CA2105691A1 - Compositions for reducing sludging during well acidizing - Google Patents
Compositions for reducing sludging during well acidizingInfo
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- CA2105691A1 CA2105691A1 CA 2105691 CA2105691A CA2105691A1 CA 2105691 A1 CA2105691 A1 CA 2105691A1 CA 2105691 CA2105691 CA 2105691 CA 2105691 A CA2105691 A CA 2105691A CA 2105691 A1 CA2105691 A1 CA 2105691A1
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Abstract
ABSTRACT OF THE DISCLOSURE
A composition and method for acidizing a subterranean formation to minimize sludge formation upon contact of the acid with the crude and any iron present. In accordance with the present invention, an additive comprising a first constituent comprising at least one member selected from the group of thiourea, monomethylthiourea, monoethylthiourea, monoisopropylthiourea, dimethylthiourea, diethylthiourea, diisopropylthiourea, imidazolidine-2-thione and hexahydropyrimidine-2-thione and a second constituent comprising an acid soluble compound capable of providing cuprous ions in solution is admixed with the acid in an amount effective to reduce the formation of sludge resulting from contact with the acid and any iron present in the formation.
A composition and method for acidizing a subterranean formation to minimize sludge formation upon contact of the acid with the crude and any iron present. In accordance with the present invention, an additive comprising a first constituent comprising at least one member selected from the group of thiourea, monomethylthiourea, monoethylthiourea, monoisopropylthiourea, dimethylthiourea, diethylthiourea, diisopropylthiourea, imidazolidine-2-thione and hexahydropyrimidine-2-thione and a second constituent comprising an acid soluble compound capable of providing cuprous ions in solution is admixed with the acid in an amount effective to reduce the formation of sludge resulting from contact with the acid and any iron present in the formation.
Description
"COMPOSITIONS ~ ~ C~G SLUDGING
DURING WELL ACIDIZING"
Backqround Of The Invention 1. Field Of The Invention The present invention relates to a method and composition for reducing the production of sludge upon acid contact with sludging crude oil, more particularly to an impxoved sludge inhibiting acidizing composition and method of use.
DURING WELL ACIDIZING"
Backqround Of The Invention 1. Field Of The Invention The present invention relates to a method and composition for reducing the production of sludge upon acid contact with sludging crude oil, more particularly to an impxoved sludge inhibiting acidizing composition and method of use.
2. De c ~ on Of The Prior Art The treatment of a hydrocarbon-containing formation with an aqueous acid solution is a commonly used technique for stimulating the production of hydrocarbons from the subterranean formation. Such a treatment generally includes the pumping of an aqueous acid solution into the formation to dissolve acid soluble materials and produce enlarged flow channels. The enlarged channels result in an increase in the quantity of hydrocarbons recovered as a result of flow through the formation into the channels and then into the wellbore.
Certain crude oils contained in subterranean formations produce sludge upon contact with aqueous acid solutions during the performance of the treatments. The sludge that is formed is an asphalt-like material which precipitates in the formation and thereafter plugs or clogs the enlarged flow channels. The potential for sludge to form has been found to be significantly increased by the presence of ferric iron in the aqueous acid solution which contacts the hydrocarbons in the formation. There are examples of crude oils which do not form a sludge upon contact with a simple acid, whereas the ~, . .
.~ ' ' ~ ' ' ' ' ' . ' " .~
presence of ferric iron in the acid induces sludge formation.
Ferric iron can be naturally present in a subterranean formation; however, the initial portion of acid introduced into the formation often is likely to contain dissolved ferric iron irrespective of any iron in the formation. This commonly results from the dissolution of rust or corrosion products from iron-containing containers or conduits for conveying the acid into the formation.
Methods for preventing or reducing sludge formation upon contact between sludging oils and an aqueous acid in the presence or absence of dissolved ferric iron in the acid have been developed and used heretofore. Such methods include combining certain anti-sludging agents or other additives with the aqueous acid solution, whereby the formation of sludge is inhibited when the acid solution contacts the oil in the formation. While such techniques have achieved varying degrees of success, the anti-sludging agents and other additives often separate and permit sludge to form in the subterranean formation.
By the present invention, an improved acidizing method and composition to reduce sludge formation are provided.
Summary Of The_Invention The present invention relates to a well treating process in which an aqueous acid solution that is capable of dissolving a portion of a subterranean formation to increase its permeability is brought into successive contact with an iron-containing source and an asphaltenic crude oil. The .
