CA1245388A - Polyvinyl alcohol based-polyvinyl aldehyde gels for retarding fluid flow - Google Patents
Polyvinyl alcohol based-polyvinyl aldehyde gels for retarding fluid flowInfo
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- CA1245388A CA1245388A CA000459116A CA459116A CA1245388A CA 1245388 A CA1245388 A CA 1245388A CA 000459116 A CA000459116 A CA 000459116A CA 459116 A CA459116 A CA 459116A CA 1245388 A CA1245388 A CA 1245388A
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Abstract
POLYVINYL ALCOHOL BASED-POLYVINYL ALDEHYDE GELS FOR RETARDING FLUID FLOWS
ABSTRACT
A gel-forming composition is provided comprising a PVA based substance selected from the group consisting of a polyvinyl alcohol, a polyvinyl alcohol copolymer, and mixtures thereof, polyvinyl aldehyde, and water. The gel-forming composition is useful for retarding the flow of fluids in subterranean formations. For example, a method is provided for retarding the flow of water in high permeability channels in an oil reservoir. Such method is particularly useful in waterflood operations to increase the sweep efficiency of the oil recovery process.
ABSTRACT
A gel-forming composition is provided comprising a PVA based substance selected from the group consisting of a polyvinyl alcohol, a polyvinyl alcohol copolymer, and mixtures thereof, polyvinyl aldehyde, and water. The gel-forming composition is useful for retarding the flow of fluids in subterranean formations. For example, a method is provided for retarding the flow of water in high permeability channels in an oil reservoir. Such method is particularly useful in waterflood operations to increase the sweep efficiency of the oil recovery process.
Description
- ` ~24S3B8 POLYVINYL ALCOHOL BASED-POLYVINYL ALDEHYDE GELS FOR RETARDING FLUID FLOWS
. .
Technical Field This invention relates to gels, methods of forming gels, and uses for gels. A polyvinyl aleohol based-polyvinyl aldehyde hydrogel, or gel, is provided which is useful for immobilizing large volumes of earth or lO water. The gel ean be used for reducing the permeabi1ity of soils and subterranean formations to the flow of fluids, waters or brines. The ge}s of this invention are particularly valuable in retarding the flow of fluids, waters or brines i~ hydrocarbon production from a wellbore, or fTom solar ponds.
15 Related Applications ~ he subjee~ m~tter of this application is related to thzt of Canadian Patent Application Serial Number 459,031, filed July 17, 1984 for "Gel for Retarding ~Vater Flow".
20 Background of the Invention ~ he recovery of hydrocarbons, both liquid and gaseous, from subterranean zones has frequently resulted in the simultaneous production of large quantities of water or brines. In some cases, even though substantial flows of hydrocarbons have been shown, water production is so 25 great and water disposal costs so high, that hydrocarbor production is not eeonomical. Such water production has in some cases been disposed of iu an abandoned or dry well by separating such water from the hydroearbons and reinjeeting the separated water into such wells. Where a disposàl well is not available nor near the producing well, pipelining 30 the water prod~uet o~er a long distance to a disposal site can become so eostIy that it renders the well noncommercial. Even if a disposal well is elose by, the disposal cost ean still be very expensive. Therefore it is desirable to find a way to reduce or shut off the flow o water while permitting hydroearbon production to continue.
It is well known that the production oE large amounts of water from hydroearbon produeing wells is a major expense item in the overall hydroearbon reeovery cost. It is not uncommon for an oil well to produee an effluent whieh is 60 - 99% by volume water and only l - 40Z by volume oil. In sueh situations, the major part of the pumping energy is 40 expended in lifting water from the well, a eost which the produeer would ` 1 :1 ~,.
lZ~S3~38 like to avoid if possible. The effluent must then be subjected to a costly separation procedure to recovery water-free hydrocarbons. The foul water separated therefrom also presents a troublesome and expensive disposal problem. Consequently, it i5 desirable to decrease the volume 5 of water produced from hydrocarbon wells. It is, of course, desirable to be able to achieve this objective and at the same time not materially affect the hydrocarbon recovery rate. ~owever, where the volume of water is very high, e.g., 80 to 99X water, and only l - 20~ oil, even sub-stantial reduction in hydrocarbon production can be tolerated if water lO production can be substantially reduced.
One such method of reducing the flow of water has been described in UOS~ Patent No, 3,762~47$ wherein a first aqueous polymer solution se}ected from the group consisting of polyacrylamide, a partially hydroly~ed polyacrylamide, a polysaccharide, a carboxymethylcellulose, a 15 polyvinyl alcohol, and polystyrene sulfonate, is injected into a gub-terrsneAn for~ation. Thereafter, a complexing ionic solution of multi~alent cstions-and re~arding anions~ and which also comprises alu~inu~ cit~ate, is injected into the subterranean formation. The multivalent cations are ~elected from the group consisting of Fe(II), 20 FetIII~, Al(III), Ti(IV),Zn(II), Sn(IV), CatII), Mg(II), Cr(III), and the retarding a~ions are selected from the group consisting of acetate, nitrilot~iacetate~ tartrate, citrate, phosphate. Brine is then injected followed by a second slug of an aqueous polymer solution which can be the ~ame or different from the first aqueous polymer solution. In any event, 25 the complexing ionic solution of multivalent cations and retarding anions is capable of gelling both the first and second aqueo~a polymer solution.
Water produced from a wellbore can come from ~he infiltration of naturally occuring subterranean water as described above, or the water can come from injected water put into the formation in those hydrocarbon 30 recovery processes which utili~e waterflooding. U S. Patent No.
4~098,337 discloses a method for forming a hydroxymethylated poly~cryla-mide gel, in situ~ to reduce the permeability of a thusly treated zone where the waterflood method of oil recovery i8 employed. In this case the gel was formed in ~itu by the injection of an aqueous polyacrylamide 35 solution snd an aqueous formaldehyde solut;on.
In waterflood operations it can be desirable to treat the water injector wells with a polymer gel forming solution to control and/or redirect the waeer flow profile. Such treatment can prevent channeling of water at the injector w~ll and/or con~rol or redirect the water flow 4~ through regions of varying permeability.
i24S388 Although polyacrylamide-based gels can be effective in retarding water production or flow in some subterranean formations, polyacrylamide-based gels will not he stable or effective in all formations. In general, polyacrylamide-based gels will work 5 satisfactorily in formations ~aving a temperature below about 65C.
Above about 65C, polyacrylamide-based gels become very sensitive to hardness of the brines, especially ~here hardness i9 above about 1000 ppm. ~he hardness of the water becomes a more detrimental factor the higher the temperature, thus for very hot regions even low hardness 10 levels can render many gels ineffective. Formations which have a higher temperature, hardness, or total dissolved solids content above the afore-mentioned ranges usually are not capable of being successfully treated with polyacrylamide-based polymers to retard the flow o water~
In-many hydrocarbon producing well3 temperatures of 80C or higher 15 are ofte~ encountered. Formation wsters frequently have hardnesses which e~ceed ~Q~O ppm. It is therefore desirable to develop a gel which can be ~ed to retard or block the flow of water in subterranean formations hav;ng a temperature of 65C or higher, and a water hardne3s of lOOO ppm or higher.
In other flooding operations, rather than water, other fluids can be used. S~me fluids which are used are carbon dioxide and stesm. Becaus2 of the high temper-a~ure required in steam flooding or other steam stimu-latio~ methods, many of the gels used for blocking water are not suitable or satisfactory for blocking steam. Qther steam treating metkods such as 25 "Push and Pull" operations, sometimes referred to as "cyclic steam injection" or "Huff and Puff" operations, where a production well i5 ~teamed for several days and then produced for a month or 80 re3ult in steam channels being formed which if not blocked will result in an inefficient steaming operation due to 1098 of steam into channels which 30 drain into nonproductive parts of the reservoir. Again because many of the existing gels degrade rapidly at steam temperatures, polymers such as - polyacryla~ides are generally not satisfactory. Other fluids auch ascarbon dioxide can also be used in push and pull operation3.
Flooding operations using csrbon dioxide snd other gase3 a~ the drive 35 fluid frequently experience a 1085 of drive fluid ~o nonproductive parts of the re~ervoir because of greater ability of ~ases to dissipate into such channel as opposed to liquids~ Lo3s of drive ga8e3 in flooding operations and steam in stimulation methods i~ more difficult to prevent because the flow chsnnel3 respon~ible for such losses can be very small 4 in diameter or width thereby ~aking it very difficult to fill ~uch ~LZ453~3~
channels with a blocking agent. Some viscous plugging substances, even though they may have the desired stability at higher temperatures, are not able to penetrate and effectively fill narrow channels, particularly as such channels become more distant from the wellbore.
Thus there is a need for plugging fluids which can be formulated to penetrate deeply into the formation. The use of this invention addresses this problem and provides polyvinyl alcohol based-polyvinyl aldehyde gels which can be tailor made to the particular problem at hand and which can overcome many of the shortcomings of prior art plugging agents and 10 gels.
Polyvinyl alcohol gels have been used to protect well casings from corrosion. U.S. Pate~t No. 2,832,414 discloses such a method wherein an aqueous solution of a ~ater soluble polyvinyl alcohol which is capable of $orming a gel if maintained in a quiescent state, i8 pumped into the 15 annular space bet~e~n the casing and the wall o~ the bore hole~ After allo~ing the poly~e~ to remain quiescent over a period of time a gel is forme~ The thusly formed gel prevents the intrusion of formation water into the annular ~pace thereby reducing corrosion o the metal ca~ing.
Apparently, no crosslinking agene is employed and for t~ae reason i5 not 20 believed that this particular gel would be useful for plugging channels or fractures on a permanent bases. Furthermore, in Patent No. 2,832,414 the gel is used to fill a relatively large but stagnant cavity compared to the volume of a typical channel in a subterranean formation associated with hydrocarbon produc~ion from a wellbore.
