CA1254731A - Phosphate ester/alcohol micellar solutions in well acidizing - Google Patents

Abstract

ABSTRACT OF THE INVENTION
An acidizing additive to be added to an oil well acidizing solution comprising a mixture of a high molecular weight substantially water insoluble alcohol (e.g. isooctyl alcohol), an effective amount of a phosphate ester surfactant (e.g. Klearfax* AA-270), to render the alcohol acid soluble, and a low molecular weight alcohol or diol with water diluent.
Such an additive can be easily delivered and mixed with an acid solution in the field to produce an acidizing medium of superior oil dispersion characteristics.

Description

3~

B
1. Field of the Invention This invention relates to a process and composition for acidizing an oil and gas well. More specifically, the inven-tion relates to an aqueous micellar acidizing solution con-taining a high molecular weight alcohol and a phosphate ester surfactant.

2. Description of the Prior Art 1~ The general concept of acidizing oil and gas wells has long been practiced commercially to clean up, stimulate, and to promote hydrocarbon production. Thus the injection of an aqueous ~olution of an acid such as hydrochloric, hydro-fluoric, acetic, or the like is a common practice. Mutual solvents such as alcohols and ethyiene glycol monobutyl ether are commonly added ~o well stimulation acids to en-hance solids wetting, lower interfacial tension between acid and oil and to break down emulsion sludges. One particular-ly useful mixture is isopropyl alcohol and isooctyl alcohol such a~ described in U. S. Patent No. 3,819,520 wherein iso-propyl alcohol act~ as a necessary cosolvent to render the isooctyl soluble and wherein the combination must be used at relatively high concent~ations to be effective.

L73~L

Surface active agents such as oxyalkylated polyols or oxyalkylated alkyl phenols with sulfated oxyalkylated alco-hols and glycol ethers are known to be used ir. acids as are oxyalkylated alcohols and al~ly sulfonate in butyl alcohol for many of the above purpose~. Other types of surfactants such as the ethylene oxide adduct of octyl alcohol or nonyl phenols have been used.
However, none of the above are as effe~ctive as is de-sired. The glycol ethers, mixed alcohols, and the like are not as good as the surfactants in wetting oily solids, dis-persing solids, or lowering surface and interfacial tension And, surfactants often form ~stablilize) harmful emulsions and are no~ as effective in promoting oil/acid miscibility as are the higher alcohols, which have very low solubility in aqueous acid solutions.

~Z5~73~

- 3 SUMMARY OF THE INVENTION
In view of the shortcomings of the prior art eomposi-tions, I have diseovered a novel oil well acidiziny solution eontaining an additive of superior oil dispersion, solubili-zation, emulsion prevention and solid wetting eharaeteristies when employed with eonventional aeidizing solutions and acid eontaining solutions, and aqueous acid containing oil and gas well treating solutions. The acid cont'aining solutions of the present invention comprise: an aqueous acid eontinu-ous phase, a C4 to C10 substantially water insolublP ali-phatie aleohol (or an aleohol of equivalent hydrophobie/
hydrophilie balanee) and an effeetive amount of a phosphate ester surfactant to render the alcohol soluble in the aqueous . aeid eontinuous phase wherein the phosphate ester surfactant is eharaeterized by the formulas:

2 CH2 O ~ CH2-CH2-o ~ ~-OH or (1) CH3 O~
[R-O~CH2-CH2-O ~ CH -CH -O ~ P-OH (2) where R is about a C8 to C18 alkyl group or about a C8 to Cg alkyl substituted phenyl group, x is from about 2 to 6 and y is from about 12 to 22 and the 2 to 6 moles of propylene oxide are subs~antially a blocl~ polymer attached (bonded)e:.-sentially adjaeent to the R-O ~roup. Aceording to the pre-sent invention at least about 75 parts and preferably 85 to95 parts by volume~of the aqueous aeid solution eontaining up to about 28 wt. ~ aeid is eombined with up to 25 parts by volume of a mixture of C4 to C10 aliphatic aleohol and - ~ -the phosphate ester surfactant wherein the mixture comprises up to about 8 parts by volume al~ohol to 5 parts by volume surfactant. Thus, the acidizing additive or concentrate according to the present invention comprises: a C4 to C10 substantially water insoluble aliphatic alcohol and the phosphate ester surfactant. It is also provided that a water soluble lower molecular weight alcohol (and/or diol) and water mixture be added to the concentrate as a diluent to make the acidizing additive composition more manageable 10 in the ~ield, particularly at low ambient temperatures.
Thus, the present invention provides an acidizing addi-tive essentially consisting of the phosphate ester surfact-ant to which has been added from about 20 to 160 parts by volume of a C4 to C10 substantially water insoluble ali-15 phatic alcohol per 10~ parts by volume of the surfactant and a volume of a mixture of a water soluble lower molecular weight alcohol or diol and water, approximately equal to the sum of the volumes of the surfactant and insoluble alcohol and wherein the water is present in a range of about 2 to 20 20 volume percent of the resulting acidizing additive.
The present invention further proivdes that the aqueous acid solution be any conventional acidizing medium, that the high molecular weight alcohol be a C6 to C8 alcohol and preferably octyl alcohol and the phosphate ester surfactant 25 preferably be a phosphate ester of an oxyalkylated fatty alcohol. I
It is a primary object of the present invention to provide an acidizing additive and solution of improved oil displacing ability during acid treatment of a well and/or ~5~ ~ 73~

aqueous acid flooding of a subterranean formation. It is another object that this additive or acid^solution be use-ful in combination with known acidizing treatments, includ-ing as a preflush or spearhead preceding or as a postflush S following other solvents and the like. It is a further obiect that the concentrate or additive be compatible with conventional oil field equipment and procedure including on site mixing with the acidi~ing solution. ~ The fulfill-ment of these objects and the presence and fulfillment of other objects will be apparent upon complete reading of the specification and attached claims.

- 6~ 7~

DESCRIPTION OF THE PREFERRED EMBODIMENTS
,, In general, fulfillment of the objects of this inven-tion are accomplished by incorporating a mixture of a specific type of phosphate ester surfactant and a re-latively high molecular weight alcohol into the acid solu-tion being u ed to treat an oil or gas well. This incorpora-tion can be accomplished by addition of the mixture to the acid solution before injection, as a separate preflush or spearhead slug of solvent, or even as a postflush associ-ated with an acid solution and allowed to mix in situ with the acid solution. The alcohol is selected such that it is substantially water, and therefore acid, insoluble but oil compatible. The phosphate ester surfactant appears to be uniquely suitable in rendering the alcohol soluble, thus producing an acidizing solution of extraordinary oil dis-placement capabilities.
In U. 5. Patent 3,819,520, the advantages of providing an acidizing solu~ion containing octyl alcohols for displac-ing oil was ~stablished by observing the interfacial tension between the acidizing solution and an oil phase. The octyl alcohols were dissolved in the acid solution due to the pre-sence of a significant (overall) percentage of a cosolvent low molecular weight alcohol. A ternary phase diagram ~ound in the patent, involving 15% HCl, isooctyl alcohol and iso-~5 propyl alcohol, indicates that 22 vol, % of isopropyl alcohol would solubilize thP octyl alcohols to the extent of 2 vol.
% in the acid, while 30 vol. ~ of isopropyl alcohol would solu-bilize 20 vol. ~ o~ octyl alcohol. The No. 3,819,520 patent also disclosed that for all practical purposes there are no ~Z5~31 alternatives to the octanols, nor to the C3 alcohol cosol-vent. Thus, the solubilization of a high molecular weight alcohol by the use of an alcohol cosolvent is no~ only re-stricted to the C8 alcohcls but also involves at a mini-mum 24 ~ by volume of the resulting acidizing solution being an additive. Categorically, the dissolving process of the prior art yields z single phase, true solution as opposed to a surfactant and higher alcohol micelle ~ispersed in a continuous phase of the present invention.
In further contrast, the present invention provides for solubilizing the high molecular weight alcohols by the addi-tion of a specific type of phosphate ester surfactant. The alcohol can be essentially any C~ through C10 substantially water insoluble alcohol. All such alcohols (rather than just the octanols) in combination with th~e phosphate ester surfactant and acid solution have been found to be effective in disintegrating and dispersing oil deposits,sludg~s and emulsions. After contact with the oil deposits or the like, they produce an essentially oil-free aqueous phase and a water-free oil phase leaving the surfaces of the solids water wet with no apparent emulsion formation. The C6 to C8 alcohols are preferred in that the rates of disintegra-tion and dispersion of the oily sludges are faster within this range. A mixture of closely related isomeric branched-chain primary alcohols of the general formula RCH20H, where R is a branched heptyl radical, and sold as isooctyl alco-hol, as well as capryl alcohol are particuiarly pr~ferred.
The surfactants employed to render the high molecular weight alcohol soluble in acid solution are categorically 73~