. ~
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:
2i ~3~ 0 -- .
process comprises including within at least the first injected portion of the aqueous acid solution an effective amount of at least one member selected from the group of thiourea, dimethylthiourea, diethylthiourea, diisopropylthiourea, imidazolidine-2-thione, hexahydropyrimidine-2~thione, monomethylthiourea, monoethylthiourea and monoisopropylthiourea together with an effective amount of a compound capable of providing cuprous ions in solution, whereby a substantial portion of any iron present in the ferric state is reduced to the ferrous oxidation state.
DesoriptionQf ?he Preferred Embodiment In accordance with the present invention, a method and composition is provided to reduce the production of sludge upon acid contact with sludging crude oil.
In general, the aqueous acid used in the present invention can be substantially any acid which is capable of dissolving solid materials located in a permeable subterranean formation in a manner to increase the permeability of such formation. Commonly used acids include hydrofluoric acid, hydrochloric acid, organic acids such as formic or acetic acids and mixtures of such acids. Aqueous solutions of the acids generally are used at a concentration in the range of from about 5% to about 28-32% by weight. An aqueous 15%
hydrochloric acid solution is particularly suita~le for u~e in accordance with ths present invention.
Included within at least a portion of the initial aqueous acid introduced into the subterranean formation is a sludge . :
,, . : . ~ : :
inhibiting effective amount of an additive comprising at least one member selected from the group of thiourea, dimethylthiourea, diethylthiourea, diisopropylthiourea, imidazolidine-2-thione, hexahydropyrimidine-2-thione, monomethylthiourea, monoethylthiourea and monoisopropylthiourea together with an effective amount of a compound capable of providing cuprous ions in the aqueous acid solution whereby a substantial portion of any iron present in the acidic solution or dissolved by the acidic solution is reduced to the ferrous oxidation state. The first member of the additive generally is present in the aqueous acid solution in an amount of from about 0.5% to about 10% by weight.
Preferably, the first member is present in an amount of from about 0.75% to about 5~ by weight. The copper containing compound is present in the additive in an amount sufficient to provide a soluble cuprous ion concentration in an amount of at least about 0.005% by weight. Generally, the concentrations can be in the range of from about 0.005% to about 0.1% by weight or greater. Preferably, the cuprous ion concentration is in a range of from about 0.005 to about 0.05% by weight of the aqueous acidic solution. The cuprous ions can be provided by compounds such as, for example, cuprous chloride, cuprous oxide, cuprous sulfite, cuprous sulfate, cuprous carbonate and the like. While the specific reaction mechanism is not known it is believed that the ferric iron in solution is reduced to ferrous iron by the following reaction sequence:
. ~ . . . . , : . . . . :
5~ ~ ~
Fe+3 + Cu (Tu)4 +~ ~ Fe+2 + Cu (Tu)4+2 (labile) Cu (Tu)4+2 ~ Cu (TU)3+l + oxidation product Cu (Tu)3+l + Tu ' Cu (Tu) 4+1 The reaction then would continue until the thiourea compound is reduced in concentration to a level below the reaction threshold or until all Fe+3 is consumed. D~pending upon the particular hydrocarbon and the quantities of sludging agents present, the composition and method of the present invention can substantially reduce the amount of sludge produced and in some instances substantially eliminate any sludge formation during the acidizing treatment.
In accordance with the present invention, the aqueous acidic solution also can contain one or more other additives such as a corrosion inhibitor, a non-emulsifying surfactant, an anti-sludging agent, a dispersing agent and substantially any other conventionally known additive used in acidizing treatments that does not adversely react with the other 1 additives present to detrimentally effect the present ;~1 invention. The corrosion inhibitor generally maybe present in an amount of from about 0.1 to about 2.0 percent by weight of the acidic solution. The non-emulsifying surfactant generally may be present in an amount of from about 0.1 to about 2.0 percent by weight of the acidizing solution. The anti-sludging agent generally may be present in an amount of from about 0.5 to about 10 percent by weight of the acidic solution. The dispersing agent generally may be present in an amount of from about 0.1 to about 2.0 percent by weight of the acidic solution. Examples of such additives are set forth in .~
~`
.. . . . , :
. . , .. ~
. . :
.
2 ~ ~ 5 ~ ~ 1 U.S. Patents 4,096,914 and 4,823,874, the entire disclosure of which is incorporated herein by references.
