CA1211622A - Gelled acid compositions and methods for acidizing subterranean formations - Google Patents
Gelled acid compositions and methods for acidizing subterranean formationsInfo
- Publication number
- CA1211622A CA1211622A CA000436974A CA436974A CA1211622A CA 1211622 A CA1211622 A CA 1211622A CA 000436974 A CA000436974 A CA 000436974A CA 436974 A CA436974 A CA 436974A CA 1211622 A CA1211622 A CA 1211622A
- Authority
- CA
- Canada
- Prior art keywords
- acid
- composition
- formation
- amount
- range
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
Abstract of the Disclosure Gelled acid compositions are disclosed which comprises:
an aqueous acid, acrylamide polymers crosslinked with an alde-hyde(s), and an iron control agent. The gelled acids are useful in acidizing subterranean formations. As an example, 28 percent hydrochloric acid was gelled with a 70:30 AMPS/acrylamide copoly-mer crosslinked with formaldehyde in the presence of erythorbic acid.
an aqueous acid, acrylamide polymers crosslinked with an alde-hyde(s), and an iron control agent. The gelled acids are useful in acidizing subterranean formations. As an example, 28 percent hydrochloric acid was gelled with a 70:30 AMPS/acrylamide copoly-mer crosslinked with formaldehyde in the presence of erythorbic acid.
Description
IMPROVED GELLED ACID COMPOSITIONS AND
METHODS FOR ACIDIZING SUBTERRANEAN FORMATIONS
This invention pertains to improved composi-tions and methods for acid treating or acidizing of subt~rranean formations.
Acid treating or acidizing of porous sub-terranean formations penetrated by a well bore has beenwidely employed for increasing the production of fluids, e.g., crude oil, natural gas, etc., from said formations.
The usual technique of acidizing a formation comprises introducing a non-oxidizing acid into the well under sufficient pressure to force the acid out into the formation where it reacts with the acid-soluble compo-neIlts of the formation. The techni~ue is not limited to formations of high acid solubility such as lime-stone, dolomite, etc. The technigue is also applicable to other types of formations such as a sandstone contain-ing streaks or striations of acid soluble components such as thè various carbonates.
During the acid treating operation, passage-ways for fluid flow are created in the formation, or 31,189-F -1- ^
~121~6;~:2 existing pasSageways therein are enlarged, khUs stimu-lating the production of fluids from the formation.
This action of the acid on the formation is often called etching. Acid treating or acidizing operations wherein the acid is injected into the formatio~ at a pressure or rate insufficient to create cracks or fractures in the formation is usually referred to as matrix acidizing.
Hydraulic fxacturing is also commonly employed to increase the production of fluids from subterranean formations. Hydraulic fracturing comprises the injec-tion of a suitable fracturing fluid down a well penetrat-ing a ~ormation and into said formation under sufficient pressure to overcome the pressure exerted by the over-burden. This results in creating a crack or fracturein the formation to provide a passageway which facili-tates flow of fluids through the formation and into the well. Combination fracture acidizing processes are well known in the art.
Thus, it is within the scope of the present invention to inject the gelled acidic compositions of the invention into the formation under insufficient pressure to cause fracturing of the formation and carry out a matrix acidizing operations, or inject said gelled acidic composition at sufficient rates and pressure to cause fracturing and carry out a combina-tion fracture-acidizing operation.
One of the problems commonly encountered in acidizing operations is insufficient penetration of the formation by the acid. It is desirable that good penetration is obtained in order to ralize maximum 31,189-F -2-121~~22 benefits from the operation. Too often the acid is essentially completely spent in the area immediately adjacent and surrounding the well bore. The severity of the problem increases as the well temperature increases because acid reactivity with the formation increases with increasing temperatures as in deeper wells.
Poor penetration can also be caused, and/or aggravated, by fluid loss tv the more porous zones of the formation where low permeability is not a problem.
Poor penetration can also be caused and/or aggravated by leak-off at the fracture faces in combination frac-turing-acidizing operations. Fluid loss or leak-off can frequently worsen the situation by leaving the tight (low permeability) zones of the formation unchan~ed and merely opening up the already high permeability zones.
One solution which has been proposed for the above discussed problem is to incorporate various polymeric thickening or viscosif~ing agents into the acid solution. Such agents thicken the acid solution and increase the viscosity thereof. It has been reported that polymer-thickened acid solutions have reduced fluid loss properties. For example, see u.s.
Patent No. 3,415,319 issued in the name of B. L.
Gibson; and U.S. Patent No. 3,434,971 issued in the name of B. L. Atkins. It has also been reported that the reaction rate of said polymer-thickened acid solutions with the acid soluble portion of the formation is lessened or retarded. See, for example, U.S. Patent No. 3,749,169 issued in the name of J. F.
Tate; U.S. PatPnt No. 3,236,305 issued in the name of 31,189-F -3-lZ116;2Z
C. F. Parks; and U.S. Patent No. 3,252,904 issued in the name of N. F. Carpenter.
Higher viscosities are also advantageous in combination fracturing-acidizing operations in that the S more viscous acidic solutions produce wider and longer fractures More ~riscous acid solutions are also more effective in carrying proplping agents into the formation when propping agents are used.
Another problem encountered in acidizing operations, particularly w~hen employing acidizing compositions having thickening or viscosifying agents incorporated therein, is stability to heat. By stability to heat, it is meant the retention of the increased or greater viscosity properties under the conditions of use. Such compositions to be satisfactory should be sufficiently stable to resist degeneration by the heat of the formation for a period of time sufficient to accomplish the intended purpose, e.g., good penetration and significant etching of the formation. The degree of stability required in any particular operation will vary with such operating variables as the type of formation being trea-ted, the temperature of the formation, the well depth (time to pump the acidic composition down the well and into the formation), the acid concentration in the composition, etc. For example, acidizing of a tight 1QW permeability formation will proceed more slowly than a more permeable formation, other factors being the same, because a longer time will be required to obtain a significant amount of etching and the composition must remain in place and effective for a longer period of time. Also, more time will be required to pump the acidic composition into place in the formation.