Studies of the macro~copic changes in polyvinyl acetate ge's ~hat -occur upon removal from swelling equilibrium with isopropyl alcohol were reported in the Journal of Colloid and Interface Science~ Vol. 90~ No. 1, No~ember 1982, pages 34 to 43. These studies were conducted using films of gels having various degrees of crosslinking and polymer concentration~
30 The polyvinyl acetate gels were formed from precursor polyvinyl alcohol gels that were csosslinked ~ith glutaric dialdeh~de which were then converted to acetate gels by polymer homologous acetylation.
U. S. Patent No. 3,265,657 discloses a process for prepsring an aqueous polyvinyl alcohol composition, which remains fluid for at least a 35 few seconds after preparation and spontsneou~ly gels thereafter. ~he gel is formed by contacting a gelable fluid aqueous polyvinyl alcohol solution with a hexavalent chromium compound and a reductive agent to convert Cr (VI) to Cr SIII). The composition~ are used to produce foam~
~uitable as insulating, acoustical, and packaging materials. The gels are 40 crosslinked with chromium, not an aldehyd2.
~ OS. Patent No. 3~658,745 discloses a hydrogel which i9 capable of significant expansion upon cooling in water and reversible shrinking upon heating which comprises a crosslinked acetalated hydrogel formed by reacting ~ polyvinyl alcohol previou~ly dissolved in water and a 5 monaldehyde and a dialdehyde. The hydrogels are alleged to have ~ufficient crosslinking to prevent imbibition of macrom~lecular materials ~uch as proteins but not the imbibition of micromolecular materials such ~s low molecular weight water solutes. These hydrogels are alleged to be useful for dialytic purification when pure water i9 added to the macro-10 molecular solution after each cycle. Apparently these particular hydro-geIs are able to absorb and desorb water and microsolutes with alternate cooling and heating cycles. Apparently a major amount of shrinkage of these gels occurs upon slight heating such as from 12 to 37C which indicates that these gels would have little value for blocking water in subterranean ormations, especislly at temperatures of 37C or higher. -Su~marv of the Invention By the term naldehyde" as used herein is meant a monoaldehyde, a tialdehyde, a polyaldehyde, and any of the ormer whether substituted or unsubstituted. Preferably the aldehyde contains two function~l groups 8uch as dialdehyde or a substituted monoaldehyde as used herein i3 meant to i~lude unsat~rated carbon-carbon bond as well as substitution of functional groups. Nonlimiting examples of substituted monoaldehyde are acrolein and acrolein dimethylscetal. Polyaldehydes can be used and may in some cases be more desirable, however, polyaldehydes are no~ as available commercially as dialdehydes and as a consequence use of poIyaldehydes may no~ be practical.
Non-limiting examples of dialdehyde crosslinking agents are glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, adipaldehyde, terephth-aldehyde. Non-limiting examples of dialdehyde deriYatives are glyoxal bisulfite addition compound Na2 HC(OH)S03CH(oH)so3, glyo~al trimeric dihydrate, malonaldehyde bisdimethylacetal,
. .
Technical Field This invention relates to gels, methods of forming gels, and uses for gels. A polyvinyl aleohol based-polyvinyl aldehyde hydrogel, or gel, is provided which is useful for immobilizing large volumes of earth or lO water. The gel ean be used for reducing the permeabi1ity of soils and subterranean formations to the flow of fluids, waters or brines. The ge}s of this invention are particularly valuable in retarding the flow of fluids, waters or brines i~ hydrocarbon production from a wellbore, or fTom solar ponds.
15 Related Applications ~ he subjee~ m~tter of this application is related to thzt of Canadian Patent Application Serial Number 459,031, filed July 17, 1984 for "Gel for Retarding ~Vater Flow".
20 Background of the Invention ~ he recovery of hydrocarbons, both liquid and gaseous, from subterranean zones has frequently resulted in the simultaneous production of large quantities of water or brines. In some cases, even though substantial flows of hydrocarbons have been shown, water production is so 25 great and water disposal costs so high, that hydrocarbor production is not eeonomical. Such water production has in some cases been disposed of iu an abandoned or dry well by separating such water from the hydroearbons and reinjeeting the separated water into such wells. Where a disposàl well is not available nor near the producing well, pipelining 30 the water prod~uet o~er a long distance to a disposal site can become so eostIy that it renders the well noncommercial. Even if a disposal well is elose by, the disposal cost ean still be very expensive. Therefore it is desirable to find a way to reduce or shut off the flow o water while permitting hydroearbon production to continue.
It is well known that the production oE large amounts of water from hydroearbon produeing wells is a major expense item in the overall hydroearbon reeovery cost. It is not uncommon for an oil well to produee an effluent whieh is 60 - 99% by volume water and only l - 40Z by volume oil. In sueh situations, the major part of the pumping energy is 40 expended in lifting water from the well, a eost which the produeer would ` 1 :1 ~,.
lZ~S3~38 like to avoid if possible. The effluent must then be subjected to a costly separation procedure to recovery water-free hydrocarbons. The foul water separated therefrom also presents a troublesome and expensive disposal problem. Consequently, it i5 desirable to decrease the volume 5 of water produced from hydrocarbon wells. It is, of course, desirable to be able to achieve this objective and at the same time not materially affect the hydrocarbon recovery rate. ~owever, where the volume of water is very high, e.g., 80 to 99X water, and only l - 20~ oil, even sub-stantial reduction in hydrocarbon production can be tolerated if water lO production can be substantially reduced.
One such method of reducing the flow of water has been described in UOS~ Patent No, 3,762~47$ wherein a first aqueous polymer solution se}ected from the group consisting of polyacrylamide, a partially hydroly~ed polyacrylamide, a polysaccharide, a carboxymethylcellulose, a 15 polyvinyl alcohol, and polystyrene sulfonate, is injected into a gub-terrsneAn for~ation. Thereafter, a complexing ionic solution of multi~alent cstions-and re~arding anions~ and which also comprises alu~inu~ cit~ate, is injected into the subterranean formation. The multivalent cations are ~elected from the group consisting of Fe(II), 20 FetIII~, Al(III), Ti(IV),Zn(II), Sn(IV), CatII), Mg(II), Cr(III), and the retarding a~ions are selected from the group consisting of acetate, nitrilot~iacetate~ tartrate, citrate, phosphate. Brine is then injected followed by a second slug of an aqueous polymer solution which can be the ~ame or different from the first aqueous polymer solution. In any event, 25 the complexing ionic solution of multivalent cations and retarding anions is capable of gelling both the first and second aqueo~a polymer solution.
Water produced from a wellbore can come from ~he infiltration of naturally occuring subterranean water as described above, or the water can come from injected water put into the formation in those hydrocarbon 30 recovery processes which utili~e waterflooding. U S. Patent No.
4~098,337 discloses a method for forming a hydroxymethylated poly~cryla-mide gel, in situ~ to reduce the permeability of a thusly treated zone where the waterflood method of oil recovery i8 employed. In this case the gel was formed in ~itu by the injection of an aqueous polyacrylamide 35 solution snd an aqueous formaldehyde solut;on.
In waterflood operations it can be desirable to treat the water injector wells with a polymer gel forming solution to control and/or redirect the waeer flow profile. Such treatment can prevent channeling of water at the injector w~ll and/or con~rol or redirect the water flow 4~ through regions of varying permeability.
i24S388 Although polyacrylamide-based gels can be effective in retarding water production or flow in some subterranean formations, polyacrylamide-based gels will not he stable or effective in all formations. In general, polyacrylamide-based gels will work 5 satisfactorily in formations ~aving a temperature below about 65C.
Above about 65C, polyacrylamide-based gels become very sensitive to hardness of the brines, especially ~here hardness i9 above about 1000 ppm. ~he hardness of the water becomes a more detrimental factor the higher the temperature, thus for very hot regions even low hardness 10 levels can render many gels ineffective. Formations which have a higher temperature, hardness, or total dissolved solids content above the afore-mentioned ranges usually are not capable of being successfully treated with polyacrylamide-based polymers to retard the flow o water~
In-many hydrocarbon producing well3 temperatures of 80C or higher 15 are ofte~ encountered. Formation wsters frequently have hardnesses which e~ceed ~Q~O ppm. It is therefore desirable to develop a gel which can be ~ed to retard or block the flow of water in subterranean formations hav;ng a temperature of 65C or higher, and a water hardne3s of lOOO ppm or higher.
In other flooding operations, rather than water, other fluids can be used. S~me fluids which are used are carbon dioxide and stesm. Becaus2 of the high temper-a~ure required in steam flooding or other steam stimu-latio~ methods, many of the gels used for blocking water are not suitable or satisfactory for blocking steam. Qther steam treating metkods such as 25 "Push and Pull" operations, sometimes referred to as "cyclic steam injection" or "Huff and Puff" operations, where a production well i5 ~teamed for several days and then produced for a month or 80 re3ult in steam channels being formed which if not blocked will result in an inefficient steaming operation due to 1098 of steam into channels which 30 drain into nonproductive parts of the reservoir. Again because many of the existing gels degrade rapidly at steam temperatures, polymers such as - polyacryla~ides are generally not satisfactory. Other fluids auch ascarbon dioxide can also be used in push and pull operation3.
Flooding operations using csrbon dioxide snd other gase3 a~ the drive 35 fluid frequently experience a 1085 of drive fluid ~o nonproductive parts of the re~ervoir because of greater ability of ~ases to dissipate into such channel as opposed to liquids~ Lo3s of drive ga8e3 in flooding operations and steam in stimulation methods i~ more difficult to prevent because the flow chsnnel3 respon~ible for such losses can be very small 4 in diameter or width thereby ~aking it very difficult to fill ~uch ~LZ453~3~
channels with a blocking agent. Some viscous plugging substances, even though they may have the desired stability at higher temperatures, are not able to penetrate and effectively fill narrow channels, particularly as such channels become more distant from the wellbore.
Thus there is a need for plugging fluids which can be formulated to penetrate deeply into the formation. The use of this invention addresses this problem and provides polyvinyl alcohol based-polyvinyl aldehyde gels which can be tailor made to the particular problem at hand and which can overcome many of the shortcomings of prior art plugging agents and 10 gels.