In general, the acidic solution of the present invention is injected down a wellbore to contact a subterranean formation. The solution may be injected into the formation either at a rate and pressure sufficient to fracture the formation or at a rate and pressure below that at which fracturing can occur. Such low-pressure or ~ow-rate injection generally is referred to as matrix acidizing. The acidic solution generally is permitted to contact the subterranean formation for a sufficient time to substantially spend by dissolution of acid soluble constituents; however, no specific contact time is required. Upon conclusion of the acidizing treatment, the at-least-partially spent solution generally is withdrawn from the formation by pumping on the wellbore.
To further illustrate the utility of the present invention, but not by way of limitation, the following examples are provided.
EXAMP~E I
An acid composition is prepared by admixing 900 parts by volume 10% HCl with 100 parts glacial acetic acid. To this composition was added the following conventional acidizing additives : 1~ by weight 19 N surfactant, 3~ by weight AS-7 additive, 0.3% by weight Sperse-All additive, 0.8~ HAI-85 corrosion inhibitor, which are proprietary chemicals available from Halliburton Services, Duncan, Oklahoma. Samples of the acid solution then were admixed with an equal volume of crude . .
- , . .
2 ~ 9 ~
oil in a series of tests to which different quantities of ferric iron had been added with different additives of the present invention. More specifically, 50 mls of the acid solution containing the ferric iron, added by dissolution of FeCl3^6H20 in the acid, was heated to 180F. and admixed with a guantity of Beaver Hill Lake crude that had been strained through a lO0 mesh screen to remove solids and heated to the same temperature. The sample was shaken for l minute upon mixing and placed in a controlled temperature both at 180F.to stand for one hour. The sample then was strained through a 100 mesh screen upon mixing and placed in a controlled temperature bath at 180F. to stand for one hour. The sample then was strained through a 100 mesh screen, any residue on the screen was washed with 140F. water and dried prior to weighing of the residue (sludge). The results of the tests are set forth below:
:
. . - -- : :
: - .
, :
2 ~
Table I
1 2 0.013 none 4.06 2 2 0.0136% thiourea 0.05 3 _ 2 0.0135% thiourea 0.19 ; _4 2 0.0134% thiourea 0.31 5 _ 2 _ 0.0133% thiourea 0.61 6 2 0.01~6% hexahydropyrimidine- 0.07 _ . 2-thione : 7 2 0.0135% hexahydropyrimidine- 0.22 :, _ 2-thione . ¦8 2 0.0134% hexahydropyrimidine- 1.11 : _ _ 2-thione _ 9 2 0.0136% imidazolidine-2-thione 0.28 : 10 0.5 _ 0.013 1.5 thiourea 0.02 11 0.50.0131.25 thiourea 0.03 12 0.5 _ 0.013 1.0 thiourea 0.05 _ 13 0.50.0130.75% thiourea 0.06 ¦14 0.50.0131.5% hexahydropyrimidine- o 0 _ 2-thione : 15 0.50.0131.25% hexahydropyrimidine- 0.42 _- _ 2-thione 16 0.50.0131.5% imidazolidine- 0 04 _ 2-thione 17 0.50.0131.25% imidazolidine- 0.04 2-thione 18 0.50.0131.0% imidazolidine- 0 08 - _ ~_ _ 2-th one To confirm the Fe+3 iron was the cause of the sludge several tests were repeated using Fe+2 in place of Fe+3. No sludge was formed in sny test - . . . .
:: . " ~: . . .
~ 2 1 0 ~ ~ 9 1 ,. ;
EXANPLE II
The preceding test was repeated using a different crude known as the Judy Lake crude. The results are set forth ~ I 2 1.00.013 0 0.76 ,~ 3 1.0 0 4% 50/50 blend thiourea- 0.39 hexahydropyrimidine-2-thione _ _ , ~;~ 4 l.o0.134% 50/50 blend thiourea- 0.01 I hexahydropyrimidine-2-thione 2.0 0 0 0.99 6 2.00.013 _1.01 , 7 2.0 04% 50/50 blend thiourea- 0.62 _ _hexahydropyrimidine-2-thione 8 2.00.0134% 50/50 blend thiourea- 0.06 _ ______ _ _ hexahydropyrimidine-2-thione .`, ~ , ,~ , __, The results of the foregoing Examples clearly illustrate the effectiveness of the present invention in substantially reducing the guantity of sludqe formed upon contacting of an acidizing solution with a crude formation where iron in a ferric oxidation state is present. These results further show that if either part of this invention is left out, the desired result is not achieved.
