FR2514364A1 - COMPOSITION AND ACIDIFICATION ADJUVANT AND PROCESS FOR TREATING PETROLEUM FORMATIONS - Google Patents

Abstract

THE INVENTION CONCERNS ACIDIFICATION COMPOSITIONS. IT RELATES TO AN ACIDIFYING ADJUVANT INTENDED TO BE ADDED TO AN ACIDIFYING SOLUTION OF AN OIL WELL, THIS ADJUVANT CONSISTING OF A MIX OF AN ALCOHOL OF HIGH MOLECULAR MASS, PRACTICALLY INSOLUBLE IN WATER, PREFERRED 'ISOOCTANOL, AND A SURFACTANT OF THE PHOSPHATE ESTER TYPE IN SUFFICIENT QUANTITY SO THAT THE ALCOHOL IS DISSOLVED, AS WELL AS A DIOL OR ALCOHOL OF LOW MOLECULAR WEIGHT AND WATER USED AS A THINNER. THIS ADJUVANT CAN BE EASILY PROVIDED AND MIXED WITH AN ACID SOLUTION, IN THE FIELD, SO THAT THE ASSEMBLY TO FORM AN ACIDIFYING FLUID WITH EXCELLENT OIL DISPERSION CHARACTERISTICS. APPLICATION TO THE TREATMENT OF GAS AND OIL WELLS THAT DEEP.

Description

The present invention relates to a composition

  and an acidifying adjuvant and an acidification process.

  However, it relates to an aqueous solution of acidification containing a high molecular weight alcohol and a surfactant.

active ingredient based on a phosphate ester.

  The principle of acidification of oil and gas wells has been used for a long time for the purification, the stimulation and the improvement of the production of hydrocarbons.

  aqueous solution of an acid such as hydrochloric acid, fluorine

  water, acetic or the like, is common practice.

  Mutual solvents such as alcohols are commonly added.

  cools and monobutyl ether of ethylene glycol to

  well stimulation acids to improve the wetting

  solids, reduce the interworking

  Mutual Acid and Petroleum, and Sludge Emulsifier A particularly useful mixture contains isopropanol and isooctanol as described in U.S. Patent No. 3,819,520 according to which

  isopropanol acts as an essential auxiliary solvent

  the solubilization of isooctanol, the combination to be used at a relatively high concentration

for it to be effective.

  It is also known that surfactants are

  such as polyols or alkylphenols oxyalkylated with glycol ethers and oxyalkylated and sulfated alcohols, in acids, for example oxyalkylated alcohols and

  alkyl sulphonate in butanol, in order to obtain

  The above-mentioned advantageous properties of other types of surfactants such as ethylene oxide adducts with octanol or nonanol have also been

been used.

  However, none of the above compositions has the desired effectiveness. The glycol ethers, the acid mixtures and the like do not have sufficient properties

  as surfactants for the wetting of

  In addition, surfactants often form troublesome emulsions (i.e., they stabilize them) and do not promote the formation of solid, oily solids, for the dispersion of solids and for the reduction of surface and interfacial tension. miscibility of oil and acid as efficiently as alcohol

  which have very low solubility in

aqueous acidic formulations.

  The invention relates to an acidifying solution

  oil wells which do not have the drawbacks of known compositions containing an adjuvant

  excellent dispersion and solubility characteristics

  The acidification solution according to the invention contains an aqueous acid solution, a C 4 to C 10 aliphatic alcohol, and is used in conventional acidification solutions. or an alcohol having an equivalent hydrophobic / hydrophilic balance) and a quantity

  of a surfactant based on a sufficient phosphate ester

  for solubilizing the alcohol in the acid solution According to the invention, at least about 75 parts and preferably

  at least 90 parts (or even more) by volume of the solu-

  Aqueous acid containing up to 20% by weight of acid is combined with not more than 25 parts by volume of a mixture of a C 4 to C 10 aliphatic alcohol and a phosphate ester surfactant. the mixture containing up to about 8 parts by volume of alcohol per 5 parts by volume of surfactant The concentrate or adjuvant

  acidification process according to the invention contains an aliphatic alcohol

  C 4 to C O tick which is practically insoluble in

  water and a surfactant based on a phosphate ester.

  A mixture of a water-soluble alcohol (and / or diol)

  reduced molecular weight can be added to the concentrate as a diluent to facilitate manipulation of the acidification composition in the field,

  especially at low ambient temperatures.

  Thus, the invention relates to an acid adjuvant

  which consists essentially of a phosphate ester surfactant to which about 20 parts by volume of a C 4 to C 18 aliphatic alcohol has been added which is substantially insoluble in water per part by volume of water. surfactant and a mixing volume of a water-soluble alcohol or diol of lower molecular weight and water in volume substantially equal to the sum of the volumes of the surfactant and the insoluble alcohol, the water being present at a rate of 2 to 20 'O in

  volume of the adjuvant resulting from acidification.

  The invention also relates to the use, as

  aqueous acid solution of any conventional acidifying fluid

  cation, the use as a high molecular weight alcohol of a C 6 to C 8 alcohol, preferably isooctanol, and the use as a phosphate surfactant

  ester, a phosphate ester of an oxyalkylated fatty alcohol.

  The invention thus relates to an adjuvant and an acidification solution having excellent properties for displacing oil during acidification treatment.

  of a well It also concerns this adjuvant or this solu-

  acidic reaction with known acidification treatments.

  particularly in the form of a flush or fluid without sand prior to other solvents and the like, or

  posterior hunt after other solvents and the like.

  According to the invention, the concentrate or adjuvant is compatible with conventional methods and apparatus used in the field, and implements in particular a mixture on site

with the acidification solution.

  More specifically, according to the invention, a mixture of a surfactant based on a phosphate ester and an alcohol is incorporated in the acid solution used for the treatment of a petroleum well. This incorporation can be carried out additionally. from mixture to solution

  acid before injection, in the form of a hunt or soil

  without prior sand and separated, or even in the form of a posterior flush, with an acid solution, the mixture resting so that it mixes in situ with the solution

  acid The alcohol is chosen in such a way that it is

  Insoluble in water and therefore in acid, but compatible with petroleum The surfactant based on qv phosphate ester seems to be suitable only for the solubilization of alcohol with formation of an acidification solution

  having extraordinary properties of moving oil.