31,189-F -4-~Z11622 The temperature of the formation usually has a pronouncPd effect on the stability of the acidizing compositions and, generally speaking, is one of the most important operating variables when considering stability. Increased formation temperatures usually have at least two undesirable effects. One such effect is degeneration of the comlposition, e.g., decrease in viscosity. Another such effect is increased rate of reaction of the acid with the formation. Thus, some compositions which would be satisfactory in a low temperature formation such as in the Hugoton field in the Anadarko basin might not be satisfactory in forma-tions encountered in deeper wells as in some West Texas fields.
lS In ordinary acidizing operations using unthick-ened acids there is usually no problem in removing the spent acid because it is essentially water. ~Iowever, a problem which is sometimes encountered when using thickened compositions in treating formations is the ~O case of removal of the treating composition after the operation is completed. Some thickened or highly viscous solutions are difficult to remove from the pores of the formation of the fracture after the opera-tion is complete. Sometimes a clogging r~sidue can be left in the pores of the formation, or in the fracture.
This can inhibit the production of fluids from the formation and can require costly cleanup operations.
It would be desirable to have gelled acidic compositions which break down to a lesser viscosity within a short time after the operation is completedO
Swanson addressed the problems set forth above and allegedly solved such problems by using 31,189-F -5-12~1~22 certain of acrylamide or methacrylamide crosslinked wth certain aldehyde crosslinkers in usP 4,103,742 and 4,191,657. From an academic standpoint, the swanson technology would appear to be viable. From a practical standpoint, however, the t:echnology is rendered com-mercially untenable by the! present discovery that an insoluble residue is formed in copious quantities when the gelled acid :reacts with the typical acid-soluble component(s) of the format:ion being treated if there is dissolved iron present. ThLe adverse ef~ect of dissolved iron on the polymeric gelling agents in Swanson was previously unknown. The problem caused by the dissolved iron is paxticularly vexat:ious because it is almost impossible to eliminate it: from acid solutions in contact with conventional steel (e.g., blending tanks, pumps, piping, etc.) and the insoluble residue that forms as the acid "spends" during the acidizing treatment could (and probably would) cause severe blockage and damage to the formation. Dissolved iron in the ferric t~3) oxidation state seems to be more troublesome than ferrous (+2) iron in these gelled acid-treatment fluids.
Several i.nvestigators have attempted to deal with problems caused by ferric ions. See, for example, Crowe (USP 4,317,735) and art cited therein. Crowe foùnd that the crosslinking and resultant precipitation of aqueous xanthan gums caused by ferric ions could be prevented by adding certain alkenoic acids having at least four (4) carbon atoms and bearing at least two
METHODS FOR ACIDIZING SUBTERRANEAN FORMATIONS
This invention pertains to improved composi-tions and methods for acid treating or acidizing of subt~rranean formations.
Acid treating or acidizing of porous sub-terranean formations penetrated by a well bore has beenwidely employed for increasing the production of fluids, e.g., crude oil, natural gas, etc., from said formations.
The usual technique of acidizing a formation comprises introducing a non-oxidizing acid into the well under sufficient pressure to force the acid out into the formation where it reacts with the acid-soluble compo-neIlts of the formation. The techni~ue is not limited to formations of high acid solubility such as lime-stone, dolomite, etc. The technigue is also applicable to other types of formations such as a sandstone contain-ing streaks or striations of acid soluble components such as thè various carbonates.
During the acid treating operation, passage-ways for fluid flow are created in the formation, or 31,189-F -1- ^
~121~6;~:2 existing pasSageways therein are enlarged, khUs stimu-lating the production of fluids from the formation.
This action of the acid on the formation is often called etching. Acid treating or acidizing operations wherein the acid is injected into the formatio~ at a pressure or rate insufficient to create cracks or fractures in the formation is usually referred to as matrix acidizing.
Hydraulic fxacturing is also commonly employed to increase the production of fluids from subterranean formations. Hydraulic fracturing comprises the injec-tion of a suitable fracturing fluid down a well penetrat-ing a ~ormation and into said formation under sufficient pressure to overcome the pressure exerted by the over-burden. This results in creating a crack or fracturein the formation to provide a passageway which facili-tates flow of fluids through the formation and into the well. Combination fracture acidizing processes are well known in the art.
Thus, it is within the scope of the present invention to inject the gelled acidic compositions of the invention into the formation under insufficient pressure to cause fracturing of the formation and carry out a matrix acidizing operations, or inject said gelled acidic composition at sufficient rates and pressure to cause fracturing and carry out a combina-tion fracture-acidizing operation.
One of the problems commonly encountered in acidizing operations is insufficient penetration of the formation by the acid. It is desirable that good penetration is obtained in order to ralize maximum 31,189-F -2-121~~22 benefits from the operation. Too often the acid is essentially completely spent in the area immediately adjacent and surrounding the well bore. The severity of the problem increases as the well temperature increases because acid reactivity with the formation increases with increasing temperatures as in deeper wells.
Poor penetration can also be caused, and/or aggravated, by fluid loss tv the more porous zones of the formation where low permeability is not a problem.
Poor penetration can also be caused and/or aggravated by leak-off at the fracture faces in combination frac-turing-acidizing operations. Fluid loss or leak-off can frequently worsen the situation by leaving the tight (low permeability) zones of the formation unchan~ed and merely opening up the already high permeability zones.
One solution which has been proposed for the above discussed problem is to incorporate various polymeric thickening or viscosif~ing agents into the acid solution. Such agents thicken the acid solution and increase the viscosity thereof. It has been reported that polymer-thickened acid solutions have reduced fluid loss properties. For example, see u.s.
Patent No. 3,415,319 issued in the name of B. L.
Gibson; and U.S. Patent No. 3,434,971 issued in the name of B. L. Atkins. It has also been reported that the reaction rate of said polymer-thickened acid solutions with the acid soluble portion of the formation is lessened or retarded. See, for example, U.S. Patent No. 3,749,169 issued in the name of J. F.