While that which applicants presently consider to be the preferred embodiments of the present invention has been described herein, it is to be understood that changes and modifications can be made to the method and composition by those skilled in the art without departing from the spirit or 1,~
21 05fi31 `~
scope of the invention as def ined by the appended claims .
Certain crude oils contained in subterranean formations produce sludge upon contact with aqueous acid solutions during the performance of the treatments. The sludge that is formed is an asphalt-like material which precipitates in the formation and thereafter plugs or clogs the enlarged flow channels. The potential for sludge to form has been found to be significantly increased by the presence of ferric iron in the aqueous acid solution which contacts the hydrocarbons in the formation. There are examples of crude oils which do not form a sludge upon contact with a simple acid, whereas the ~, . .
.~ ' ' ~ ' ' ' ' ' . ' " .~
presence of ferric iron in the acid induces sludge formation.
Ferric iron can be naturally present in a subterranean formation; however, the initial portion of acid introduced into the formation often is likely to contain dissolved ferric iron irrespective of any iron in the formation. This commonly results from the dissolution of rust or corrosion products from iron-containing containers or conduits for conveying the acid into the formation.
Methods for preventing or reducing sludge formation upon contact between sludging oils and an aqueous acid in the presence or absence of dissolved ferric iron in the acid have been developed and used heretofore. Such methods include combining certain anti-sludging agents or other additives with the aqueous acid solution, whereby the formation of sludge is inhibited when the acid solution contacts the oil in the formation. While such techniques have achieved varying degrees of success, the anti-sludging agents and other additives often separate and permit sludge to form in the subterranean formation.
By the present invention, an improved acidizing method and composition to reduce sludge formation are provided.
Summary Of The_Invention The present invention relates to a well treating process in which an aqueous acid solution that is capable of dissolving a portion of a subterranean formation to increase its permeability is brought into successive contact with an iron-containing source and an asphaltenic crude oil. The .
. ~
' ' , "~'' ' `: " `, ';,'.. ', ''' '` '.' ' , ~
:
2i ~3~ 0 -- .
process comprises including within at least the first injected portion of the aqueous acid solution an effective amount of at least one member selected from the group of thiourea, dimethylthiourea, diethylthiourea, diisopropylthiourea, imidazolidine-2-thione, hexahydropyrimidine-2~thione, monomethylthiourea, monoethylthiourea and monoisopropylthiourea together with an effective amount of a compound capable of providing cuprous ions in solution, whereby a substantial portion of any iron present in the ferric state is reduced to the ferrous oxidation state.
DesoriptionQf ?he Preferred Embodiment In accordance with the present invention, a method and composition is provided to reduce the production of sludge upon acid contact with sludging crude oil.
In general, the aqueous acid used in the present invention can be substantially any acid which is capable of dissolving solid materials located in a permeable subterranean formation in a manner to increase the permeability of such formation. Commonly used acids include hydrofluoric acid, hydrochloric acid, organic acids such as formic or acetic acids and mixtures of such acids. Aqueous solutions of the acids generally are used at a concentration in the range of from about 5% to about 28-32% by weight. An aqueous 15%
hydrochloric acid solution is particularly suita~le for u~e in accordance with ths present invention.
Included within at least a portion of the initial aqueous acid introduced into the subterranean formation is a sludge . :
,, . : . ~ : :
inhibiting effective amount of an additive comprising at least one member selected from the group of thiourea, dimethylthiourea, diethylthiourea, diisopropylthiourea, imidazolidine-2-thione, hexahydropyrimidine-2-thione, monomethylthiourea, monoethylthiourea and monoisopropylthiourea together with an effective amount of a compound capable of providing cuprous ions in the aqueous acid solution whereby a substantial portion of any iron present in the acidic solution or dissolved by the acidic solution is reduced to the ferrous oxidation state. The first member of the additive generally is present in the aqueous acid solution in an amount of from about 0.5% to about 10% by weight.