pho~phate ester surfactants. They are anionic detergents made of mixtures oX mono- and di- phosphate esters of oxyalkylated alcohols or oxyalkylated phenols, producing compounds of ~he following general formulas:

~-o-~CH2-CH2-0 ~ CH2-cH2 0 ~ OH (1) [R-o-~cH2-cH2-o ~ cH2-cH2-o)y}2-P-O~ I (2) where R is a C8 to C18 alkyl group or a C8 to Cg alkyl sub-stituted phenyl group and x and y represent the degree of propoxylation and degree of ethoxylation, respectively.
Preferably, the average degxee of propoxylation is from about 2 to 6 wherein the distribution of species can vary from x equals to 0 to about 10, while the-average degree of lS e hoxylation is from about 12 to about 18 with the actual distribution of species again ranging from y equals 0 to over 20. For all practical purposes, the presence of an average of 2 moles of propylene oxide essentially adjacent (i.e., bonded) to the hydrophobic starting alcohol or alkylated phenyl is considered critical in that the desired solvency and micellar stability in an aqueous acid media is achieved with as little as ~ moles of propylene oxide.
However, the presence of additional propylene oxide (i.e., up to x equal~ 6) is acceptable. The relationship between th~ degree of propoxylation and ethoxylation is also con-~idered critical infthat a balance of both the relatively hydrophobic proplylene oxide and relatively hydrophilic ethylene oxide as well as the sequential transition from the strongly hydrophobic alkyl group to the highly hydro-7~

_g_ philic phosphate group through the blocks of propylene oxide followed hy ethylene oxide is felt to enhance the stability of the micelle containing the high molecular weight, water insoluble, alcohol while dispersed in the continuous aqueous acid phase. Preferably, at the 2 moles of propylene oxide level, an averaqe of about 14 moles of ethylene oxide is to be present. As the avera~e value of the x approaches 6, more ethylene oxide (i.e., y 7 14) is required to maintain the hydrophobic/hydrophilic balance. The phosphate ester surfactant is preferably employed in the acid form; however, the partially neutralized form is equivalent for purposes of this invention to the extent that it is converted to the acid form in an acidizin~ solution. The particularly preferred phosphate ester surfactants useful in the present invention and their method of synthesis are the phosphate esters of the oxyalkylated fatty alcohols as described in V.S. Patent 3,629,127.
In preparin~ the acidizing solution, it i9 preferred that the surfactant and high molecular weight alcohol be preblended, thus producing a concentrated additive that is then mixed with the acidizing solution. However, the mixing of the aqueous acidizin~ solution with the surfactant and alcohol in any order is equivalently effective, but not as convenient in that the concentrated additive can be transported to the field and then added at the well site as needed.
When employing a concentrate of the surfactant and higher alcohol, the presence of a diluent to suppress the freezing point and control the viscosity of the mix ~.

~Z~7~

i5 preferred. The diluent preferably is a low molecular weigh~ water soluble alcohol or diol, such as methanol, ethanol, n-propanol, isopropyl alcohol, ~-butyl alcohol, ethylene glycol or the llke. Advantageously, the diluent 5 should also contain some water to maintain the highly polar surfactant in solution, particularly in cold weather applica-tions.
The continuous aqueous acid phase of th~ improved mi-cellar oil and gas well treating solutions according to the 0 present invention can be any of the aqueous solutions of water soluble acids and acid precursors or acid anhydrides as commonly employed for acidizing formations and/or acidic water flooding and the like. Thus, acceptable acids to be employed in the present invention include by way of example, !5 but not limited thereto, HCl, HF, glycolic acid,sulfamic acid, acetic acid, NH4~F2 as well as a C02 flooding media and mix-tures thereof.
In preparing either the acidizing solution per se, or the additive concentrate composition, the amount of the high molecular weight alcohol present relative to surfactant is preferably at least one part by volume high molecular weight alcohol to four parts by volume phosphate ester surfactant.
At this concentration, the acidizing solution will exhibit superior oil dispersion relative to either component in-~S dividually used with acid. Preferably, the ratio of alcoholto surfactan~ should no~ exceed about eight parts by volume alcohol to five parts by volume surfactant. Although con-centrations beyond this limit are not considered deliterious, th 8:5 ratio roughly corresponds to the upper limit of the 73~

surfactant's ability to solubilize the higher alcohol into acid solution. The ratio of two parts by volume alcohol to three parts by volume surfactant is felt to be a particularly preferred ratio for most alcohol/surfactant compositions.
When preparing a concentrate to be added later to the aqueous acidizing solution, the diluent lower molecular weight alcohol or diol plus water mixture should be present in sufficient quantity to suppress the freezing point, re-duce the viscosity and hold the highly polar surfactant in solution. Generally, improvement in the ability to handle the concentrate is observed upon addition of any volume of the alcohol (diol)/water mixture. Preferably, about 50 (or even higher) volume percent alcohol (diol)/water mixture per total volume of the resulting diluted concentrate additive is employed. The corresponding resulting water content should be from about 2 to 20 volume percent in order to pre-vent the separation of surfactant at low temperatures.
In preparing the acidizing solution, the relative quantity of concentrate to acid solution can be as low as O. 2 vol. ~ for prevention of acid/oil emulsion. Maximum effectiveness of the additive will occur at up to a~out 10 to 20 volume percent depending on the relative quantity of surfactant and high molecular weight alcohol, with even higher percentages bcing operable. A 95 vol. ~ acid/5 vol.
~5 % additive mixture is partiGularly preferred and suitable for most applications. ~his concentration is also particularly ad-vantageous relatlve to the prior art in that presence of the additive does not represent a major economic factor and the resulting acidizing solution is essentially still full ~2~k~73~