Tate; U.S. PatPnt No. 3,236,305 issued in the name of 31,189-F -3-lZ116;2Z
C. F. Parks; and U.S. Patent No. 3,252,904 issued in the name of N. F. Carpenter.
Higher viscosities are also advantageous in combination fracturing-acidizing operations in that the S more viscous acidic solutions produce wider and longer fractures More ~riscous acid solutions are also more effective in carrying proplping agents into the formation when propping agents are used.
Another problem encountered in acidizing operations, particularly w~hen employing acidizing compositions having thickening or viscosifying agents incorporated therein, is stability to heat. By stability to heat, it is meant the retention of the increased or greater viscosity properties under the conditions of use. Such compositions to be satisfactory should be sufficiently stable to resist degeneration by the heat of the formation for a period of time sufficient to accomplish the intended purpose, e.g., good penetration and significant etching of the formation. The degree of stability required in any particular operation will vary with such operating variables as the type of formation being trea-ted, the temperature of the formation, the well depth (time to pump the acidic composition down the well and into the formation), the acid concentration in the composition, etc. For example, acidizing of a tight 1QW permeability formation will proceed more slowly than a more permeable formation, other factors being the same, because a longer time will be required to obtain a significant amount of etching and the composition must remain in place and effective for a longer period of time. Also, more time will be required to pump the acidic composition into place in the formation.
31,189-F -4-~Z11622 The temperature of the formation usually has a pronouncPd effect on the stability of the acidizing compositions and, generally speaking, is one of the most important operating variables when considering stability. Increased formation temperatures usually have at least two undesirable effects. One such effect is degeneration of the comlposition, e.g., decrease in viscosity. Another such effect is increased rate of reaction of the acid with the formation. Thus, some compositions which would be satisfactory in a low temperature formation such as in the Hugoton field in the Anadarko basin might not be satisfactory in forma-tions encountered in deeper wells as in some West Texas fields.
lS In ordinary acidizing operations using unthick-ened acids there is usually no problem in removing the spent acid because it is essentially water. ~Iowever, a problem which is sometimes encountered when using thickened compositions in treating formations is the ~O case of removal of the treating composition after the operation is completed. Some thickened or highly viscous solutions are difficult to remove from the pores of the formation of the fracture after the opera-tion is complete. Sometimes a clogging r~sidue can be left in the pores of the formation, or in the fracture.
This can inhibit the production of fluids from the formation and can require costly cleanup operations.
It would be desirable to have gelled acidic compositions which break down to a lesser viscosity within a short time after the operation is completedO
Swanson addressed the problems set forth above and allegedly solved such problems by using 31,189-F -5-12~1~22 certain of acrylamide or methacrylamide crosslinked wth certain aldehyde crosslinkers in usP 4,103,742 and 4,191,657. From an academic standpoint, the swanson technology would appear to be viable. From a practical standpoint, however, the t:echnology is rendered com-mercially untenable by the! present discovery that an insoluble residue is formed in copious quantities when the gelled acid :reacts with the typical acid-soluble component(s) of the format:ion being treated if there is dissolved iron present. ThLe adverse ef~ect of dissolved iron on the polymeric gelling agents in Swanson was previously unknown. The problem caused by the dissolved iron is paxticularly vexat:ious because it is almost impossible to eliminate it: from acid solutions in contact with conventional steel (e.g., blending tanks, pumps, piping, etc.) and the insoluble residue that forms as the acid "spends" during the acidizing treatment could (and probably would) cause severe blockage and damage to the formation. Dissolved iron in the ferric t~3) oxidation state seems to be more troublesome than ferrous (+2) iron in these gelled acid-treatment fluids.
Several i.nvestigators have attempted to deal with problems caused by ferric ions. See, for example, Crowe (USP 4,317,735) and art cited therein. Crowe foùnd that the crosslinking and resultant precipitation of aqueous xanthan gums caused by ferric ions could be prevented by adding certain alkenoic acids having at least four (4) carbon atoms and bearing at least two
(2) alcoholic hydroxyl groups per molecule (e.g. ascor bic acid and/or erythorbic acid).
It has now been discovered that the inclusion of a reducing agent and/or a chelant will prevent or 31,189-F -6--121~6~2 substantially prevent the formation of -the insoluble residue noted when the gelled acidic compositions of Swanson are reacted with acid-soluble components of a subterranean formation in the presence of dissolved iron. Thus, the present invention is a subs-tantial improvement over Swanson.
The present invention, in particular, relates to a method for acid treating a porous subterranean formation susceptible of a.ttack by an acid and penetrated by a well bore, whiCh meth.od comprises:
injecting into said formation via said well bore a gelled acidic composition comprising water;
a water-thickening amount of a water~disper-sible polymer selected from the group consisting of polyacrylamides and polymethacrylamides; partially hydrolyzed polyacrylamides and partially hydrolyzed polymethacrylamides wherein a portion of the carboxamide groups are initially hydrolyzed to carboxyl groups;
crosslinked polyacrylamides and crosslinked polymethacry-lamides; partially hydrolyzed crosslinked polyacrylamidesand partially hydrolyzed crosslinked polymethacrylamides wherein a portion of the carboxamide groups are initially hydrolyzed to carboxyl groups; copolymers of acrylamide or methacrylamides with another ethylenically unsaturated monomer copolymerizable therewith, sufficient acrylamide or methacrylamide being present in the monomer mixture to impart said water-dispersible properties to the resulting copolymer when it is mixed with water; and mixtures thereof;
an amount of an acid which is capable of, and sufficiènt for, reacting with a significant amount of the acid-soluble components of said formation;
: 31,189-F -7-~Z1~6~
a small but effective amount of at least one water-dispersible aldehyde which is suf~icient to cause gelation of an aqueous dispersion of said polymer, said acid, and said aldehyde;
said polymer, said acid, and said aldehydes, in the amoun~s u~;ed, being sufficiently compatible with each other in an aqueous dispersion thereof to permit said gelation ancl thus form a said composition having sufficient stability to degeneration by the heat of said formation to permit good penetration of said composition into said ormation; and maintaining said composition in said formation in contact therewith for a period of time sufficient usually for the acid in said composition to react significantly with the acid-soluble components of said formation and stimulate the production of fluids there-from, the improvement comprising including in said gelled acidic composition at least one compatible iron control agent in an amount sufficient to prevent or substantially prevent the ~ormation of an insoluble residue as the gelled acid reacts with the acid-soluble components of said formation in the presence of dissolved ferric iron.