Preferably, the first member is present in an amount of from about 0.75% to about 5~ by weight. The copper containing compound is present in the additive in an amount sufficient to provide a soluble cuprous ion concentration in an amount of at least about 0.005% by weight. Generally, the concentrations can be in the range of from about 0.005% to about 0.1% by weight or greater. Preferably, the cuprous ion concentration is in a range of from about 0.005 to about 0.05% by weight of the aqueous acidic solution. The cuprous ions can be provided by compounds such as, for example, cuprous chloride, cuprous oxide, cuprous sulfite, cuprous sulfate, cuprous carbonate and the like. While the specific reaction mechanism is not known it is believed that the ferric iron in solution is reduced to ferrous iron by the following reaction sequence:
. ~ . . . . , : . . . . :
5~ ~ ~
Fe+3 + Cu (Tu)4 +~ ~ Fe+2 + Cu (Tu)4+2 (labile) Cu (Tu)4+2 ~ Cu (TU)3+l + oxidation product Cu (Tu)3+l + Tu ' Cu (Tu) 4+1 The reaction then would continue until the thiourea compound is reduced in concentration to a level below the reaction threshold or until all Fe+3 is consumed. D~pending upon the particular hydrocarbon and the quantities of sludging agents present, the composition and method of the present invention can substantially reduce the amount of sludge produced and in some instances substantially eliminate any sludge formation during the acidizing treatment.
In accordance with the present invention, the aqueous acidic solution also can contain one or more other additives such as a corrosion inhibitor, a non-emulsifying surfactant, an anti-sludging agent, a dispersing agent and substantially any other conventionally known additive used in acidizing treatments that does not adversely react with the other 1 additives present to detrimentally effect the present ;~1 invention. The corrosion inhibitor generally maybe present in an amount of from about 0.1 to about 2.0 percent by weight of the acidic solution. The non-emulsifying surfactant generally may be present in an amount of from about 0.1 to about 2.0 percent by weight of the acidizing solution. The anti-sludging agent generally may be present in an amount of from about 0.5 to about 10 percent by weight of the acidic solution. The dispersing agent generally may be present in an amount of from about 0.1 to about 2.0 percent by weight of the acidic solution. Examples of such additives are set forth in .~
~`
.. . . . , :
. . , .. ~
. . :
.
2 ~ ~ 5 ~ ~ 1 U.S. Patents 4,096,914 and 4,823,874, the entire disclosure of which is incorporated herein by references.
In general, the acidic solution of the present invention is injected down a wellbore to contact a subterranean formation. The solution may be injected into the formation either at a rate and pressure sufficient to fracture the formation or at a rate and pressure below that at which fracturing can occur. Such low-pressure or ~ow-rate injection generally is referred to as matrix acidizing. The acidic solution generally is permitted to contact the subterranean formation for a sufficient time to substantially spend by dissolution of acid soluble constituents; however, no specific contact time is required. Upon conclusion of the acidizing treatment, the at-least-partially spent solution generally is withdrawn from the formation by pumping on the wellbore.
To further illustrate the utility of the present invention, but not by way of limitation, the following examples are provided.
EXAMP~E I
An acid composition is prepared by admixing 900 parts by volume 10% HCl with 100 parts glacial acetic acid. To this composition was added the following conventional acidizing additives : 1~ by weight 19 N surfactant, 3~ by weight AS-7 additive, 0.3% by weight Sperse-All additive, 0.8~ HAI-85 corrosion inhibitor, which are proprietary chemicals available from Halliburton Services, Duncan, Oklahoma. Samples of the acid solution then were admixed with an equal volume of crude . .
- , . .
2 ~ 9 ~
oil in a series of tests to which different quantities of ferric iron had been added with different additives of the present invention. More specifically, 50 mls of the acid solution containing the ferric iron, added by dissolution of FeCl3^6H20 in the acid, was heated to 180F. and admixed with a guantity of Beaver Hill Lake crude that had been strained through a lO0 mesh screen to remove solids and heated to the same temperature. The sample was shaken for l minute upon mixing and placed in a controlled temperature both at 180F.to stand for one hour. The sample then was strained through a 100 mesh screen upon mixing and placed in a controlled temperature bath at 180F. to stand for one hour. The sample then was strained through a 100 mesh screen, any residue on the screen was washed with 140F. water and dried prior to weighing of the residue (sludge). The results of the tests are set forth below:
:
. . - -- : :
: - .