  The advantages of using an acid solution containing octyl alcohols for the displacement of oil have been established, according to U.S. Patent No. 3,819,520, by observing the interfacial tension of the solution. acid and an oil phase Octanols dissolve in the acidic solution because of the presence of a significant (overall) percentage of a low molecular weight alcohol acting as an auxiliary solvent A ternary diagram of the phases, represented in this patent, corresponding to 15% of HC 1, isooctanol and isopropanol, indicates that 22% by volume of isopropanol ensure the solubilization of octanols at a rate of 2% by volume in the acid. , while 30 volumes of isopropanol solubilize 20% by volume octanol This patent also indicates that in

  practical conditions, there are no other products of

  such as octanols and C 3 alcohol as sol-

  Thus, the solubilization of an alcohol of high molecular weight with an alcohol acting as an auxiliary solvent is not only limited to C 8 alcohols but also implies that a minimum of 24% by volume. of

  the resulting solution of acidification is formed of an ad-

juvant.

  On the contrary, the invention ensures the solubilization

  alcohols of high molecular weight by addition

  of a surfactant based on a phosphate-ester L'al-

  Cool can be virtually any C 4 to C 10 alcohol that is practically insoluble in water. All of these alcohols, in combination with the phosphate ester surfactant and the acid solution, effectively disintegrate and disperse. emulsions, sludge and oil deposits They form an aqueous phase

  practically free of oil and an oily phase

  provided with water, the surfaces of the solids remaining

  wetted by water saps apparent formation of an emulsion.

  C 6 to C 8 alcohols are advantageous because the rates of disintegration and dispersion of oily sludge are

  in this range A particularly good mix

  tageux contains primary alcohols with branched isomers very close to the general formula RCH 20 H, R being a radical

  branched heptyl, this product being sold as isooctanol '.

  The surfactants used for the solubilization

  The high molecular weight alcohol in the acidic solution must be phosphate ester surfactants. These are anionic detergents formed from mixtures of monophosphates and diphosphates esters of alkyl alcohols, alcohols or phenols. oxyalkylated or the like, one or more terminal hydroxyl groups

  being phosphorylated, so that the compound has the general form

next:

CH _

R-O - CH CH 2 CH 2 CH 2 CH 2 OH

  Where R is an alkyl radical, a phenyl or alkylphenol group, hydrogen or a phosphate group, x and y represent

  the degrees of propoxylation and ethoxylation respectively.

  This surfactant is advantageously used in its acid form; however, the partially neutralized form is equivalent within the scope of the invention to the extent

  o It is transformed in the acid form into a solution

  acidification agent The surfactants of the phosphorus type

  According to the invention, the most preferred ester-esters are phosphatesters of the fatty or oxyalkylated alcohols described in United States Patent No. 3,629,127.

  another advantageous series of surfactants of the phosphorus type

  ester-ester useful according to the invention is that of phosphates-

  esters of "Pluronic" polyols described in US Pat.

  United States of America N 2 674 619.

  When preparing the acid solution

  cation, it is preferable that the surfactant and

  high molecular weight alcohol are pre-mixed

  and form a concentrated adjuvant which is then

  same mixture with the acidificat-ion solution However, the mixture of the aqueous solution of acidification and

  surfactant and alcohol, in any order

  It is also effective, but is not as convenient as the concentrated additive can be transported in the field and then added at will to the location of the well to be treated. When using a concentrate of surfactant and alcohol, the presence of a diluent for reducing the freezing temperature and controlling the viscosity of the mixture is advantageous. advantageously a water-soluble alcohol or diol of low

  molecular weight such as methanol, ethanol, n-propanol

  The diluent also advantageously contains a certain amount of water so that the very polar surfactant remains in solution, especially during applications by

cold weather.

  When preparing the acid solution

  cation itself, or the composition forming the adjunct concentrate the amount of high molecular weight alcohol present relative to the amount of surfactant is preferably at least 1 part by volume of this alcohol to 4 parts by weight. volume of the surfactant based on

  At this concentration, the acid solution

  The invention has excellent petroleum dispersing properties, as compared to any ingredient used individually with the acid. The ratio of alcohol to surfactant preferably does not exceed about 8 parts by volume of alcohol. 5 parts by volume of surfactant Although concentrations exceeding this limit are not troublesome, this ratio 8/5 substantially corresponds to the upper limit of the agent's ability

  surfactant to solubilize the alcohol in the acid solution.

  The ratio of 2 parts by volume of alcohol for 3 parts

  volume of surfactant is a particular ratio

  advantageously for most alcoholic compositions

and surfactant.

  When preparing a concentrate that must

  to be added later to the aqueous acid solution

  cation, the mixture of diol or alcohol of molecular weight

  Reduced pressure and water, forming the diluent, must be present in an amount that is sufficient to reduce the freezing temperature, reduce the viscosity and keep in solution the surfactant very polar It is generally noted a increasing the convenience of handling the concentrate after addition of any volume of the alcohol (diol) / water mixture. Preferably, about 50% by volume of the alcohol (diol) / water mixture (and even more) is used for

  the total volume of the concentrated adjuvant which is thus diluted.

  The resulting water content should be between about 2 and 20% by volume so that the surfactant can not

  not separate at low temperatures.

  During the preparation of the acidification solution

  the relative amount of the concentrate relative to the acid solution can be as low as 0.2% by volume

  so that the emulsification of the acid and water is avoided.

  The adjuvant has maximum effectiveness for values

  to about 10 to 20% by volume, depending on the amount

  relative strength of surfactant and molecular weight alcohol

  However, a mixture of 95% acid and 5% adjuvant, by volume, is particularly advantageous and is suitable for most applications. This concentration is also very advantageous, compared with the prior art, since the presence of the adjuvant does not represent an essential parameter of the cost and the resulting solution of acidification

  still retains its original concentration.

  Higher concentrations, up to 25%

  viron, are very useful when it is desirable that the

  oil deposits are solubilized to the maximum.

  Experimental results and observations need to be examined in more detail in order to better understand the implementation of the invention, its properties, how it differs from the prior art, and

  what conditions it is used.

  A series of systematic experi-

  with the help of various known categories of surfactants.

  active agents to determine the desired surfactant, i.e., effective for the solubilization of high molecular weight alcohols in acids.

  experimental design involves the addition of approximately 40 cm 3 3 of a solution

  selected acid concentration and about 5 cm 3 of surfactant to a graduated test tube of 50 cm having a glass stopper The combination is carefully mixed to check the solubility is then added a quantity of 1 cm 3 of alcohol high molecular weight

  the graduated test tube and shake it

  observed behavior of the resulting mixture with regard to the solubilization

  This addition of another quantity is repeated.

  1 cm 3 of alcohol and shaking, until no appreciable variation can be detected.

  of these systematic tests are as follows.