The present invention also resides in a gelled acidic composition, suitable for matrix-acidizing or fracture-acidizing of a porous subterranean formation susceptible of attack oy an acid, comprising:
~l~ an aqueous medium;
(2) a water thickening amount of a water-dispersible random copolymer represented by the formula 31,189-F -8-lZ~162Z
CH2 C ~CH2-C ~
. 0=C 0=C C~3 L x HN-C-C~2-SO3M
I II
wherein: R and R" are each a hydrogen atom, or a methyl radical; M is hydrogen, sodium, or potassium, Z is either -NH2 or -OM in the above Type I monomer units, with the proviso t~hat the copolymer contains at least 10 mol percent of said Type I monomer units in which Z is -NH2; and x and y are the mol percent values o~ the respective monomer units I and II, with x being in the range o~ from 20 to 9S and with y being in the range of from 5 to 80;
It has now been discovered that the inclusion of a reducing agent and/or a chelant will prevent or 31,189-F -6--121~6~2 substantially prevent the formation of -the insoluble residue noted when the gelled acidic compositions of Swanson are reacted with acid-soluble components of a subterranean formation in the presence of dissolved iron. Thus, the present invention is a subs-tantial improvement over Swanson.
The present invention, in particular, relates to a method for acid treating a porous subterranean formation susceptible of a.ttack by an acid and penetrated by a well bore, whiCh meth.od comprises:
injecting into said formation via said well bore a gelled acidic composition comprising water;
a water-thickening amount of a water~disper-sible polymer selected from the group consisting of polyacrylamides and polymethacrylamides; partially hydrolyzed polyacrylamides and partially hydrolyzed polymethacrylamides wherein a portion of the carboxamide groups are initially hydrolyzed to carboxyl groups;
crosslinked polyacrylamides and crosslinked polymethacry-lamides; partially hydrolyzed crosslinked polyacrylamidesand partially hydrolyzed crosslinked polymethacrylamides wherein a portion of the carboxamide groups are initially hydrolyzed to carboxyl groups; copolymers of acrylamide or methacrylamides with another ethylenically unsaturated monomer copolymerizable therewith, sufficient acrylamide or methacrylamide being present in the monomer mixture to impart said water-dispersible properties to the resulting copolymer when it is mixed with water; and mixtures thereof;
an amount of an acid which is capable of, and sufficiènt for, reacting with a significant amount of the acid-soluble components of said formation;
: 31,189-F -7-~Z1~6~
a small but effective amount of at least one water-dispersible aldehyde which is suf~icient to cause gelation of an aqueous dispersion of said polymer, said acid, and said aldehyde;
said polymer, said acid, and said aldehydes, in the amoun~s u~;ed, being sufficiently compatible with each other in an aqueous dispersion thereof to permit said gelation ancl thus form a said composition having sufficient stability to degeneration by the heat of said formation to permit good penetration of said composition into said ormation; and maintaining said composition in said formation in contact therewith for a period of time sufficient usually for the acid in said composition to react significantly with the acid-soluble components of said formation and stimulate the production of fluids there-from, the improvement comprising including in said gelled acidic composition at least one compatible iron control agent in an amount sufficient to prevent or substantially prevent the ~ormation of an insoluble residue as the gelled acid reacts with the acid-soluble components of said formation in the presence of dissolved ferric iron.
The present invention also resides in a gelled acidic composition, suitable for matrix-acidizing or fracture-acidizing of a porous subterranean formation susceptible of attack oy an acid, comprising:
~l~ an aqueous medium;
(2) a water thickening amount of a water-dispersible random copolymer represented by the formula 31,189-F -8-lZ~162Z
CH2 C ~CH2-C ~
. 0=C 0=C C~3 L x HN-C-C~2-SO3M
I II
wherein: R and R" are each a hydrogen atom, or a methyl radical; M is hydrogen, sodium, or potassium, Z is either -NH2 or -OM in the above Type I monomer units, with the proviso t~hat the copolymer contains at least 10 mol percent of said Type I monomer units in which Z is -NH2; and x and y are the mol percent values o~ the respective monomer units I and II, with x being in the range o~ from 20 to 9S and with y being in the range of from 5 to 80;
(3) an amount of a non-oxidizing acid which is capable of, and sufficient for, reacting with a significant amount of the acid-soluble components of sand formation,
(4) a small but effective amount of at least one water dispersible aldehyde selected from the group consisting of aliphatic monoaldehydes having from 1 to 10 carbon atoms, glyoxal, glutaraldehyde and
5 terephthaldehyde;
said polymer, said acid, and said aldehyde, in the amounts used, being sufficiently compatible with each other in an aqueous dispersi~n thereof to permit gelation and thus form a said compo-sition having sufficient stability to degeneration bythe heat of said formation to permit good penetration of said composition into said formation when injected 31,189-F -9-lZ1162Z
thereinto and the maintenance of said composition in said formation in contact therewith for a period of time usually sufficient for ~he acid in said composition to react significantly with the acid-soluble components of said formation and stimulate the production of fluid therefrom; and ~ 5) at least one compatible iron control agent in an amount sufficient to prevent or substantially prevent the formation of aln insoluble residue as the gelled acid reacts with the acid-soluble components of said formation in the pres'ence of dissolved ferric ron .
The "iron control agents" useful herein are reducing agents and/ox chelating agents, both of which are known class~s o~ compounds having many members.