Polyvinyl alcohol gels have been used to protect well casings from corrosion. U.S. Pate~t No. 2,832,414 discloses such a method wherein an aqueous solution of a ~ater soluble polyvinyl alcohol which is capable of $orming a gel if maintained in a quiescent state, i8 pumped into the 15 annular space bet~e~n the casing and the wall o~ the bore hole~ After allo~ing the poly~e~ to remain quiescent over a period of time a gel is forme~ The thusly formed gel prevents the intrusion of formation water into the annular ~pace thereby reducing corrosion o the metal ca~ing.
Apparently, no crosslinking agene is employed and for t~ae reason i5 not 20 believed that this particular gel would be useful for plugging channels or fractures on a permanent bases. Furthermore, in Patent No. 2,832,414 the gel is used to fill a relatively large but stagnant cavity compared to the volume of a typical channel in a subterranean formation associated with hydrocarbon produc~ion from a wellbore.
Studies of the macro~copic changes in polyvinyl acetate ge's ~hat -occur upon removal from swelling equilibrium with isopropyl alcohol were reported in the Journal of Colloid and Interface Science~ Vol. 90~ No. 1, No~ember 1982, pages 34 to 43. These studies were conducted using films of gels having various degrees of crosslinking and polymer concentration~
30 The polyvinyl acetate gels were formed from precursor polyvinyl alcohol gels that were csosslinked ~ith glutaric dialdeh~de which were then converted to acetate gels by polymer homologous acetylation.
U. S. Patent No. 3,265,657 discloses a process for prepsring an aqueous polyvinyl alcohol composition, which remains fluid for at least a 35 few seconds after preparation and spontsneou~ly gels thereafter. ~he gel is formed by contacting a gelable fluid aqueous polyvinyl alcohol solution with a hexavalent chromium compound and a reductive agent to convert Cr (VI) to Cr SIII). The composition~ are used to produce foam~
~uitable as insulating, acoustical, and packaging materials. The gels are 40 crosslinked with chromium, not an aldehyd2.
~ OS. Patent No. 3~658,745 discloses a hydrogel which i9 capable of significant expansion upon cooling in water and reversible shrinking upon heating which comprises a crosslinked acetalated hydrogel formed by reacting ~ polyvinyl alcohol previou~ly dissolved in water and a 5 monaldehyde and a dialdehyde. The hydrogels are alleged to have ~ufficient crosslinking to prevent imbibition of macrom~lecular materials ~uch as proteins but not the imbibition of micromolecular materials such ~s low molecular weight water solutes. These hydrogels are alleged to be useful for dialytic purification when pure water i9 added to the macro-10 molecular solution after each cycle. Apparently these particular hydro-geIs are able to absorb and desorb water and microsolutes with alternate cooling and heating cycles. Apparently a major amount of shrinkage of these gels occurs upon slight heating such as from 12 to 37C which indicates that these gels would have little value for blocking water in subterranean ormations, especislly at temperatures of 37C or higher. -Su~marv of the Invention By the term naldehyde" as used herein is meant a monoaldehyde, a tialdehyde, a polyaldehyde, and any of the ormer whether substituted or unsubstituted. Preferably the aldehyde contains two function~l groups 8uch as dialdehyde or a substituted monoaldehyde as used herein i3 meant to i~lude unsat~rated carbon-carbon bond as well as substitution of functional groups. Nonlimiting examples of substituted monoaldehyde are acrolein and acrolein dimethylscetal. Polyaldehydes can be used and may in some cases be more desirable, however, polyaldehydes are no~ as available commercially as dialdehydes and as a consequence use of poIyaldehydes may no~ be practical.
Non-limiting examples of dialdehyde crosslinking agents are glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, adipaldehyde, terephth-aldehyde. Non-limiting examples of dialdehyde deriYatives are glyoxal bisulfite addition compound Na2 HC(OH)S03CH(oH)so3, glyo~al trimeric dihydrate, malonaldehyde bisdimethylacetal,
2,5-dimethoxytetrahydrofuran, 3,4-dihydro-2-methoxy-2H-pyran, and furfural. Acetal~, hemiacetals, cycli~ acetals, bisulfite addition compounds~ ~hiff's bases or other compoundR which generate dialdehydes in water, either alone or in response to an additional agent such as an acid or a condition such as heat are also meant to be included in the term "aldehyde" a~ used and claimed herein.
Non-limiting exPmples of monoaldehyde with a second functional group in addition to the aldehyde group are acrolein and acrolein iZ~53~38 dimethylacetal.
Non limiting examples of polyaldehydes are polyacrolein dimethyl-acetal, addition products of acrolein for example, ethylene glycol plus acrolein9 and glycerol plus acrolein.
8y the term "acidic catalyst" or "crosslinking catalyzing substance"
as used herein is meant a substance which is a proton donor or a substance which in its environment will form or become a proton donor.
All acid6 are operable as an acidic catalyst in the gel systems described herein, for example, Bronsted acids such as mineral and carboxylic acids, 10 or Lewis acids. Non-limiting examples of a Lewis acid are zinc chloride, ferrous chloride, stannous chloride, aluminum chloride, barium fluoride, a~d sulfur trioxide. Some of these chemicalfi hydrolyse in water to produce metal oxides or hydroxides and HCl or HF. The rate of hydrolysis of many Lewis acids ifi dependent on temperature and the other dissolved 15 co~pounds in the solution. The rate of production of the acidic catal~st, HCl, from 30me of the above Lewis acids deter~ine~ the rate of gel foLmation A delayed action catalyst is a substance which is not acidic in and of itself, but which generates an acidic catalyst 810wly on interaction 20 with water at the temperature of interest. For example, the rate of generation of the acid in oil well usage is usually controlled by the reservoir temperature experienced during the in-situ gel formation. In many applications ~he rate of acidic catalyst generatiGn or release can be controlled by the gel-forming fluid formulation to range from a few 25 minutes to a few days or more.
The acid catalyst can be a two component system, for example, a two component delayed action catalyst can comprise a first compone~t which will react with a second component, to form an acidic catalyst. A
non-limiting example of such a two component delayed action catalyst is 30 sodium persulfate and a reducing agent. In such a delayed catalyst system the s`odium persulfate reacts with the reducing agent to produce sulfuric acid. In another two component delayed action catalyst system the reaction product of the two components can react with ~ater to form the acidic catalyst.
The acidic catalyst and/or delayed action catalyst must, of course, have some 601ubility in water. However~ in some oil field usages the partial solubi}ity of the acidic catalyst in the oil product caD be advantageous if treatment is to include subterran2an zones containing both oil and water. The fraction of the acidic catalyst or delayed 40 action catalyst which dissolutes in oil willt of course~ not be available ~2~S3~38 ~ 7 to catalyze the gel formation reaction in such zones of high oil content;
consequently such oil-water 70nes will not be blocked by gel formation to the same extent as those ~ones with little or no oil present.
Non-limiting examples of delayed action catalysts are methyl formate, 5 ethyl formate, methyl acetate, ethyl acetate, glycerol monoacetate or ~cetin and glycerol diacetate or diacetin.
Laboratory tests conducted on core samples have shown that diacetin hydrolysis more 810wly than methyl formate at all temperatures including the higher temperatures. Therefore, where subterranenan formations 10 having higher temperatures are encountered, diactin or acetin because of their slower rate of hydrolysis are used to provide a longer time for cros~linkiog seaceions to occur and hence provide a longer time for the gelling forming fluids to penetrate into the pores of such subterranean zones before gelation occurs. Non-limiting example~ of delayed action 15 catalyst and their acidic catalyst product are:
De1ayed Actio~ Catalyst Acidic Catalyst Product Met~yl formate Formic acid Glyc~rol diac~tate Acetic acid Sodium persulfate Sulfusic ~cid Sodium dodecyl sulfate Sulfuric acid Methyl methane sulfonate Methylsulfonic acid Sodium triiodidelsodium Hydroiodic acid -bisulfate/water Therefore~ delayed action acidic catalysts can be esters which slowly 25 hydrolyze in water~ the rate of hydrolysis being dependent on temperature -and initial pH. Other delayed action catalysts are the analogs of esters and acids such as sulfones, xanthates, xanthic acids, thiocyanates, and the like~ In some of theYe examples, hydrolysis produces an acidic catalys~ which speeds the crosslinking reaction and an alcohol which does 30 not affect ~el formation. An example of a delayed action acidic catalyst is methyl formate which i8 influenced by the environment with respect to the rate of for~ation of acid. For example, the higher the temperature, the faster methyl formate will hydrolyze and generate formic acid.
By the term "Bronsted acid" as used herein is meant a chemical which can act a~ a source of protonY. By the term "Lewis acid" as used herein is meant a chemical that csn accept an electron pair from a base. By the ~erm "delayed action acid" as used herein is meant any acidic catalyst which makes available or generates donor proton over a period of time or after an initial period of time either as a consequence of its character-istic or ~he~characteri~tics of the environment in which it iY used.
. , ~
:ILZ~53~8 By the term "gel'1 as used herein is meant a chemically crosslinkedthree-dimensional elastic network of long-chain molecules with a certain amount of immobilized solvent ~diluent) molecules.
By the term "PVA based substance" or "PVA" (frequently reerred to 5 herein as the "first substance") as used herein is meant long-chain mole-cules selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof.
By the ter~ "PVA-aldehyde gel" as used herein is meant a chemically crosslinked three-dimensional elastic net~ork of longchain molecules 10 selected from the group consistin~ of a polyvinyl alcohol, a polyvinyl alcohol copolymer, and mixtures thereof, crosslinked with an aldehyde, ana containing a certain amount of immobilized and chemically bound water molecules.