strength, Higher concentrations of up to about 25~ is very useful where maxium solubilization of oil deposits is de-sired.
In order to more fully describe and explain the present invention, how it functions and differs from the prior art, and how it is used, a more detailed examination of the ex-perimental basis and observation-is appropriate.
In order to find the desired surfactant,~ one that is effective in solubilizing high molecular weight alcohols in 0 acids, a series of screening experiments was performed using the various known classes of surfactants. The experimental procedure involved adding approximately 40 ml. of a selected concentration of acid solution and approximately 5 ml. of surfactant to a 50 ml. glass-stoppered graduated cylinder.
The combination was thoroughly mixed to check solubility. A
1 ml. aliquot of the high molecular weight alco`nol was ther.
added. The graduated cylinder was stoppered and shaken. Ob-servation of the behavior of the resulting mixture for solu-bilization of the alcohol was recorded. The procedure of adding another 1 ml. aliquot of alcohol and shaking was re-peated until no further significant change could be detected.
The results of the screening tests are as follows.
EXAMPLE I
As a control or blank test, q5 ml. of 15 wt. % HCl and 5 ml. of isooctyl alcohol were added to a S0 ml. glass-stopper-ed graduated cylinder and vigorously shaken. A hazy disper-qion formed which immediately separa~ed into tWQ digtinct ~5~73~ 522~-345 , immiscible layers. After standing ~or 5 minutes, a 6 ml.
~lightly hazy oil layer was present on top of a slightly hazy lower acid phase. Thi~ behavior was considered typical oÇ the essentially insoluble high molecular weight a~cohol in an acid medium.
EXAMPLE I I
A 40 ml. aliquot of 15 wt.~ HCl and S ml~ of a liquid surfactant (oxyalkylated polyol~, oxyalkylated alkyl phenols with sulfated oxyalkyla~ed alcohols and glycol ethers) sold under the trade name Tretolite AY 31, were placed in the graduated cylinder and mixed. A clear solution with Eoam resulted. ~pon adding the first ml. of isooctyl alcohol, a hazy dispersion was observed. The second ml. o~ isooctyl alcohol prod~ced a cloudy dispersion with evidence oE separa-tion. Thlrd, fourth, and fifth mls. of isooctyl alcoholwere added with separation of an amber oil emulsion which rose to the top. After the fifth ml. was added, the emul sion phase was 7 ml. in volume after flve minutes of stand-ing F~om this it was concluded that llttle or no solubll~-zation of ~he isooctyl alcohol take~ place when AY ~1 is thesurfactant.
EXAMPLES III-V
.__ The above procedure of EXA~PLE II was repea~ed substitu-tinq 5 ml. of capryl alcohol, normal octanol, or decyl alco-hol for the isooctyl alcohol. The results were ~dentical to EXAMPLE II except the separation dev~loped ~ore rapldly ln the case o decyl alcohol.

* Trade Mark ;. .~ .
,..~ ~., ~Z5~73~ 5224-3~5 EXA~P~E VI
The procedure of EXAMPLE II was repeated using 40 ml.
o~ 15 wt.g HCl and S ml. of the 9.5 mole ethylene oxide adduct of nonyl phenol, sold under the trade name Surfonic N-95, wa~ added a~ the surfactant. The Surfonic N-95 lumped and curdled when added to the acid. Heating and vigorous stirring resulted in a clear, very foamy ~olut~ion. Upon add-ing the first ml. of isooctyl alcohol and shaking, a clear solution except for aLr bubbles resulted. The second ml. of isooctyl alcohol was essentially identical in res-llts with some phase qeparation. The third ml. produced a hazy solu-tion with entrained air bubble~ and a separation of an oillayer. With the fourth ml. of isooctyl alcohol the solution appeared to clear somewhat but a fi~th ml. resulted in an opaque emulslon and no foam. The solutions after the second ~1. addition were viscous. After fifteen minutes of stand-~ng (5 ml. o~ isooctyl3, 3 ml. o~ clear oil developed on top of about 36 ml. of an intermediate layer of hazy loose emul-sion. Apparently more i~ooctyl alcohol phase was still sep-~rating, After one hour, three clear layers ~ere observed;

10 ml, on the bottom, 31 ml. intermediate and 9 ml. o~ oil on top. Surfonic N-95 is concluded to be a weak solubilizer for isooctyl a~cohol In acid and it st~bilizes emulsions.

EXAMPLE VII
.
The above procedure was repeated using 40 ml. of 15 ~wt.~ HCl. and 5 ml. of commercial ~urfactant b?elieved to be oxyalkylated alcohol and alkyl sulfonate in butyl alcohol * Trade Mar]

i ~?~

~Z5~73~
6522~-3~5 sold under the trade name of ~orflo *II. A clear amber solu-tion with a slight haze resu]ted. Upon addition of successive 1 ml. aliquots of isooctyl alcohol the solution turned to:
a hazy dispersion after the first ml., to a cloudy dispersion after the second, and to an emulsion with oil phase separation from the third and subsequent aliquots. After a total of 5 ml.
of isooctyl alcohol was added, 1 1/2 ml. of separation was observed. After 5 minutes of standing, 12 ml. of heavy emulsion was present with the rest being hazy. It is concluded that Morflo II is a poor solubilizer of isooctyl alcohol in 15 wt.
% HCl.

EXAMPL~ VIII
Using the same screening procedure, 40 ml. of 15 wt. ~
HCl was mixed with 5 ml. of a phosphate ester surfactant sold under the trade name Klearfac AA-420 by BASF Wyandotte Corpora-tion and identified (see Toxic Substances Control Act (TSCA) Chemical Substance Inventory, vol III, "User Guide and Indices -to the Initial Inventory; Substance Name Index", May 1979) as oxirane, methyl-, polymer with oxirane, mono-C12-Clg-alkyl ethers, phosphates consistent with the formulas (1) and (2).
A clear solution with slight foam resulted. The Eirst three additions of 1 ml. aliquots of isooctyl alcohol were solubilized resulting in a clear solution. The fourth ml. produced a hazy stable mixture and the fifth~a stable emulsion. After a total of 5 ml. of isooctyl alcohol added and fifteen minutes of standing, 1 ml. of clear oil separated on top. The performance of this phosphate ester surfactan-t appears superior to other surfactants previously tested.

*Trade i~ar~

.~,~ .
..~

-16~ ~L~rZ~j~ /3 EXP~MP LE I X
A second phosphate ester surfactant sold under the trade name Klearfac AA-040 and similar to AA-420 was tested by making a clear solution from a combination of S ml. of s surfactant with 40 ml. of 14 wt. ~ HCl. Again the addition of the first ml. of isooctyl alcohol produced a clear solu-bilized solution, with slight hazing produced by the addi-tion of the second ml. of alcohol. The thir~ ml. produced a hazy dispersion of emulsion with the fourth resulting in o an emulsion. The fifth ml. of isooctyl alcohol produced a white emulsion which after fifteen minutes of standing re-sulted in 2 ml. of slightly hazy oil coming to the top of the emulsion.
EXAMPLE X
A third phosphate ester surfactant marketed as Klearfac AA-270 and identified as oxirane, methyl-, polymer with oxirane, mono-C10-C16-alkyl ethers, phosphates again con-sistent with formulas (1) and (2) was similarly tested. To the clear solution~ successive 1 ml. aliquots of isooctyl alcohol were added followed by mixing. However, in this case a total of 9 ml. was added before the resulting mixture changed ~rom a clear solution with possibly very slight haze (8 ml.) to a translucent haze (9 ml.) but still cate-gorically a stable mixture. Even after two hours, the 9 ml.
S mixture was still a hazy stable dispersion with no apparent separation. Only slight foam and opalescence from about the fourth through ~he qeventh ml. of isooctyl alcohol was observed. This composition (9 ml. isooctyl alcohol, 5 ml.