Any member(s) of these known classes of compounds can be used herein so long as the chosen member(s) is compatible with the gelled acidic composition; i.e., the chosen member~s) is soluble or dispersible in the acidic comosition and doesn't prevent formation of the gelled acidic composition or cause premature breaking of the gel. Examples of suitable reducing agents include, reducing organic acids (e.g. ascorbic acid, erythorbic acid, and the like) and soluble salts thereof (e.g. sodium erythorbate, potassium erythorbate, ammo-nium ascorbate, and the like), hydrazine, iodide salts (e.g. sodium iodide, and the like), and other such compounds. Of these, the organic reducing acids are preferred, and ascorbic acid, erythorbic acid and/or the soluble salts thereof are most preferred. Examples of the class of chelating agents for iron include, the polyalkylenepolyaminepolycarboxylic acids (e.g., N, N,N',N'-ethylenediaminetetraacetic acid, ~EDTA), 31,189-F -10-1~11622 N-2-hydroxyethyl-N,N',N'-ethylenediaminetriacetic acid (HEDTA), and the like3 and soluble salts thereof (e.g.
tetrasodium EDTA, ammonium salts of EDTA or HEDTA), the hydroxy-containing organic acids (e.g. citric acid, lactic acid, and the like), and other such compounds.
The reducing agent and/or chelating agent is included in the gelled aci.dic composition in an effective amount, i.e., an amount sufficient to prevent or substantially prevent the formation of an insoluble residue when the gelled acidic composition is con~acted with calcium carbonate (e.g. small marble chips) in the presence of dissolved iron.
The gelled acidic com~ositions, and the components thereof, as well as the process of using such gelled acidic compositions to treat subterranean formation is described by Swanson, suPra.
Experimental:
The following experiments will further illus-trate the invention:
A~ueous 28 percent hydrochloric acid was gelled by dissolving 0.8 weight percent, total weight basis, of a copolymer having about 70 mole percent of AMPS monomer and 30 mole percent acrylamide monomer in interpolymeri~ed form. The polymer in the gelled acid was then crosslinked by blending in 0.3 weight percent formaldehyde, various amounts of ferric chloride were dissolved into aliquots of the crosslinked gelled acid and the acid subsequently spent by contacting it with marble chips. The results of this series of experiments are shown in Table I below.
31,1&~-F 11-~11622 TABLE_I
Example Fe 3(ppm) Appearance of Spent Fluid 1 0 no residue 2 250 small amount of residue 3 500 small amount of residue 4 .L000 large amount of residue .'OOo large amount of residue 6 3000 large amount of residue The residue was a gelatinous mass that floated on the surface of the spent fluid. The residue contained the AMPS/acrylamide copolymer. In a similar series of ex-periments, a ferrous salt was added in place of ferric chloride - no residue was observed.
In another series of experiments, various amounts of erythorbic acid was added to aliquots of the above crosslinked gelled`acid containing 3000 ppm ferric ion (added as ferric chloride). These novel gelled acids ~ere then spent by contact with marble chips in the sarne manner as above. The results of this series of experiments are shown in Table II below.
TABLE II
Example Erythorbic Acid Appearance of Spent Fluid (wt. pexcent) 7 0 large arnount of residue 8 0.05 large amount of residue 9 0.10 large amount of residue 0.15 no residue 11 0.20 no residue 31,189-F 12-121~l6ZZ
This series of experiments show the effectiveness of erythorbic acid in preventing the formation of the in-soluble polymer-containing residue. Erythorbic acid and ascorbic acid are unusually effective in the present invention. For example, H:EDTA was also effective in preventing formation of the insoluble residue, but more was required (on a mole basis relative to the amoun~ of initial ferric ion in solution). The above experiments also show the rel.ative ease by which a skilled artisan can determine the effective concentration level of a reducing agent and/or a chelating agent in any chosen crosslinked gelled acid of the present invention.
31,189-F -13-
said polymer, said acid, and said aldehyde, in the amounts used, being sufficiently compatible with each other in an aqueous dispersi~n thereof to permit gelation and thus form a said compo-sition having sufficient stability to degeneration bythe heat of said formation to permit good penetration of said composition into said formation when injected 31,189-F -9-lZ1162Z
thereinto and the maintenance of said composition in said formation in contact therewith for a period of time usually sufficient for ~he acid in said composition to react significantly with the acid-soluble components of said formation and stimulate the production of fluid therefrom; and ~ 5) at least one compatible iron control agent in an amount sufficient to prevent or substantially prevent the formation of aln insoluble residue as the gelled acid reacts with the acid-soluble components of said formation in the pres'ence of dissolved ferric ron .
The "iron control agents" useful herein are reducing agents and/ox chelating agents, both of which are known class~s o~ compounds having many members.
Any member(s) of these known classes of compounds can be used herein so long as the chosen member(s) is compatible with the gelled acidic composition; i.e., the chosen member~s) is soluble or dispersible in the acidic comosition and doesn't prevent formation of the gelled acidic composition or cause premature breaking of the gel. Examples of suitable reducing agents include, reducing organic acids (e.g. ascorbic acid, erythorbic acid, and the like) and soluble salts thereof (e.g. sodium erythorbate, potassium erythorbate, ammo-nium ascorbate, and the like), hydrazine, iodide salts (e.g. sodium iodide, and the like), and other such compounds. Of these, the organic reducing acids are preferred, and ascorbic acid, erythorbic acid and/or the soluble salts thereof are most preferred. Examples of the class of chelating agents for iron include, the polyalkylenepolyaminepolycarboxylic acids (e.g., N, N,N',N'-ethylenediaminetetraacetic acid, ~EDTA), 31,189-F -10-1~11622 N-2-hydroxyethyl-N,N',N'-ethylenediaminetriacetic acid (HEDTA), and the like3 and soluble salts thereof (e.g.
tetrasodium EDTA, ammonium salts of EDTA or HEDTA), the hydroxy-containing organic acids (e.g. citric acid, lactic acid, and the like), and other such compounds.