Example 1

  In a control test, 45 cm 3 of HCl are added at 15% by weight and 5 cm 3 of isooctanol in a test tube.

  graduated 50 cm 3, with a glass stopper, and vigorous shaking

  The formation of a cloudy dispersion that separates

  mediately in two distinct layers immiscible After minutes of rest, an oily layer slightly cloudy

  6 cm is present on a slightly

  This behavior is considered to be

  of high molecular weight alcohol practically

  insoluble in an acidic fluid.

Example 2

  40 cm 3 of HCl at 15 A by weight and 5 cm 3 of a liquid surfactant (oxyalkylated polyols, alkylphenols oxyalkylated with glycol ether and oxyalkylated and sulphated alcohols) sold under the trade name are placed in the graduated cylinder. "Tretolite" AY 31, and we mix It is

  forms a clear solution with foam after

  of the first cubic centimeters of isooctanol,

  a cloudy dispersion The second cubic centimeter of iso-

  octanol gives a more turbid dispersion with appearance of a separation A third, a fourth and a fifth cubic centimeters of isooctanol are added, with separation

  an oily amber emulsion rising to the upper

  After adding the fifth cm 3, the phase of

  the emulsion has a volume of 7 cm 3 after 5 minutes of rest.

  It is concluded that the solubilization of isooctanol is

  when the surfactant is of the AY 31 type.

Examples 3 to 5

  The procedure of Example 2 is repeated, but

  using, in place of isooctanol, 5 cm 3 of caprylic alcohol

  The results are the same as in Example 2, but the separation is more

fast in the case of decanol.

Example 6

  The procedure of Example 2 is repeated with 40 cm 3 of HCl at 15% by weight and 5 cm 3 of the addition product of 9.5 moles of ethylene oxide with nonylphenol, sold under the brand name of "Surfonic" N-95 factory, forming the agent

  surfactant This agent forms a precipitate and flocculates during

  it is added to the acid Heating and vigorous stirring cause the formation of a clear solution but with a lot of foam After addition of the first cubic centimeter of isooctanol and shaking, a clear solution is formed, apart from the air bubbles The second cubic centimeter of isooctanol gives practically the same

  results with some phase separation The third

  second cubic centimeter gives a cloudy solution with

  entrained air bubbles and the separation of an oil layer

  After the fourth cubic centimeter of isooctanol, the solution seems quite clear, but a fifth centimeter

  cube causes the formation of an opaque emulsion, without foam.

  After the addition of the second cubic centimeter, the solutions

  are viscous After 15 minutes of rest (5 cm 3 of

  octanol), 3 cm 3 of limpid oil is formed in the

  approximately 36 cm 3 of an intermediate layer of emul-

  low density cloudiness Apparently, most of the

  of the isooctanol phase is still being separated.

  An hour later, we observe three clear layers: 10 cm 3

  at the bottom, 31 cm 3 in the middle and 9 cm 3 of oil in the upper part.

  It is concluded that this surfactant is a poor

  solubilising agent for isooctanol in acid and

stabilizes the emulsions.

Example 7

  The above process is repeated with 40 cc of HC 1 to 15% by weight and 5 cc of a commercial surfactant "Morflo" II which is probably an oxyalkylated alcohol.

  and an alkylsulfonate in butanol A solution is formed

  limpid amber complex with a very slight cloudiness after ad-

  After the addition of 1 cm 3 of isooctanol, the solution forms a cloudy dispersion after the first cubic centimeter, a very cloudy dispersion after the second, and an emulsion with separation of an oily phase from

  from the third addition and subsequently after

  of 5 cm 3 of isooctanol in total, a

  paration of 1.5 cm 3 After 5 minutes of rest, 12 cm 3 of a dense emulsion are present, the rest being turbid On

  concludes that the agent "Morflo IV" is a poor solubilizing agent

  reading isooctanol in HC 1 to 5% by weight.

Example 8

  40 cm 3 of HCl at 15% by weight are mixed with 5 cm 3 of phosphate-ester surfactant sold under the trademark using the same empirical method.

  "Klearfac" AA-420 A lim-

  The first three additions of 1 cm 3 of isooctanol dissolve, so that the solution is clear The fourth centimeter-cube forms a stable cloudy mixture and the fifth a stable emulsion After cm 3 of isooctanol added in total and 15 minutes of rest,

  1 cm 3 of a limpid oil separates at the top.

  Properties of this phosphate ester surfactant appear to be superior to those of other agents

previously tried.

Example 9

  A second phosphate-ester surfactant sold under the tradename "Klearfsc" AA-040 is tested by forming a clear solution using a combination of 5 cm 3 of the surfactant and 40% of the surfactant. cm 3 of HC 1 to 15% by weight The addition of the first cubic centimeter 1 l of isooctanol still gives a clear solubilized solution, with a slight haze formed by adding the second centimeter

  cube of alcohol The third centimeter-cube gives a dis-

  persion or cloudy emulsion while the fourth form an emulsion The fifth cubic centimeter-isooctanol gives a white emulsion which, after 15 minutes of rest, forms 2 cm 3 of a slightly cloudy oil coming to the part

upper emulsion.

Example 10

  One experiences in a similar way a third

  "Klearfac" AA-270 phosphate ester surfactant.

  1 cm 3 of isooctanol is added to the clear solution and mixed. However, in this case, a total of 9 cm 3 is added before the resulting mixture passes from a clear solution with possibly a very slight cloudiness. cm) to a translucent disorder (9 cm 3) but still in the form of a stable mixture 2 hours later, the mixture at 9 cm 3 is still in the form of a stable dispersion and cloudy without apparent separation There is little observed moss and some opalescence from the fourth to the seventh

  cubic centimeter of isooctanol This composition (9 cm 3 of iso-

  octanol, 5 cm 3 of "Klearfac" AA-270 and 40 cm 3 of HCl at% by weight) rests overnight The next day,

  it is observed that 4 cm 3 of limpid oil form a superior layer.

  and 50 cm 3 of the bottom layer form a

  Thus, 5 cm 3 of "Klearfac" AA-270 allow a permanent solubilization of at least 5 cm 3

  about 15% by weight of isooctanol in HCl, more specifically

  in a solution at about 25% by volume of surfactant and 75% by volume of HCl at 15% by weight Ce

  result suggests the presence of a specific characteristic

  possibly stoichiometric corresponding to the

  mation of a coordination complex or the like in the solution. The foregoing examples show that phosphate esters are a much higher class

  other types of surfactants for the solubilisa-

  isooctanol in hydrochloric acid.