-17- ~Z~73~
Xlearfac AA-270, and 40 ml. of 15 wt. % HCl) was left standing overnight. When observed the next day, 4 ml. of clear oil formed a top layer and the bottom 50 ml. layer was a clear, stable solution. Thus, 5 ml. of Xlearfac AA-270 can permanently ~olubilize at least about 5 ml.
of isooctyl alcohol into 15 wt. ~ HCl; more speci-fically, into an approximately 25% solution by volume of sur-factant and 75% by v~lume of 15 wt. % HCl. This suggests the presence of a specific stoichiometry possibly character-istic of the formation of a coordination complex or the like in solution.
In view of the above EXAMPLES, bhe specific phosphate esters of equation (1) and (2) as a class appear far superior to ~ther types of surfactants for solubilizing isoloctyl alcohol into hydrochloric acid.
EXAMPLES XI-XIV
In order to test the solubility (more specifically the solubilization) of other alcohols by the phosphate ester surfactant in acid solution, 5 ml. samples of hexanol, capryl alcohol, n-octanol, and decyl alcohol were added to separate graduates containing mixtures of 40 ml. of 15 wt. ~ HCl and S ml. of Klearfac AA-270. All but the decyl alcohol results in a clear solution indicative of excellent solubilization of the alcohol. The decyl alcohol resulted in a hazy, stable dispersion character-istic of good solubilization.
i! O EXAMPLES XV- XVI I I
In order to determine alternate commercially acceptable compositions, a series of experiments was performed to test the concept of producing a concentrate of a high molecular weight alcohol admixed with a phosphate ester surfactant that could be dissolved at any concentration in well treat-ing acids, such as 5% to 20% HCl and HCl/HF mixtures (i.e., mud acidq). The experiments were designed to develope a con-~i4~

centrate that could be ea~ily marketed as a well acidi~inq addltive that could be delivered directly to the field and then added to the acidlzing medium. As such, the concen-trate need~ to be stable, of low vlscosity to facilitate handling, and have a low freezing point. To achieve these pragmatic consideration~ the presence o~ various carriers was explored.
In EXAMPLE XV, 25 ml. of phosphate ester surfactant ~Klearfac AA~270) was added to 25 ml. of isooctyl alcoho' and 50 ml. of isopropyl alcohol as a carrier (viscosity low-ering agent and freezing-point depressant). Upon stirring, a clear solution reQulted. A 5 ml. sample of the above mix-ture was added to g5 ml. of a 15 wt.~ HCl ~olution. ~pon shaking a hazy dispersion resulted. An additional 5 ml. sam-ple of the original alcohol/~ur~actant mixture was added to the acid dispersion wi~h agitation. A clear solution result-ed. From this it was concluded that an incease in the ratic of surfactant to high molecular weight alcohol is needed for solubil$ty at low totai concentrations.
~0 In EXAMPLE XVI, a concentrate was prepared by mixin~ 35 ml. of ~learfac AA-270, 15 ml. of i~ooctyl alcohol, and 50 ml. of isopropyl alcohol. Again a clear solution resulted.
Us~ng this concentrate, clear solution~ were made at 0.5, 1.0, 3.0, 5.0, and 10.0 vol.~ of concentrate in 5 wt.~ HCl, 10 wt.~ HCl, 15 w~,~ HCll and 20 wt.~ HCl, indicative of 501-ubili~y at all con~enltratlong. Solub~lity was also observed in HCl/HF mixture~.

~ ~5~3~ 5224-~5 In EXAMPLE XVII, in order to establish other possible viscosity lowering agents and free~in~-point depressants, 30 ml. of ~learfac AA-270 and 20 ml. of isooctyl alcohol were combined to form a clear solutlon. This mixture was tested and found to be soluble at all concentrations in methanol, isopropyl alcohol, butyl alcohol and ethylene gl yco 1, In ~XAMPLE XVIII, a mixture of 300 ml. of Klearfac AA-270, 200 ml. of isooctyl alcohol, ~00 ml of isopropyl alcohol, and 100 ml. of water was prepared. The clear solution wassaved for pour point and physical property testing. The wa~er was added to ensure that the very polar phosphate ester surfactant would remain in solution when the mixture was chilled.
From the above da~a, it was felt that the concentrate compositions of EXAMPLES XI-XIV were acceptable for use as acid additives for emulsion prevent, well cleaning and stimulation in general and as a desludger, wetting agent, dispersant, mutual solvent, and solubilizer. It was fur-ther found that the amount of concentrate needed in the final acid was as lLttle as 0.2~ for prevention of acid/
oil emulsions and up to 10 to 20~ by volume for maximum effectiveness. About 5 vol. ~ of concentrate in acid should be suitable for most applications.
EX~PLE XIX
~nother commer&ially available phosphate ester surfact-ant sold under the trade name Pluraflo OF-90 (now Pluradyne OF-90) by BASF Wyandotte Corporation under the representa-tion as bein~ compositionally the same as Klearfac A~-270 * Trade rlark ~`

-21- , and independently confirmed by mass spectral analysis as a propoxylated Cl0~2l fatty alcohol with 2 moles of propylene oxide (PO) being the major series and 3 moles of PO also present as a minor series followed by an ethylene oxide (EO) bloc~ terminating in a phosphate unit, wherein up to 6 moles of PO were observed and up to 22 moles of EO were observed, was tested in a manner similar to EXAMPLE II
by placing 40 ml. of 15 wt. %

~;~5~7~1 ~Cl and 5 ml. of Pluraflo OF-90 in a glass-~toppered gradu-ated cyllnder. ~fter mixing, a clear solution was produced to which succes~ive l ml. allquot~ of isooctyl alcohol were added with agitation. After the third 1 ml. addition a slight opalescence wa~ obqerved in the otherwise clear single-phase solution. At the end of the fifth or sixth ml. allquot, the opale~cence developed into a slight hazy appearance. ~he seventh ml. of lsooctyl alcohol exhibited a stable dispers10n with the eighth addition requlting in a cloudy emulsion. The overall performance oE Pluroflo OP-90 was consistent with that of EXAMP~E II except that the surfactant i9 probably not as concentrated as indicated by the some~hat lower capability to solubilize the higher alcohol, but overall it is a highly acceptable alternative to the Klearfac AA-270.
EXP.MPLE_XX
In order to te-qt the effect of mixing types or classes of surfactants, a 20 ml. s~mple of Klearfac AA-270 was added to a lO ml. sample of Surfonlc N-95 (phosphate ester nonion-ic surfactant mixture). To 40 ml. of lS wt.~ ~Cl was added5 ml. of the surfacta nt mixture producing a clear solution.
Again, upon addition of l ml. aliquots of isooctyl alcohol a light haze to hazy dlspersion develo?ed afte~ the third suc-cessive ml. The Eourth ml. cleared to a slight haze and the '5 fifth produced a cloudy emulsion that appeared unstable.
From this it was concluded that there is no advantage assocl-ated wlth the use of mlxed types or cla~ses of ~urfactants.

522~-345 EXAMPLE XXI
To illustrate t~le beneficial effects of the present in-vention, a comparative visual test of the dissolving charac-teristics of a series of six acidizing compositions was per-formed. The ~irst acidizing composition was a 5 vol.% solu-tion of the composition of EXAMPLE XV using a phosphateester/ high molecular weight alcohol in 95 vol~ of 15 wt.
HCl. The five other comparators were known commercially available alternatLves lncluding: a 10 vol.~ ethylene glycol monobutyl ether ln lS wt.~ HCl~ a 35 vol.% blend of iso-propyl and lsooctyl alcohol ln 15 Wt.~ HCl sold under thetrade name A-Sol and prepared according to U.S. Patent No.
3,819,520; a 5 vol.~ of surfactant AY 31 in 15 wt.3 HCl (EXAMPLE II); a 5 vol.~ of surfactant Morflo II in 15 wt.3 HCl (EXAMP~E VII~; and a 5 vol.~ of sur~actant Surfonic N-95 ~n 15 wt.~ HC1 (EXAMPLE VI). Each was used to dissolve an ~oily scale sludge recovered from a water injection well.
The sludge contalned about 20~ by weight heavy hydrocarbons, 70~ by weight acid soluble mineral~ (primarily calcium car-bonate) and 10~ by weight clays and silica silt (acid insol-uble fines). Essentlally identical samples of the sludgewere submerged in an excess of each oE the respective acidiz-ing solutions. The phosphate ester/ high alcohol acidizing solutlon broke down; di9~01ved, and dispersed the semisolid sludge much faster than any of the other solutions~ The oil 2S ~floated free to the top and the silt dispersed into the aqueous acld phase.