The reducing agent and/or chelating agent is included in the gelled aci.dic composition in an effective amount, i.e., an amount sufficient to prevent or substantially prevent the formation of an insoluble residue when the gelled acidic composition is con~acted with calcium carbonate (e.g. small marble chips) in the presence of dissolved iron.
The gelled acidic com~ositions, and the components thereof, as well as the process of using such gelled acidic compositions to treat subterranean formation is described by Swanson, suPra.
Experimental:
The following experiments will further illus-trate the invention:
A~ueous 28 percent hydrochloric acid was gelled by dissolving 0.8 weight percent, total weight basis, of a copolymer having about 70 mole percent of AMPS monomer and 30 mole percent acrylamide monomer in interpolymeri~ed form. The polymer in the gelled acid was then crosslinked by blending in 0.3 weight percent formaldehyde, various amounts of ferric chloride were dissolved into aliquots of the crosslinked gelled acid and the acid subsequently spent by contacting it with marble chips. The results of this series of experiments are shown in Table I below.
31,1&~-F 11-~11622 TABLE_I
Example Fe 3(ppm) Appearance of Spent Fluid 1 0 no residue 2 250 small amount of residue 3 500 small amount of residue 4 .L000 large amount of residue .'OOo large amount of residue 6 3000 large amount of residue The residue was a gelatinous mass that floated on the surface of the spent fluid. The residue contained the AMPS/acrylamide copolymer. In a similar series of ex-periments, a ferrous salt was added in place of ferric chloride - no residue was observed.
In another series of experiments, various amounts of erythorbic acid was added to aliquots of the above crosslinked gelled`acid containing 3000 ppm ferric ion (added as ferric chloride). These novel gelled acids ~ere then spent by contact with marble chips in the sarne manner as above. The results of this series of experiments are shown in Table II below.
TABLE II
Example Erythorbic Acid Appearance of Spent Fluid (wt. pexcent) 7 0 large arnount of residue 8 0.05 large amount of residue 9 0.10 large amount of residue 0.15 no residue 11 0.20 no residue 31,189-F 12-121~l6ZZ
This series of experiments show the effectiveness of erythorbic acid in preventing the formation of the in-soluble polymer-containing residue. Erythorbic acid and ascorbic acid are unusually effective in the present invention. For example, H:EDTA was also effective in preventing formation of the insoluble residue, but more was required (on a mole basis relative to the amoun~ of initial ferric ion in solution). The above experiments also show the rel.ative ease by which a skilled artisan can determine the effective concentration level of a reducing agent and/or a chelating agent in any chosen crosslinked gelled acid of the present invention.
31,189-F -13-
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In the method for acid treating a porous subterranean formation susceptible of attack by an acid and penetrated by a well bore, which method comprises:
injecting into said formation via said well bore a gelled acidic composition comprising water;
a water-thickening amount of a water-disper-sible polymer selected from the group consisting of polyacrylamides and polymethacrylamides; partially hydrolyzed polyacrylamides and partially hydrolyzed polymethacrylamides wherein a portion of the carboxamide groups are initially hydrolyzed to carboxyl groups;
crosslinked polyacrylamides and crosslinked polymethacry-lamides; partially hydrolyzed crosslinked polyacrylamides and partially hydrolyzed crosslinked polymethacrylamides wherein a portion of the carboxamide groups are initially hydrolyzed to carboxyl groups; copolymers of acrylamide or methacrylamides with another ethylenically unsaturated monomer copolymerizable therewith, sufficient acrylamide or methacrylamide being present in the monomer mixture to impart said water-dispersible properties to the resulting copolymer when it is mixed with water; and mixtures thereof;
an amount of an acid which is capable of, and sufficient for, reacting with a significant amount of the acid-soluble components of said formation;
a small but effective amount of at least one water-dispersible aldehyde which is sufficient to cause gelation of an aqueous dispersion of said polymer, said acid, and said aldehyde;
said polymer, said acid, and said aldehydes, in the amounts used, being sufficiently compatible with each other in an aqueous dispersion thereof to permit said gelation and thus form a said composition having sufficient stability to degeneration by the heat of said formation to permit good penetration of said composition into said formation; and maintaining said composition in said formation in contact therewith for a period of time sufficient usually for the acid in said composition to react significantly with the acid-soluble components of said formation and stimulate the production of fluids there-from, the improvement comprising including in said gelled acidic composition at least one compatible iron control agent in an amount sufficient to prevent or substantially prevent the formation of an insoluble residue as the gelled acid reacts with the acid-soluble components of said formation in the presence of dissolved ferric iron.
injecting into said formation via said well bore a gelled acidic composition comprising water;
a water-thickening amount of a water-disper-sible polymer selected from the group consisting of polyacrylamides and polymethacrylamides; partially hydrolyzed polyacrylamides and partially hydrolyzed polymethacrylamides wherein a portion of the carboxamide groups are initially hydrolyzed to carboxyl groups;
crosslinked polyacrylamides and crosslinked polymethacry-lamides; partially hydrolyzed crosslinked polyacrylamides and partially hydrolyzed crosslinked polymethacrylamides wherein a portion of the carboxamide groups are initially hydrolyzed to carboxyl groups; copolymers of acrylamide or methacrylamides with another ethylenically unsaturated monomer copolymerizable therewith, sufficient acrylamide or methacrylamide being present in the monomer mixture to impart said water-dispersible properties to the resulting copolymer when it is mixed with water; and mixtures thereof;
an amount of an acid which is capable of, and sufficient for, reacting with a significant amount of the acid-soluble components of said formation;
a small but effective amount of at least one water-dispersible aldehyde which is sufficient to cause gelation of an aqueous dispersion of said polymer, said acid, and said aldehyde;
said polymer, said acid, and said aldehydes, in the amounts used, being sufficiently compatible with each other in an aqueous dispersion thereof to permit said gelation and thus form a said composition having sufficient stability to degeneration by the heat of said formation to permit good penetration of said composition into said formation; and maintaining said composition in said formation in contact therewith for a period of time sufficient usually for the acid in said composition to react significantly with the acid-soluble components of said formation and stimulate the production of fluids there-from, the improvement comprising including in said gelled acidic composition at least one compatible iron control agent in an amount sufficient to prevent or substantially prevent the formation of an insoluble residue as the gelled acid reacts with the acid-soluble components of said formation in the presence of dissolved ferric iron.