  Examples 11 to 14 Samples of 5 cm 3 of hexanol are added,

  of caprylic alcohol, n-octanol and decanol to

  separate vials containing mixtures of 40 cm 3 of HC 1 to 15% by weight and 5 cm 3 of "Klearfac" AA-270, in order to verify the solubility (more precisely the solubilization,

  that is to say, it is not necessarily a question of equi-

  free thermodynamics) of other alcohols by the surfactant

  phosphate ester type active acid solution in all

  the cases except for decanol, we obtain a lim-

  pide indicating excellent solubilization of alcohol.

  Decanol gives a stable dispersion and haze characterized

tick of good solubilization.

Examples 15 to 18

  A series of experiments are carried out to de-

  terminate other commercially acceptable compositions and verify that a concentrate of a high molecular weight alcohol can be prepared in admixture with a surfactant

  phosphate ester type, which can be dissolved at any concentration

  in well-treating acids, for example HC 1 and HCl / HF mixtures at a concentration of 5 to 20%

  (sludge acids) The experiments are aimed at

  a concentrate that could be easily

  as a well acidification additive, which can be

  supplied directly in the field and added to the acid

  In this form, the concentrate must be stable, must have a low viscosity which facilitates handling and must have a low freezing temperature. The presence of various vehicles is therefore studied so that the

  concentrate has the properties corresponding to these

pragmatic deeds.

In Example 15, 25 cm 3 of phosphate ester-type surfactant ("Klearfac" AA-270) is added to cm 3 of isooctanol and 50 cm 3 of isopropanol acting as a vehicle (adjuvant reducing the viscosity and reducing the freezing temperature) After stirring, a clear solution is obtained. A sample of 5 cm 3 of the above mixture is added to 95 cm 3 of a 15% solution by weight.

  After shaking, a cloudy dispersion is formed.

  An additional 5 cm 3 sample of the original mixture of alcohol and surfactant is added to the acidic dispersion with stirring. A clear solution is obtained. It is concluded that the ratio of surfactant to High molecular weight alcohol is increased so that solubilization is achieved at low total concentrations. In Example 16, a concentrate is prepared by mixing 35 cm 3 of "Klearfac" AA-270 agent, 15 cm 3 of isooctanol and 50 cm 3 of isopropanol. A clear solution is again obtained. clear solutions with this concentrate for 0.5, 1.0, 3.0, 5.0 and 10.0% by volume of concentrate in HC 1 at 5%, 10%, 15% and 20% by weight,

  showing good solubility for all concentrations.

  Good solubility in the blends is also observed

HC 1 / HF.

  In Example 17, 30 cm of "Klearfac" AA-270 and 20 cm 3 of isooctanol are combined to determine which are the viscosity reducing agents and freezing temperature reducers that can be used.

  We experience this mixture and we see that it is soluble

  at all concentrations in methanol, isopropanol

  nol, butanol and ethylene glycol.

  In Example 18, a mixture of 300 cm 3 of "Klearfac" AA-270, 200 cm 3 of isooctanol, 400 cm 3 is prepared.

  isopropanol and 100 cm 3 of water.

  Clarity to determine pour point and physical properties Water is added so that the very polar phosphate ester type surfactant

  remains in solution when the mixture is cooled.

  From the foregoing results, it is considered that the concentrated compositions of Examples 11 to 14 are acceptable as acidic adjuvants for preventing the formation of emulsions, for the purification of wells and for the general stimulation thereof, and in the form of A sludge removing agent, a wetting agent, a dispersing agent, a mutual solvent and a solubilizing agent. It is furthermore ascertained that the amount of concentrate required in the final acid is also low than 0.2% for prevention of emulsion formation

  acid-oil, and can reach 10 to 20% by volume

  that the efficiency must be maximum 5% in volume

  viron concentrate in the acid must be suitable for

most applications.

EXAMPLE 19

  Another phosphate ester surfactant available in the "Pluraflo" F-90 panel as described in Example 11 was tested by placing 40 cm 3 of HCl at 15 wt% and 5 cm of "Pluraflo".

  OF-90 in a graduated cylinder with a glass stopper.

  After mixing, a clear solution is formed in which

  1 cm 3 of isoocta-

  After addition of the first cubic centimeter, a slight opalescence is observed in the single-phase solution, which is otherwise clear. At the end of the fifth or sixth cubic centimeter, the opalescence gives a slightly hazy appearance. The seventh centimeter Iso-octanol cube forms a stable dispersion and the oil

  addition produces a very cloudy emulsion.

  Overall characteristics obtained with "Pluroflo" OF-90 correspond to Example 2, but the surfactant is probably not as concentrated as indicated by the lower ability to solubilize the higher alcohol, but, bluntly it is a very product

  acceptable replacement of the agent "Klearfac" AA-270.

EXAMPLE 20

  A 20 cm sample of "Klearfac" AA-270 was added to a 10 cm 3 sample of "Surfonic" N-95

  (mixture of nonionic surfactants you type phos-

  ester phase) in order to determine the effects of the mixing of different categories of surfactants.

  at 40 cm 3 of HCl at 15% by weight, 5 cm 3 of the agent mixture.

  surfactants and a clear solution is obtained After addition of successive amounts of 1 cm 3 of isooctanol, it is noted that a slight disorder evolving to a cloudy dispersion & appears after the third cubic centimeter The fourth cubic centimeter gives a lightening with a slight haze and the fifth gives a very turbid emulsion that appears unstable One concludes that the use

  mixtures of categories of surfactants do not

do not feel any special benefits.

EXAMPLE 21

  A comparative visual test of the characters is performed.

  Characteristics of Dissolution of a Series of Six Acidification Compositions to Indicate the Advantageous Effects of the Invention The first acidification composition is a 5% by volume solution of the composition of Example 15, employing a mixture of phosphate ester and a high molecular weight alcohol, from% by volume of HCI to 15% by weight The other five

  Comparative compositions are available in the

  and comprise 10% by volume of ethylene glycol monobutyl ether in 15% by weight HCl, 35% by volume of a mixture of isopropanol and isooctanol in 15% by weight HCl sold under the trademark "A-Sol" and prepared according to U.S. Patent No. 3,819,520, 5% by volume of "AY 31" surfactant in 15% by weight HCl (Example 2), 5% by volume of surfactant "Morflo" II in HCl at 15% by weight (Example 7), and 5% by volume of "Surfonic" surfactant N-95 in HCl at 15% by weight, for example 6) We use each

  composition for the dissolution of an oil deposit sludge

  The sludge contains about 20% by weight of heavy hydrocarbons, 70% by weight of acid-soluble inorganic materials (essentially calcium carbonate), and 10% by weight of water. clays and silica silt (insoluble fines in

  acid) The samples are immersed almost identically

  sludge ticks in excess of each of the indicated acidification solutions The phosphate ester and higher alcohol acidification solution breaks, dissolves and disperses the semi-solid sludge faster than all

  the other solutions The oil floats to the upper part

  and the silt is dispersed in the aqueous acid phase.

EXAMPLE 22

  A synthetic slurry is prepared by mixing 90 parts by weight of calcium carbonate (CaCO 3) and 10 parts by weight of kaolinite clay in additional tests.

  crude waxy and heavy, until a firm paste is formed.

EXAMPLE 23

  5 g of the paste are added to 100 cm 3 of HCl in% by weight in a beaker. Only a slow action is observed as indicated by a bubbling (release of CO 2) and the release of oil. released oil is sticky and is emulsified and the clay remains in the form of an oily block The piece of dough to

  not disintegrate after one hour at room temperature.

EXAMPLES 24 TO 26

  A phosphate ester and high molecular weight alcohol concentrate according to the invention is prepared containing 20% by volume of "Klearfac" AA-270, 20% by volume isooctanol, 40% by volume isopropanol and 10% by weight. Therefore, a 100 cm 3 sample of a 5% by volume mixture of the concentrate in HCl at 15% by weight

3 1

  weight contains the equivalent of 1.5 cm of "Klearfac",

  1.0 cm 3 of isooctanol and 2.0 cm 3 of isopropanol.

  An analogous acidification solution of 100 cm 3 was prepared without the high molecular weight alcohol but containing 1.5 cm 3 of "Klearfac", 2.0 cm 3 of isopropanol and 96.5 cm 3 of HCl. % by weight 100 cm 3 of an acidification mixture is also prepared by combining 1.0 cm 3 of isooctanol, 2.0 cm 3 of isopropanol and 97.0 cm 3 of HCl at 15% by weight; without the surfactant phosphate ester type is present The mixture is cloudy

  and separation occurs unless frequent agitation occurs.

  A 5 g sample of the syn-

  the example of Example 22 in each of the acid solutions

  100 cm 3 solution The solution does not contain iso-

  octanol disintegrates the sludge more rapidly than the HCl solution at 15% by weight alone of Example 23 It takes about 30 min for the disappearance of the mass The oil

  placed above is emulsified (gum) with no indication of

  Persion Solids appear wet by

  The result is better than nothing but is not enough

  cient. The solution containing no surfactant is only slightly better than the solution containing only HC 1 Most of the isooctanol appears to float at the top No foam is observed The released oil is present in the Isooctanol phase No emulsion is observed After one hour, the sample of 5 g of oily dough did not

not totally disintegrated.

  In the case of the acidification solution

  keeping both the isooctanol and the surfactant "Klearfac", the disintegration of the oily dough is very fast with release of large amounts of foam is not observed emulsion The solution becomes dark because of the dissolved oil ( some of the oil is free in the foam) All the sludge disappears in min The suspended solids in the phase

  lower water are wetted with water.

  The above description shows that the mixture

  of phosphate ester and a high molecular weight alcohol, with a suitable ratio, allows the formation, in combination, of an acid-soluble composition

  (HCl at 15% by weight), this composition being well above

  to each of the separate constituents for disintegration

  the dissolution and dispersion of the oil sludge

  The composition according to the invention prevents emulsification and gives better foaming than the surfactant alone, thus indicating that its properties of

  surfactant or detergency are improved.

EXAMPLES 27 AND 28

  The following two concentrated compositions are prepared in order to determine the effect of the variation of

  the relative proportion of the surfactant and the

  cool high molecular weight.

  Concentrate NO 1 Concentrate NO 2% vol of "Klearfac X AA-270 40% vol of" Klearfac "AA-270% vol isooctanol 10% vol isooctanol 40% vol isopropanol 40% vol isopropanol% vol of water 10% vol of water 5 cm 3 of the concentrate NO 1 is added to 95 cm 3 of HCl at 15% by weight and a cloudy dispersion (emulsion) is obtained. After addition of 5 g of the oily mud of Example 22, a slow reaction occurs with less foam than in Example 26 It takes 20 to 30 minutes for the oily mass to be broken The excess of isooctanol may be responsible for the slow reaction because of the "wetting by oil "solids present

in the mud.

  cm 2 of the NO 2 concentrate, added to 95 ml of 15% by weight HCl gives a clear solution of acidification The addition of 5 g of the oily sludge to 100 cm 3 of the acidification fluid containing the NO concentrate 2 gives a faster reaction but is not as fast as in example 26 It takes about 20 minutes for

that the mud be dispersed.

  The foregoing examples taken together show that phosphate ester surfactants such as "Klearfac" AA-270 can solubilize ("by micellar dissolution") high molecular weight alcohols such as octanols, by

  acid solution with a ratio of up to 8

  about 5 parts of surfactant.

  The most stable solution is obtained with equal parts of surfactant and high molecular weight alcohol, the total concentration of the composition (agent and alcohol complex) being about 25% by volume

  in acid When the total concentration is only

  5% by volume in the acid (value desirable for reasons of economy>, the best ratio corresponds to about 3 parts of surfactant for

  2 parts of high molecular weight alcohol A quantity

  as low as a proportion of alcohol of molecular weight

  high volume for 4 parts of surfactant gives

  properties superior to those of the surfactant

  active alone Alcohol alone is not acceptable at almost

  from all points of view, given its low solubility.

EXAMPLES 29 AND 30

  A series of three concentrates are prepared with n-butanol of normal hexanol and normal decanol.

  to try various high molecular weight alcohols.

  Each concentrate contains 30% by volume of "Klearfac",% by volume of alcohol of high molecular weight,% by volume of isopropanol and 10% by volume 3 'water,

  Three corresponding solutions of acidification are prepared

  addition of 5% by volume of the 95% concentrate

  in volume of HCl at 15% by weight.

  decomposition properties of synthetic sludge as

  described in the previous examples, with each of the

  All the solutions give good sludge disintegration and dispersion properties, but the solutions with butanol and decanol are not much faster than using the surfactant alone, thus confirming that the alcohols C 6 to C 8 are preferable although the C 4 to C 10 alcohols are suitable. All the higher alcohols (C 4 to C 10) cause the oily phase of the sludge to break without any apparent formation of an emulsion. a

  progress, even with slower-acting alcohols (C 4-

  C 10) with respect to the use of the surfactant

  only (phosphate ester) for the treatment of oils.

  This property is probably related to solubility

  preferential higher alcohols in the oil phase.

  For example, isopropanol, which is much more water soluble than butanol, does not give the emulsion prevention effect when used with the agent.

  "Klearfac" As a result, the compositions according to

  The invention requires an alcohol with low solubility in water so that the penetration of oily sludge is improved and the formation of emulsions is minimal.

EXAMPLES 31 TO 37

  A series of seven concentrated solutions is

  to determine the recommended concentrations

of water in the concentrate.

  Concentrate 1 2 3 4 5 6 7% by volume of "Klearfac" AA-270 30 30 30 30 30 30% by volume of isooctanol 20 20 20 20 20 20% by volume of isopropanol 50 48 47 45 40 35 30% vol of water O 2 3 5 10 15 20 On each of the solutions, the point is determined

  casting according to the ASTM D-97 method.

  I gives the results obtained.

TABLE I

  Concentrate Observations i significant separation of white solid pieces

at 1300

  2 important separation of white solid pieces

at 330 C

  3 no separation, but high viscosity at 370 C 4 no separation, but high viscosity at 370 C no separation, but high viscosity at 370 C 6 no separation, but high viscosity at 370 C 7 pieces separation-at 320 C, solidification

at 370 C

  The table above shows that 2% of water

  at least 18% of water are

  The densities of concentrate 4 (5% water) and concentrate 6 <15% water) are determined to be equal to 0.925 and 0.950 respectively. determines, for the concentrate 6, a flash point of 780 C, a combustion point of 880 C, and a viscosity of 38 c P to 1000

(ASTM D-93).

EXAMPLE 38

  60 cm 3 of Klearfac® AA-270 are mixed with 40 cm 3 of isooctanol, with formation of a viscous solution

  limpid, in order to demonstrate that phosphate ester and

  high molecular weight coolants are soluble in an acid without the presence of a diluent and the resulting acidification solution is very effective after mixing

  5% hydrochloric acid and 15% by weight respectively.

  it is determined that the mixture of the agent and the

  cool is soluble in any proportion Thus, reduced molecular weight alcohol is not indispensable for the solubilization of high molecular weight alcohol

in the acid.

  5 cm of the aforementioned mixture of agent and alcohol are mixed with 95 cm 3 of HCl at 5% by weight, and the mixture obtained is added to 5 g of the synthetic sludge.

  disintegrates and dissolves quickly.

  1 cm 3 of the agent and alcohol mixture are then added to 99 cm HCl at 5% by weight, and

  all to a second sample of 5 g of synthetic sludge.

  This one disintegrates and dissolves again quickly.

  Dement. The operation is repeated with 3 cm 3 of the agent and alcohol mixture and 97 cm 3 of sludge acid (12% by weight of HCl and 3% of HF). The sludge decays and

dissolve again quickly.

  It is concluded that the complex of the phosphate ester and the high molecular weight alcohol has good properties in the acid, alone and without diluent, for example in the form of low molecular weight alcohol.

or water.

EXAMPLES 39 TO 45

  A series of eight acid solutions is prepared

  with 30% surfactant, 20% isooctanol,% isopropanol and 10% water (composition of Example 24) forming a phosphate ester and alcohol concentrate,

  as shown in Table II which follows, in order to determine

  the compatibility of the acidification compositions

  according to the invention with other acids.

TABLE II

  Concentration-Acidification 1 2% by volume Concentrate 20 20

Glycolic acid 40 -

  Sulfamic acid Acetic acid 40 Citric acid HCl (32%)

NH 4 HF 2

Isopropanol 10 10

Methanol _ -

4 5 6 7 8

2015

8 12

10 25

10 10

_ 5 -

10

10 10

_ 10 10 15

30 30 50 55 40 55 30

  As previously indicated, the acidic solutions to which the agent-alcohol mixtures are added can be any aqueous solutions of water-soluble acids.

  commonly used for acidification of formations.

  The aqueous acidic solutions may contain from less than about 5% to more than about 30% by weight of acid, and the mixture of the surfactant and the high molecular weight alcohol remains soluble, the acid solution remaining stable A solution is preferably used

  of HCl at 7-15% by weight, for the acidification of the wells.

  The acidification adjuvant according to the invention is essentially compatible with all the processes

  acidification It can be used for the treatment of

  wells in production, for example in the injection

  water in an oil formation or during the implementation of secondary and tertiary recovery operations In a production well, the aqueous acid solution and the adjuvant formed by the agent and the alcohol are injected into the oil formation and the well is returned to production In a water injection well, the acid and the adjuvant are injected into the oil formation, and an additional amount of fluid

and then injected.

  Whether it is a production well or a well

  In addition, the adjuvant can be mixed with the acid solution or it can follow and / or precede the acid solution, any combination that can be used. These processes are also suitable in the case of fluids without flush sand or other solvents. known for various purposes without being limited to various aromatic solvents for the removal of asphaltenes or other

  heavy, various sulfur solvents and the like.

  The main characteristic of the transmission of the adjuvant formed by the surfactant and the alcohol before the acid solution is the displacement of the oil lying in front of the acid, so that the mixing and optionally the emulsification are reduced.

2 5 143-64

  batch process also ensures the dissol-

  1-ubilization of organic deposits that could prevent

  the circulation of acids in the oil layers.

  This batch process of injection of the adjuvant formed by the agent and the alcohol also breaks the emulsions which

  tend to form under the action of emulsifying agents

  present The setting of the concentration of the ad-

  The present invention, which is present in a successive injection, can also be used to selectively adjust, at will, the particular functions of breaking emulsions, removing

  organic deposits and acidification.

  The advantages of admixture with acid are the solubilization of the oil in contact with the acid, and the better displacement by the acid, so that the surfaces of the solids, especially when they are finely divided, remain The adjuvant, used after the acid, is useful for moving and

  the dissolution of oil and organic solids

  which have not been moved or dissolved in previous operations This applies in particular where the adjuvant has not been used in operations

  An adjuvant transmitted in a discon-

  after the acid solution is especially interesting

  in a water injection well so that it ensures

  placement of all remaining oil so that a larger pore space is available for circulation

  water injected into the formation.

  The amount of acid can be between less than one cubic meter and several tens of cubic meters, as usually used for acidification

  However, the treatment is usually

  essentially to the area immediately surrounding the borehole so that the volumes are less than the average value

  between 2 and 20 m 3 In other words, a

  from 0.13 to 7 m 3 of acid per meter of thickness of the forma-

  as recommended by the United States Patent

  of America No. 3,548,945, gives satisfaction.

  When a pre-flush solution or sandless surfactant-alcohol adjuvant precedes the acidic solution, its volume may vary between about 1% of that of the acidic solution for the important acid treatments and about 100% of the volume of the acid solution. In this case, the ratio of the surfactant to the high molecular weight alcohol can also be adjusted taking into account the individual interaction with the oil deposits. volumes for adjuvant solutions used as posterior hunt for displacement

  of the acid solution in the formation.

  When cleaning injection wells, that means

  that is, the removal of sludge, emulsions and deposits that form plugs, when the acidification of the formation is not the main objective, it is often advantageous to reduce the total volume of the acidic solution

  and to increase the concentration of additive

  It is interesting from the point of view of the profitability

  because it reduces costs In addition, the report of the

  cool higher than the surfactant can be increased as described in Example 15 so that the cost is reduced

  (since the surfactant has the most expensive agent).

  As mentioned above, the main application

  of the invention are oil wells and injection wells in water injection operations

  The process is sometimes useful for the treatment of

  gas wells and gas condensate wells.

  Many gas wells produce some oil, just as many oil wells produce a little gas As a result, organic deposits can form in and around wells Many gas wells form water As a result, mineral deposits may also form in and around wells where wells are acidified to remove mineral deposits or

  flow of gas to the well is increased, the oil

  In these applications, the ability of the adjuvant according to the invention to form a foam is an advantage for the recovery of the acid from the formation in which the formation can be emulsified with the acid as in the oil wells. and when using nitrogen in

  the same purpose. Thus, many similar problems,

  it is desirable to use the additive adjuvant

  alcohol-active in the acidification of oil wells,

  often arise in the case of gas wells and

  densat. The method and advantages of using surfactant-alcohol adjuvant according to the invention during acidification are clearly apparent in the

examples that follow.

EXAMPLE 46

  An ethoxylated nonylphenol (an adduct of 4 moles of ethylene oxide (having a

  terminal hydroxyl sold under the trademark "Sur-

  Fig. 40 shows the use of a high molecular weight alcohol replacement alcohol in the adjuvant according to the invention. This surfactant has practically no solubility in 15% by weight HCl ( as isooctanol) but it disperses in this

  acid (emulsification) An adjuvant composition is prepared

  boasting 25 cm 3 of "Surfonic" N 40, 25 cm 3 of "Puraflo"

  OF-90 and 50 cm of isopropanol The adjuvant forms a solution

  2% to 10% by volume in HCl at 15% by weight is added. 100 cm 3 of the adjuvant at 5% by volume in HCl at 15% by weight are added to 5 g of a sludge containing 15% by weight.

  The observed rate of dissolution and dispersal

  is not as great as isooctanol-containing adjuvants or as complete, but the results are acceptable because the solids are wetted with water and do not appear at the top.

  a thick oily layer (emulsion) The experiment is repeated

  without ethoxylated nonylphenol and a layer is obtained

* oily viscous much too thick at the upper part

  It is concluded that the agent "Surfonic" N 40 can be used but is not as good as the alcohols

  linear high molecular weight.

  Although Oleo mono-functional alcohols

  soluble but practically water-insoluble

  other alcohols with soluble properties.

  hydrophilic-lipophilic balance and similar to those

  linear C 6 to C 8 alcohols can be used.

  For example, the solubility and hydrophilic-lipophilic balance of very high molecular weight (C 12 to C 22) fatty alcohols, polypropylene glycol or polybutylene glycol, alkyl-substituted phenols and C 12 to C 22 fatty acids can be achieved. under favorable conditions of use by reaction with a few moles of ethylene oxide The substances formed which have the necessary solubility in the oil and at least one terminal hydroxyl group so that they possess the alcohol character, can be represented by the general formula:

R-R O + CH 2 CH 2 O XCH 2 CH 2 OH

  in which R 1 represents CH 3 or -CH 2 CH 2 OH, R 2 represents

  A C 11 to C 21 hydrocarbon chain, polypropylene oxide or polybutylene oxide or a fatty acid residue - (CH 2 to C 10 -C 20), a C 8 to C 8 alkyl substituted phenyl moiety. at C 10, and x is an integer from 3 to 15 and represents the number of moles of oxide

  ethylene added to the radical R 2.

EXAMPLES 47 TO 53

  We run a series of field tests

  for the implementation of the invention, on

  water, oil production and gas production Each test employs an adjuvant containing

  % by volume of "Klearfac" AA-270 agent as surfactant

  phosphate ester, 20% by volume of isooctanol, 40% by volume of isopropanol and 10% by volume of water.

  The results of the tests are shown in Table III.

  Type Location (Texas County) pie * Cass gas ** Panola pet *** Rusk pet Wood gas Marion gas Henderson pet Cherokee

TABLE III

  Formation / depth Volume (m 3) m Acid / Adjuvant Haynes Mitchell / 1370 3, 6 / 0.19 Pettit / 1950 1.8 / 0.015 Woodbine / 1130 4.3 / 0.23 Subclarsville / 1220 3.6 / 0, 19 Travis Peak / 2650 3.6 / 0.19 Rodessa / 2130 10.8 / 0.57 Woodbine / 1100 3.6 / 0.19 Production before / after 1654 m 3 at 6.65 106 Pa 1665 m 3 at 2 , 8 10 Pa 7080/17000 m 3 petroleum 1,59; water 33.5 / petroleum 8.9; water 26.7 m 3 petroleum 1,7; water 5.1 / petroleum 2,5; water 11.1 m 3 8500 m 3 to 4, 2 10 Pa without throttling 3400 m 3 to 1.2 10 Pa throttling 6.7 mm 283 / petroleum 3.0; water 4.4 / petroleum 9.4; water 4.4 m 3 * water injection well ** gas production *** oil production Co A p. w

EXAMPLE 54

  A water injection well placed in Smith County, Texas, is used for the injection of water into the Paluxy formation at 200 m, with a flow rate of 320 m 3 per day at 1.4 107 Pa, with a mixture of 1.9 m 3

  of 15% by weight HCl containing 5% by volume of the adjuvant

  Examples 47 to 53 and 0.76 m 3 of xylene are mixed.

  xylene and the acidification solution, and they are

  It is then used a mixture of salt water and a deflecting agent to flush out the formation and an additional quantity of 13.2 m 3 is injected into the formation.

  acidification solution (with 5% by volume of adjuvant).

  The injection of water is then resumed. Before the treatment, the well accepts 320 W 3 of water per day at 1.4 107 Pa After

  treatment, the injection of water is 720 m 3 to 3.5 10 Pa.

  We easily note from the description that

  precedes that, in addition to the advantages of economy of the adjuvant used compared to known compositions, the method of use of the compositions according to the invention allows

  savings associated with the implementation of

  and increasing the production of wells

oil and gas.

  It is understood that the invention was not -

  described as a preferred example and that any technical equivalence in its elements can be

  constituents, in particular in the preparation and use of

  addition of surfactant-alcohol adjuvant and

  acidification, without departing from its scope.

  Thus, other acid stable additives

  Various functions may be present, including adjuvants such as corrosion inhibitors, formation stabilizing additives, tracers, anti-emulsion agents, asphaltene solvents.

and the like.

Claims (30)

  1 Acidification composition for processing   of the oil-bearing formations, characterized in that it comprises: (a) an aqueous acid solution, (b) a C 4 to C 10 aliphatic alcohol, and (c) an amount of a surfactant of the type   phosphate ester effective for the solubilization of cool in the acid solution.   Composition according to Claim 1, characterized   In this process at least 70 parts by volume of the aqueous acid solution containing not more than 20% by weight of acid are combined with not more than about 25 parts by volume of a mixture of the aliphatic alcohol and the surfactant of the mixture. phosphate ester type, the mixture containing at most about 8 parts by volume of alcohol   parts by volume of surfactant.   3 Composition according to one of claims 1   and 2, characterized in that the acid is selected from   group that includes HCl, HF, acetic acid, sulpha   mic, citric and glycolic, NH 4 HF 2, and mixtures thereof.   4 Composition according to one of claims 1   and 2, characterized in that the aliphatic alcohol is a C 6 to C 8 alcohol.   5 Composition according to one of claims 1   and 2, characterized in that the phoshate ester surfactant is a phosphate ester of a fatty alcohol oxyalkylated -   6 Composition according to one of claims 1   and 2, characterized in that the acid is selected from   HCl, HF and their mixtures, the aliphatic alcohol is the   tanol, and phosphate ester surfactant   is an oxyalkylated fatty alcohol ester phosphate.   Composition according to claim 6, characterized   in that the aqueous acid solution is 15% by weight HCl, the aliphatic alcohol is isooctanol and the phosphate ester type surfactant is selected from   group that includes "Klearfac" AA-270 and "Plurafo" OF-90.   8 Composition according to one of claims 1 and   2, characterized in that it further contains a quantity   effective efficiency of an alcohol or low water soluble diol molecular weight.   Composition according to claim 2, characterized in that 90 parts by volume of the at least one acid are combined with 10 parts by volume of the mixture at the most. Acification builder, characterized in that it contains:   (a) a C 4 -C 10 aliphatic alcohol, practicing insoluble in water, and   (b) a phosphate ester surfactant.   An adjuvant according to claim 10, characterized in that it further contains: (a) a water-soluble alcohol or diol of low molecular weight, and b) water.   Adjuvant according to Claim 11, characterized in that the water-soluble alcohol or diol of low molecular weight is selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, t-butanol and ethylene glycol.   Adjuvant according to any one of the claims   10 to 12, characterized in that the alcohol is an alcohol   cool C 6 d C 8, and the surfactant is a phosphate ester of an oxyalkylated fatty alcohol.   Adjuvant according to one of claims 10 and   11, characterized in that the ratio of the alcohol to the surfactant is between about one part by volume of alcohol to 4 parts by volume of surfactant, and 8 part by volume of alcohol for 5 parts by weight. volume of surfactant.   Adjuvant according to Claim 14, characterized in that the ratio of the alcohol to the surfactant is between about 2/3.   Adjuvant according to claim 11, characterized in that the water-soluble alcohol and water represent   at most about 50% of the volume of the resulting adjuvant.   Adjuvant according to Claim 16, characterized in that the water is present in an amount of at least 2% by volume but less than 20% by volume approximately.   Adjuvant according to one of claims 16 and   17, characterized in that the ratio of the alcohol to the surfactant is between about one part by volume of alcohol to 4 parts by volume of surfactant, and 8 parts by volume of alcohol for 5 parts by weight. volume of surfactant.   Adjuvant according to Claim 18, characterized in that the ratio of the alcohol to the surfactant is about 2/3.   Adjuvant according to Claim 18, characterized   in that the alcohol is a C 6 -C 8 alcohol.   Adjuvant according to Claim 18, characterized   in that the insoluble alcohol is isooctanol.   Adjuvant according to Claim 18, characterized in that the acid is H Cl.   Adjuvant according to Claim 18, characterized   in that the low molecular weight alcohol is iso-   propanol. Acidification admixture, characterized in that it essentially contains a phosphate ester surfactant to which 20 to 160 parts by volume of a C 4 to C 10 aliphatic alcohol, practically insoluble in water, per 100 parts in volume of surfactant were added, and a volume of a mixture of a water-soluble alcohol or diol of low molecular weight and water   practically equal to the sum of the volumes of the surfactant   active ingredient and insoluble alcohol, with water being   about 2 to 20% by volume of the acid adjuvant formed.   Adjuvant according to claim 24, characterized in that the surfactant is a phosphate ester of an oxyalkylated fatty alcohol, the substantially water-insoluble aliphatic alcohol is a C 6 to C alcohol present at about 150 parts by volume, and the mixture of the low molecular weight alcohol and water is present in volume substantially equal to the sum of the volumes of the surfactant and the insoluble alcohol, the water   being present at about 18% by volume.   Adjuvant according to claim 25, characterized   in that the insoluble alcohol is isooctanol, and the   Cool low molecular weight is isopropanol.   Process for the treatment of an oil-bearing formation, characterized in that it comprises bringing the formation into contact with an aqueous acid solution containing a C 4 to C 10 aliphatic alcohol and an amount of a phosphate-type surfactant. ester sufficient for   that the alcohol is solubilized in the acid solution.   Process according to Claim 27, characterized in that the surfactant of the phosphate ester type   is an ester phosphate of an oxyalkylated fatty alcohol.   Method according to one of claims 26 and   27, characterized in that the aliphatic alcohol is a C 6 to C 8 alcohol.   Method according to one of claims 26 and   27, characterized in that the aliphatic alcohol is V'iso-   octanol. Process according to claim 28, characterized in that the phosphate ester surfactant is selected from the group consisting of "Klearfac" AA-270 and "Pluraflcy" OF-90.   Process according to Claim 27, characterized in that the aqueous acid solution also contains a   alcohol or a low molecular weight diol.   33 Acidification composition for processing   of oil-bearing formations, characterized in that it contains: (a) an aqueous acid solution, (b) an alcohol of formula:   R 1 -R 2 -O- (CH 2 CH 2 -O) CH 2 CH 2 OH   in which R 1 represents CH or -CH CH OH, R represents   R 2 represents a C 11 to C 21 hydrocarbon chain, polypropylene oxide, polybutylene oxide or a fatty acid residue - (CH 2 + -a 20 CO-, a phenyl group, and x is an integer of from about 3 to 15, and (c) an amount of a phosphate ester surfactant sufficient to make the alcohol soluble in the acid solution.   34 Process for treating an oil formation   characterized in that it comprises contacting the formation with a composition according to claim 33.