CN111892920A - Viscosity reducer for reducing viscosity of fracturing fluid or flowback fluid, preparation method thereof, compound enzyme gel breaking capsule and application thereof - Google Patents
Viscosity reducer for reducing viscosity of fracturing fluid or flowback fluid, preparation method thereof, compound enzyme gel breaking capsule and application thereof Download PDFInfo
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- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
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- 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
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Abstract
The invention provides a viscosity reducer for reducing viscosity of fracturing fluid or flowback fluid, a preparation method thereof, a compound enzyme gel breaking capsule and application thereof. The viscosity reducing agent comprises an enzyme component, wherein the enzyme component comprises one or more of mannanase, pectinase and cellulase. The viscosity reducer does not contain oxidation type chemical agents, enzymes of enzyme components can directionally destroy glycosidic bonds in guanidine gum molecular chains, the viscosity reducer is not influenced by oxidizable substances in fracturing fluid or flowback fluid, the gel breaking speed is high, the viscosity of the fracturing fluid or the flowback fluid can be quickly reduced to about 1mPa & lt.S, and compared with conventional oxidation type gel breakers, the viscosity reducer is small in agent usage amount, low in cost, high in safety and high in application value.
Description
Technical Field
The invention relates to the technical field of oilfield fracturing construction, in particular to a viscosity reducer for viscosity reduction of fracturing fluid or flowback fluid, a preparation method thereof, a compound enzyme gel breaking capsule and application thereof.
Background
With the continuous development of oil fields, fracturing construction operations are the main mode of exploitation of low permeability oil fields. After the fracturing fluid (the viscosity is generally 30-60 mPa & lt S & gt) is injected into the stratum and the seam is formed, the fracturing fluid needs to be quickly discharged out of the stratum, so that secondary damage and pollution to the stratum are reduced. This requires the addition of viscosity reducing breakers to reduce the viscosity of the fracturing fluid to below 15mPa S to quickly expel it from the formation. The returned fracturing fluid still has certain viscosity (the viscosity is generally 2 to 15mPa & lt S & gt), and the fracturing returned fluid (hereinafter referred to as returned fluid) contains a large amount of organic matters and inorganic matters, and needs to be further treated for recycling or reinjection. In the process of treating the flowback liquid, the general treatment method is to perform viscosity reduction treatment firstly and then perform advanced treatment by combining other processes. Currently, an oxidation agent is generally added for viscosity reduction and gel breaking treatment of fracturing fluid and flowback fluid, persulfate is generally used as a viscosity reduction and gel breaking agent used for the fracturing fluid, and ammonium salt, ferrous iron and other inorganic salts are compounded for preparing a compound type fracturing fluid gel breaking and viscosity reducing agent as disclosed in the patent application with the publication number of CN 108276981A; the patent application with the publication number of CN106318364A adopts the complex formulation of the persulfide (potassium persulfate and sodium persulfate) and the biological hydrolase to prepare the composite gel breaker. The viscosity reduction gel breaker of the return liquid generally uses persulfate and hypochlorite to reduce viscosity, and for example, in patent with publication number of CN106318363A, chlorine dioxide, sodium hypochlorite and calcium hypochlorite are compounded to prepare the oxidation gel breaker; patent publication No. CN106566517A adopts a persulfate as an accelerator, and is mixed with an oxidant (sodium hypochlorite, peroxide) and a reductive inorganic salt to prepare the backflow fluid gel breaking viscosity reducer. That is to say, the persulfate or hypochlorite is generally required to be adopted to reduce viscosity of the fracturing fluid or the flowback fluid in the prior art, however, the viscosity of the fracturing fluid is mainly contributed by a thickening agent (usually hydroxypropyl guar gum or guar gum), although the chemical agent oxidant can effectively destroy the molecular chain of the guar gum to reduce the viscosity of the fracturing fluid and the flowback fluid, a large amount of oxidant is consumed by a large amount of oxidizable substances contained in the fracturing fluid and the flowback fluid, so that the dosage of the oxidant is large, and the cost is high.
Disclosure of Invention
The invention mainly aims to provide a viscosity reducing agent for reducing viscosity of fracturing fluid or flowback fluid, a preparation method thereof, a compound enzyme gel breaking capsule and application thereof, so as to solve the problem of high viscosity reducing cost of the fracturing fluid or the flowback fluid in the prior art.
To achieve the above object, according to one aspect of the present invention, there is provided a viscosity reducing agent for reducing viscosity of a fracturing fluid or a flowback fluid, the viscosity reducing agent comprising an enzyme component including a combination of any one or more of mannanase, pectinase and cellulase.
Further, the viscosity reducer is composed of an enzyme component dispersed in a dispersion medium, wherein the enzyme component comprises the following components in percentage by weight: 50-75% of mannase, 10-20% of pectinase and 10-40% of cellulase, wherein the preferable enzyme components comprise: 57-75% of mannase, 12-20% of pectinase and 10-30% of cellulase.
Furthermore, the specific activity of the mannanase is 40000U/g, preferably the specific activity of the pectinase is 30000U/g, and more preferably the specific activity of the cellulase is 35000U/g.
Further, the pectinase is polygalacturonase.
Further, the dispersion medium includes water.
Further, the dispersion medium further comprises a pH value regulator, preferably, the pH value regulator is acid or alkali, and the pH value of the viscosity reducer is 5-8.
According to another aspect of the invention, a compound enzyme gel breaking capsule is provided, which comprises a viscosity reducer and a capsule coat, wherein the capsule coat is used for coating the viscosity reducer, and the viscosity reducer is any one of the viscosity reducers.
According to another aspect of the present invention, there is provided a method of preparing any one of the above viscosity reducing agents, the enzyme component comprising a combination of any plurality of mannanase, pectinase and cellulase, the method comprising: any enzymes in the enzyme component are mixed.
Further, the viscosity reducer is composed of the enzyme component and a dispersion medium, and the preparation method further comprises the step of mixing the mixed enzyme component and the dispersion medium to obtain the viscosity reducer.
Further, the preparation method comprises the following steps: adding at least part of the dispersion medium to the enzyme component to obtain a primary mixture; stirring the primary mixture to form a stirring system, heating the stirring system to 50 ℃ in the stirring process, and controlling the pH value of the stirring system to be 5-8 to obtain the viscosity reducer, wherein preferably, the stirring speed is 50-100 r/min, and the stirring lasts for 40-60 h.
According to another aspect of the invention, a viscosity reducing method for fracturing fluid or flowback fluid is provided, wherein any viscosity reducing agent is adopted to reduce viscosity of the fracturing fluid or flowback fluid.
By applying the technical scheme of the invention, the viscosity reducer does not contain an oxidation type chemical agent, enzymes of an enzyme component can directionally destroy glycosidic bonds in a guanidine gum molecular chain, and is not influenced by oxidizable substances in fracturing fluid or flowback fluid, the gel breaking speed is high, the viscosity of the fracturing fluid or the flowback fluid can be quickly reduced to about 1mPa & lt S & gt, and compared with a conventional oxidation type gel breaker, the viscosity reducer is low in agent consumption, low in cost, high in safety and high in application value.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
When utilizing the oxidant to reduce fracturing fluid or flowback fluid viscosity among the prior art, the oxidant can effectively destroy the molecular chain of guar gum and reduce the viscosity of fracturing fluid and flowback fluid, but contains a large amount of oxidizable substances in fracturing fluid and flowback fluid and can consume a large amount of oxidant for the charge of oxidant is big, with high costs. In order to solve the problem, the application provides a viscosity reducer for reducing viscosity of fracturing fluid or flowback fluid, a preparation method thereof, a compound enzyme gel breaking capsule and application thereof.
In an exemplary embodiment of the present application, there is provided a viscosifier for viscosification of a fracturing fluid or flowback fluid, the viscosifier comprising an enzyme component comprising a combination of any one or more of mannanase, pectinase and cellulase.