B~ tbe term "polyvinyl aldehyde" or "PV aldehyde" as used herein is 15 meant ~ aldehyde produced from a polyvinyl alcohol, a polyvinyl c~po~y~er, a~d ~tures thereof. In some embodiments the PV aldehyde is prod~ced by oxidat~on of the first substance~ that i8 the aame PVA com-positio~ as-the PVA composition from which the PV aldehyde was produced.
In so~e e~bodiments the PV aldehyde also contains some hydroxyl groups `20 which have not~been oxidized to aldo groups.
By the term "PVA-PV sldehyde gel" as used herein i~ meant a chemically crossl-inked three-dimensional elastic network of long-chain molecules selected from the group consisting of a polyvinyl alcohol, a - polyvinyl copolymer, ant mixtures thereof, crosslinked with a polyvinyl aldehyde, and containing a certain amount of unmobili~ed and chemically bound ~ater molecules.
All of the above mentioned acidic cstalysts are effective cross-linking ~atalyzing substances for PVA-aldehyde and PVA-PV aldehyde gel sys tems .
Non-limiting e~amples of polyvinyl alcohol copolymers are polyvinyl alcohol-co-crotonic acid, polyvinyl alcohol-co-acrylic acid, paly~inyl alcohol-co-met~acryIic acid, polyvinyl alcohol-co-vinylpyridine, and polyvinyl alcohol-co-vinylacetate, the latter of which is fre~uently present in small amoull~s in commercial grade polyvinyl alcohols.
There is provided a gel formed by reacting a PVA based subseance, PV
aldehyde, and water in an acidic mixture. In a furthes embodiment of the above gel, the PV aldehyde is produced by the oxidation of a PVA based substance. ln a further embodiment, the PV aldehyde i3 produced by oxitation of the same PYA based substance uaed eo form the gel. In still another embodimene the PV aldehyde is produced by a process comprising ~Z453~3~
g reacting a first substance selected from the group consisting of polyvi~yl alcohols, polyvinyl alcohol copolymers, and mixtures thereof, with hydrogen peroxide in water at an elevated temperature in the presence of a metallic ion catalyst. In a further embodiment the 5 metallic ion catalyst is selected from the group consisting of Cu(II), Cu(III), Fe(II), Fe(III) and mixtures thereof. In yet another embodiment, PV aldehyde is produced by oxidation of a PVA with periodic acid. In still another embodiment the PV aldehyde has, on the average, ` about 5 to about 500 carbon atoms per PV aldehyde molecule. In still 10 another embodiment, the PV aldehyde has at least two aldo groups on the ave~age per molecule of PV aldehyde. In a still further embodiment, the PV a}dehyde has a plurality of hydroxyl groups on the average per molecule of PV aldehyde. In a still further embodiment, the amount of PV
aldehy~e is more than about 0.7% of the stoichiometric amount required to 15 react with all of the crosslinkable sites of the PVA based substance. In yet an~ther embodiment the PV sldehyde provides from about 0.01 to about - 4~ of the ~eight of the gel.
1~ another embodîment, the water of the gel-forming composition provides-at least about 64% of the weight of the gel. In yet another 20 embodiment the PVA ba~ed substance provides from about 0.1 to about 5% of the weight of the gel. In one embodiment the PVA based substance is polyvinyl alcohol~ In another embodiment the PVA based ~ubstance has an averag~ molecular weight of at least 30,000 and preferably at least 100 ,0~0 .
In further embodiments of all of the above-identified gels, the gel is for~ed by reacting the PVA based subseance~ PV aldehyde and wa~er in the presence of an acidic catalyst.
There is also provided a process for retarding the flow of fluids in high permeability channels in a subterranean formation comprising intro-
Non-limiting exPmples of monoaldehyde with a second functional group in addition to the aldehyde group are acrolein and acrolein iZ~53~38 dimethylacetal.
Non limiting examples of polyaldehydes are polyacrolein dimethyl-acetal, addition products of acrolein for example, ethylene glycol plus acrolein9 and glycerol plus acrolein.
8y the term "acidic catalyst" or "crosslinking catalyzing substance"
as used herein is meant a substance which is a proton donor or a substance which in its environment will form or become a proton donor.
All acid6 are operable as an acidic catalyst in the gel systems described herein, for example, Bronsted acids such as mineral and carboxylic acids, 10 or Lewis acids. Non-limiting examples of a Lewis acid are zinc chloride, ferrous chloride, stannous chloride, aluminum chloride, barium fluoride, a~d sulfur trioxide. Some of these chemicalfi hydrolyse in water to produce metal oxides or hydroxides and HCl or HF. The rate of hydrolysis of many Lewis acids ifi dependent on temperature and the other dissolved 15 co~pounds in the solution. The rate of production of the acidic catal~st, HCl, from 30me of the above Lewis acids deter~ine~ the rate of gel foLmation A delayed action catalyst is a substance which is not acidic in and of itself, but which generates an acidic catalyst 810wly on interaction 20 with water at the temperature of interest. For example, the rate of generation of the acid in oil well usage is usually controlled by the reservoir temperature experienced during the in-situ gel formation. In many applications ~he rate of acidic catalyst generatiGn or release can be controlled by the gel-forming fluid formulation to range from a few 25 minutes to a few days or more.
The acid catalyst can be a two component system, for example, a two component delayed action catalyst can comprise a first compone~t which will react with a second component, to form an acidic catalyst. A
non-limiting example of such a two component delayed action catalyst is 30 sodium persulfate and a reducing agent. In such a delayed catalyst system the s`odium persulfate reacts with the reducing agent to produce sulfuric acid. In another two component delayed action catalyst system the reaction product of the two components can react with ~ater to form the acidic catalyst.
The acidic catalyst and/or delayed action catalyst must, of course, have some 601ubility in water. However~ in some oil field usages the partial solubi}ity of the acidic catalyst in the oil product caD be advantageous if treatment is to include subterran2an zones containing both oil and water. The fraction of the acidic catalyst or delayed 40 action catalyst which dissolutes in oil willt of course~ not be available ~2~S3~38 ~ 7 to catalyze the gel formation reaction in such zones of high oil content;
consequently such oil-water 70nes will not be blocked by gel formation to the same extent as those ~ones with little or no oil present.
Non-limiting examples of delayed action catalysts are methyl formate, 5 ethyl formate, methyl acetate, ethyl acetate, glycerol monoacetate or ~cetin and glycerol diacetate or diacetin.
Laboratory tests conducted on core samples have shown that diacetin hydrolysis more 810wly than methyl formate at all temperatures including the higher temperatures. Therefore, where subterranenan formations 10 having higher temperatures are encountered, diactin or acetin because of their slower rate of hydrolysis are used to provide a longer time for cros~linkiog seaceions to occur and hence provide a longer time for the gelling forming fluids to penetrate into the pores of such subterranean zones before gelation occurs. Non-limiting example~ of delayed action 15 catalyst and their acidic catalyst product are:
De1ayed Actio~ Catalyst Acidic Catalyst Product Met~yl formate Formic acid Glyc~rol diac~tate Acetic acid Sodium persulfate Sulfusic ~cid Sodium dodecyl sulfate Sulfuric acid Methyl methane sulfonate Methylsulfonic acid Sodium triiodidelsodium Hydroiodic acid -bisulfate/water Therefore~ delayed action acidic catalysts can be esters which slowly 25 hydrolyze in water~ the rate of hydrolysis being dependent on temperature -and initial pH. Other delayed action catalysts are the analogs of esters and acids such as sulfones, xanthates, xanthic acids, thiocyanates, and the like~ In some of theYe examples, hydrolysis produces an acidic catalys~ which speeds the crosslinking reaction and an alcohol which does 30 not affect ~el formation. An example of a delayed action acidic catalyst is methyl formate which i8 influenced by the environment with respect to the rate of for~ation of acid. For example, the higher the temperature, the faster methyl formate will hydrolyze and generate formic acid.
By the term "Bronsted acid" as used herein is meant a chemical which can act a~ a source of protonY. By the term "Lewis acid" as used herein is meant a chemical that csn accept an electron pair from a base. By the ~erm "delayed action acid" as used herein is meant any acidic catalyst which makes available or generates donor proton over a period of time or after an initial period of time either as a consequence of its character-istic or ~he~characteri~tics of the environment in which it iY used.
. , ~
:ILZ~53~8 By the term "gel'1 as used herein is meant a chemically crosslinkedthree-dimensional elastic network of long-chain molecules with a certain amount of immobilized solvent ~diluent) molecules.
By the term "PVA based substance" or "PVA" (frequently reerred to 5 herein as the "first substance") as used herein is meant long-chain mole-cules selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof.
By the ter~ "PVA-aldehyde gel" as used herein is meant a chemically crosslinked three-dimensional elastic net~ork of longchain molecules 10 selected from the group consistin~ of a polyvinyl alcohol, a polyvinyl alcohol copolymer, and mixtures thereof, crosslinked with an aldehyde, ana containing a certain amount of immobilized and chemically bound water molecules.
B~ tbe term "polyvinyl aldehyde" or "PV aldehyde" as used herein is 15 meant ~ aldehyde produced from a polyvinyl alcohol, a polyvinyl c~po~y~er, a~d ~tures thereof. In some embodiments the PV aldehyde is prod~ced by oxidat~on of the first substance~ that i8 the aame PVA com-positio~ as-the PVA composition from which the PV aldehyde was produced.
In so~e e~bodiments the PV aldehyde also contains some hydroxyl groups `20 which have not~been oxidized to aldo groups.
By the term "PVA-PV sldehyde gel" as used herein i~ meant a chemically crossl-inked three-dimensional elastic network of long-chain molecules selected from the group consisting of a polyvinyl alcohol, a - polyvinyl copolymer, ant mixtures thereof, crosslinked with a polyvinyl aldehyde, and containing a certain amount of unmobili~ed and chemically bound ~ater molecules.
All of the above mentioned acidic cstalysts are effective cross-linking ~atalyzing substances for PVA-aldehyde and PVA-PV aldehyde gel sys tems .