, :
2 ~
Table I
1 2 0.013 none 4.06 2 2 0.0136% thiourea 0.05 3 _ 2 0.0135% thiourea 0.19 ; _4 2 0.0134% thiourea 0.31 5 _ 2 _ 0.0133% thiourea 0.61 6 2 0.01~6% hexahydropyrimidine- 0.07 _ . 2-thione : 7 2 0.0135% hexahydropyrimidine- 0.22 :, _ 2-thione . ¦8 2 0.0134% hexahydropyrimidine- 1.11 : _ _ 2-thione _ 9 2 0.0136% imidazolidine-2-thione 0.28 : 10 0.5 _ 0.013 1.5 thiourea 0.02 11 0.50.0131.25 thiourea 0.03 12 0.5 _ 0.013 1.0 thiourea 0.05 _ 13 0.50.0130.75% thiourea 0.06 ¦14 0.50.0131.5% hexahydropyrimidine- o 0 _ 2-thione : 15 0.50.0131.25% hexahydropyrimidine- 0.42 _- _ 2-thione 16 0.50.0131.5% imidazolidine- 0 04 _ 2-thione 17 0.50.0131.25% imidazolidine- 0.04 2-thione 18 0.50.0131.0% imidazolidine- 0 08 - _ ~_ _ 2-th one To confirm the Fe+3 iron was the cause of the sludge several tests were repeated using Fe+2 in place of Fe+3. No sludge was formed in sny test - . . . .
:: . " ~: . . .
~ 2 1 0 ~ ~ 9 1 ,. ;
EXANPLE II
The preceding test was repeated using a different crude known as the Judy Lake crude. The results are set forth ~ I 2 1.00.013 0 0.76 ,~ 3 1.0 0 4% 50/50 blend thiourea- 0.39 hexahydropyrimidine-2-thione _ _ , ~;~ 4 l.o0.134% 50/50 blend thiourea- 0.01 I hexahydropyrimidine-2-thione 2.0 0 0 0.99 6 2.00.013 _1.01 , 7 2.0 04% 50/50 blend thiourea- 0.62 _ _hexahydropyrimidine-2-thione 8 2.00.0134% 50/50 blend thiourea- 0.06 _ ______ _ _ hexahydropyrimidine-2-thione .`, ~ , ,~ , __, The results of the foregoing Examples clearly illustrate the effectiveness of the present invention in substantially reducing the guantity of sludqe formed upon contacting of an acidizing solution with a crude formation where iron in a ferric oxidation state is present. These results further show that if either part of this invention is left out, the desired result is not achieved.
While that which applicants presently consider to be the preferred embodiments of the present invention has been described herein, it is to be understood that changes and modifications can be made to the method and composition by those skilled in the art without departing from the spirit or 1,~
21 05fi31 `~
scope of the invention as def ined by the appended claims .
Claims (19)
1. A method of reducing the production of sludge when contacting a subterranean formation containing oil which is prone to sludging in the presence of dissolved iron when contacted by an aqueous acid comprising:
contacting said subterranean formation with an aqueous acidic solution including an additive comprising a sludge reducing effective amount of a first constituent comprising at least one member selected from the group of thiourea, dimethylthiourea, diethylthiourea, diisopropylthiourea, imidazolidine-2-thione, h e x a h y d r o p yr i m i d i n e - 2 - t h i o n e , monomethylthiourea, monoethylthiourea and monoisopropylthiourea together with a second constituent comprising an effective amount of a compound capable of providing cuprous ions in the acidic solution whereby at least some acid soluble constituents in said formation are dissolved by the acidic solution without the significant precipitation of sludge in the oil present in the formation.
contacting said subterranean formation with an aqueous acidic solution including an additive comprising a sludge reducing effective amount of a first constituent comprising at least one member selected from the group of thiourea, dimethylthiourea, diethylthiourea, diisopropylthiourea, imidazolidine-2-thione, h e x a h y d r o p yr i m i d i n e - 2 - t h i o n e , monomethylthiourea, monoethylthiourea and monoisopropylthiourea together with a second constituent comprising an effective amount of a compound capable of providing cuprous ions in the acidic solution whereby at least some acid soluble constituents in said formation are dissolved by the acidic solution without the significant precipitation of sludge in the oil present in the formation.
2. The method of claim 1 wherein said first constituent of said additive is present in an amount of from about 0.5%
to about 10% by weight of said acidic solution.
to about 10% by weight of said acidic solution.
3. The method of claim 1 wherein said first constituent of said additive is present in an amount of from about 0.75%
to about 5% by weight of said acidic solution.
to about 5% by weight of said acidic solution.
4. The method of claim 1 wherein said second constituent of said additive is present in an amount sufficient to provide a cuprous ion concentration of at least about 0.005 percent by weight.