2. The method of Claim 1 wherein said water-dispersible polymer is selected from the group consisting of polyacrylamides and polymethacrylamides wherein up to 45 percent of the carboxamide groups can be initially hydrolyzed to carboxyl groups.
3. The method of Claim 1 wherein said water-dispersible polymer is a random copolymer repre-sented by the formula wherein: R is hydrogen or a lower alkyl radical containing from 1 to 6 carbon atoms; R' is an alkylene radical containing from 1 to 24 carbon catoms or is an arylene radical containing from 6 to 10 carbon atoms; R" is hydrogen or a methyl radical; M is hydrogen, ammonium, or an alkali metal; Z is either -NH2 or -OM in the above Type I monomer units, with the proviso that the copolymer contains at least 10 mol percent of said Type I monomer units in which Z is -NH2; and x and y are the mol percent values of the respective individual monomer units I and II, with x being in the range of from 10 to 99 and with y being in the range of from 1 to 90.
4. The method of Claim 1 wherein said water-dispersible polymer is a random copolymer repre-sented by the formula wherein: R' and R" are each a hydrogen atom, or a methyl radical; M is hydrogen, sodium, or potassium; Z
is either -NH2 or -OM in the above Type I monomer units, with the proviso that the copolymer contains at least 10 mol percent of said Type I monomer units in which z is -NH2; and x and y are the mol percent values of the respective monomer units I and II with x being in the range of from 20 to 95 and with y being in the range of from 5 to 80.
is either -NH2 or -OM in the above Type I monomer units, with the proviso that the copolymer contains at least 10 mol percent of said Type I monomer units in which z is -NH2; and x and y are the mol percent values of the respective monomer units I and II with x being in the range of from 20 to 95 and with y being in the range of from 5 to 80.
5. The method of Claim 1 wherein said aldehyde is formaldehyde, acetaldehyde, or a mixture of formaldehyde and acetaldehyde.
6. The method of Claim 1 wherein said acid is hydrochloric acid.
7. The method of Claim 1 wherein said iron control agent is a reducing agent or chelating agent selected from the group consisting of erythorbic acid, ascorbic acid, ethylenedi aminetetraacetic acid, N-2-hydroxyethyl, N,N',N"-ethylenediaminetriacetic acid, and a soluble salt thereof.
8. The method of Claim 7 wherein said reducing agent or chelating agent is erythorbic acid and/or a soluble salt thereof.
9. The method of Claim 1 wherein:
the amount of said polymer is within the range of from 0.2 to 3 weight percent based upon the total weight of said composition;
the amount of said aldehydes is within the range of from 0.001 to 5 weight percent, based upon the total weight of said composition; and the amount of said acid is within the range of from 0.4 to 60 weight percent, based on the total weight of said composition.
the amount of said polymer is within the range of from 0.2 to 3 weight percent based upon the total weight of said composition;
the amount of said aldehydes is within the range of from 0.001 to 5 weight percent, based upon the total weight of said composition; and the amount of said acid is within the range of from 0.4 to 60 weight percent, based on the total weight of said composition.
10. The method of Claim 9 wherein:
said acid is hydrochloric acid, and the amount thereof is sufficient to provide an amount of HCl within the range of from 0.4 to 35 weight percent.
said acid is hydrochloric acid, and the amount thereof is sufficient to provide an amount of HCl within the range of from 0.4 to 35 weight percent.
11. The method according to Claim 9 wherein:
said aldehydes are present within the range of from 0.004 to 2 weight percent, based on the total weight of said composition.
said aldehydes are present within the range of from 0.004 to 2 weight percent, based on the total weight of said composition.
12. A gelled acidic composition, suitable for matrix-acidizing or fracture-acidizing of a porous subterranean formation susceptible of attack by an acid, comprising:
(1) an aqueous medium;
(2) a water thickening amount of a water-dispersible random copolymer represented by the formula wherein: R and R" are each a hydrogen atom, or a methyl radical; M is hydrogen, sodium, or potassium, Z is either -NH2 or -OM in the above Type I monomer units, with the proviso that the copolymer contains at least 10 mol percent of said Type I monomer units in which Z is -NH2; and x and y are the mol percent values of the respective monomer units I and II, with x being in the range of from 20 to 95 and with y being in the range of from 5 to 80;
(3) an amount of a non-oxidizing acid which is capable of, and sufficient for, reacting with a significant amount of the acid-soluble components of sand formation, (4) a small but effective amount of at least one water dispersible aldehyde selected from the group consisting of aliphatic monoaldehydes having from 1 to 10 carbon atoms, glyoxal, glutaraldehyde and terephthaldehyde;
said polymer, said acid, and said aldehyde, in the amounts used, being sufficiently compatible with each other in an aqueous dispersion thereof to permit gelation and thus form a said compo-sition having sufficient stability to degeneration by the heat of said formation to permit good penetration of said composition into said formation when injected thereinto and the maintenance of said composition in said formation in contact therewith for a period of time usually sufficient for the acid in said composition to react significantly with the acid-soluble components of said formation and stimulate the production of fluid therefrom; and (5) at least one compatible iron control agent in an amount sufficient to prevent or substantially prevent the formation of an insoluble residue as the gelled acid reacts with the acid-soluble components of said formation in the presence of dissolved ferric iron.