Non-limiting e~amples of polyvinyl alcohol copolymers are polyvinyl alcohol-co-crotonic acid, polyvinyl alcohol-co-acrylic acid, paly~inyl alcohol-co-met~acryIic acid, polyvinyl alcohol-co-vinylpyridine, and polyvinyl alcohol-co-vinylacetate, the latter of which is fre~uently present in small amoull~s in commercial grade polyvinyl alcohols.
There is provided a gel formed by reacting a PVA based subseance, PV
aldehyde, and water in an acidic mixture. In a furthes embodiment of the above gel, the PV aldehyde is produced by the oxidation of a PVA based substance. ln a further embodiment, the PV aldehyde i3 produced by oxitation of the same PYA based substance uaed eo form the gel. In still another embodimene the PV aldehyde is produced by a process comprising ~Z453~3~
g reacting a first substance selected from the group consisting of polyvi~yl alcohols, polyvinyl alcohol copolymers, and mixtures thereof, with hydrogen peroxide in water at an elevated temperature in the presence of a metallic ion catalyst. In a further embodiment the 5 metallic ion catalyst is selected from the group consisting of Cu(II), Cu(III), Fe(II), Fe(III) and mixtures thereof. In yet another embodiment, PV aldehyde is produced by oxidation of a PVA with periodic acid. In still another embodiment the PV aldehyde has, on the average, ` about 5 to about 500 carbon atoms per PV aldehyde molecule. In still 10 another embodiment, the PV aldehyde has at least two aldo groups on the ave~age per molecule of PV aldehyde. In a still further embodiment, the PV a}dehyde has a plurality of hydroxyl groups on the average per molecule of PV aldehyde. In a still further embodiment, the amount of PV
aldehy~e is more than about 0.7% of the stoichiometric amount required to 15 react with all of the crosslinkable sites of the PVA based substance. In yet an~ther embodiment the PV sldehyde provides from about 0.01 to about - 4~ of the ~eight of the gel.
1~ another embodîment, the water of the gel-forming composition provides-at least about 64% of the weight of the gel. In yet another 20 embodiment the PVA ba~ed substance provides from about 0.1 to about 5% of the weight of the gel. In one embodiment the PVA based substance is polyvinyl alcohol~ In another embodiment the PVA based ~ubstance has an averag~ molecular weight of at least 30,000 and preferably at least 100 ,0~0 .
In further embodiments of all of the above-identified gels, the gel is for~ed by reacting the PVA based subseance~ PV aldehyde and wa~er in the presence of an acidic catalyst.
There is also provided a process for retarding the flow of fluids in high permeability channels in a subterranean formation comprising intro-
3~ ducing an effective amount of a gel-forming composition into the sub-terranean formation, and into the high permeability channels, the gel-forming composition being operable when gelled in the high permeability channels for retarding the flow of fluids therein, ~he gel-forming composition comprising a aqueous solution of PVA based substance, and an 35 effectiYe amount of PV altehyde sufficient to form a gel with the aqueous solution; and allowing the gel forming composition to form a gel in the high permeability channels which is effective for retarding the flow of fluids therein. In other embodiments of the above described process, the particular gels which are described above can be u~ed. In one embodiment 40 the gel is formed in the presence of a crosslinking catalyzing substance.
.:
12~531~
-In another embodiment the acidic catalyst is a delayed action acidic catalyst, preferably an ester which hydrolyzes slowly in the formation producing a weak acid.
As discussed above, in one embodiment of the invention, a PVA based substance has been oxidized so that some of diol groups thereof have been converted to aldo groups thereby pro-ducing a PV aldehyde. In this embodiment, the size and reactivity of the PV aldehyde crosslinking agent can be varied to optimize the performance of the gel for the particular reservoir conditions encountered. The PVA based substance used to form the PV aldehyde, does not necessarily have to have the same high molecular weight as the PVA based substance with which it is crosslinked. Accord-ingly, the molecular size and the structure of the diol groups on the PVA based substance which is used to produce the PV aldehyde can be tailored to produce a gel having properties best suited to the particular reservoir conditions of interest. Acetalization reactions between the PVA based substance and PV aldehyde provide the crosslinking required. Gels of varying degrees of stiffness and stickiness can be prepared by changing the ratio of PVA based substance to PV aldehyde.
Methods for the self-crosslinking of prefabricated polyvinyl alcohol structures by preferentially oxidizing 1,2 diol units are described in U.S. Patent Nos. 3,859,269; 4,154,912;
.:
12~531~
-In another embodiment the acidic catalyst is a delayed action acidic catalyst, preferably an ester which hydrolyzes slowly in the formation producing a weak acid.
As discussed above, in one embodiment of the invention, a PVA based substance has been oxidized so that some of diol groups thereof have been converted to aldo groups thereby pro-ducing a PV aldehyde. In this embodiment, the size and reactivity of the PV aldehyde crosslinking agent can be varied to optimize the performance of the gel for the particular reservoir conditions encountered. The PVA based substance used to form the PV aldehyde, does not necessarily have to have the same high molecular weight as the PVA based substance with which it is crosslinked. Accord-ingly, the molecular size and the structure of the diol groups on the PVA based substance which is used to produce the PV aldehyde can be tailored to produce a gel having properties best suited to the particular reservoir conditions of interest. Acetalization reactions between the PVA based substance and PV aldehyde provide the crosslinking required. Gels of varying degrees of stiffness and stickiness can be prepared by changing the ratio of PVA based substance to PV aldehyde.
Methods for the self-crosslinking of prefabricated polyvinyl alcohol structures by preferentially oxidizing 1,2 diol units are described in U.S. Patent Nos. 3,859,269; 4,154,912;
4,262,067; and ~,272,470. These patented processes, while not directed towards the formation of gels, are of interest because they disclose methods generating aldehydic groups on polyvinyl alcohol, and for self-crosslinking a prefabricated polyvinyl alcohol sheet. These patents disclose that 0.5 to 20% of the hydroxyl groups in polyvinyl alcohol can exist as 1,2 diols and the remainder as 1,3 diols.
~r ~2~53~38 - lOa - 71440-7 The formation of 1,2 and 1,3 diols depend on the poly-merization temperature in the polyvinyl acetate step. During oxidation of polyvinyl alcohol, the chain is cleaved at the 1,2 diol sites leaving aldo groups at the end of the chains. The 1,3 diols on one chain can then react the aldo groups on another chain when the pH is below 7 to form the PVA-PV aldehyde-water gel.
In still further embodiments of the above described gels, the water used to form the gel has a hardness of at least about 1000 ppm. In further embodiments the water has a hardness of at least about 3000 ppm, or 6000 ppm, or higher. In other further embodiments of the above described gels, the water used to form the gel has a total dissolved solids content of at least about 30,000 ppm. In a still further embodiment such water has a total dissolved solids content of at least ~2~538~
about 80,000 ppm.
~ n the embodiments of this invention the PV aldehyde crosslinks with the polyvinyl alcohol or polyvinyl alcohol copolymer through formation of acetals. Gels formed in this way are adaptable to the hardness of the water from which they are formed or exposed. These gels are also more stable at high temperatures than polyacrylamide based gels or gels made from biopolymers or polyvinyl alcohols gelled by other crosslinking agents such as borate.
Because of the ~daptability and compatibility of these gels to water hardness or total dissolved solids content, these gel~ can be prepared using formation water, brackish water, sea water or usually any other available source of water conveniently at hand. Because the largest ingredient used to formulate the above described gels is principally water, substantiaL economic advantage is provided by this invention which per~its ge~s to be formèd with the cheapest source of available water.
Ho~e~er, the ad~snta~es of this invention are not limited merely to econ~mic advantages because these gels also provide substantial technical advantages over other gels. For example, in many of their uses these ge}fi are subjected to the infusion o severely contaminated water into the gelling ma~s prior to reaching its gelation point. Where such contaminated water infusion occurs in many other gelling fluids the gelation thereof is destroyed or so severely harmed that such other gels, if in fact they do gel, would be rendered ineffective for their intended use.
~ue to their stability at elevated temperatures, the above described gel~ can also be formed and used in formations having an average in-situ temperature o about 80C or higher, and in some embodiments where the a~erage in-situ temperature is 125C or higher.
The above described methods of forming a gel in situ in subterranean 30 formations can be practiced using all of the gels provided by this invention.
The principles of this invention can be used where the subterranean water-conveying zone is under ~he subterranean hydrocarbon-producing zone; or where the subterranean water-conveying ~one surrounds the 35 subterranean hydrocarbon-producing zone; or where at least part of the subterranean water-conveying zone coincides with at least part of the ~ubterranean hydrocarbon-protucing zone.
In one embodiment of this invention directed to a water flood operations, it frequently is desirable to treat the water injector wells 40 with a polymer gel-forming solution to control the water flow profile.
53~38 In this embodiment such tr~atment prevents channeling of water at the injector ~ell and/or controls and/or redirects water flow through regions of varying permeability. Since in this embodiment the polymer is injected as a relatively low viscosity aqueous phase it penetrates
~r ~2~53~38 - lOa - 71440-7 The formation of 1,2 and 1,3 diols depend on the poly-merization temperature in the polyvinyl acetate step. During oxidation of polyvinyl alcohol, the chain is cleaved at the 1,2 diol sites leaving aldo groups at the end of the chains. The 1,3 diols on one chain can then react the aldo groups on another chain when the pH is below 7 to form the PVA-PV aldehyde-water gel.
In still further embodiments of the above described gels, the water used to form the gel has a hardness of at least about 1000 ppm. In further embodiments the water has a hardness of at least about 3000 ppm, or 6000 ppm, or higher. In other further embodiments of the above described gels, the water used to form the gel has a total dissolved solids content of at least about 30,000 ppm. In a still further embodiment such water has a total dissolved solids content of at least ~2~538~
about 80,000 ppm.
~ n the embodiments of this invention the PV aldehyde crosslinks with the polyvinyl alcohol or polyvinyl alcohol copolymer through formation of acetals. Gels formed in this way are adaptable to the hardness of the water from which they are formed or exposed. These gels are also more stable at high temperatures than polyacrylamide based gels or gels made from biopolymers or polyvinyl alcohols gelled by other crosslinking agents such as borate.