5. The method of claim 1 wherein said second constituent of said additive is present in an amount sufficient to provide a cuprous ion concentration of from about 0.005%
to about 0.1% by weight.
to about 0.1% by weight.
6. The method of claim l wherein said second constituent of said additive is present in an amount sufficient to provide a cuprous ion concentration of from about 0.005%
to about 0.05% by weight.
to about 0.05% by weight.
7. The method of claim 1 wherein said acidic solution is comprised of at least one member selected from the group of hydrochloric acid, hydrofluoric acid, formic acid and acetic acid.
8. The method of claim 1 wherein said first constituent of said additive comprises at least one member selected from the group of thiourea, imidazolidine-2-thione and hexahydropyrimidine-2-thione.
9. The method of claim 1 wherein said second constituent of said additive comprises at least one member selected from the group of cuprous chloride, cuprous oxide, cuprous sulfite, cuprous sulfate and cuprous carbonate.
10. An acidizing composition comprising an aqueous acidic solution containing an additive comprising a sludge reducing effective amount of a first constituent comprising at least one member selected from the group of thiourea, dimethylthiourea, diethylthiourea, diisopropylthiourea, imidazolidine-2-thione, hexahydropyrimidine-2-thione, monomethylthiourea, monoethylthiourea and monoisopropylthiourea together with an effective amount of a second constituent comprising a compound capable of providing cuprous ions in the acidic solution.
11. The composition of claim 10 wherein said first constituent of said additive is present in an amount of from about 0.5% to about 10% by weight of said acidic solution.
12. The composition of claim 10 wherein said first constituent of said additive is present in an amount of from about 0.75% to about 5% by weight of said acidic solution.
13. The composition of claim 10 wherein said second constituent of said additive is present in an amount sufficient to provide a cuprous ion concentration of at least about 0.005 percent by weight.
14. The composition of claim 10 wherein said second constituent of said additive is present in an amount sufficient to provide a cuprous ion concentration of from about 0.005% to about 0.1% by weight.
15. The composition of claim 10 wherein said second constituent of said additive is present in an amount sufficient to provide a cuprous ion concentration of from about 0.005% to about 0.05% by weight.
16. A method of acidizing a subterranean formation comprising:
contacting said formation with an aqueous acidic solution including an additive having a first constituent comprising at least one member selected from the group of thiourea, dimethylthiourea, diethylthiourea, monoethylthiourea, monomethylthiourea, monoisopropylthiourea, diisopropylthiourea, imidazolidine-2-thione, and hexahydropyrimidine-2-thione present in an amount of from about 0.5% to about 10% by weight of said acidic solution and a second constituent comprising a compound capable of providing cuprous ions in the acidic solution present in an amount of at least about 0.005 percent by weight of said acidic solution and dissolving at least a portion of any acid soluble constituents present in said formation which are contacted by said acidic solution.
contacting said formation with an aqueous acidic solution including an additive having a first constituent comprising at least one member selected from the group of thiourea, dimethylthiourea, diethylthiourea, monoethylthiourea, monomethylthiourea, monoisopropylthiourea, diisopropylthiourea, imidazolidine-2-thione, and hexahydropyrimidine-2-thione present in an amount of from about 0.5% to about 10% by weight of said acidic solution and a second constituent comprising a compound capable of providing cuprous ions in the acidic solution present in an amount of at least about 0.005 percent by weight of said acidic solution and dissolving at least a portion of any acid soluble constituents present in said formation which are contacted by said acidic solution.
17. The method of claim 16 wherein said first constituent of said additive is present in an amount of from about 0.75%
to about 5% by weight.
to about 5% by weight.
18. The method of claim 16 wherein said second constituent of said additive is present in an amount of from about 0.005% to about 0.05% by weight.
19. The method of claim 16 wherein said acidic solution is defined further to include at least one member selected from the group of a corrosion inhibitor, a non-emulsifying surfactant, an anti-sludging agent and a dispersing agent.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US94327792A | 1992-09-10 | 1992-09-10 | |
| US943,277 | 1992-09-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2105691A1 true CA2105691A1 (en) | 1994-03-11 |
Family
ID=25479362
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2105691 Abandoned CA2105691A1 (en) | 1992-09-10 | 1993-09-08 | Compositions for reducing sludging during well acidizing |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2105691A1 (en) |
-
1993
- 1993-09-08 CA CA 2105691 patent/CA2105691A1/en not_active Abandoned
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