(1) an aqueous medium;
(2) a water thickening amount of a water-dispersible random copolymer represented by the formula wherein: R and R" are each a hydrogen atom, or a methyl radical; M is hydrogen, sodium, or potassium, Z is either -NH2 or -OM in the above Type I monomer units, with the proviso that the copolymer contains at least 10 mol percent of said Type I monomer units in which Z is -NH2; and x and y are the mol percent values of the respective monomer units I and II, with x being in the range of from 20 to 95 and with y being in the range of from 5 to 80;
(3) an amount of a non-oxidizing acid which is capable of, and sufficient for, reacting with a significant amount of the acid-soluble components of sand formation, (4) a small but effective amount of at least one water dispersible aldehyde selected from the group consisting of aliphatic monoaldehydes having from 1 to 10 carbon atoms, glyoxal, glutaraldehyde and terephthaldehyde;
said polymer, said acid, and said aldehyde, in the amounts used, being sufficiently compatible with each other in an aqueous dispersion thereof to permit gelation and thus form a said compo-sition having sufficient stability to degeneration by the heat of said formation to permit good penetration of said composition into said formation when injected thereinto and the maintenance of said composition in said formation in contact therewith for a period of time usually sufficient for the acid in said composition to react significantly with the acid-soluble components of said formation and stimulate the production of fluid therefrom; and (5) at least one compatible iron control agent in an amount sufficient to prevent or substantially prevent the formation of an insoluble residue as the gelled acid reacts with the acid-soluble components of said formation in the presence of dissolved ferric iron.
13. The composition of Claim 12 wherein said aldehyde is formaldehyde, acetaldehyde or a mixture of formaldehyde and acetaldehyde.
14. The composition of Claim 12 wherein said acid is hydrochloric acid.
15. The composition of Claims 12 wherein said iron control agent is a reducing agent or chelating agent selected from the group consisting of erythorbic acid ascorbic acid, ethylenediaminetetra-acetic acid, N-2-hydroxyethyl, N,N',N'-ethylenediamine-triacetic acid, and a soluble salt thereof.
16. The composition of Claim 15 wherein said reducing agent or chelating agent is erythorbic acid and/or a soluble salt thereof.
17. The composition of Claim 12, wherein the random polymer is present within the range of from 0.2 to 3 weight percent, based on the total weight of the composition, said acid is present in an amount of from 0.4 to 60 weight percent, based on the total weight of the composition, and said aldehyde is present in an amount of from 0.001 to 5 weight percent, based on the total weight of said composition.
18. The composition of Claim 17 wherein:
the amount of said copolymer is within the range of from 0.75 to 2 weight percent;
said acid is hydrochloric acid, and the amount thereof is sufficient to provide an amount of HCl within the range of from 0.4 to 35 weight percent;
and said aldehyde is selected from the group consisting of the C1 to C10 aliphatic monoaldehydes, and mixtures thereof, and the amount of said aldehyde is within the range of from 0.004 to 2 weight percent.
the amount of said copolymer is within the range of from 0.75 to 2 weight percent;
said acid is hydrochloric acid, and the amount thereof is sufficient to provide an amount of HCl within the range of from 0.4 to 35 weight percent;
and said aldehyde is selected from the group consisting of the C1 to C10 aliphatic monoaldehydes, and mixtures thereof, and the amount of said aldehyde is within the range of from 0.004 to 2 weight percent.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US42935582A | 1982-09-30 | 1982-09-30 | |
| US429,355 | 1982-09-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1211622A true CA1211622A (en) | 1986-09-23 |
Family
ID=23702880
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000436974A Expired CA1211622A (en) | 1982-09-30 | 1983-09-19 | Gelled acid compositions and methods for acidizing subterranean formations |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1211622A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111394083A (en) * | 2014-07-29 | 2020-07-10 | 艺康美国股份有限公司 | Polymer emulsions for crude oil recovery |
-
1983
- 1983-09-19 CA CA000436974A patent/CA1211622A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111394083A (en) * | 2014-07-29 | 2020-07-10 | 艺康美国股份有限公司 | Polymer emulsions for crude oil recovery |
| CN111394083B (en) * | 2014-07-29 | 2022-10-21 | 艺康美国股份有限公司 | Polymer emulsions for crude oil recovery |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4460751A (en) | Crosslinking composition and method of preparation | |
| US4524829A (en) | Method of altering the permeability of a subterranean formation | |
| US4055502A (en) | Method and composition for acidizing subterranean formations | |
| CA1116388A (en) | Gelled acid composition and well treating | |
| US4683954A (en) | Composition and method of stimulating subterranean formations | |
| US4624795A (en) | Aqueous acid gels and use thereof | |
| US3791446A (en) | Method for stimulating well production | |
| US4574050A (en) | Method for preventing the precipitation of ferric compounds during the acid treatment of wells | |
| US4200154A (en) | Composition and method for stimulating well production | |
| US4103742A (en) | Method for acidizing subterranean formations | |
| US4664713A (en) | Composition for and method of altering the permeability of a subterranean formation | |
| US4191657A (en) | Compositions for acidizing subterranean formations | |
| CA1280589C (en) | Composition and method of stimulating subterranean formations | |
| CA1158428A (en) | Method of inhibiting crosslinking of aqueous xanthan gums in the presence of ferric acid | |
| US20050197257A1 (en) | Subterranean acidizing treatment fluids and methods of using these fluids in subterranean formations | |
| US4240505A (en) | Well acidizing compositions and methods | |
| AU2014373886B2 (en) | Cross-linked acrylamide polymer or copolymer gel and breaker compositions and methods of use | |
| US4163727A (en) | Acidizing-gel composition | |
| US4606772A (en) | Composition for and method of altering the permeability of a subterranean formation | |
| EP1576253A2 (en) | Method using particulate chelates to stimulate production of petroleum in carbonate formations | |
| US4068719A (en) | Method for acidizing subterranean formations | |
| GB2163790A (en) | Methods for acidizing subterranean formations and gelled acid compositions | |
| EP0136773B1 (en) | Composition for cross-linking carboxyl polymers and the use thereof in treating subterranean formations | |
| US4426296A (en) | Method of acidizing wells using gelled acids | |
| US4172041A (en) | Composition for acidizing subterranean formations |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |