is approximately 1 . 2 feet per day . oil recovery is greater than 80 percent based on the volume of the residual oil . a crude oil sulfonate is prepared by treating an illinois crude with sulfur trioxide , and neutralizing and stripping as in example i . water is added to the neutralized sulfonation reaction effluent to cause separation of a raffinate phase . after removal of the raffinate phase , p - nonyl phenol ( pnp ) is then added to effect separation of a brine phase containing water , ammonium sulfate , and some hydrophilic sulfonate material . the resulting petroleum sulfonate was used to formulate a slug containing 3 . 5 weight percent so 3 nh 4 , 60 weight percent h 2 o , 1 . 6 weight percent ( nh 4 ) 2 so 4 , and 2 . 3 weight percent pnp , the remainder comprising the hydrocarbon portion of the sulfonate molecules and crude which was added in example i to achieve the above composition . isopropanol ( 8 . 0 lb / 100 lb of alcohol - free micellar system ) is added . this micellar system is indicated by the droplet test not to be water - external , is indicated by the dilution test to be neither water - nor oil - external , and the micellar system has a conductivity of 8 . 5 × 10 . sup . - 3 ohm . sup . - 1 cm . sup . - 1 , all indicating that the micellar system was an &# 34 ; intermediate micellar system &# 34 ;. when the micellar system of example iii was tested for oil recovery according to example ii , the oil recovery was found to be greater than 80 percent . when a micellar system produced according to the technique of example i and using the compositions of example i and demonstrated by the above test to be an intermediate micellar system is injected into an injection well and driven through a subterranean oil - bearing formation by the use of thickened water drive fluid , it effectively displaces tertiary oil through the formation and through a producing well located greater than 300 feet away from the injection well . it should be understood that the claims appended hereto include those variations of the invention obvious to persons skilled in the art on reading of the present application .