Because of the ~daptability and compatibility of these gels to water hardness or total dissolved solids content, these gel~ can be prepared using formation water, brackish water, sea water or usually any other available source of water conveniently at hand. Because the largest ingredient used to formulate the above described gels is principally water, substantiaL economic advantage is provided by this invention which per~its ge~s to be formèd with the cheapest source of available water.
Ho~e~er, the ad~snta~es of this invention are not limited merely to econ~mic advantages because these gels also provide substantial technical advantages over other gels. For example, in many of their uses these ge}fi are subjected to the infusion o severely contaminated water into the gelling ma~s prior to reaching its gelation point. Where such contaminated water infusion occurs in many other gelling fluids the gelation thereof is destroyed or so severely harmed that such other gels, if in fact they do gel, would be rendered ineffective for their intended use.
~ue to their stability at elevated temperatures, the above described gel~ can also be formed and used in formations having an average in-situ temperature o about 80C or higher, and in some embodiments where the a~erage in-situ temperature is 125C or higher.
The above described methods of forming a gel in situ in subterranean 30 formations can be practiced using all of the gels provided by this invention.
The principles of this invention can be used where the subterranean water-conveying zone is under ~he subterranean hydrocarbon-producing zone; or where the subterranean water-conveying ~one surrounds the 35 subterranean hydrocarbon-producing zone; or where at least part of the subterranean water-conveying zone coincides with at least part of the ~ubterranean hydrocarbon-protucing zone.
In one embodiment of this invention directed to a water flood operations, it frequently is desirable to treat the water injector wells 40 with a polymer gel-forming solution to control the water flow profile.
53~38 In this embodiment such tr~atment prevents channeling of water at the injector ~ell and/or controls and/or redirects water flow through regions of varying permeability. Since in this embodiment the polymer is injected as a relatively low viscosity aqueous phase it penetrates
5 preferentially the region of highe~t permeability to water. Accordingly, after formation of the gel in high permeability regions, such regions are converted to low permeability to further retard water flow thereby causing, upon further water injection, a water sweep of previously in-accessible areas in the formation which usually have relatively low 10 permeability. ~y extending the water flow to such previously inaccess-ible regions, more hydrocarbons can be recovered than would be recovered in ~he absence of such polymer treatment.
The gels of this invention have improved resistance to heat and are stable in hard water. These characteristics make these gels particularly 15 useful or many oil field applications such as water ~obility control.
These ~els ca~ be a~vantageou~ly u~ed in other har~h environments such as ~olar pond construc~ion where they can be used to consolidate loose soil and ~o-~etard ~r stop the leakage of brine through the pond floor, or to prevent convective flow o hot water in lower intervals into upper 20 intervals contai~ing cooler water. For oil field application~ the stability and durability of the PVA-PV aldehyde gels of this invention make them particularly useful in reservoirs having an average in ~itu temperature greater than 65C.
Accordingly, one objective of this invention is to provide a means of 25 controlling water movement, and other fluids mobility, in oil wells and nubterranean formation~ especially in formations having temperatures 80~C
or higher~ or where the waters involved are saline or hard.
Another object of this invention i8 to provide a means to thic~en a gel water with an inexpensive polymer for other oil field developmental 30 u~es su~h as frac~ure fluids and fluids for secondary and tertiary oil recovery. It i8 another object of thia invention to provide a gel which can be formulated using hard water and water containing a high level of dissol~ed solids such as ~ea water and formation water encountered in deep of-shore hydrocarbon fields.
Another object of this invention is to psovide a gel ~hich i~ stable at high temperatures and in par~icular more stable than other gels at 3uch high temperatures.
Descrip_i ~
An oil well having an average in-situ temperature of 80C or higher, 40 and also having an undesirable amount of water production, i~ treated by ~Z~53~3~
-injecting a polyvinyl alcohol-polyvinyl aldehyde-waeer mixture into the wellbore and from the wellbore into the reservoir. The mixture contains aboue 2.5% polyvinyl alcohol ha~ing an average molecular weight of 125,000 or higher, from abo~t 0.2 to about 0.5% PV aldehyde, preferably 5 about 0.3% PV aldehyde, and the remainder of a brine having a total dissolved solids content of about 50,000 and a hardness of about 5,000 ppm. The pH of the gel-forming composition is then adjusted to about 5.5 by adding 12% HCl solution~ The polymer will then undergo crosslinking and gel in situ in a period of time ranging between several hours to 10 several days depending upon, in part, the average in situ temperature and amount of acid catalyst. The following examples demo~strate how the gels of this inventio~ can be tested and used for reducing the permeability of reservoirs to the flow of brines.
Example No. 1 The exa~ple shows how to determine the proper gel-fonming composition for a reservoir experiencing inefficient water usage in a water flood -operaion~ Preferably a reservoir brine is used to prepare the gel-formrng compoaition, however, if desired a synthetic brine which smulates the reservoir brine can be used. A useful formulation for a 2b simulated brine is 2.7% NaCl~ 0.1% CaC12 and 0.2% MgC12. The gel-for~ing composition is prepared by adding about 2.5% of polyvinyl alcohol having an avera~e molecular weight of about 125,000 and containing about 1.7X of its diol groups as 1,2 diols, to the brine, and heating the mixture for 45 ~inutes at 95C to completely dissolve the polymer in the brine.
A 10% PV aldehyde solution is then prepared by adding a low molecular weight polyvinyl alcohol having an a~erage molecular weight of about 30~000 and containing about lOZ of its diol groups as 1,2 diols to another quantity of brine and heating the mixture at 95C for 45 minutes to completely dissolve the polymer in the brine. To the mixture is then 30 added 1% hydrogen peroxide solution containing 0.1% CuS04 5H20, as a catalyst, at a S0:50 ratio with the 10% polyvinyl alcohol solution. The thusly formed ~ixture is then heated for 45 minutes at 95C. The hydrogen peroxide reacts with the low molecular weight polyvinyl alcohol to produce a 5Z PV aldehyde solution. Just before its use, the 5Z PV
35 aldehyde ~olution is mixed at a concentration of 0.5X in the 2.5% poly-~inyl alcohol-brine mixture to produce the gel forming mixture.
A 60 centimeters (60 cm) long, 5 cm diameter high pressure core holder is packed with cru~hed reservoir rock to form a packed test core sample which is then ~aturated with brine and heated to 80C. Brine i~
40 then pumped through the core sample at ~ rate of about 30 cm per day or ~Z~53~8 one foot per day (1 FPD) and the pressure drop across ehe core sample determined. Mineral oil having a viscosity of 10 centipoise (10 cp) at 25C i~ then pumped through the core sample at 30 cm per day until no more brine i8 displaced therefrom. Additional brine is then pumped 5 through the core sample at 30 cm per day until no more mineral oil is displaced therefrom and the pressure drop measured. Thereafter, the freshly mixed gel-forming composition is pumped into the core sample at 30 cm per day until the gel point i3 reached which is indicated by a rapid increase in pressure. A gel time of about 30 hours is desired.
10 Example No- 2 A producing well, hsving an average formation temperature about 93C i~ prepared or treatment by running tubing dowm the wellbore to the for~ation depth. About 16~ cubic meters of a gel-~orming composition containing 2.5~ polyvinyl alcohol and 0.5% PV aldehyde, having on the 15 average about 40 ca~bon atoms per PV aldehyde molecule~ is injected thr~g~ the tubing ~neo th~ formation. The well is then 6hut-in for about 48 houri a~d thereafter production is resumed. After about one month a reduction in water pressure of about 60% and an increase in oil production of about 20g is to be expected.
~ nles~ other~ise specified herein, all percents are weight percents.
- The PVA-PV aldehyde gels~ the methods of forming the gels, and the proces~es for retarding the flow of fluids have some degree of flexi-bili~y. For example, if the environment in which the gels are to be used 25 hs~ ~ ~elatively high temperature, gel time can be slowed by using a smaller amount of acidic catalyst and/or PV aldehyde. Similarly, if the environmental temperature is relatively low, gelation can be speeded by the use of larger amounts of acidic catalyst andlor PV aldehyde~ It is permissible to use the formation brine of the ~ubterranean ~one as the 30 ~ater part of the gel-forming composition since the~e geLs will form even with hard water. Other variations of formulations, methods and processe~
will be apparent from ~his invention to tho~e 6killed in the art.
The foregoing disclosure and description of the present invention is illustrative and explanatory thereof and various chan~es in gel formation procedures and gel composition as well as the uses and applicstions of cuch gels to ~orm them in situ in subterranean fo~mations and to retard or block fluids in subterranean formation6~ may be made within the scope nf the appending claims without departing from the spirit of the invent-ion. For example, many gel formulations can be produced and many methods 40 of forming such gels in 8itU in subterranean formation~ will be ~pparent iZ453B8 to one skilled in the art from this invention. For example~ any number of sequential injection steps of the gel-forming compositions can be made. Furthermore, the necessary concentrations, amountq and sequence of ;njection of the gel-forming compositions can be tailored to suit the particular well or subterranean formation being treated.
.
The gels of this invention have improved resistance to heat and are stable in hard water. These characteristics make these gels particularly 15 useful or many oil field applications such as water ~obility control.
These ~els ca~ be a~vantageou~ly u~ed in other har~h environments such as ~olar pond construc~ion where they can be used to consolidate loose soil and ~o-~etard ~r stop the leakage of brine through the pond floor, or to prevent convective flow o hot water in lower intervals into upper 20 intervals contai~ing cooler water. For oil field application~ the stability and durability of the PVA-PV aldehyde gels of this invention make them particularly useful in reservoirs having an average in ~itu temperature greater than 65C.
Accordingly, one objective of this invention is to provide a means of 25 controlling water movement, and other fluids mobility, in oil wells and nubterranean formation~ especially in formations having temperatures 80~C
or higher~ or where the waters involved are saline or hard.
