US20160289548A1 - Well Treatment Methods and Fluids - Google Patents
Well Treatment Methods and Fluids Download PDFInfo
- Publication number
- US20160289548A1 US20160289548A1 US15/178,140 US201615178140A US2016289548A1 US 20160289548 A1 US20160289548 A1 US 20160289548A1 US 201615178140 A US201615178140 A US 201615178140A US 2016289548 A1 US2016289548 A1 US 2016289548A1
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- US
- United States
- Prior art keywords
- well treatment
- viscosity
- fluid
- treatment fluid
- zirconium
- 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.)
- Abandoned
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- 239000012530 fluid Substances 0.000 title claims abstract description 114
- 238000000034 method Methods 0.000 title claims abstract description 58
- 238000011282 treatment Methods 0.000 title claims description 17
- 239000003180 well treatment fluid Substances 0.000 claims abstract description 87
- LEQAOMBKQFMDFZ-UHFFFAOYSA-N glyoxal Chemical compound O=CC=O LEQAOMBKQFMDFZ-UHFFFAOYSA-N 0.000 claims abstract description 70
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims abstract description 63
- 238000004132 cross linking Methods 0.000 claims abstract description 52
- 239000004971 Cross linker Substances 0.000 claims abstract description 50
- 150000001299 aldehydes Chemical class 0.000 claims abstract description 37
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 37
- 239000002253 acid Substances 0.000 claims abstract description 35
- 229940015043 glyoxal Drugs 0.000 claims abstract description 35
- 239000006254 rheological additive Substances 0.000 claims abstract description 29
- 230000003247 decreasing effect Effects 0.000 claims abstract description 24
- 235000006408 oxalic acid Nutrition 0.000 claims abstract description 21
- 239000004615 ingredient Substances 0.000 claims abstract description 19
- 230000001747 exhibiting effect Effects 0.000 claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 64
- 150000003754 zirconium Chemical class 0.000 claims description 27
- 230000007423 decrease Effects 0.000 claims description 25
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 20
- 229910052726 zirconium Inorganic materials 0.000 claims description 20
- 229910052751 metal Inorganic materials 0.000 claims description 19
- 239000002184 metal Substances 0.000 claims description 19
- 150000001768 cations Chemical class 0.000 claims description 17
- 229920000642 polymer Polymers 0.000 claims description 13
- IVORCBKUUYGUOL-UHFFFAOYSA-N 1-ethynyl-2,4-dimethoxybenzene Chemical compound COC1=CC=C(C#C)C(OC)=C1 IVORCBKUUYGUOL-UHFFFAOYSA-N 0.000 claims description 12
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 12
- ZNZYKNKBJPZETN-WELNAUFTSA-N Dialdehyde 11678 Chemical compound N1C2=CC=CC=C2C2=C1[C@H](C[C@H](/C(=C/O)C(=O)OC)[C@@H](C=C)C=O)NCC2 ZNZYKNKBJPZETN-WELNAUFTSA-N 0.000 claims description 8
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 8
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims description 8
- 230000000694 effects Effects 0.000 claims description 7
- 238000005903 acid hydrolysis reaction Methods 0.000 claims description 4
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- 230000000087 stabilizing effect Effects 0.000 claims description 2
- 239000000654 additive Substances 0.000 abstract description 14
- 230000000996 additive effect Effects 0.000 abstract description 9
- 239000000499 gel Substances 0.000 description 69
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 23
- 229920000663 Hydroxyethyl cellulose Polymers 0.000 description 20
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- XJUNLJFOHNHSAR-UHFFFAOYSA-J zirconium(4+);dicarbonate Chemical compound [Zr+4].[O-]C([O-])=O.[O-]C([O-])=O XJUNLJFOHNHSAR-UHFFFAOYSA-J 0.000 description 6
- 244000303965 Cyamopsis psoralioides Species 0.000 description 5
- -1 carboxymethyl hydroxypropyl Chemical group 0.000 description 5
- 230000001590 oxidative effect Effects 0.000 description 5
- 239000003349 gelling agent Substances 0.000 description 4
- 229920002401 polyacrylamide Polymers 0.000 description 4
- 238000004064 recycling Methods 0.000 description 4
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- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000008186 active pharmaceutical agent Substances 0.000 description 3
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- 239000008399 tap water Substances 0.000 description 3
- 235000020679 tap water Nutrition 0.000 description 3
- 229910021512 zirconium (IV) hydroxide Inorganic materials 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- FBPFZTCFMRRESA-FSIIMWSLSA-N D-Glucitol Natural products OC[C@H](O)[C@H](O)[C@@H](O)[C@H](O)CO FBPFZTCFMRRESA-FSIIMWSLSA-N 0.000 description 2
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-M Formate Chemical compound [O-]C=O BDAGIHXWWSANSR-UHFFFAOYSA-M 0.000 description 2
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- 230000009471 action Effects 0.000 description 2
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- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 description 2
- 235000019345 sodium thiosulphate Nutrition 0.000 description 2
- 239000000600 sorbitol Substances 0.000 description 2
- 238000004457 water analysis Methods 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 208000010392 Bone Fractures Diseases 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- SPAGIJMPHSUYSE-UHFFFAOYSA-N Magnesium peroxide Chemical compound [Mg+2].[O-][O-] SPAGIJMPHSUYSE-UHFFFAOYSA-N 0.000 description 1
- 208000002565 Open Fractures Diseases 0.000 description 1
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 description 1
- LCKIEQZJEYYRIY-UHFFFAOYSA-N Titanium ion Chemical compound [Ti+4] LCKIEQZJEYYRIY-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000000844 anti-bacterial effect Effects 0.000 description 1
- 230000008953 bacterial degradation Effects 0.000 description 1
- 239000003899 bactericide agent Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 125000002057 carboxymethyl group Chemical group [H]OC(=O)C([H])([H])[*] 0.000 description 1
- 239000013522 chelant Substances 0.000 description 1
- 230000009920 chelation Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 239000003398 denaturant Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 150000002009 diols Chemical class 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000007515 enzymatic degradation Effects 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
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- 238000004519 manufacturing process Methods 0.000 description 1
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- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 229920000747 poly(lactic acid) Polymers 0.000 description 1
- 239000004626 polylactic acid Substances 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- DHCDFWKWKRSZHF-UHFFFAOYSA-N sulfurothioic S-acid Chemical compound OS(O)(=O)=S DHCDFWKWKRSZHF-UHFFFAOYSA-N 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- HAIMOVORXAUUQK-UHFFFAOYSA-J zirconium(iv) hydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[Zr+4] HAIMOVORXAUUQK-UHFFFAOYSA-J 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/66—Compositions based on water or polar solvents
- C09K8/68—Compositions based on water or polar solvents containing organic compounds
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/66—Compositions based on water or polar solvents
- C09K8/68—Compositions based on water or polar solvents containing organic compounds
- C09K8/685—Compositions based on water or polar solvents containing organic compounds containing cross-linking agents
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/70—Compositions for forming crevices or fractures characterised by their form or by the form of their components, e.g. foams
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/84—Compositions based on water or polar solvents
- C09K8/86—Compositions based on water or polar solvents containing organic compounds
- C09K8/88—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
- C09K8/887—Compositions based on water or polar solvents containing organic compounds macromolecular compounds containing cross-linking agents
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
- C09K2208/26—Gel breakers other than bacteria or enzymes
Definitions
- controllable-release rheology modifier for example, a controllable-release breaker, including a slow-release breaker.
- High viscosity fluids may be employed to carry proppant down-hole to prop open fractures in the formation.
- Known linear gels water containing a gelling agent only
- crosslinkers may be used to increase fluid viscosity, providing adequate transport of larger proppant sizes or larger proppant quantity.
- Higher viscosity fluids also create wider fractures within the formation.
- Guar and guar derivatives are among the most often used viscosifying agents, such as polymers, in hydraulic fracturing treatment. Guar derivatives, such as carboxymethyl guar (CMG) and carboxymethyl hydroxypropyl guar (CMHPG), are predominantly used in wells with a high bottom-hole temperature (BHT). Interest in cellulose derivatives, such as hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), and carboxymethyl hydroxyethyl cellulose (CMHEC), has increased for fracturing treatment due to the natural abundance of cellulose.
- CMG carboxymethyl guar
- CMHPG carboxymethyl hydroxypropyl guar
- BHT bottom-hole temperature
- hydraulic fracturing gels include cross-linking delay additives, gel breakers, and fluid loss control additives among many other possible additives to adapt hydraulic fracturing gel to the circumstances of hydraulic fracturing.
- a variety of gelling agents and cross-linkers are known for use in hydraulic fracturing gel.
- cross-linking reactions are so designed that viscosity development begins after placement of hydraulic fracturing gel deep within a well.
- rheology modifiers such as gel breakers
- the gel breaker may be configured for delayed action to maintain desirable properties of the cross-linked gel while fracturing. Even so, additional delay chemistries are desired to adapt rheology modifiers to an increased variety of viscosifying agents and related components.
- Produced water refers to water generated from hydrocarbon wells. Generally the term is used in the oil industry to describe water that is produced along with oil and/or gas. “Flowback water” is a subcategory of produced water referring to fracturing fluid that flows back through the well, which may account for some fraction of the original fracture fluid volume.
- TDS total dissolved solids
- a well treatment method includes forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker, and a rheology modifier containing an aldehyde.
- the viscosifying agent is crosslinked in the aqueous fluid using the crosslinker, the crosslinking increasing viscosity of the well treatment fluid.
- the method includes treating a well with the well treatment fluid exhibiting the increased viscosity, chemically changing the aldehyde after the crosslinking and thereby forming an acid, and decreasing viscosity of the crosslinked well treatment fluid as a result of forming the acid.
- Another well treatment method includes forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker containing zirconium, and a rheology modifier containing glyoxal.
- the viscosifying agent is crosslinked in the aqueous fluid using the crosslinker, the crosslinking increasing viscosity of the well treatment fluid.
- the method includes treating a well with the well treatment fluid exhibiting the increased viscosity, chemically changing the glyoxal after the crosslinking and thereby forming oxalic acid, the oxalic acid breaking a crosslink formed by the zirconium, and decreasing viscosity of the crosslinked well treatment fluid using the oxalic acid.
- a well treatment fluid is formulated with ingredients including an aqueous fluid and a viscosifying agent and a crosslinker configured to crosslink the viscosifying agent in the aqueous fluid and thereby to increase viscosity of the well treatment fluid.
- the fluid includes a rheology modifier containing an aldehyde.
- the well treatment fluid is configured to chemically change the aldehyde after the crosslinking and thereby to form an acid configured to decrease viscosity of the crosslinked well treatment fluid.
- the well treatment fluid lacks an aldehyde crosslinking delay additive.
- FIGS. 1-5 are charts of viscosity over time for crosslinked fluids prepared with rheology modifiers respective to Examples 1-5.
- FIGS. 6-10 are charts of viscosity over time for crosslinked fluids prepared with produced water respective to Examples 6-10.
- a rheology modifier such as a crosslinked gel breaker, may be based on an aldehyde, including a dialdehyde, for example glyoxal.
- the aldehyde may release an acid slowly and controllably into a well treatment fluid, such as a crosslinked gel, and decrease viscosity of the gel over a sufficient time to complete use of the well treatment fluid before substantial viscosity loss.
- the dialdehyde might provide the benefit over monoaldehyde of forming a di-acid, such as oxalic acid, capable of chelating crosslinkers to break crosslinks.
- the rheology modifier may be an aqueous solution of the aldehyde.
- a well treatment method includes forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker, and a rheology modifier containing an aldehyde.
- the viscosifying agent in the aqueous fluid is crosslinked using the crosslinker, the crosslinking increasing viscosity of the well treatment fluid.
- the method includes treating a well with the well treatment fluid exhibiting the increased viscosity and chemically changing the aldehyde after the crosslinking, thereby forming an acid. Viscosity of the crosslinked well treatment fluid is decreased using the acid.
- the well treatment fluid may lack an aldehyde crosslinking delay additive. That is, glyoxal is known for use in gels as a crosslinking delay additive (see, U.S. Pat. No. 5,160,643 issued to Dawson). Nevertheless, the well treatment fluids herein may lack a crosslinking delay additive or the well treatment fluid may include a crosslinking delay additive different from the aldehyde functioning herein as a viscosity breaker. In other words, the aldehyde rheology modifier herein need not delay the crosslinking.
- the aldehyde might not substantially chemically change before the crosslinking. Even so, some insubstantial or de minimis chemical change to the aldehyde may occur before the crosslinking.
- formulation of the well treatment fluid, or both lack of a pH decrease or lack of a viscosity decrease before the crosslinking could be evidence of no or only insubstantial chemical change to the aldehyde.
- Chemically changing the aldehyde to an acid may involve one or more reaction mechanisms not completely defined in the literature. Even so, one or more chemical reactions are believed to occur in the change, one of which may be oxidation of the aldehyde or of an intermediate component to form acid. Chemically changing the glyoxal may instead or additionally yield other acid(s) and/or other chemical(s) involved in decreasing viscosity of the crosslinked well treatment fluid.
- decreasing viscosity of the crosslinked well treatment fluid as a result of forming the acid may involve one or more incompletely defined effects.
- One possible effect includes damage to the viscosifying agent, such as polymer, due a pH decrease upon generation of the acid.
- Another possible effect includes the acid directly interacting with and breaking the crosslinks. The two described effects and other viscosity decreases as a result of forming the acid may function in combination.
- the viscosifying agent may contain a polymer and the crosslinker may contain a metal cation or borate.
- the method may further include breaking a crosslink formed by the metal cation or borate to effect the viscosity decrease. Breaking the crosslink may include chelating the metal cation with the acid.
- the metal cation may be a zirconium or titanium ion. It follows that decreasing viscosity may occur by a stepwise process, namely, chemically changing the aldehyde, forming the acid, and the acid breaking the crosslink formed by the metal cation or borate. The stepwise process may also include the acid competing for chelation of the metal cation to break the crosslink. It is conceivable that decreasing viscosity may occur by a different process that does not break the crosslink.
- viscosity may decrease at a faster rate.
- the numerical value for the decrease in viscosity and the time over which it occurs varies depending on the application. Consequently, the rate of decrease also varies.
- the fluid viscosity can be very high (as in gel plugs), just several hundred centiPoise (as in frac fluids), or just a few centiPoise (as in slickwater). It will be appreciated that the larger viscosity decreases may occur in the higher viscosity fluids.
- fluids may be formulated to break in 2 days, or to break in 2 hours. Even so, for the methods and compositions herein, the viscosity may decrease at a faster rate compared to known fluids and compared to the well treatment fluid herein without the rheology modifier.
- the aldehyde selected may be glyoxal and the acid may be oxalic acid.
- the intermediate products in the chemical change of glyoxal to oxalic acid, may be present, but likely not participating appreciably in breaking metal cation crosslinking.
- the well treatment fluid ingredients may contain up to 10 weight % (wt %) rheology modifier, such as up to 5 wt %, including up to 1 wt %, for example, from about 0.01 wt % to about 0.5 wt %.
- the rheology modifier may be an aqueous solution of the aldehyde, such as a 40 wt % solution.
- the well treatment fluid may contain additional components known for suitability in a selected fluid application, such as hydraulic fracturing.
- additional components known for suitability in a selected fluid application, such as hydraulic fracturing.
- examples include gel stabilizer, buffer, etc.
- the gel stabilizer may include sodium thiosulfate, thiosulfate, alkoxylated sorbitol, sorbitol, methanol, formate, and combinations thereof.
- the buffer may include sodium bicarbonate, bicarbonate, carbonate, hydroxide, acetate, formate, zirconium hydroxide, zirconium carbonate, and combinations thereof.
- the well treatment fluid may also contain diol, such as ethylene glycol.
- Treating the well with the well treatment fluid may include hydraulic fracturing, gravel packing, sand control, or other known applications for crosslinked well treatment fluid.
- the aqueous fluid may beneficially include produced water, allowing recycling of produced water from a well treatment method, as described in the Background section above.
- the ingredients may further include a zirconium salt, described further below, which may increase viscosity of the fluid prior to breaking, even being useful to such effect when the aqueous fluid is produced water.
- the zirconium salt may be selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium dioxide, and combinations thereof.
- the well treatment fluid ingredients may contain up to 20 wt % zirconium salt, such as up to 5 wt %, for example, from about 0.01 wt % to about 2 wt %.
- Latent acids such as esters and polylactic acid
- Glyoxal chemically changes to oxalic acid at increasing rates for increased temperature and increased pH. Accordingly, release rate may be controlled in the environment of a well treatment fluid, such as a hydraulic fracturing gel.
- Other dialdehydes may exhibit similar properties.
- Another well treatment method includes forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker containing zirconium, and a rheology modifier containing glyoxal.
- the viscosifying agent is crosslinked in the aqueous fluid using the crosslinker, the crosslinking increasing viscosity of the well treatment fluid.
- the method includes treating a well with the well treatment fluid exhibiting the increased viscosity, chemically changing the glyoxal after the crosslinking, thereby forming oxalic acid, and the oxalic acid breaking a crosslink formed by the zirconium. Viscosity of the crosslinked well treatment fluid is decreased using the oxalic acid.
- the well treatment fluid may lack a glyoxal crosslinking delay additive. Breaking the crosslink may include chelating the zirconium with the oxalic acid. Breaking the crosslink may instead or additionally include the oxalic acid decreasing pH.
- the viscosity may decrease at a faster rate compared to the well treatment fluid without the rheology modifier.
- the aqueous fluid may be produced water and the ingredients may further include a zirconium salt selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium dioxide, and combinations thereof.
- a well treatment fluid may be described as formulated with ingredients including an aqueous fluid, a viscosifying agent, a crosslinker, and a rheology modifier containing an aldehyde.
- the viscosifying agent and crosslinker are configured to crosslink the viscosifying agent in the aqueous fluid and thereby to increase viscosity of the well treatment fluid.
- the well treatment fluid is configured to chemically change the aldehyde after the crosslinking and thereby to form an acid configured to decrease viscosity of the crosslinked well treatment fluid.
- the well treatment fluid lacks an aldehyde crosslinking delay additive.
- the crosslinker may contain a metal cation or borate, the acid being configured to break a crosslink formed by the metal cation or borate.
- the acid may further be configured to chelate the metal cation to break the crosslink.
- the acid may instead or additionally be configured to decrease pH to break the crosslink.
- the aldehyde may be glyoxal and the acid may be oxalic acid.
- the aqueous fluid may be produced water and the ingredients may further comprise a zirconium salt.
- the zirconium salt may be selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium dioxide, and combinations thereof.
- Zr salt may be beneficially used in a well treatment fluid.
- Zr salt exhibits known properties as a metal denaturant and/or bactericide in well treatment fluids susceptible to enzymatic or bacterial degradation of gelling agents, such as polymers (see, U.S. Pat. Pub. No. 2008/0287323 by Li et al.).
- Gelling agents such as polymers
- the Zr salt additionally increases viscosity stability since the Zr(IV) ions may also contribute to crosslinking of the viscosifying agent. In a system susceptible to Zr crosslinking, Zr salt may thus serve a dual function.
- Incorporating a buffer to clamp the pH at about 5.0 to 6.0 in a well treatment fluid containing Zr salt may provide a system compatible with otherwise unsuitable levels of TDS and hardness from produced water.
- the pH may control hardness
- the Zr salt may control pH
- the Zr salt may also maintain crosslinking.
- a further well treatment method includes forming a well treatment fluid by combining ingredients including produced water, a viscosifying agent, a crosslinker containing a metal cation, a rheology modifier containing an aldehyde, and a zirconium salt.
- the produced water contains more than 1,000 ppm total dissolved solids.
- the method includes dissolving at least a portion of the zirconium salt in the well treatment fluid and stabilizing pH of the well treatment fluid with the zirconium salt.
- the viscosifying agent is crosslinked in the aqueous fluid using the crosslinker and the dissolved zirconium from the zirconium salt, the crosslinking increasing viscosity of the well treatment fluid compared to the well treatment fluid without the zirconium salt.
- a well is treated with the well treatment fluid exhibiting the increased viscosity.
- the aldehyde is chemically changed after the crosslinking, thereby forming an acid.
- the method includes decreasing pH and chelating the metal cation and the dissolved zirconium with the acid, thus breaking the crosslinked well treatment fluid.
- viscosity of the crosslinked well treatment fluid is decreased compared to the crosslinked well treatment fluid without the rheology modifier.
- TDS may be more than 10,000 ppm, such as more than 100,000 ppm, including more than 300,000 ppm.
- Hardness measured as CaCO 3 equivalent may be more than 20,000 ppm, such as more than 40,000 ppm, including more than 60,000 ppm.
- the aldehyde may be glyoxal and the acid may be oxalic acid.
- the zirconium salt may be selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium dioxide, and combinations thereof.
- pH may be controlled to facilitate different portions of the method.
- pH may be maintained below about 7 during crosslinking and use of the crosslinked well treatment fluid.
- the gel contained spheres of crosslinked polyacrylamide. Near neutral pH, the polyacrylamide chains anchored on these spheres are believed to stretch and touch each other, giving viscosity to the gel through physical entanglement. At lowered pH, the polyacrylamide chains are believed to shrink back to the spheres, reducing the contact with each other and decreasing the gel viscosity.
- the rheology modifier herein as slow release breaker may be used to control the fluid pH which, in turn, controls the fluid viscosity.
- Zr-crosslinked HEC fluid prepared with slow-release breaker and oxidative breaker. See FIG. 5 .
- the slow release breaker used included glyoxal (40 weight % glyoxal solution in water) buffered with pH buffer B to a pH of about 7.1-7.2. When 0.52 mL pH buffer B was added to 60 mL glyoxal solution, the resulting pH at room temperature (RT) was about 7.14-7.16.
- a borate-crosslinked guar baseline fluid (no breaker or 0 gpt breaker used) was prepared with tap water, 30 ppt (pounds per thousand gallons) guar, 1 gpt (gallon per thousand gallons) clay control agent, and 2 gpt borate crosslinker A. The viscosity at 200° F. was tested with a Chandler 5550 viscometer, following the API RP 39 schedule (American Petroleum Institute Recommended Procedure). The viscosity is shown in FIG. 1 . The baseline viscosity stayed at about 600 cPs.
- Another borate crosslinked guar baseline fluid (no breaker or 0 gpt breaker used) was prepared with tap water, 25 ppt guar, 1 gpt clay control agent, 1.5 gpt pH buffer E, and 0.75 gpt borate crosslinker B.
- the viscosity at 200° F. was tested with a Chandler 5550 viscometer, following the API RP 39 schedule. The viscosity is shown in FIG. 3 .
- the baseline viscosity stayed at about 400 cPs.
- 0.8 gpt breaker was added to the center of the baseline gel in the viscometer, and the viscosity at 200° F. was similarly measured and is shown in FIG. 3 .
- the viscosity dropped gradually and in a controllable way.
- HEC solution was crosslinked with zirconium crosslinkers to form a gel at pH above about 9-10.
- the crosslinking was gradually reversed, causing the gel viscosity to drop gradually.
- the metal-crosslinked HEC fluid without the glyoxal solution was prepared first as the baseline gel.
- 500 ml of tap water with 2% potassium chloride (KCl) was added to a 1-liter Waring blender. While blending, 80 ppt (could be more based on the operational needs) of HEC powder was added to the blender, and hydrated for about 20 minutes. After the hydration, appropriate amounts of additives including the crosslinking delay agent, gel stabilizer such as sodium thiosulfate, and buffer such as sodium hydroxide, etc., could be added into the fluid and allowed to be evenly mixed and dispersed.
- the metal crosslinker such as the zirconate crosslinker was then added.
- the gel thus prepared had a pH of about 12 to 13 at room temperature. The vortex did not appear to close at room temperature even after 10 minutes.
- the crosslinking delay in the HEC fluid was temperature delay-based. The crosslink in the HEC fluid was activated by heating the fluid above a certain temperature. This intentional crosslinking delay decreases friction pressure and thus the pumping power to deliver the HEC fluid downhole.
- the viscosity of the baseline HEC gel at 200° F. was measured with the Fann50-type viscometer. The viscosity curve is recorded in FIG. 4 . The viscosity of the baseline gel at 200° F. slowly decreased from about 550 cPs in the beginning to about 350 cPs at 350 minutes.
- the breaking tests were carried out at 200° F. to assess the breaking performance of the glyoxal solution (the breaker) in the metal-crosslinked HEC fluids.
- the crosslinked HEC fluid with the glyoxal solution was similarly prepared.
- the glyoxal solution was added immediately before the crosslinker.
- 2 gpt of the glyoxal solution was used.