The mannase is beta-mannase, and is a hydrolytic endonuclease capable of hydrolyzing mannan oligosaccharide and mannan (including mannan, galactomannan, glucomannan and the like) containing beta-l, 4-mannoside bonds. Pectinase is a lyase which can directionally break glycosidic bonds at the C-4 position, a polysaccharide substance is catalyzed to remove methyl ester groups to generate pectic acid, and the pectic acid is degraded by the pectic acid to generate galacturonic acid. Glucanase is a group of enzymes that specifically act on the 1,3 and 1,4 glycosidic linkages of beta-glucan to produce oligosaccharides of 3-5 glucose units and glucose, each of which can break the glycosidic linkages in the guar molecule chain.
Therefore, the viscosity reducer does not contain oxidation type chemical agents, enzymes of enzyme components can directionally destroy glycosidic bonds in guanidine gum molecular chains, the viscosity reducer is not influenced by oxidizable substances in fracturing fluid or flowback fluid, the gel breaking speed is high, the viscosity of the fracturing fluid or the flowback fluid can be quickly reduced to about 1mPa & lt.S, and compared with the conventional oxidation type gel breakers, the viscosity reducer is small in dosage, low in cost, high in safety and high in application value.
Preferably, the viscosity-reducing agent of the present application consists of an enzyme component dispersed in a dispersion medium. In order to optimize the viscosity reducing effect, the enzyme component preferably comprises, in weight percent: 50-75% of mannase, 10-20% of pectinase and 10-40% of cellulase. Further preferably, the compound enzyme component comprises: 57-75% of mannase, 12-20% of pectinase and 10-30% of cellulase. The three enzymes are combined for use, and the effects of the enzymes are complemented through the cooperation of the three enzymes, so that the viscosity reducing effect is further optimized.
In order to sufficiently exert the enzyme action and accelerate the viscosity reduction, the specific activity of the mannanase is preferably 40000U/g, the specific activity of the pectinase is preferably 30000U/g, and the specific activity of the cellulase is more preferably 35000U/g. Further preferably, the pectinase is polygalacturonase.
In addition, for the convenience of use of the viscosity reducing agent of the present application, it is preferable that the dispersion medium includes water, and the enzyme component is present in the form of a solution by using water, thereby facilitating addition to the fracturing fluid or flowback fluid. In order to maintain high activity of each enzyme in the enzyme component after dispersion, the dispersion medium preferably further comprises a pH adjuster, and the pH adjuster is preferably an acid or an alkali, such as a common inorganic acid and inorganic alkali, and a short-chain organic acid and organic alkali, more specifically, the alkali may be an amine compound such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, or triethylamine, or an alkali metal salt of an alcohol such as sodium methoxide or potassium ethoxide, the acid may be hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, or acetic acid, and the pH of the viscosity reducer is preferably controlled to be 5 to 8. Since the oxidation type chemical agents such as persulfate and hypochlorite used in the prior art do not have the effect of adjusting the pH value and the effect thereof is that the oxidation effect is not a dispersion effect, they do not belong to the dispersion medium of the present application.
In another exemplary embodiment of the present application, there is provided a complex enzyme gel-breaking capsule, comprising a viscosity-reducing agent and a capsule coat, wherein the capsule coat encapsulates the viscosity-reducing agent, and the viscosity-reducing agent is any one of the above viscosity-reducing agents.
By coating the capsule coat on the surface of the viscosity reducer, the gel breaking time is effectively controlled, enzymes of the enzyme component can directionally break glycosidic bonds in a guanidine gum molecular chain in effective time, the gel breaking speed is high, the viscosity of fracturing fluid or flowback fluid can be quickly reduced to about 1mPa & lt.S, and compared with the conventional oxidation type gel breaker, the gel breaker has the advantages of small dosage, low cost, high safety and great application value.
The preparation method of the complex enzyme gel breaking capsule can adopt the preparation method of the capsule type gel breaking agent commonly used in the prior art, such as:
preparing the compound enzyme gel breaking capsule by adopting an in-situ polymerization method. Dissolving gelatin in water at 55 ℃ to prepare a gelatin solution with the mass fraction of 3-10%; and meanwhile, adding the viscosity reducer into the kerosene at 55 ℃, wherein the mass ratio of the viscosity reducer to the gelatin is 2: 1-9: 1, and the ratio of the kerosene to the distilled water is 3: 1-8: 1. And after stirring for 30 minutes at a constant speed, slowly pouring the mixture of the viscosity reducer and the kerosene into a 3-10% gelatin solution, continuously stirring for 30 minutes, and stirring for 1 hour at room temperature to form the composite emulsion. Adding absolute ethyl alcohol into the composite emulsion, continuously stirring, slowly adding glutaraldehyde (the mass ratio of the glutaraldehyde to the gelatin is 100: 1-20: 1), stirring for 1 hour, and standing, settling and layering. The lower layer is the complex enzyme capsule gel breaker. Repeatedly washing with solvent oil, and drying to obtain the compound enzyme gel breaking capsule.
In another exemplary embodiment of the present application, there is provided a method for preparing the above viscosity-reducing agent, wherein the enzyme component includes a combination of any more of mannanase, pectinase and cellulase, and the method comprises: any enzymes in the enzyme component are mixed. The preparation method of the viscosity reducer is simple, and the viscosity reducer can be prepared by mixing the enzymes, so that the industrial application range of the viscosity reducer is expanded.
In addition, for the convenience of the viscosity reducing agent of the present application, it is preferable that the viscosity reducing agent is composed of the enzyme component and a dispersion medium, and when the dispersion medium is included, the preparation method further comprises mixing the mixed enzyme component and the dispersion medium to obtain the viscosity reducing agent.
In order to improve the dispersion uniformity of the complex enzyme component, the preparation method preferably comprises the following steps: adding at least part of the dispersion medium to the enzyme component to obtain a primary mixture; and stirring the primary mixture to form a stirring system, heating the stirring system to 50 ℃ in the stirring process, and simultaneously controlling the pH value of the stirring system to be 5-8 to obtain the viscosity reducer. The dispersion rate of each enzyme is accelerated by stirring under the heating condition, and the high activity of each enzyme is kept by controlling the temperature to be below 50 ℃ and the pH value to be 5-8. In order to improve the mixing efficiency, the stirring speed is preferably 50-100 r/min, and the stirring lasts 40-60 h.
In another exemplary embodiment of the present application, a method for viscosity reduction of a fracturing fluid or flowback fluid is provided, wherein the viscosity reducer is used for viscosity reduction of the fracturing fluid or flowback fluid.
The viscosity reducer does not contain oxidation type chemical agents, enzymes of enzyme components can directionally destroy glycosidic bonds in guanidine gum molecular chains, the viscosity reducer is not influenced by oxidizable substances in fracturing fluid or flowback fluid, the gel breaking speed is high, the viscosity of the fracturing fluid or the flowback fluid can be quickly reduced to about 1mPa & lt.S, and compared with conventional oxidation type gel breakers, the viscosity reducer is small in agent usage amount, low in cost, high in safety and high in application value.
The advantageous effects of the present application will be further described below with reference to examples and comparative examples.
According to the weight proportion in the table 1, mannase, pectinase and cellulase are taken and mixed to form an enzyme component, tap water is added into the enzyme component to form a primary mixture, the primary mixture is stirred for 20min to form a stirring system, the stirring system is slowly heated to 50 ℃, the pH value of the stirring system is controlled to be 5-8 by adopting a sodium hydroxide solution and a triethylamine solution, and the viscosity reducer is prepared after continuous stirring is carried out for 48h at the speed of 80 r/min.
Wherein, the mannase is a purchased commodity, the commodity is an enzyme preparation produced by fermenting bacillus, the specific activity is 40000U/g, white powder is used, the use temperature is 25-52 ℃, and the use pH value is 5-8; the pectinase is an outsourcing commodity, the commodity is an enzyme preparation produced by fermenting aspergillus niger, the specific activity is 30000U/g, the usage temperature is 28-55 ℃, and the usage pH range is 5-8; the cellulase is an outsourced commodity, the commodity is prepared by liquid submerged fermentation of Bacillus Lichenifomis strain, the enzyme is an endonuclease, the effective component is 35000U/g, the cellulase is brown powder, the use temperature is 30-50 ℃, and the use pH value is 5-8.
TABLE 1
The viscosity-reducing agents of examples 1 to 20 were used to treat fracturing fluids used in a well in the midge region of the mare in Xinjiang oil field,
preparing the compound enzyme gel breaking capsule by adopting an in-situ polymerization method. Dissolving gelatin in water at 55 ℃ to prepare a gelatin solution with the mass fraction of 6%; meanwhile, the complex enzyme of each embodiment is added into kerosene at 55 ℃, the mass ratio of the complex enzyme to gelatin is 5:1, and the ratio of the kerosene to distilled water is 5: 1. After stirring at a constant speed for 30 minutes, 6 percent gelatin solution is slowly poured into the mixture, and after stirring for 30 minutes, the mixture is stirred at room temperature for 1 hour to form composite emulsion. Adding absolute ethyl alcohol into the composite emulsion, continuously stirring, slowly adding glutaraldehyde (the mass ratio of the glutaraldehyde to the gelatin is 50:1), stirring for 1 hour, standing, settling and layering. The lower layer is the compound enzyme gel breaking capsule. Repeatedly washing with solvent oil, and drying. The evaluation method comprises the following steps:
the parameters of the fracturing fluid are as follows: and (2) taking a fracturing stock solution (consisting of 0.3% of guanidine gum, 2% of KCl, 0.5% of cleanup additive, 0.5% of demulsifier and 0.1% of bactericide) on site, adding complex enzyme gel breaking capsules with different concentrations, adding a cross-linking agent (the mass ratio of the cross-linking agent to the fracturing stock solution is 100: 1), and respectively measuring the viscosity of the fracturing fluid at different times. Wherein the concentrations in table 2 represent the viscosities (mPa · S) at different time points after treatment, relative to the mass of the enzyme component or the mass of sodium hypochlorite or the mass of ammonium persulfate in 1L of the fracturing fluid, as shown in table 2 below.
TABLE 2
The viscosity reducing agent of the embodiment 1 to 20 is adopted to treat fracturing flowback fluid obtained from a certain well in the Madong area of the Xinjiang oil field, and the parameters of the flowback fluid are as follows: viscosity of 8.03 mPa.S, suspended matter value of 1160mg/L, mineralization degree of 37142mg/L, chloride ion content of 22120mg/L, COD of 5439mg/L, BOD of 928mg/L, pH value of 5.7, undetermined oil content, and water type of CaCl2. Viscosity reduction agents of different types and concentrations were added, wherein the concentrations in table 3 represent the viscosity (mPa · S) at different time points after treatment relative to the mass of the enzyme component or the mass of sodium hypochlorite or the mass of ammonium persulfate in 1L of the fracturing fluid as shown in table 3 below.
TABLE 3
Tables 2 and 3 show that the viscosity reducer provided by the invention has good viscosity reducing and gel breaking effects on the fracturing fluid and the fracturing flowback fluid used on site, and compared with the conventional oxidation gel breaker sodium hypochlorite and ammonium persulfate, the viscosity reducer has higher gel breaking speed and lower dosage of the used agent. Meanwhile, because the fracturing fluid and the flowback fluid thereof contain a large amount of reducing substances, the oxidant can react with the reducing substances preferentially and then react with the guar gum to reduce the viscosity, so that the viscosity reduction efficiency of the conventional oxidant and enzyme compounded gel breaker is not improved compared with that of the single enzyme compounded gel breaker, and the viscosity reduction efficiency is reduced at the same dosing concentration. The conclusion shows that the biological complex enzyme has strong practicability for reducing viscosity and breaking gel of the fracturing fluid and the fracturing flow-back fluid of the guanidine gum system. The viscosity reducing agent has the advantages that the viscosity reducing effect on the fracturing flow-back fluid is not as outstanding as the viscosity reducing effect on the fracturing fluid, and the viscosity reducing agent is consistent with the performance of sodium hypochlorite and ammonium persulfate, and probably because the components in the fracturing flow-back fluid are complex.
In addition, the present application found that the mixing effect of each enzyme in the formed viscosity-reducing agent was changed by adjusting the stirring speed and the stirring time: the viscosity reducing effect of the formed viscosity reducing agent is better when the stirring time is longer under the same stirring speed, and the viscosity reducing effect of the formed viscosity reducing agent is better when the stirring time is higher under the same stirring speed, but the viscosity reducing effect is not continuously improved. In a word, no matter how the mixing effect of the enzymes is, the viscosity reducing effect is obviously better than that of the sodium hypochlorite and the ammonium persulfate which are commonly used at present.
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
the viscosity reducer does not contain an oxidation type chemical agent, enzymes of a complex enzyme component can directionally destroy glycosidic bonds in a guanidine gum molecular chain, the influence of oxidizable substances in fracturing fluid or flowback fluid is avoided, the gel breaking speed is high, the viscosity of the fracturing fluid or the flowback fluid can be quickly reduced to about 1mPa & lt.S, and compared with a conventional oxidation type gel breaker, the viscosity reducer is small in using amount, low in cost, high in safety and high in application value.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A viscosifier for viscosification of fracturing fluids or flowback fluids, wherein the viscosifier comprises an enzyme component comprising a combination of any one or more of mannanase, pectinase and cellulase.
2. The viscosity reducer of claim 1, wherein the viscosity reducer is comprised of the enzyme component dispersed in a dispersion medium, the enzyme component comprising, in weight percent: 50-75% of mannase, 10-20% of pectinase and 10-40% of cellulase, preferably, the enzyme components comprise: 57-75% of mannase, 12-20% of pectinase and 10-30% of cellulase.
3. The viscosity reducer of claim 1, wherein the specific activity of the mannanase is 40000U/g, preferably the specific activity of the pectinase is 30000U/g, more preferably the specific activity of the cellulase is 35000U/g, and preferably the pectinase is polygalacturonase.
4. The adhesion reducing agent of claim 2, wherein the dispersion medium comprises water.
5. The viscosity reducer according to claim 4, wherein the dispersion medium further comprises a pH regulator, preferably the pH regulator is an acid or an alkali, and the pH of the viscosity reducer is 5-8.
6. A compound enzyme gel breaking capsule, which comprises a viscosity reducer and a capsule coat, wherein the capsule coat wraps the viscosity reducer, and the viscosity reducer is the viscosity reducer of any one of claims 1 to 5.
7. A method of preparing the viscosity-reducing agent of any one of claims 1 to 5, wherein the enzyme component comprises a combination of any plurality of mannanase, pectinase, and cellulase, the method comprising: mixing any enzymes in the enzyme component.
8. The method according to claim 7, wherein the viscosity-reducing agent is composed of the enzyme component and a dispersion medium, and the method further comprises mixing the mixed enzyme component and the dispersion medium to obtain the viscosity-reducing agent.
9. The method of manufacturing according to claim 8, comprising:
adding at least part of the dispersion medium to the enzyme component to obtain a primary mixture;
stirring the primary mixture to form a stirring system, heating the stirring system to 50 ℃ in the stirring process, and controlling the pH value of the stirring system to be 5-8 to obtain the viscosity reducer, wherein preferably, the stirring speed is 50-100 r/min, and the stirring lasts for 40-60 hours.
10. A viscosity reducing method for fracturing fluid or flowback fluid, which is characterized in that the viscosity reducing agent of any one of claims 1 to 5 or the compound enzyme gel breaking capsule of claim 6 is adopted to reduce the viscosity of the fracturing fluid or the flowback fluid.
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| CN106566517A (en) * | 2016-10-21 | 2017-04-19 | 长江大学 | Low temperature gel breaking viscosity reducer of crosslinked guar gum backflow fracturing fluid, and preparation method thereof |
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2019
- 2019-05-05 CN CN201910369026.6A patent/CN111892920A/en active Pending
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101781552A (en) * | 2009-12-21 | 2010-07-21 | 陕西延长石油(集团)有限责任公司研究院 | Bio-enzyme gel breaker and technique for water-based guargum fracturing gel breaking with the same |
| US20130157905A1 (en) * | 2011-12-20 | 2013-06-20 | Halliburton Energy Services, Inc. | Method for the Removal or Suppression of Interfering Metal Ions Using Environmentally Friendly Competitive Binders |
| CN106566517A (en) * | 2016-10-21 | 2017-04-19 | 长江大学 | Low temperature gel breaking viscosity reducer of crosslinked guar gum backflow fracturing fluid, and preparation method thereof |
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