Another object of this invention i8 to provide a means to thic~en a gel water with an inexpensive polymer for other oil field developmental 30 u~es su~h as frac~ure fluids and fluids for secondary and tertiary oil recovery. It i8 another object of thia invention to provide a gel which can be formulated using hard water and water containing a high level of dissol~ed solids such as ~ea water and formation water encountered in deep of-shore hydrocarbon fields.
Another object of this invention is to psovide a gel ~hich i~ stable at high temperatures and in par~icular more stable than other gels at 3uch high temperatures.
Descrip_i ~
An oil well having an average in-situ temperature of 80C or higher, 40 and also having an undesirable amount of water production, i~ treated by ~Z~53~3~
-injecting a polyvinyl alcohol-polyvinyl aldehyde-waeer mixture into the wellbore and from the wellbore into the reservoir. The mixture contains aboue 2.5% polyvinyl alcohol ha~ing an average molecular weight of 125,000 or higher, from abo~t 0.2 to about 0.5% PV aldehyde, preferably 5 about 0.3% PV aldehyde, and the remainder of a brine having a total dissolved solids content of about 50,000 and a hardness of about 5,000 ppm. The pH of the gel-forming composition is then adjusted to about 5.5 by adding 12% HCl solution~ The polymer will then undergo crosslinking and gel in situ in a period of time ranging between several hours to 10 several days depending upon, in part, the average in situ temperature and amount of acid catalyst. The following examples demo~strate how the gels of this inventio~ can be tested and used for reducing the permeability of reservoirs to the flow of brines.
Example No. 1 The exa~ple shows how to determine the proper gel-fonming composition for a reservoir experiencing inefficient water usage in a water flood -operaion~ Preferably a reservoir brine is used to prepare the gel-formrng compoaition, however, if desired a synthetic brine which smulates the reservoir brine can be used. A useful formulation for a 2b simulated brine is 2.7% NaCl~ 0.1% CaC12 and 0.2% MgC12. The gel-for~ing composition is prepared by adding about 2.5% of polyvinyl alcohol having an avera~e molecular weight of about 125,000 and containing about 1.7X of its diol groups as 1,2 diols, to the brine, and heating the mixture for 45 ~inutes at 95C to completely dissolve the polymer in the brine.
A 10% PV aldehyde solution is then prepared by adding a low molecular weight polyvinyl alcohol having an a~erage molecular weight of about 30~000 and containing about lOZ of its diol groups as 1,2 diols to another quantity of brine and heating the mixture at 95C for 45 minutes to completely dissolve the polymer in the brine. To the mixture is then 30 added 1% hydrogen peroxide solution containing 0.1% CuS04 5H20, as a catalyst, at a S0:50 ratio with the 10% polyvinyl alcohol solution. The thusly formed ~ixture is then heated for 45 minutes at 95C. The hydrogen peroxide reacts with the low molecular weight polyvinyl alcohol to produce a 5Z PV aldehyde solution. Just before its use, the 5Z PV
35 aldehyde ~olution is mixed at a concentration of 0.5X in the 2.5% poly-~inyl alcohol-brine mixture to produce the gel forming mixture.
A 60 centimeters (60 cm) long, 5 cm diameter high pressure core holder is packed with cru~hed reservoir rock to form a packed test core sample which is then ~aturated with brine and heated to 80C. Brine i~
40 then pumped through the core sample at ~ rate of about 30 cm per day or ~Z~53~8 one foot per day (1 FPD) and the pressure drop across ehe core sample determined. Mineral oil having a viscosity of 10 centipoise (10 cp) at 25C i~ then pumped through the core sample at 30 cm per day until no more brine i8 displaced therefrom. Additional brine is then pumped 5 through the core sample at 30 cm per day until no more mineral oil is displaced therefrom and the pressure drop measured. Thereafter, the freshly mixed gel-forming composition is pumped into the core sample at 30 cm per day until the gel point i3 reached which is indicated by a rapid increase in pressure. A gel time of about 30 hours is desired.
10 Example No- 2 A producing well, hsving an average formation temperature about 93C i~ prepared or treatment by running tubing dowm the wellbore to the for~ation depth. About 16~ cubic meters of a gel-~orming composition containing 2.5~ polyvinyl alcohol and 0.5% PV aldehyde, having on the 15 average about 40 ca~bon atoms per PV aldehyde molecule~ is injected thr~g~ the tubing ~neo th~ formation. The well is then 6hut-in for about 48 houri a~d thereafter production is resumed. After about one month a reduction in water pressure of about 60% and an increase in oil production of about 20g is to be expected.
~ nles~ other~ise specified herein, all percents are weight percents.
- The PVA-PV aldehyde gels~ the methods of forming the gels, and the proces~es for retarding the flow of fluids have some degree of flexi-bili~y. For example, if the environment in which the gels are to be used 25 hs~ ~ ~elatively high temperature, gel time can be slowed by using a smaller amount of acidic catalyst and/or PV aldehyde. Similarly, if the environmental temperature is relatively low, gelation can be speeded by the use of larger amounts of acidic catalyst andlor PV aldehyde~ It is permissible to use the formation brine of the ~ubterranean ~one as the 30 ~ater part of the gel-forming composition since the~e geLs will form even with hard water. Other variations of formulations, methods and processe~
will be apparent from ~his invention to tho~e 6killed in the art.
The foregoing disclosure and description of the present invention is illustrative and explanatory thereof and various chan~es in gel formation procedures and gel composition as well as the uses and applicstions of cuch gels to ~orm them in situ in subterranean fo~mations and to retard or block fluids in subterranean formation6~ may be made within the scope nf the appending claims without departing from the spirit of the invent-ion. For example, many gel formulations can be produced and many methods 40 of forming such gels in 8itU in subterranean formation~ will be ~pparent iZ453B8 to one skilled in the art from this invention. For example~ any number of sequential injection steps of the gel-forming compositions can be made. Furthermore, the necessary concentrations, amountq and sequence of ;njection of the gel-forming compositions can be tailored to suit the particular well or subterranean formation being treated.
.
Claims (61)
1. A gel formed by reacting i. a first substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof, ii. polyvinyl aldehyde, and iii. water.
2. The gel of claim 1, wherein said first substance is polyvinyl alcohol.
3. The gel of claim 1, wherein said gel is formed in the presence of an acidic catalyst.
4. The gel of claim 1, wherein said first substance provides from about 0-1 to about 5% of the weight of said gel.
5. The gel of claim 1, wherein said polyvinyl aldehyde provides from about 0.01 to about 4% of the weight of said gel.
6. The gel of claim 1, wherein said water provides at least about 64% of the weight of said gel.
7. The gel of claim 1, wherein said water is part of a brine, and wherein said brine provides at least about 91% of the weight of said gel.
8. The gel of claim 1, wherein said first substance has an average molecular weight of at least about 30,000.
9. The gel of claim 1, wherein said first substance has an average molecular weight of at least about 100,000.
10. The gel of claim 1, wherein said amount of said polyvinyl aldehyde is at least about 0.7% of the stoichiometric amount required to react with all of the crosslinkable sites of said first substance.
11. The gel of claim 1, wherein said polyvinyl aldehyde is produced by oxidation of a PVA based substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof.
12. The gel of claim 1, wherein said polyvinyl aldehyde is produced by oxidation of a part of said first substance.
13. The gel of claim 1, wherein said polyvinyl aldehyde is produced by a process comprising reacting a PVA based substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers and mixtures thereof with hydrogen peroxide in water at an elevated temperature in the presence of a metallic ion catalyst.
14. The gel of claim 13, wherein said metallic ion catalyst is selected from the group consisting of Cu(II), Cu(III), Fe(II), Fe(III) and mixtures thereof.
15. The gel of claim 1, wherein said polyvinyl aldehyde is produced by oxidation of a PVA based substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof with periodic acid.
16. The gel of claim 1, wherein said polyvinyl aldehyde has, on the average, from about five to about 500 carbon atoms per polyvinyl aldehyde molecule.
17. The gel of claim 1, wherein said polyvinyl aldehyde has at least two aldo groups on the average per molecule of polyvinyl aldehyde.
18. The gel of claim 1, wherein said polyvinyl aldehyde has a plurality of hydroxyl groups on the average per molecule of polyvinyl aldehyde.
19. A process for retarding the flow of fluids in high permeability channels in a subterranean formation comprising:
(a) introducing an effective amount of a gel-forming composition into said subterranean formation, and into said high permeability channels, said gel-forming composition being operable when gelled in said high permeability channels for retarding the flow of fluids therein, said gel-forming composition comprising i. an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof ii. an effective amount of a polyvinyl aldehyde sufficient to form a gel with said aqueous solution; and (b) allowing said gel forming composition to form a gel in said high permeability channels which is effective for retarding the flow of fluids therein.
(a) introducing an effective amount of a gel-forming composition into said subterranean formation, and into said high permeability channels, said gel-forming composition being operable when gelled in said high permeability channels for retarding the flow of fluids therein, said gel-forming composition comprising i. an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof ii. an effective amount of a polyvinyl aldehyde sufficient to form a gel with said aqueous solution; and (b) allowing said gel forming composition to form a gel in said high permeability channels which is effective for retarding the flow of fluids therein.
20. The process of claim 19, wherein said first substance is polyvinyl alcohol.
21. The process of claim 19, wherein said gel is formed in the presence of an acidic catalyst.
22. The process of claim 19, wherein said gel-forming composition is from about 0.01 to about 4% by weight polyvinyl aldehyde.
23. The process of claim 19, wherein said gel-forming composition is from about 1.5 to about 5% by weight said first substance.
24. The process of claim 19, wherein said gel-forming composition is at least about 64% by weight water.
25. The process of claim 19, wherein said gel-forming composition is at least about 91% by weight brine.
26. The process of claim 19, wherein said first substance has an average molecular weight of at least about 30,000.
27. The process of claim 19, wherein said first substance has an average molecular weight of at least about 100,000.
28. The process of claim 19, wherein said amount of polyvinyl aldehyde is at least about 0.7% of the stoichiometric amount required to react with all of the crosslinkable sites of said first substance.