- the viscosity of the resulting gel at 200° F. was similarly measured with the viscometer. As shown in FIG. 4 , at 200° F. the viscosity of the gel with 2 gpt of the glyoxal solution gradually decreased to about 250 cPs after 350 minutes.
- the glyoxal solution (the breaker) performance was also assessed in conjunction with regular oxidative breakers.
- the baseline HEC gel in FIG. 5 was the same as that in FIG. 4 .
- the viscosity of the baseline gel at 200° F. slowly decreased from about 550 cPs in the beginning to about 350 cPs at 350 minutes.
- 2 gpt of the glyoxal solution and 5 ppt of an oxidative breaker (magnesium peroxide) were added together to the similar HEC gel before adding the crosslinker.
- the viscosity of the resulting gel at 200° F. was similarly measured with the viscometer, as shown in FIG. 5 .
- the viscosity at 200° F. of the HEC gel with both the oxidative breaker and the glyoxal solution gradually decreased from about 550 cPs in the beginning to about 140 cPs after 350 minutes.
- Produced water #1 was used in this example.
- Produced water #1 was offered by an oilfield operator from the field.
- the water had a pH of about 5.6 at RT.
- the water analysis of produced water #1 is listed in Table 2.
- the water had a TDS of over 280,000 mg/L, and hardness of over 46,000 mg/L.
- Another fluid was similarly prepared and tested.
- 50 ppt HPG powder was added to produced water #1 in the blender while blending.
- 2 ppt buffer D, 6 gpt gel stabilizer A, and 2 gpt gel stabilizer B were added while blending.
- 2 gpt zirconium crosslinker was then added as the crosslinker.
- the gel thus formed had a pH of about 5.7 at RT.
- the viscosity at 240° F. was similarly tested and shown in FIG. 6 .
- the fluid showed a decent viscosity, over 500 cPs right before the second ramp peak.
- Two Zr-crosslinked HPG fluids were prepared with produced water #1. The influence of the gel pH was observed.
- To prepare the first fluid about 250 mL of produced water #1 was placed in the Waring blender. 50 ppt HPG powder was added to the blender while blending. Some pH buffer C was applied during the hydration. After the hydration of the HPG polymer, 6 gpt gel stabilizer A and 2 gpt gel stabilizer B were added while blending. 2 gpt zirconium crosslinker was then added as the crosslinker.
- the gel thus formed had a pH of about 5.2 at RT.
- the viscosity at 240° F. was tested with the Chandler 5550 viscometer and is shown in FIG. 7 .
- the fluid with the slightly higher pH at 5.7 showed a more stable viscosity profile at 240° F., for example, beyond about 25 minutes, as shown in FIG. 7 .
- the fluid with the lower pH at 5.2 had a larger starting viscosity, which may or may not be desirable in operations, but its viscosity dropped more quickly over time (lower pH might have caused more damage to the fluid at high temperature) than the fluid with the pH at 5.7.
- the example shows that, by selecting appropriate fluid pH, the fluid could have increased long-term stability.
- zirconium (IV) hydroxide fine powder was evenly mixed into the above base gel, and the viscosity at 240° F. was similarly tested and shown in FIG. 8 .
- the fluid with 1% zirconium hydroxide showed significantly enhanced viscosity. For example, at 60 minutes, the viscosity of the fluid with 1% zirconium hydroxide was about 2.7 times that of the base fluid.
- zirconium salts may also be used, such as zirconium carbonate or zirconium dioxide.
- Produced water #2 was used in this example.
- Produced water #2 was offered by another oilfield operator from the field.
- the water had a pH of about 5.6 at RT.
- the water analysis of produced water #2 is listed in Table 3.
- the water had a TDS of over 210,000 mg/L, and hardness of over 43,000 mg/L.
- B 1.6 gpt 2 gpt 2 gpt 2 gpt 2 gpt 1 gpt Zr x-linker 1.6 gpt 2 gpt 2 gpt 2 gpt 2 gpt 2 gpt 2 gpt 1.4 gpt Zr(OH) 4 — — — — 1 wt % — — methanol — — — — — 0-7.5 vol % —
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Abstract
A method includes forming a well treatment fluid by combining an aqueous fluid, a viscosifying agent, a crosslinker, and a rheology modifier containing an aldehyde. The viscosifying agent is crosslinked, increasing viscosity of the fluid. The method includes treating a well with the fluid exhibiting the increased viscosity, chemically changing the aldehyde after the crosslinking and thereby forming an acid, and decreasing viscosity of the crosslinked fluid as a result of forming the acid. The aldehyde may be glyoxal which forms oxalic acid, breaking a crosslink. A well treatment fluid is formulated with ingredients including an aqueous fluid and a viscosifying agent and a crosslinker configured to crosslink the viscosifying agent. The fluid includes a rheology modifier containing an aldehyde. The fluid may lack an aldehyde crosslinking delay additive.
Description
- The present application is a continuation under 35 U.S.C. §120 of U.S. patent application Ser. No. 14/187,544, filed Feb. 24, 2014, entitled “Well Treatment Methods and Fluids,” the entire contents of which are incorporated herein by reference.
- The methods and compositions herein pertain to well treatment methods and fluids, such as those with a controllable-release rheology modifier, for example, a controllable-release breaker, including a slow-release breaker.
- Wells drilled in low-permeability subterranean formations are often treated by reservoir stimulation techniques, such as hydraulic fracturing, to increase hydrocarbon production rate. High viscosity fluids may be employed to carry proppant down-hole to prop open fractures in the formation. Known linear gels (water containing a gelling agent only) that can be operated at ambient temperature at the surface generally do not exhibit a sufficiently high viscosity to transfer proppant of a large size or large quantity. Consequently, crosslinkers may be used to increase fluid viscosity, providing adequate transport of larger proppant sizes or larger proppant quantity. Higher viscosity fluids also create wider fractures within the formation.
- Guar and guar derivatives are among the most often used viscosifying agents, such as polymers, in hydraulic fracturing treatment. Guar derivatives, such as carboxymethyl guar (CMG) and carboxymethyl hydroxypropyl guar (CMHPG), are predominantly used in wells with a high bottom-hole temperature (BHT). Interest in cellulose derivatives, such as hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), and carboxymethyl hydroxyethyl cellulose (CMHEC), has increased for fracturing treatment due to the natural abundance of cellulose.
- Often, hydraulic fracturing gels include cross-linking delay additives, gel breakers, and fluid loss control additives among many other possible additives to adapt hydraulic fracturing gel to the circumstances of hydraulic fracturing. A variety of gelling agents and cross-linkers are known for use in hydraulic fracturing gel. For a delay additive, cross-linking reactions are so designed that viscosity development begins after placement of hydraulic fracturing gel deep within a well.
- In a related manner, rheology modifiers, such as gel breakers, may be included in hydraulic fracturing gel to significantly decrease viscosity after fracturing for easier removal of the gel from the well. To the extent that the cross-linked gel contains a gel breaker, the gel breaker may be configured for delayed action to maintain desirable properties of the cross-linked gel while fracturing. Even so, additional delay chemistries are desired to adapt rheology modifiers to an increased variety of viscosifying agents and related components.
- In addition, fluid volumes in fracturing treatments have increased substantially, while public concern for water use and disposal has also increased. Rather than paying to treat and dispose of produced and flowback water, service companies and operators have pursued recycling in subsequent stimulation operations. “Produced water” refers to water generated from hydrocarbon wells. Generally the term is used in the oil industry to describe water that is produced along with oil and/or gas. “Flowback water” is a subcategory of produced water referring to fracturing fluid that flows back through the well, which may account for some fraction of the original fracture fluid volume.
- Produced water, especially from shale plays such as Marcellus and Bakken, is known for its high total dissolved solids (TDS) content. TDS pose challenges for known guar- and guar derivative-based fracturing fluids. Further, various well treatment fluids that are originally prepared with clean water may show lower performance or even fail completely if salty and hard produced water is used in place of clean water. Consequently, produced water intended for recycling in subsequent stimulation operations is treated to obtain a water quality suitable for the fracturing fluids. Even so, such treatment is often cost-prohibitive and time-consuming. Accordingly, other fluids suitable for recycling of produced water are desirable.
- A well treatment method includes forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker, and a rheology modifier containing an aldehyde. The viscosifying agent is crosslinked in the aqueous fluid using the crosslinker, the crosslinking increasing viscosity of the well treatment fluid. The method includes treating a well with the well treatment fluid exhibiting the increased viscosity, chemically changing the aldehyde after the crosslinking and thereby forming an acid, and decreasing viscosity of the crosslinked well treatment fluid as a result of forming the acid.
- Another well treatment method includes forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker containing zirconium, and a rheology modifier containing glyoxal. The viscosifying agent is crosslinked in the aqueous fluid using the crosslinker, the crosslinking increasing viscosity of the well treatment fluid. The method includes treating a well with the well treatment fluid exhibiting the increased viscosity, chemically changing the glyoxal after the crosslinking and thereby forming oxalic acid, the oxalic acid breaking a crosslink formed by the zirconium, and decreasing viscosity of the crosslinked well treatment fluid using the oxalic acid.
- A well treatment fluid is formulated with ingredients including an aqueous fluid and a viscosifying agent and a crosslinker configured to crosslink the viscosifying agent in the aqueous fluid and thereby to increase viscosity of the well treatment fluid. The fluid includes a rheology modifier containing an aldehyde. The well treatment fluid is configured to chemically change the aldehyde after the crosslinking and thereby to form an acid configured to decrease viscosity of the crosslinked well treatment fluid. The well treatment fluid lacks an aldehyde crosslinking delay additive.
- Some embodiments are described below with reference to the following accompanying drawings.
-
FIGS. 1-5 are charts of viscosity over time for crosslinked fluids prepared with rheology modifiers respective to Examples 1-5. -
FIGS. 6-10 are charts of viscosity over time for crosslinked fluids prepared with produced water respective to Examples 6-10. - A rheology modifier, such as a crosslinked gel breaker, may be based on an aldehyde, including a dialdehyde, for example glyoxal. The aldehyde may release an acid slowly and controllably into a well treatment fluid, such as a crosslinked gel, and decrease viscosity of the gel over a sufficient time to complete use of the well treatment fluid before substantial viscosity loss. Without being limited to any particular theory, the dialdehyde might provide the benefit over monoaldehyde of forming a di-acid, such as oxalic acid, capable of chelating crosslinkers to break crosslinks. The rheology modifier may be an aqueous solution of the aldehyde.
- Accordingly, a well treatment method includes forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker, and a rheology modifier containing an aldehyde. The viscosifying agent in the aqueous fluid is crosslinked using the crosslinker, the crosslinking increasing viscosity of the well treatment fluid. The method includes treating a well with the well treatment fluid exhibiting the increased viscosity and chemically changing the aldehyde after the crosslinking, thereby forming an acid. Viscosity of the crosslinked well treatment fluid is decreased using the acid.
- Features of the various methods and compositions described herein may also be included in the above method as consistent and appropriate. By way of example, the well treatment fluid may lack an aldehyde crosslinking delay additive. That is, glyoxal is known for use in gels as a crosslinking delay additive (see, U.S. Pat. No. 5,160,643 issued to Dawson). Nevertheless, the well treatment fluids herein may lack a crosslinking delay additive or the well treatment fluid may include a crosslinking delay additive different from the aldehyde functioning herein as a viscosity breaker. In other words, the aldehyde rheology modifier herein need not delay the crosslinking.
- Also, the aldehyde might not substantially chemically change before the crosslinking. Even so, some insubstantial or de minimis chemical change to the aldehyde may occur before the crosslinking. Depending on the aldehyde used, formulation of the well treatment fluid, or both, lack of a pH decrease or lack of a viscosity decrease before the crosslinking could be evidence of no or only insubstantial chemical change to the aldehyde.
- Chemically changing the aldehyde to an acid, as in the case of glyoxal forming oxalic acid, may involve one or more reaction mechanisms not completely defined in the literature. Even so, one or more chemical reactions are believed to occur in the change, one of which may be oxidation of the aldehyde or of an intermediate component to form acid. Chemically changing the glyoxal may instead or additionally yield other acid(s) and/or other chemical(s) involved in decreasing viscosity of the crosslinked well treatment fluid.
- Likewise, decreasing viscosity of the crosslinked well treatment fluid as a result of forming the acid may involve one or more incompletely defined effects. One possible effect includes damage to the viscosifying agent, such as polymer, due a pH decrease upon generation of the acid. Another possible effect includes the acid directly interacting with and breaking the crosslinks. The two described effects and other viscosity decreases as a result of forming the acid may function in combination.
- The viscosifying agent may contain a polymer and the crosslinker may contain a metal cation or borate. The method may further include breaking a crosslink formed by the metal cation or borate to effect the viscosity decrease. Breaking the crosslink may include chelating the metal cation with the acid. The metal cation may be a zirconium or titanium ion. It follows that decreasing viscosity may occur by a stepwise process, namely, chemically changing the aldehyde, forming the acid, and the acid breaking the crosslink formed by the metal cation or borate. The stepwise process may also include the acid competing for chelation of the metal cation to break the crosslink. It is conceivable that decreasing viscosity may occur by a different process that does not break the crosslink.
- Compared to the well treatment fluid without the rheology modifier, viscosity may decrease at a faster rate. The numerical value for the decrease in viscosity and the time over which it occurs varies depending on the application. Consequently, the rate of decrease also varies. In field operations, the fluid viscosity can be very high (as in gel plugs), just several hundred centiPoise (as in frac fluids), or just a few centiPoise (as in slickwater). It will be appreciated that the larger viscosity decreases may occur in the higher viscosity fluids. Also, fluids may be formulated to break in 2 days, or to break in 2 hours. Even so, for the methods and compositions herein, the viscosity may decrease at a faster rate compared to known fluids and compared to the well treatment fluid herein without the rheology modifier.
- The aldehyde selected may be glyoxal and the acid may be oxalic acid. The intermediate products in the chemical change of glyoxal to oxalic acid, may be present, but likely not participating appreciably in breaking metal cation crosslinking. The well treatment fluid ingredients may contain up to 10 weight % (wt %) rheology modifier, such as up to 5 wt %, including up to 1 wt %, for example, from about 0.01 wt % to about 0.5 wt %. The rheology modifier may be an aqueous solution of the aldehyde, such as a 40 wt % solution. The well treatment fluid may contain additional components known for suitability in a selected fluid application, such as hydraulic fracturing. Examples include gel stabilizer, buffer, etc. The gel stabilizer may include sodium thiosulfate, thiosulfate, alkoxylated sorbitol, sorbitol, methanol, formate, and combinations thereof. The buffer may include sodium bicarbonate, bicarbonate, carbonate, hydroxide, acetate, formate, zirconium hydroxide, zirconium carbonate, and combinations thereof. The well treatment fluid may also contain diol, such as ethylene glycol.
- Treating the well with the well treatment fluid may include hydraulic fracturing, gravel packing, sand control, or other known applications for crosslinked well treatment fluid. The aqueous fluid may beneficially include produced water, allowing recycling of produced water from a well treatment method, as described in the Background section above.
- The ingredients may further include a zirconium salt, described further below, which may increase viscosity of the fluid prior to breaking, even being useful to such effect when the aqueous fluid is produced water. The zirconium salt may be selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium dioxide, and combinations thereof. The well treatment fluid ingredients may contain up to 20 wt % zirconium salt, such as up to 5 wt %, for example, from about 0.01 wt % to about 2 wt %.
- Latent acids, such as esters and polylactic acid, are known for use as slow-release breakers. Glyoxal chemically changes to oxalic acid at increasing rates for increased temperature and increased pH. Accordingly, release rate may be controlled in the environment of a well treatment fluid, such as a hydraulic fracturing gel. Other dialdehydes may exhibit similar properties.
- Another well treatment method includes forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker containing zirconium, and a rheology modifier containing glyoxal. The viscosifying agent is crosslinked in the aqueous fluid using the crosslinker, the crosslinking increasing viscosity of the well treatment fluid. The method includes treating a well with the well treatment fluid exhibiting the increased viscosity, chemically changing the glyoxal after the crosslinking, thereby forming oxalic acid, and the oxalic acid breaking a crosslink formed by the zirconium. Viscosity of the crosslinked well treatment fluid is decreased using the oxalic acid.
- Features of the various methods and compositions described herein may also be included in the above method as consistent and appropriate. By way of example, the well treatment fluid may lack a glyoxal crosslinking delay additive. Breaking the crosslink may include chelating the zirconium with the oxalic acid. Breaking the crosslink may instead or additionally include the oxalic acid decreasing pH.
- The viscosity may decrease at a faster rate compared to the well treatment fluid without the rheology modifier. The aqueous fluid may be produced water and the ingredients may further include a zirconium salt selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium dioxide, and combinations thereof.
- As will be appreciated from the methods herein, a well treatment fluid may be described as formulated with ingredients including an aqueous fluid, a viscosifying agent, a crosslinker, and a rheology modifier containing an aldehyde. The viscosifying agent and crosslinker are configured to crosslink the viscosifying agent in the aqueous fluid and thereby to increase viscosity of the well treatment fluid. The well treatment fluid is configured to chemically change the aldehyde after the crosslinking and thereby to form an acid configured to decrease viscosity of the crosslinked well treatment fluid. The well treatment fluid lacks an aldehyde crosslinking delay additive.
- Features of the various methods and compositions described herein may also be included in the above method as consistent and appropriate. By way of example, the crosslinker may contain a metal cation or borate, the acid being configured to break a crosslink formed by the metal cation or borate. The acid may further be configured to chelate the metal cation to break the crosslink. The acid may instead or additionally be configured to decrease pH to break the crosslink. The aldehyde may be glyoxal and the acid may be oxalic acid. The aqueous fluid may be produced water and the ingredients may further comprise a zirconium salt. The zirconium salt may be selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium dioxide, and combinations thereof.
- As introduced above, Zr salt may be beneficially used in a well treatment fluid. Zr salt exhibits known properties as a metal denaturant and/or bactericide in well treatment fluids susceptible to enzymatic or bacterial degradation of gelling agents, such as polymers (see, U.S. Pat. Pub. No. 2008/0287323 by Li et al.). Alternative uses of Zr salt are described herein.
- A discussion of temperature stability for gelling agents affected by bottom hole temperature is introduced in the Background section above. Acid hydrolysis of polymer often increases with increasing temperature, resulting in a pH decrease in well treatment fluids with increasing placement depth. Zr salt, such as Zr(OH)4, may dissolve more readily as pH decreases in a well treatment fluid at depth. Accordingly, the presence of Zr salt may operate to stabilize fluid pH as Zr salt disassociates into Zr(IV) and hydroxide ions, or other components, counteracting a pH decrease. The stabilized pH then also increases viscosity stability, reducing acid hydrolysis.
- The Zr salt additionally increases viscosity stability since the Zr(IV) ions may also contribute to crosslinking of the viscosifying agent. In a system susceptible to Zr crosslinking, Zr salt may thus serve a dual function.
- Beneficially, even though well treatment fluids using produced water may be difficult to crosslink, observation indicates that Zr-based crosslinking systems may be compatible with use of produced water. Increasing hardness in produced water decreases suitability of using produced water, so hardness damage may be mitigated by keeping pH below about 9, such as below about 8, for example below about 7, including between about 6 and about 5, at least during crosslinking.
- Incorporating a buffer to clamp the pH at about 5.0 to 6.0 in a well treatment fluid containing Zr salt may provide a system compatible with otherwise unsuitable levels of TDS and hardness from produced water. For treatment fluids including produced water, the pH may control hardness, the Zr salt may control pH, and the Zr salt may also maintain crosslinking.
- Therefore, a further well treatment method includes forming a well treatment fluid by combining ingredients including produced water, a viscosifying agent, a crosslinker containing a metal cation, a rheology modifier containing an aldehyde, and a zirconium salt. The produced water contains more than 1,000 ppm total dissolved solids. The method includes dissolving at least a portion of the zirconium salt in the well treatment fluid and stabilizing pH of the well treatment fluid with the zirconium salt. The viscosifying agent is crosslinked in the aqueous fluid using the crosslinker and the dissolved zirconium from the zirconium salt, the crosslinking increasing viscosity of the well treatment fluid compared to the well treatment fluid without the zirconium salt. A well is treated with the well treatment fluid exhibiting the increased viscosity.
- The aldehyde is chemically changed after the crosslinking, thereby forming an acid. The method includes decreasing pH and chelating the metal cation and the dissolved zirconium with the acid, thus breaking the crosslinked well treatment fluid. Using the acid, viscosity of the crosslinked well treatment fluid is decreased compared to the crosslinked well treatment fluid without the rheology modifier.
- Features of the various methods and compositions described herein may also be included in the above method as consistent and appropriate. By way of example, TDS may be more than 10,000 ppm, such as more than 100,000 ppm, including more than 300,000 ppm. Hardness measured as CaCO3 equivalent may be more than 20,000 ppm, such as more than 40,000 ppm, including more than 60,000 ppm. The aldehyde may be glyoxal and the acid may be oxalic acid. The zirconium salt may be selected from the group consisting of zirconium hydroxide, zirconium carbonate, zirconium dioxide, and combinations thereof.
- It is conceivable that pH may be controlled to facilitate different portions of the method. For example, pH may be maintained below about 7 during crosslinking and use of the crosslinked well treatment fluid.
- In another well treatment fluid system, observation indicated that decreasing pH may decrease pre-crosslinked polyacrylamide gel viscosity. The gel contained spheres of crosslinked polyacrylamide. Near neutral pH, the polyacrylamide chains anchored on these spheres are believed to stretch and touch each other, giving viscosity to the gel through physical entanglement. At lowered pH, the polyacrylamide chains are believed to shrink back to the spheres, reducing the contact with each other and decreasing the gel viscosity. The rheology modifier herein as slow release breaker may be used to control the fluid pH which, in turn, controls the fluid viscosity.
- The methods and fluids described herein may be further understood from the examples below.
- Borate-crosslinked guar fluid prepared with 0.4 gpt slow-release breaker. See
FIG. 1 and Table 1. - Borate-crosslinked guar fluid prepared with 2 gpt slow-release breaker. See
FIG. 2 and Table 1. - Borate-crosslinked guar fluid prepared with 0.8 gpt slow-release breaker. See
FIG. 3 and Table 1. - Zr-crosslinked HEC fluid prepared with slow-release breaker. See
FIG. 4 . - Zr-crosslinked HEC fluid prepared with slow-release breaker and oxidative breaker. See
FIG. 5 . - Zr-crosslinked HPG fluid prepared with produced water See
FIG. 6 and Table 4. - Zr-crosslinked HPG fluid prepared with produced water and varying gel pH. See
FIG. 7 and Table 4. - Zr-crosslinked HPG fluid prepared with produced water and zirconium salt. See
FIG. 8 and Table 4. - Zr-crosslinked HPG fluid prepared with produced water and methanol. See
FIG. 9 and Table 4. - Zr-crosslinked CMHEC fluid prepared with produced water. See
FIG. 10 and Table 4. - The slow release breaker used included glyoxal (40 weight % glyoxal solution in water) buffered with pH buffer B to a pH of about 7.1-7.2. When 0.52 mL pH buffer B was added to 60 mL glyoxal solution, the resulting pH at room temperature (RT) was about 7.14-7.16. A borate-crosslinked guar baseline fluid (no breaker or 0 gpt breaker used) was prepared with tap water, 30 ppt (pounds per thousand gallons) guar, 1 gpt (gallon per thousand gallons) clay control agent, and 2 gpt borate crosslinker A. The viscosity at 200° F. was tested with a Chandler 5550 viscometer, following the API RP 39 schedule (American Petroleum Institute Recommended Procedure). The viscosity is shown in
FIG. 1 . The baseline viscosity stayed at about 600 cPs. - In another test, 0.4 gpt of the breaker was added to the center of the baseline gel in the viscometer, and the viscosity at 200° F. was similarly measured and shown in
FIG. 1 . The viscosity dropped gradually from about 600 cPs to about 100 cPs in about 4 hours. - When the dose of the breaker increased to, for example, 2 gpt, the breaking action was much faster. In
FIG. 2 , the viscosity of the same baseline fluid and the fluid with 2 gpt breaker is shown. The viscosity of the fluid with 2 gpt breaker quickly dropped to below 100 cPs. - Another borate crosslinked guar baseline fluid (no breaker or 0 gpt breaker used) was prepared with tap water, 25 ppt guar, 1 gpt clay control agent, 1.5 gpt pH buffer E, and 0.75 gpt borate crosslinker B. The viscosity at 200° F. was tested with a Chandler 5550 viscometer, following the API RP 39 schedule. The viscosity is shown in
FIG. 3 . The baseline viscosity stayed at about 400 cPs. In another test, 0.8 gpt breaker was added to the center of the baseline gel in the viscometer, and the viscosity at 200° F. was similarly measured and is shown inFIG. 3 . The viscosity dropped gradually and in a controllable way. -
TABLE 1 Glyoxal Breaker Examples Ex. 1 Ex. 2 Ex. 3 guar 30 ppt 30 ppt 25 ppt clay control agent 1 gpt 1 gpt 1 gpt pH buffer E — — 1.5 gpt borate crosslinker A 2 gpt 2 gpt — borate crosslinker B — — 0.75 gpt breaker 0-0.4 gpt 0-2 gpt 0-0.8 gpt - HEC solution was crosslinked with zirconium crosslinkers to form a gel at pH above about 9-10. When adding the breaker to the crosslinked HEC gel, the crosslinking was gradually reversed, causing the gel viscosity to drop gradually.
- The metal-crosslinked HEC fluid without the glyoxal solution was prepared first as the baseline gel. To prepare the fluid, 500 ml of tap water with 2% potassium chloride (KCl) was added to a 1-liter Waring blender. While blending, 80 ppt (could be more based on the operational needs) of HEC powder was added to the blender, and hydrated for about 20 minutes. After the hydration, appropriate amounts of additives including the crosslinking delay agent, gel stabilizer such as sodium thiosulfate, and buffer such as sodium hydroxide, etc., could be added into the fluid and allowed to be evenly mixed and dispersed. The metal crosslinker such as the zirconate crosslinker was then added.
- The gel thus prepared had a pH of about 12 to 13 at room temperature. The vortex did not appear to close at room temperature even after 10 minutes. The crosslinking delay in the HEC fluid was temperature delay-based. The crosslink in the HEC fluid was activated by heating the fluid above a certain temperature. This intentional crosslinking delay decreases friction pressure and thus the pumping power to deliver the HEC fluid downhole. The viscosity of the baseline HEC gel at 200° F. was measured with the Fann50-type viscometer. The viscosity curve is recorded in
FIG. 4 . The viscosity of the baseline gel at 200° F. slowly decreased from about 550 cPs in the beginning to about 350 cPs at 350 minutes. - The breaking tests were carried out at 200° F. to assess the breaking performance of the glyoxal solution (the breaker) in the metal-crosslinked HEC fluids. The crosslinked HEC fluid with the glyoxal solution was similarly prepared. The glyoxal solution was added immediately before the crosslinker. In one test, 2 gpt of the glyoxal solution was used. The viscosity of the resulting gel at 200° F. was similarly measured with the viscometer. As shown in
FIG. 4 , at 200° F. the viscosity of the gel with 2 gpt of the glyoxal solution gradually decreased to about 250 cPs after 350 minutes. In another test, 4 gpt of the glyoxal solution was used in the same HEC gel. As shown inFIG. 4 , at the higher glyoxal solution dose of 4 gpt and at 200° F., the viscosity gradually decreased to about 200 cPs after 350 minutes. - The glyoxal solution (the breaker) performance was also assessed in conjunction with regular oxidative breakers. The baseline HEC gel in
FIG. 5 was the same as that inFIG. 4 . The viscosity of the baseline gel at 200° F. slowly decreased from about 550 cPs in the beginning to about 350 cPs at 350 minutes. In the breaking test, 2 gpt of the glyoxal solution and 5 ppt of an oxidative breaker (magnesium peroxide) were added together to the similar HEC gel before adding the crosslinker. The viscosity of the resulting gel at 200° F. was similarly measured with the viscometer, as shown inFIG. 5 . The viscosity at 200° F. of the HEC gel with both the oxidative breaker and the glyoxal solution gradually decreased from about 550 cPs in the beginning to about 140 cPs after 350 minutes. - Produced
water # 1 was used in this example. Producedwater # 1 was offered by an oilfield operator from the field. The water had a pH of about 5.6 at RT. The water analysis of producedwater # 1 is listed in Table 2. The water had a TDS of over 280,000 mg/L, and hardness of over 46,000 mg/L. -
TABLE 2 Analyte mg/L Al 0.14 B 280 Ba 17.7 Ca 16100 Fe 75.2 K 4960 Mg 1220 Mn 9.54 Na 91600 SO4 403 Si 14.5 Sr 1170 Zn 3.56 Cl 172000 HCO3 128 OH 0 CO 30 - To prepare the fluid, about 250 mL of produced
water # 1 was placed in a 1 L Waring blender. The mixing speed was adjusted so that the blade nut was just exposed. 40 ppt HPG powder was added to the blender while blending. The blending duration was usually over 10 minutes. After the hydration of the HPG polymer, 2 ppt buffer D, 6 gpt gel stabilizer A, and 1.6 gpt gel stabilizer B were added while blending. Finally, 1.6 gpt zirconium crosslinker was added as the crosslinker. The gel thus formed had a pH of about 5.7 at RT. The viscosity at 240° F. was tested with a Chandler 5550 viscometer, following the API RP 39 schedule. The viscosity is shown inFIG. 6 . The fluid showed a decent viscosity, over 400 cPs right before the second ramp peak. - Another fluid was similarly prepared and tested. 50 ppt HPG powder was added to produced
water # 1 in the blender while blending. After the hydration of the HPG polymer, 2 ppt buffer D, 6 gpt gel stabilizer A, and 2 gpt gel stabilizer B were added while blending. 2 gpt zirconium crosslinker was then added as the crosslinker. The gel thus formed had a pH of about 5.7 at RT. The viscosity at 240° F. was similarly tested and shown inFIG. 6 . The fluid showed a decent viscosity, over 500 cPs right before the second ramp peak. - Two Zr-crosslinked HPG fluids were prepared with produced
water # 1. The influence of the gel pH was observed. To prepare the first fluid, about 250 mL of producedwater # 1 was placed in the Waring blender. 50 ppt HPG powder was added to the blender while blending. Some pH buffer C was applied during the hydration. After the hydration of the HPG polymer, 6 gpt gel stabilizer A and 2 gpt gel stabilizer B were added while blending. 2 gpt zirconium crosslinker was then added as the crosslinker. The gel thus formed had a pH of about 5.2 at RT. The viscosity at 240° F. was tested with the Chandler 5550 viscometer and is shown inFIG. 7 . - To prepare the other fluid, 50 ppt HPG powder was added to produced
water # 1 in the blender while blending. After the hydration of the HPG polymer, 2 ppt buffer D, 6 gpt gel stabilizer A, and 2 gpt gel stabilizer B were added while blending. 2 gpt zirconium crosslinker was then added as the crosslinker. The gel thus formed had a pH of about 5.7 at RT. The viscosity at 240° F. was similarly tested and is shown inFIG. 7 . - The fluid with the slightly higher pH at 5.7 showed a more stable viscosity profile at 240° F., for example, beyond about 25 minutes, as shown in
FIG. 7 . The fluid with the lower pH at 5.2 had a larger starting viscosity, which may or may not be desirable in operations, but its viscosity dropped more quickly over time (lower pH might have caused more damage to the fluid at high temperature) than the fluid with the pH at 5.7. The example shows that, by selecting appropriate fluid pH, the fluid could have increased long-term stability. - To prepare the base fluid, about 250 mL of produced
water # 1 was placed in the Waring blender. 50 ppt HPG powder was added to the blender while blending. Some pH buffer C was applied during the hydration. After the hydration of the HPG polymer, 6 gpt gel stabilizer A and 2 gpt gel stabilizer B were added while blending. 2 gpt zirconium crosslinker was then added as the crosslinker. The gel thus formed had a pH of about 5.2 at RT. The viscosity at 240° F. was tested with the Chandler 5550 viscometer and is shown inFIG. 8 . - About 1% by weight zirconium (IV) hydroxide fine powder was evenly mixed into the above base gel, and the viscosity at 240° F. was similarly tested and shown in
FIG. 8 . The fluid with 1% zirconium hydroxide showed significantly enhanced viscosity. For example, at 60 minutes, the viscosity of the fluid with 1% zirconium hydroxide was about 2.7 times that of the base fluid. - Other zirconium salts may also be used, such as zirconium carbonate or zirconium dioxide.
- To prepare the base fluid, about 250 mL of produced
water # 1 was placed in the Waring blender. 50 ppt HPG powder was added to the blender while blending. Some pH buffer C was applied during the hydration. After the hydration of the HPG polymer, 3 gpt gel stabilizer A and 2 gpt gel stabilizer B were added while blending. 2 gpt zirconium crosslinker was then added as the crosslinker. The gel thus formed had a pH of about 5.3 at RT. The viscosity at 240° F. was tested with the Chandler 5550 viscometer and is shown inFIG. 9 . - To test the function of methanol, 7.5% by volume methanol was added to the HPG fluid right after hydration. Other additives were similarly added thereafter. The viscosity at 240° F. was tested similarly and is shown in
FIG. 9 . As shown inFIG. 9 , methanol volume percentages at 7.5% significantly enhanced the fluid viscosity at 240° F. It is expected that use of methanol to increase viscosity will be compatible with the methods and compositions described herein that use zirconium salt also to increase viscosity. - Produced water #2 was used in this example. Produced water #2 was offered by another oilfield operator from the field. The water had a pH of about 5.6 at RT. The water analysis of produced water #2 is listed in Table 3. The water had a TDS of over 210,000 mg/L, and hardness of over 43,000 mg/L.
-
TABLE 3 Analyte mg/L Al 0 B 17.5 Ba 0.87 Ca 13900 Fe 7.93 K 639 Mg 2120 Mn 0.88 Na 67700 SO4 471 Si 5.31 Sr 500 Zn 0.05 Cl 133000 HCO 360 OH 0 CO 30 - To prepare the fluid, 40 ppt CMHEC powder was hydrated in produced water #2. After the hydration of the polymer, 0.2 gpt pH buffer A and 1 gpt gel stabilizer B were added while blending. 1.4 gpt zirconium crosslinker was then added as the crosslinker. The gel thus formed had a pH of about 4.9 at RT. The viscosity at 200° F. was tested with a Fann50-type viscometer and is shown in
FIG. 10 . The fluid showed decent viscosity, over 600 cPs (at 100/s shear rate) for at least 2 hours. It is expected that use of CMHEC will be compatible with the methods and compositions described herein that use zirconium salt to increase viscosity. -
TABLE 4 Produced Water Examples Ex. 6 Ex. 6 Ex. 7 Ex. 7, 8 Ex. 8 Ex. 9 Ex. 10 pH (RT) 5.7 5.7 5.7 5.2 5.2 5.3 4.9 HPG 40 ppt 50 ppt 50 ppt 50 ppt 50 ppt 50 ppt — CMHEC — — — — — — 40 ppt pH buffer A — — — — — — 0.2 gpt pH buffer C — — — yes yes yes — buffer D 2 ppt 2 ppt 2 ppt — — — — gel stab. A 6 gpt 6 gpt 6 gpt 6 gpt 6 gpt 3 gpt — gel stab. B 1.6 gpt 2 gpt 2 gpt 2 gpt 2 gpt 2 gpt 1 gpt Zr x-linker 1.6 gpt 2 gpt 2 gpt 2 gpt 2 gpt 2 gpt 1.4 gpt Zr(OH)4 — — — — 1 wt % — — methanol — — — — — 0-7.5 vol % — - In compliance with the statute, the embodiments have been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the embodiments are not limited to the specific features shown and described. The embodiments are, therefore, claimed in any of their forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.
Claims (18)
1. A well treatment method comprising:
forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker, and a rheology modifier containing a dialdehyde;
crosslinking the viscosifying agent in the aqueous fluid using the crosslinker, the dialdehyde not delaying the crosslinking and the crosslinking increasing viscosity of the well treatment fluid to a first viscosity;
treating a well with the well treatment fluid exhibiting the first viscosity;
chemically changing the dialdehyde after the crosslinking and thereby forming a diacid, the dialdehyde not being substantially chemically changed before the crosslinking; and
after treating the well, decreasing viscosity of the crosslinked well treatment fluid to a second viscosity less than the first viscosity as a result of forming the diacid.
2. The method of claim 1 , wherein the viscosifying agent comprises a polymer and the crosslinker comprises a metal cation or borate, the method further comprising breaking a crosslink formed by the metal cation or borate to effect the viscosity decrease.
3. The method of claim 2 wherein decreasing viscosity occurs by a stepwise process including chemically changing the dialdehyde, forming the diacid, and the diacid breaking the crosslink formed by the metal cation or borate.
4. The method of claim 1 wherein the viscosity decreases at a faster rate compared to the well treatment fluid without the rheology modifier.
5. The method of claim 1 wherein the dialdehyde is glyoxal and the diacid is oxalic acid.
6. The method of claim 1 wherein the aqueous fluid is produced water and the ingredients further include a zirconium salt.
7. The method of claim 6 wherein the zirconium salt is selected from the group consisting of zirconium hydroxide, zirconium dioxide, and combinations thereof.
8. The method of claim 6 wherein the produced water contains more than 100,000 ppm total dissolved solids.
9. The method of claim 8 wherein the zirconium salt comprises zirconium hydroxide.
10. The method of claim 9 wherein the well treatment fluid ingredients contain 0.01 to 20 wt % zirconium hydroxide.
11. The method of claim 8 wherein the well treatment fluid exhibits a pH below 7 at least during the crosslinking.
12. The method of claim 8 wherein the well treatment fluid exhibits a pH between about 6 and about 5 at least during the crosslinking and the treating.
13. A well treatment method comprising:
forming a well treatment fluid by combining ingredients including an aqueous fluid, a viscosifying agent, a crosslinker containing zirconium, and a rheology modifier containing glyoxal;
crosslinking the viscosifying agent in the aqueous fluid using the crosslinker, the glyoxal not delaying the crosslinking and the crosslinking increasing viscosity of the well treatment fluid;
treating a well with the well treatment fluid exhibiting the increased viscosity;
chemically changing the glyoxal after the crosslinking and thereby forming oxalic acid;
the oxalic acid breaking a crosslink formed by the zirconium and decreasing viscosity of the crosslinked well treatment fluid using the oxalic acid.
14. The method of claim 13 wherein the viscosity decreases at a faster rate compared to the well treatment fluid without the rheology modifier.
15. The method of claim 13 wherein the aqueous fluid is produced water and the ingredients further include a zirconium salt selected from the group consisting of zirconium hydroxide, zirconium dioxide, and combinations thereof.
16. A well treatment method comprising:
forming a well treatment fluid by combining ingredients including produced water, a viscosifying agent, a crosslinker containing a metal cation, a rheology modifier containing an aldehyde, and a zirconium salt, the produced water containing more than 1,000 ppm total dissolved solids;
dissolving at least a portion of the zirconium salt in the well treatment fluid;
crosslinking the viscosifying agent in the aqueous fluid using the crosslinker and the dissolved zirconium from the zirconium salt, the crosslinking increasing viscosity of the well treatment fluid compared to the well treatment fluid without the zirconium salt;
treating a well with the well treatment fluid exhibiting the increased viscosity, acid hydrolysis of the crosslinked viscosifying agent occurring in the well;
stabilizing pH of the well treatment fluid with the zirconium salt during the acid hydrolysis of the viscosifying agent in the well;
chemically changing the aldehyde after the crosslinking and thereby forming an acid;
decreasing pH and chelating the metal cation and the dissolved zirconium with the acid, thus breaking the crosslinked well treatment fluid and, using the acid, decreasing viscosity of the crosslinked well treatment fluid compared to the crosslinked well treatment fluid without the rheology modifier.
17. The method of claim 16 wherein the aldehyde is glyoxal and the acid is oxalic acid.
18. The method of claim 16 wherein the zirconium salt is selected from the group consisting of zirconium hydroxide, zirconium dioxide, and combinations thereof.
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EP3110902A4 (en) | 2017-10-18 |
CN106164209B (en) | 2019-03-12 |
EP3110902A1 (en) | 2017-01-04 |
AR099527A1 (en) | 2016-07-27 |
AU2015219372B2 (en) | 2018-03-15 |
MX2016010913A (en) | 2016-11-14 |
SA516371690B1 (en) | 2019-03-10 |
WO2015126676A1 (en) | 2015-08-27 |
CA2940517A1 (en) | 2015-08-27 |
US20150240149A1 (en) | 2015-08-27 |
AU2015219372A1 (en) | 2016-08-25 |
RU2016138017A3 (en) | 2018-07-26 |
RU2016138017A (en) | 2018-03-29 |
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