* Trade ~lark 3,~J

3~

~XAMP LE X X I I
For further testlng, a synthetic well sludge was prepar-ed by blend$ng 90 parts by welght calcium carbonate (CaC03) and 10 parts by weight kaolini~e clay. To this S mixture was added a heavy, waxy crude oil ~ntil a stiff paste wa~ produced.
EXAMPLE XXIII
Five gram~ of the pastQ wa~ added to 100 ml. of 15 wt.~
HCl in a beaker. Only slow action was observed as evidenced by fizzing ~C02 release~ and release of oil. The small amount o~ erated oll wa~ sticky and emulsi~ied and the clay stayed in an oily clump. The paQte lump was not disin-tegrated aftcr one hour at room temperature.
EXAMPLES XXIV-XXVI

. _ A phosphate ~ster/ high molecular weight alcohol concen-trate o the present invention w~s prepared containing 30~
by volume Xlearf~c AA-270 , 20~ by volume i~ooctyl alcohol, 40~ by volume isopropyl alcohol and 10~ by volume water.
Therefore, a 100 ml. test sample of 5 vol.~ mixture of the concentrate in 15 wt.~ HCl would contain the equivalent of 1.5 ml. of ~learfac, 1.0 ml. of 1~ooctyl alcohol, and 2.0 ml. of isopropyl alcohol.
A Yimilar 100 ml. acid~zing solution without the high ~olecular weight alcohol wa~ prepared, containing 1.5 ml.
2S Klearfac, 2 . O ~1. isopropyl al~ohol, and 96.5 ml. of 15 wt.3 ;HCl, Al~o, a 100 ml.l acidizlng mixture was prepared by com-bining 1.0 ml. Oe isooctyl alcohol, 2.0 ml. i90propyl alco-~5~3~

hol and 97.0 ml. of 15 wt.~ HCl, without the pho~phate e~ter surfactant be~ng present. Thi8 mixture was hazy and qepara-tion w~uld ~ake place unless frequently agitated.
A 5 gram sample of the ~ynthetic oil well sludge of EXAMPLE XXII was placed in each of the 100 ml. acidizing sol-utions. The ~olution containing no isooctyl alcohol dlsin-tegrated the ~ludge fa~ter than the plain lS w~.~ HCl solu-tion of EXAMPLE XXXII. It took about thirty minutes for the glob to disappear. The o$1 on top was emul~lfied (gummy) 10 with no evidence of being di3persed. The solid~ appeared to ~e water wetted. The results were better than nothing but not su f~icient.
The solution containing no ~urfactant wa~ only slightly better than plain HCI; Most of the isooctyl alcohol appear-ed to ~loat to the top. No foamlng wa~ ob~erved. F,eed oilwa~ present In the i~ooc~yl alcohol pha~e. No emul~ion was 'observed. After one hour the 5 gram sample of o$1y pa-~te ~ad not entirely di~integrated.
In the case o~ the acidizing solution containing both the l~ooc~yl alcohol and the ~learfac surfactant, very rapid disintegrat~on oE the oily pa~te took place with evolution of copiou~ amount~ of foam. No emulsion was ob~erved. The solution tùrned dark from solubilized oll ~some free oll in the foam~. All of ~he ~ludge wa~ qone in ten minutes. The solids su~pended in the lower aqueous phase were water wetted.
From the above lt wa~ concluded that the phosphate 3~L

~er/.h~gh molecular alcohol mixture, in proper ratlo, com-bines to m2ke a compos~tion that i~ soluble in acid (15 wt.~
HCl) and the re~ultlng compositlon i9 far ~uperior to either con~tituent alon~ in dlsintegrating, dissolving, and dispers-ing oily ~ludge~ that clog oil wells and injection wells.
The new compos~ion prevent5 emul~ification and foam~ better than the ~u~factant alone, indlcating lt haq ~pre surfact-ancy or detergency.
EXAMP~ES XXVII-XXVIII
_ In order to determine the effect of varying the rela-tive proport~on of the surfactant to high molecular weight alcohol, the followlng two concentrate compositions were prepared.
CONCENTRAT~ 1 _ CONCEN~RATE 2 20 vol.~ Xlear~ac AA-270 40 vol.~ Klearfac AA-270 30 vol.~ i~ooctyl alcohol 10 vol.~ isooctyl alcohol 40 vol.~ isopropyl alcohol 40 vol.~ isopropyl alcohol 10 vol.~ wat~r 10 vol.~ water A 5 ml. sample of Concentrate 1 wa~ added to 95 ml. of 15 wt ~ HCl, produclng a cloudy di~persion temulsion~. Upon adding 5 gram~ of the oily well sludge of EXAMPLE XXII, a slow reaction took place w~th much le~ foaming than EXA~PLE
XXVI. It took 20 to 30 minute~ to break down the aily glob.
The exce~s isoocty~ alcohol may have been responsible ~or the ~low r~action becau~e of ~oil wetting" of the solids in the sludge.
S ml. o~ ConcentFate 2 added to 95 ml. of 15 wt.~ HCl produced a clear acidlzlng qolut~on. Addlng 5 gmq. of the 312~3~L

olly sludge to 100 ml. of the the acidizing medium contain-lng Concentrate 2 resulted in a more rapid reaction but not as aqt as EXAMPLE XXVI. It took about 20 minute~ to dis-perse the sludge.
From the composite oE the previous examples, it can be seen that phosphate ester surfactants such a~ Klearfac AA-270 can solubilize ~probably by micellar solution) high molecular welght alcohols, such as octyl alcohols, into acid solution at a ratio oE up to about 8 parts alcohol to 5 parts qurfactant, The most stable solution was achieved with equal parts of surfactant and high molecular weight al-cohol where ~he total concentration of the compositlon ~sur-factant/ alcohol complex) is about 25 vol.~ in the acid.
When total concentration iq only 5 vol.~ in acid (desirable ~or economic re~sons) the best rat~o is about 3 parts sur-factant and 2 partq hLgh molecular weight alcohol. As little a~ 1 par~ high molecular weigh~ alcohol to 4 parts surfactant is superior to the surfactant alone. For most purpo~es th~ alcohol alone iQ not accept~ble due to low ~olubility, EXAMP~ES XXIX-XXX
In order to test various high molecular weight alco-hols, a series of three concentrates was prepared uq~ng n-butyl alcohol, normal hexanol and normal decanol. Each concentrate wa~ made up of 30 vol.~ Klearfac, 20 vol.~ h~gh ~olecular we~ght alcohol, 40 vol.~ isopropyl~alcohol and 10 vol.~ water, Three corresponding acidizing solutiQns were ~73~ --2a-prepared by adding 5 vol.~ of the concentrate to 9S vol.~ of 15 wt,~ HCl. Each resulting acldizing solutlon was tested for ability to decompo~e the synthetic oil well sludge in a manner identlcal to the previou~ examples. All worked fair-ly well to d~lntegrate and disperse the sludge but the solu-tlons wlth bu~yl alcohol and decanol were not much faster than the surfactant alone, confirming that C6JC8 alco-hols are preferred but C~-C10 will work. All the higher alcohols ~C4-C10) cause the oil phase of the sludge to break out clean with no apparent emulsion formation. This is an improvement, even for the slower acting alcohols tC4-Clo1, over the use of the fiurfactant (phosphate ester) alone for well treatment. This property is probably related to the preferential solubility of the higher alco-hol~ into the oil phase of the qludge. For example, iso-propyl alcohol which is much more water soluble than butyl alcohol dld not produce the emulsion prevention effect when used with Klearfac. Therefore it is apparent that the com-po~ltlons of ~he present invention require an alcohol with low water solubility to achleve enhanced penetration of the oily ~ludge~ and to mlnlm~ze formation of emulsion~.

~'3~

EXAMPLES XXXI -XXXVI I
In order to establish recommended levels of water in the concentrate a serie~ of 7 concentrate solutions were prepared as follows:
CONCENTRATE 1_ 2 3 4 5 6 7 Vol.~ Klearfac AA-27030 30 30 30 30 30 30 Vol.~ i300ctyl alcohol 20 20 20 20 20 20 20 Vol.~ isopropyl alcohol 50 48 47 45 ~0 35 30 Vol.% water 0 2 3 5 1~ 15 20 A pour point te~t according to ASTM method D-97 was per-formed on each of the above solution~. TABLE I summari2es the result~.

TABLE I

CONCENTRATE _ OBSERVATION _ _ _ 1 heavy separatlo~ of white ~olld lumps at +8 F
2 heavy separation of white solid lump~ at -27 F
3 no ~eparat$on but high viscoQity at -34 F

4 no -4eparatlon but high viscosity at -34 F
, 5 no separation but high visco~ity at -34 F
6 no separa~ion but high vi~cosity at -34 F
7 lumpy separation at -25 F;froze solid at -34 F
From the above lt was concluded that at least 2~ water ~nd not greater than about 18~ water is preferred in produc-ing ~ concentrate that will flow under a broad range of temp-erature3. The specific gravitle~ of concentrate 4 (5~
water) and concentrate 6 (15~ water) were determined to be 0.92S and 0.950, re~pectlvely. A fla~h point of 7BC, ~ire point of 88C, and vi~cosity ~at 10 ~) of 38 cp were deter-,~ined for concentrat~ 6 ~ASTM D-93).

~2~7~
~ -30-EXAMPLE XXXVIII
In order to further demon~trate that the phosphate ester and high molecular we$ght alcohol are soluble in acid without the presence of a dlluent and that the re~ulting S aCidiZihg 801ution i9 highly effective, a 60 ml. sample of Klearfac AA~270 was mlxed with 40 ml. of i~ooctyl alcohol making a clear viscou~ qolution. ~pon mlxinq,the above witn hydrochloric acid at both the 5 and 15 wt.~ strengths, it wa~ establi~hed that the ~urfactant/ high molecular weight alcohol blend i8 qoluble at all proportions. Thus the lower molecular weight alcohol ~ not neces~ary for solubilizatlon of the high molecular alcohol in acid.
A 5 ml. sample of the surfactant/alcohol blend above was mixed with 95 ml. o~ 5 wt.~ HCl and added to 5 grams of the synthetic olly 31udge. The sludge disintegrated and di~solved rapldly.
A 1 ml. sampl~ of ~he ur~actant/slcohol blend waQ then added to 99 ml. of 5 wt.~ HCl and thls wa~ then added to a ~econd 5 gra~ ~ample of ~ynthet$c oil sludge. Again, the sludge dLsintegrated and dissolved rapidly.
The proce~ wa~ repeated u~ing 3 ml. of the surfactant!-alcohol blend and 97 ml. of mud acid (12 wt,~ HCl/ 3 wt.
HF). The olly ~ludq~ ag~in dis$nte~rated and dissolved r~pidly.
From thi~ it wa~ concluded that the phosphate e~ter/
hlgh molecula~ weigh~ glcohol complex perorm~ well ln acld alone without dlluence, such a3 by the lower molecular 7~

welght alcohol or water.
EXA~IPLES XXX I X-XLV
In order to test the compatibility of the acidizing composltlon3 of the present lnvention with other type~ of S acids, a series of 8 ac$dlzing solutions was prepared using the 30~ 3urfactant, 20~ isooctyl alcohol, 40~ i~opropyl alcohol and 10~ water composltlon (EXAMPLE XX~V) as a pho~phate ester/alcohol concentrate as specified in the following TABLE II.

TABLE I I
ACIDIZING SOLVTI0~ 1 2 3 4 _ S 6 7 8 Vol,~ Concentrate 20 20 20 20 15 20 10 25 Vol,~ glycolic acld 40 ~ 8 - - -Vol.i sulfamic acld - - - 10 12 lS Vol,~ ac~tic acid - 40 - - - 15 10 20 Vol.~ citrlc ac~d - - 40 - - 10 10 Yol.~ HCl (32~) - - - - - 5 Vol,~ NH HF - - - - - 5 10 Vol,~ isdpr~pyl alcohol 10 10 10 10 10 Vol,~ methyl alcohol - - - - - 10 10 15 Vol,~ wate~ 30 30 30 50 55 40SS 30 As previously lndlc~ted the acid ~olution~ to which the ~urfactant/alcohol mixtures are added may be any of the aque-OU~ 901utlons of water soluble acid~ commonly employed for ac$dizlng formations, The ~queous acid solutions may con-taLn from le~ than about 5~ up to about 30~ by welght of the acid, yet the phospha~e ester ~urfactant/high molecular weight slcohol m$x~ure remain~ ~oluble and the acid solution remains ~t~ble, Preferrably, about a 7 to 15 wt.~ HCl solutlon i~ used in w~ll acldlzlng.
The present acidizing addltive is viewed as being essen-~s~

tially compatible with any of the well known acidizing pro-cesqes. It can be used to treat oil producing wells, such as in a water flooding process for an oil-bearing formation, and in other secondary and tertiary recovery schemes. In a s produc~ng well, the aqueous acld solution and surfactant/-alcohol ~dditive are in~ected into the oil-bearing forma-tion, after which the well is returned to oil.production.
In a water-injection well, the acid and surfactant/alcohol additive are injected into the oil-bearing formation, which 10 i~ followed by further fluld in~ection.
In elther a producing or in~ectlon well, the s~r~c-tant/alcohol additive can be mixed with the acid ~olution or can prPcede and/or follow the acid solution, or any combina-tion thereof. These proce~ses can also be uqed in conjunc-tion with spearheads and postflu~hes of other well known sol-vents for a variety of purpo~es ~uch as but not limited to various aromatic solvents to remove asphaltene and other heavy depos~tq, var~ous sulphur solvents and the like.
The prlnclple value of the surfactant/alcohol additive preceding the acid solution is the displacement of the oil ahead of tha acld, thus decrea~ing mixing and possibly emul-sification, Such a batch or ~lug process also acts to dis-solv~ or ~olubillze organlc deposits which ~ay otherwise block the flow of acids into the oil-bearing strata. Thl~
batch proces~ of lnjecting a ~urfactant/alcohol addi~ive also a~ts to breakdo~n emul~ions which tend to form due to naturally present emulsifylnq agents. It is contemplated L7~
~33-that by controlllng the concentration of the additive present In sequential ~lug or batch injection, the specific functions of emulslon breakdown, organic deposit removal, and acidizing can be -qelectively controlled as required.
The advantaye~ of the surfactant/alcohol additive being mixed with the acid are the solubilization of the oil in con-tact with the acid and the improved displaceme~t of the oiI
by the acid, leaving ~olid surfaces, particularly finely divided solid3, water-wet. Surfactant/alcohol additive following the acid i9 of value in displacing and dissolving oil and organic solids not displaced or dissolved by pre-vious steps. This i9 particularly true if the additive has ~ot been u~ed in the previous steps. A batch of additive following the acid solution i~ particularly valuable in a water ln~ectlon well to i~ure displacement of any remaininq oill thu makin~ more pore space available for flow of lnjected water into the formation.
The amount of acid may be anywhere within the range from the few hundred to the ~everal thousand gallons ordinar-20 ~ ily u5ed ln welI-ac~dizing, However, treatment i~ generally intended primarily for the zone immediately surrounding a well bore, so that volume~ are usually somewhat smaller than average. Preferrably, they are from about 50C to about

5,000 U. S. ~allons Stated ln another way, use of from about 10 to about 500 gallons of acid per foot of formation thlcknes~, as recomme~ded in U. S. Patent ~o. 3,548,945, iY
satisfactory.

73~
-3~- , If a ~pearhead or preflu~h batch of ~urfactant/alcohol additlve precedes the acid solution, the volume of thi~
spearhead should vary from about 1~ of the volume of acld solution for large ~cld treatments to about 1003 of the acid solution volume for ~mall acid treatments. In such case~
the ratio of surfactant to high ~olecular welght alcohol can also be adjustd to Bccount for their individua~l interaction with the oil deposit~. About the same volumes should be used for batches o~ surfactant/alcohol additive used as an after~lush to dispace the acld solution into the formatlon.
When cleanin~ out injectlon wells, viz: removal o~ clog-ging sludges,emulsions and ~cales, where formation acidizing i5 no~ the primary objecive, lt i~ often advantageous to decrease tha total volume of acid solution and increase tha concentration of additive. Thls is economically attractive to keep cost low. ~urther, the ratio of higher alcohol/-pho~phate e3ter surfactant can be increased as in Example XV~ ln order to lower C03t ~ince the surfactant i~ the most expen3iv~).
As indlcated above, the principal applicatlon of the pre~en~ inventlon is to oll-producing wells and to injection wells in w~terfloodinq operatlons or the llke. ~he process is al30 some~imes helpful for treating gag wells and gas con-densate well3. Many ga~ wells produce some oll, just a~
many oil well~ produce ~ome ga~. Therefore, organic ;deposits can form in ~nd around gaB well~. ~any gas well9 produce water. ThereEore, mineral depo~its can also ~orm in and around gas wells, When gas well~ are acidized to remove such mlneral deposits and otherwi~e lncrease the flow of gas to the well~, oil present ln the formation can emulsify with the acid ju~t as it can in oil wells. In such applications, the present inventlon''s ability to foam is considered an advantage In recovering acid ~rom the formation and when employing nitrogen for the same purpose.Thu~ i~t will be apparent that many of the same problems, which maXe the use of a surfactant/alcohol additive advisable ln oil well acidiz~ng, frequently also occur in gas and gas condensate wells.
The process for, and the advantages of, using the present surfactant/alcohol additive during acidizing can be better understood from the following examples.
EXAMPLE XLVI
In order ~o demonstrate the concept of using a substitu-t~d alcohol aq the high molecular weight alcohol in the sur-factant/alcohol addltive, an ethoxyl~ted nonyl phenol ~4 mole ethylene oxlde adduct) having a terminal hydroxyl group and aold undar th~ tradename Surfonlc N40 was employed. The Surfonic N40 had practlcally no solubility in 15 w~.~ HCL
(same as i~ooc~yl) but does disperse (emulsify) into 1~. An additive composltion of 25 ml. Surfonic N40, 2S ml. of Pluraflo OF-90, and 50 ml. of lsopropyl alcohol was prepared, The additive made a clear solution from 2 to 10 ~vol.~ in 15 wt.~ HCl.~ 100 ml. of the 5 vol.3 additive in 15 wt.~ HCl was added to 5 gramg o~ oily ~ludge. The observed -36- ~ Z ~

solutlon/dlsperlon rate was not a~ fast or complete as pre-viou~ isooctyl addi~ive~ bu~ the results were acceptable in that the solids were water wetted and no thick temulsion) oil layer appeared on top. The experiment was repeated with-out the ethoxylated nonyl phenol, resulting in an unaccept-able heavy visCou5 oil layer on top. It was concluded that Surfonic N~0 W2-~ workable but not as good a~ t~e linear hi~h molecular weight alcohols.
While the oil soluble, substantially water insoluble monohydric alcohols are preferred, other alcohols hav.ing similar solubilj.ty and hydrophile/lipophile balance (HLB) to the C6 to C8 linear alcohols may be employed. For example, the solubility and H~B of very high molecular weight (C12-C22) fatty alcohols, polypropylene or polybutylene qlycols, alkyl substituted phenols and Cl2_~2 f2tty acids can be shifted ~o the operable range by reactlng these with a few moles of ethylene oxide. The resulting substance~, having the requlred oil solubility and at least one terminal hydroxyl group to provide alcoholic character, can be represented by the general formula:
RlR2 0~cH2cH2-o~xcH2cH2oH
where Rl is a CH3- or--CH2CH20H, R2 is a C to C21 hydrocarbon cha~n, polypropylene oxide, polybutylene CH2~10 to 20C- fatty acid residue, alkyl ~C8-C}~ substltuted phenyl moiety, and x is an integer ranqing from 3 to 15 lepre~enting the number of mole~ of ethylene oxide added to R2.

~S~'73~

EXAMPLES XLVI I -LI I I
A serle~ of field test~ of th~ present invention were performed on water injection wells, oil producing wells and gas produclng we113. Each field test involved the use of an additive contalnlng 30 vol.~ Klearfax AA-270 as the phosphate este~ surfactant, 20 vol.~ isooctyl alcohol, 40 vol.~ isopropyl alcohol and 10 vol.~ water. ~he results o~
these tests are presented in TABLE III.
TA8IJ?~ I I 1 Type Location Forma~ion/ Volume ~gal) Production ~ TX) _ Depth Acid~Additive Before/After __ wiw~ Cass Haynes Mitchell/ 950/ 10,407 bbl @950psig/
4500' 5010,482 bbl Q400p~ig gas*t Panola Pettit/ 475/ 250 MCFD/600 MCFD
6400' 25 oil~ Ru~k . Woodbine/1140/10 oil; 211 water/
3700' 6056 oil;168 water bbl , oil W~od Subclarksville/950/ 11 oll; 32 water/
4000' 5016 oil; 70 water bbl ga~ Marlon Travis Peak/ 950/ 300 MCFD Q 600~;
no choke 8700' 50 1.2M MCFD Q 1700~;
17/64 choke ga~Hender~on Rodes~a/2850/10 MCFD/
7000' 150710 MCFD

oilCherokee Woodblne/ 950/ 19 oil; 28 water/
3600' 5059 oil;28 water bbl ~wiw - water injection well ~tgag 5 gas production ~oil ~ oil production ! ExAMpLE LIV
A water injec~ion well, located in Smith County, Texas, and ~eing u-~ed to in~ect water into the Palùxy formatLon at 650 f t. at the rate of 2000 bbl~ per day at 2000 psig, was treated with a mixture of 500 gallon~ of 15 wt.~ HCl containing 5 voI.~ of the additive of EXAMPLES XLVII-LIII
and 200 gallon~ of xylene. The xylene and acidizing solution were mixed, then injected into the formation and allowed to soa~ for one hour A salt water plu5 diverter mixture was then used to Plush the formation and an additi~nal 3500 gallons of the acidizing solution (with 5 vol.~ additive) was injected. Water injection was then resumed. Before treatment the well was accepting 2000 bbls of water per day at 2000 psig. After treatment water injection was 4500 bbls at 500 psig.
It should be readily apparent from the above that in addition to the advantages of economy of additive employed relative to pr$or art compositions, the proces~ Oe ~mploying the present compo~itions lead~ to a savings as~ociated with operating lnjection well~ and increased production associated wi~h ga~ and oil producing wells.~
Having thus de~cribed the preferred embodiments of the invention with a certaln degree o particularity, it i9 to be recognized and understood that many changes can be made in the detail~ of preparing and using the surfactant/alcohol additive and acidizlng solution without departing from the spirit and scope of tllis disclosure. Thus it is contem-plated that other acid gtable additives intended for variousspecif~c purposes can~be pre~ent, including by way of exam-ple such additive~ as corrosion inhibitors, formation stabil-_39- ~z54 7~

izlng addLtlves, tracer compounds, emulsion.breakers, asphal-tene solvents and the like. Therefore, it is to be under-stood that the invention is not limited to the embodiments set forth herein ~or purposes of exempli~ication, but is to be limited only by the ~cope of the attached claims includ-inq a full range of equivalents to which each element thereof 1~ entitled.