29. The process of claim 19, wherein said polyvinyl aldehyde is produced by oxidation of a PVA based substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof.
30. The process of claim 19, wherein said polyvinyl aldehyde is produced by oxidation of a part of said first substance.
31. The process of claim 19, wherein said polyvinyl aldehyde is produced by a process comprising reacting a PVA based substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof with hydrogen peroxide in water at an elevated temperature in the presence of a metallic ion catalyst.
32. The process of claim 31, wherein said metallic ion catalyst is selected from the group consisting of Cu(II), Cu(III), Fe(II), Fe(III) and mixtures thereof.
33. The process of claim 19, wherein said polyvinyl aldehyde is produced by oxidation of a PVA based substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof with periodic acid.
34. The process of claim 19, wherein said polyvinyl aldehyde has, on the average, from about 5 to about 500 carbon atoms per polyvinyl aldehyde molecule.
35. The process of claim 19, wherein said polyvinyl aldehyde has at least two aldo groups on the average per molecule of polyvinyl aldehyde.
36. The process of claim 19, wherein said polyvinyl aldehyde has a plurality of hydroxyl groups on the average per molecule of polyvinyl aldehyde.
37. The process of claim 19, wherein said first substance is polyvinyl alcohol having an average molecular weight of at least about 30,000;
wherein said polyvinyl aldehyde has at least two aldo groups on the average per molecule of polyvinyl aldehyde; and wherein said gel-forming composition is at least about 64% by weight water.
wherein said polyvinyl aldehyde has at least two aldo groups on the average per molecule of polyvinyl aldehyde; and wherein said gel-forming composition is at least about 64% by weight water.
38. The process of claim 37, wherein said polyvinyl aldehyde is from about 0.2 to about 0.5% by weight of said gel-forming composition.
39. The process of claim 38, wherein said polyvinyl alcohol is about 2.5%
of the weight of said gel-forming composition.
of the weight of said gel-forming composition.
40. The process of claim 39, wherein said subterranean formation has an average formation temperature of at least about 80°C.
41. The process of claim 19, wherein said polyvinyl aldehyde is produced by oxidation of a part of said first substance.
42 . A process for retarding the flow of fluids in high permeability channels in a subterranean formation comprising:
(a) introducing an effective amount of a gel-forming composition into said subterranean formation, and into said high permeability channels, said gel-forming composition being operable when gelled in said high permeability channels for retarding the flow of fluids therein, said gel-forming composition comprising i. an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof, wherein said first substance is from about 0.1 to about 5% by weight of said gel-forming composition, and 11. an amount of polyvinyl aldehyde from about 0.1 to about 4 by weight of said gel-forming composition; and (b) allowing said gel-forming composition to form a gel in said high permeability channels which is effective for retarding the flow of fluids therein.
(a) introducing an effective amount of a gel-forming composition into said subterranean formation, and into said high permeability channels, said gel-forming composition being operable when gelled in said high permeability channels for retarding the flow of fluids therein, said gel-forming composition comprising i. an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof, wherein said first substance is from about 0.1 to about 5% by weight of said gel-forming composition, and 11. an amount of polyvinyl aldehyde from about 0.1 to about 4 by weight of said gel-forming composition; and (b) allowing said gel-forming composition to form a gel in said high permeability channels which is effective for retarding the flow of fluids therein.
43. The process of claim 42 wherein said first substance is polyvinyl alcohol.
44. The process of claim 42 wherein said gel is formed in the presence of an acidic catalyst.
45. The process of claim 42 wherein said gel-forming composition is from about 1.5 to about 5% by weight said first substance.
46. The process of claim 42 wherein said gel-forming composition is at least about 91% by weight brine.
47. The process of claim 42 wherein said first substance has an average molecular weight of at least about 100,000.
48. The process of claim 42 wherein said amount of polyvinyl aldehyde is at least about 0.7% of the stoichlometric amount required to react with all of the crosslinkable sites of said first substance.
49. The process of claim 42 wherein said polyvinyl aldehyde is produced by oxidation of a PVA based substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof.
50. The process of claim 42 wherein said polyvinyl aldehyde is produced by oxidation of a part of said first substance.
51. The process of claim 42 wherein said polyvinyl aldehyde is produced by a process comprising reacting a PVA based substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof with hydrogen peroxide in water at an elevated temperature in the presence of a metallic ion catalyst selected from the group consisting of Cu(II), Cu(III), Fe(II), Fe(III) and mixtures thereof.
52. The process of claim 42 wherein said polyvinyl aldehyde is produced by oxidation of a PVA based substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof with periodic acid.
53. The process of claim 42 wherein said polyvinyl aldehyde has at least two aldo groups on the average per molecule of polyvinyl aldehyde.
54. The process of claim 42 wherein said polyvinyl aldehyde has a plurality of hydroxyl groups on the average per molecule of polyvinyl aldehyde.
55. The process of claim 42 wherein said polyvinyl aldehyde is from about 0.2 to about 0.5% by weight of said gel-forming composition.
56. The process of claim 42 wherein said polyvinyl alcohol is about 2.5%
of the weight of said gel-forming composition.
of the weight of said gel-forming composition.
57. A process for retarding the flow of fluids in high permeability channels in a subterranean formation comprising:
(a) introducing an effective amount of a gel-forming composition into said subterranean formation, and into said high permeability channels, said gel-forming composition being operable when gelled in said high permeability channels for retarding the flow of fluids therein, said gel-forming composition comprising i. an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof, wherein said first substance is from about 0.1 to about 5% by weight of said gel-forming composition and has an average molecular weight of at least about 30,000, ii. an amount of polyvinyl aldehyde from about 0,1 to about 4%
by weight of said gel-forming composition, wherein said polyvinyl aldehyde has, on an average, from about 5 to about 500 carbon atoms per polyvinyl aldehyde molecule, and has at least two aldo groups on the average per molecule of polyvinyl aldehyde, and wherein H20 provides at least about 64% of the weight of said gel-forming composition; and (b) allowing said gel-forming composition to form a gel in said high permeability channels which is effective for retarding the flow of fluids therein.
(a) introducing an effective amount of a gel-forming composition into said subterranean formation, and into said high permeability channels, said gel-forming composition being operable when gelled in said high permeability channels for retarding the flow of fluids therein, said gel-forming composition comprising i. an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof, wherein said first substance is from about 0.1 to about 5% by weight of said gel-forming composition and has an average molecular weight of at least about 30,000, ii. an amount of polyvinyl aldehyde from about 0,1 to about 4%
by weight of said gel-forming composition, wherein said polyvinyl aldehyde has, on an average, from about 5 to about 500 carbon atoms per polyvinyl aldehyde molecule, and has at least two aldo groups on the average per molecule of polyvinyl aldehyde, and wherein H20 provides at least about 64% of the weight of said gel-forming composition; and (b) allowing said gel-forming composition to form a gel in said high permeability channels which is effective for retarding the flow of fluids therein.
58. The process of claim 57, wherein said gel is formed in the presence of, an acidic catalyst, wherein said first substance is polyvinyl alcohol, wherein said polyvinyl alcohol is from about 1.5 to about 5%
by weight of said gel-forming composition, and wherein said polyvinyl aldehyde is from about 0.2 to about 0.5% by weight of said gel-forming composition.
by weight of said gel-forming composition, and wherein said polyvinyl aldehyde is from about 0.2 to about 0.5% by weight of said gel-forming composition.
59. The process of claim 58, wherein said first substance has an average molecular weight of from about 100,000 to about 1,000,000, and where-in said gel-forming composition is at least about 91% by weight brine.
60. The process of claim 57, wherein said polyvinyl aldehyde is produced by oxidation of a part of said first substance.
61. A gel formed by reacting components of a gel-forming composition comprising i. water, ii. a first substance dissolved in said water and selected from the group consisting of polyvinyl alcohols, polyvinyl alcohol copolymers, and mixtures thereof, wherein said first substance is from about 0.1 to about 5% by weight of said gel-forming composition and has an average molecular weight of at least about 30,000, iii. an amount of polyvinyl aldehyde from about 0.1 to about 4%
by weight of said gel-forming composition, wherein said polyvinyl aldehyde has, on an average, from about 5 to about 500 carbon atoms per polyvinyl aldehyde molecule, and wherein H2O provides at least about 64% of the weight of said gel-forming composition.
by weight of said gel-forming composition, wherein said polyvinyl aldehyde has, on an average, from about 5 to about 500 carbon atoms per polyvinyl aldehyde molecule, and wherein H2O provides at least about 64% of the weight of said gel-forming composition.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US62391684A | 1984-06-25 | 1984-06-25 | |
| US623,916 | 1984-06-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1245388A true CA1245388A (en) | 1988-11-22 |
Family
ID=24499891
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000459116A Expired CA1245388A (en) | 1984-06-25 | 1984-07-18 | Polyvinyl alcohol based-polyvinyl aldehyde gels for retarding fluid flow |
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| Country | Link |
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| CA (1) | CA1245388A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10214683B2 (en) | 2015-01-13 | 2019-02-26 | Bp Corporation North America Inc | Systems and methods for producing hydrocarbons from hydrocarbon bearing rock via combined treatment of the rock and subsequent waterflooding |
| CN112456853A (en) * | 2020-12-16 | 2021-03-09 | 湖南加美乐素新材料股份有限公司 | High-strength alkali-free liquid accelerator and preparation method thereof |
-
1984
- 1984-07-18 CA CA000459116A patent/CA1245388A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10214683B2 (en) | 2015-01-13 | 2019-02-26 | Bp Corporation North America Inc | Systems and methods for producing hydrocarbons from hydrocarbon bearing rock via combined treatment of the rock and subsequent waterflooding |
| CN112456853A (en) * | 2020-12-16 | 2021-03-09 | 湖南加美乐素新材料股份有限公司 | High-strength alkali-free liquid accelerator and preparation method thereof |
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