Claims (36)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An aqueous acid containing oil and gas well treating solution comprising:
(a) an aqueous acid continuous phase;
(b) a C4 to C10 substantially water insoluble aliphatic alcohol; and (c) an effective amount of a phosphate ester surfactant to render said alcohol soluble in said aqueous acid continuous phase wherein said phosphate ester surfactant is characterized by the formulas:

where R is about a C8 to C18 alkyl group or about a C8 to C9 alkyl substituted phenyl group, x is from about 2 to 6 and y is from about 12 to 22 and the 2 to 6 moles of propylene oxide are substantially a block polymer attached to the R-O group, and wherein at least 75 parts by volume of said aqueous acid contin-uous phase, containing up to 28 wt. % acid, is combined with up to about 25 parts by volume of a mixture of said aliphatic alcohol and said phosphate ester surfactant, wherein said mixture comprises up to about 8 parts by volume alcohol to 5 parts by volume surfactant.

2. A treating solution of claim 1 wherein said acid is selected from the group consisting of HCl, HF, acetic, sulfamic, citric, glycolic, NH4HF2, and mixtures thereof.

3. A treating solution of claim 1 wherein said ali-phatic alcohol is a C6 to C8 alcohol.

4. A treating solution of claim 1 wherein said phosphate ester surfactant is a phosphate ester of an oxyalkylated fatty alcohol.

5. A treating solution of claim 1 wherein said acid is HCl, HF or mixtures thereof, said aliphatic alcohol is octyl or capryl alcohol, and said phosphate ester surfactant is a phosphate ester of oxyalkylated fatty alcohol.

6. A treating solution of claim 5 wherein said aqueous acid continuous phase is a 15 wt. % HCl, said aliphatic alcohol is isooctyl alcohol, and said phosphate ester surfactant is oxirane, methyl-, polymer with oxirane, mono-C10-C18-alkyl ethers, phosphates.

7. A treating solution of claim 1 further comprising an effective amount of a low molecular weight water soluble alcohol or diol.

8. A treating solution of claim 1 wherein at least 90 parts by volume of said acid is combined with up to 10 parts by volume of said mixture.

9. An acidizing additive comprising:
(a) a C4 to C10 substantially water insoluble aliphatic alcohol;
(b) a phosphate ester surfactant characterized by the formulas:

where R is about a C8 to C18 alkyl group or about a C8 to C9 alkyl substituted phenyl group, x is from about 2 to 6 and y is from about 12 to 22 and the 2 to 6 moles of propylene oxide are substantially a block polymer attached to the R-O group;
(c) a water soluble low molecular weight alcohol or diol;
and (d) water.

10. An acidizing additive of claim 9 wherein said water soluble low molecular weight alcohol or diol is selected from the group consisting of methanol, ethanol, n-propanol, isopropyl alcohol, t-butyl alcohol, and ethylene glycol.

11. An acidizing additive of claim 9 wherein said alcohol is a C6 to C8 alcohol and said surfactant is a phosphate ester of an oxyalkylated fatty alcohol.

12. An acidizing additive of claim 10 wherein said alcohol is a C6 to C8 alcohol and said surfactant is a phosphate ester of an oxyalkylated fatty alcohol.

13. An acidizing additive of claim 9 wherein the ratio of alcohol to surfactant ranges from about 1 part by volume alcohol per 4 parts by volume surfactant to 8 parts by volume alcohol per 5 parts by volume surfactant.

14. An acidizing additive of claim 13 wherein the ratio of alcohol to surfactant is about two to three.

15. An acidizing additive of claim 9 wherein the water soluble alcohol and water represent up to about 50% by volume of said resulting additive.

16. An acidizing additive of claim 15 wherein said water is present in at least 2% by volume and less than about 20%
by volume.

17. An acidizing additive of claim 15 wherein the ratio of alcohol to surfactant ranges from about 1 part by volume alcohol per 4 parts by volume surfactant to 8 parts by volume alcohol per 5 parts per volume surfactant.

18. An acidizing additive of claim 16 wherein the ratio of alcohol to surfactant ranges from about 1 part by volume alcohol per 4 parts by volume surfactant to 8 parts by volume alcohol per 5 parts per volume surfactant.

19. An acidizing additive of claim 17 wherein said ratio of alcohol to surfactant is about two to three.

20. An acidizing additive of claim 18 wherein said ratio of alcohol to surfactant is about two to three.

21. An acidizing additive of claim 17 wherein said alcohol is a C6 to C8 alcohol.

22. An acidizing additive of claim 18 wherein said alcohol is a C6 to C8 alcohol.

23. An acidizing additive of claim 17 wherein said insoluble alcohol is isooctyl alcohol.

24. An acidizing additive of claim 18 wherein said insoluble alcohol is isooctyl alcohol.

25. An acidizing additive of claim 17 wherein said acid is HCl.

26. An acidizing additive of claim 18 wherein said acid is HCl.

27. A process for treating an oil-bearing formation comprising the step of contacting said formation with an aqueous acid solution containing a C4 to C10 substantially water insolu-ble aliphatic alcohol and an effective amount of a phosphate ester surfactant to render said alcohol soluble in said acid solution wherein said phosphate ester surfactant is characterized by the formulas:

where R is about a C8 to C18 alkyl group or about a C8 to C9 alkyl substituted phenyl group, x is from about 2 to 6 and y is from about 12 to 22 and the 2 to 6 moles of propylene oxide are substantially a block polymer attached to the R-O group, and wherein at least 75 parts by volume of said aqueous acid con-tinuous phase, containing up to 28 wt. % acid, is combined with up to about 25 parts by volume of a mixture of said aliphatic alcohol and said phosphate ester surfactant, wherein said mixture comprises up to about 8 parts by volume alcohol to 5 parts by volume surfactant.

28. A process of claim 27 wherein said phosphate ester surfactant is a phosphate ester of an oxyalkylated fatty alcohol.

29. A process of claim 27 wherein said aliphatic alcohol is a C6 to C8 alcohol.

30. A process of claim 28 wherein said aliphatic alcohol is a C6 to C8 alcohol.

31. A process of claim 27 wherein said aliphatic alcohol is isooctyl alcohol.

32. A process of claim 28 wherein said aliphatic alcohol is isooctyl alcohol.

33. A process of claim 28 wherein said phosphate ester surfactant is oxirane, methyl-, polymer with oxirane, mono-C10-C18-alkyl ethers, phosphates.

34. A process of claim 27 wherein said aqueous acid solution also contains a low molecular weight alcohol or diol.

35. An aqueous acid containing oil and gas well treating solution comprising:
(a) an aqueous acid continuous phase;
(b) a substantially water insoluble alcohol of the formula:

R1-R2-O ? CH2CH2-O ? CH2CH2OH
where R1 is a CH3- or -CH2CH2OH; R2 is a C11 to C21 hydrocarbon chain, polypropylene oxide, polybutylene oxide or -(CH2-)10 to 20CO- fatty acid residue, C8 to C10-alkyl substituted phenyl group, and x is an integer from about 3 to 15; and (c) an effective amount of a phosphate ester surfactant to render said alcohol soluble in said aqueous acid continuous phase wherein said phosphate ester surfactant is characterized by the formulas:

where R is about a C8 to C18 alkyl group or about a C8 to C9 alkyl substituted phenyl group, x is from about 2 to 6 and y is from about 12 to 22 and the 2 to 6 moles of propylene oxide are substantially a block polymer attached to the R-O group, and wherein at least 75 parts by volume of said aqueous acid continuous phase, containing up to 28 wt. % acid, is combined with up to about 25 parts by volume of a mixture of said ali-phatic alcohol and said phosphate ester surfactant, wherein said mixture comprises up to about 8 parts by volume alcohol to 5 parts by volume surfactant.

36. A process for treating an oil bearing formation comprising the stpe of contacting said formation with a composition of claim 35.