Method for low-temperature gel breaking of guar-based fracturing fluid by amino acid-modified prussian blue analog nanoszyme

Abstract

This invention relates to a method for low-temperature decomposition of guar gum-based fracturing fluid using an amino acid-modified Prussian blue-like nanozyme. The invention synthesizes an amino acid-stabilized copper-cobalt-based Prussian blue-like nanozyme using potassium cobalt cyanide as a reactant precursor, amino acids as stabilizers and modifiers, and copper sulfate as a precipitant. Adding this nanozyme and hydrogen peroxide simultaneously to a guar gum aqueous solution enables rapid decomposition and degradation of guar gum even at low temperatures. The advantages of this invention are its simple preparation method, high safety, ease of operation, and suitability for mass production; it exhibits high peroxidase-like activity under neutral and low-temperature conditions, rapidly degrading guar gum aqueous solutions in the presence of hydrogen peroxide; the reaction conditions are mild, requiring minimal equipment investment and offering good reproducibility; guar gum is widely used not only in petroleum but also in food, agriculture, textiles, papermaking, pharmaceuticals, water treatment, and cosmetics, thus this invention has significant value and importance.

Description

Technical Field

[0001] This invention relates to fracturing fluid degelling technology, specifically to a low-temperature degelling method for guar gum-based fracturing fluid using amino acid-modified Prussian blue nanozymes. Background Technology

[0002] In oil extraction, fracturing technology is one of the main methods for enhancing oil and gas well production and water injection well injection, with hydraulic fracturing accounting for over 70% of fracturing operations in China. Fracturing fluid, as the working fluid in hydraulic fracturing during oil and gas reservoir modification, plays a crucial role in creating formation fractures, transmitting pressure, and carrying proppant into the fractures. After the fracturing fluid completes its functions of creating fractures and carrying proppant, it needs to be rapidly broken up and flowed back to clear reservoir channels and improve oil and gas recovery. Referring to the petroleum industry standard SY / T 6376-2008 "General Technical Conditions for Fracturing Fluids," the viscosity value is measured using an Ubbelohde viscometer within 12 hours at the experimental temperature. A fracturing fluid viscosity less than 5 mPa·s is considered to be broken up.

[0003] Currently, water-based fracturing fluids are widely used both domestically and internationally, mainly including fracturing fluids based on guar gum and its derivatives, which are natural plant gums. Guar gum is the most viscous natural polymer and has the largest molecular weight among water-soluble polysaccharides. Currently, the methods for breaking up guar gum-based fracturing fluids are mainly divided into two categories: one uses natural enzymes to hydrolyze the glycosidic bonds in guar gum to obtain oligosaccharides, thus achieving the effect of breaking up the gum; the other is chemical degradation. Chemical degradation includes acid degradation and oxidative degradation. Oxidative degradation mainly uses persulfate and hydrogen peroxide to generate free radicals, causing the acetal bonds in plant gums and their derivatives to oxidize and break down, thereby degrading and breaking up the gum. However, the decomposition temperature of persulfate breaker is usually above 45℃, making it difficult to generate free radicals at low temperatures, thus hindering hydration and breaking up the gum; while hydrogen peroxide itself generates free radicals slowly and cannot be used alone, requiring the addition of an activator to achieve the desired degradation effect. Furthermore, most fracturing fluids currently in use operate under neutral conditions, and there are few reports on materials that can activate hydrogen peroxide to generate free radicals under neutral conditions. Therefore, developing materials that can catalyze the generation of free radicals from hydrogen peroxide at neutral and low temperatures is an important area of ​​research. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to utilize the peroxidase-like activity of amino acid-modified Prussian blue to catalyze the degradation of guar gum. This method can be carried out under neutral and low-temperature conditions, with mild reaction conditions, which greatly reduces production input costs.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for low-temperature gel breaking of guar gum-based fracturing fluid using amino acid-modified Prussian blue nanozymes, comprising the following steps:

[0007] 1) Add the freshly prepared potassium cobalt cyanide solution dropwise into the amino acid aqueous solution, and then stir at room temperature for 10-30 minutes;

[0008] 2) Slowly add freshly prepared copper sulfate solution to the solution in step 1), stir at room temperature for 0.5 to 2 hours, and then age at room temperature for 24 hours to obtain an amino acid-modified Prussian blue nanozyme aqueous solution.

[0009] 3) The obtained amino acid-modified Prussian blue nanozyme aqueous solution and hydrogen peroxide were added simultaneously to the guar gum-based fracturing fluid, and the gel was broken up at 10-40℃ for 10-110 min.

[0010] Furthermore, the molar ratio of the amino acid to potassium cobalt cyanide is 1 to 2:1; the concentration of the amino acid aqueous solution is 10 mM, and the concentration of the potassium cobalt cyanide solution is 50 mM.

[0011] Furthermore, the amino acids used are lysine, histidine, or arginine.

[0012] Furthermore, the concentration of the copper sulfate solution is 7.5 mM.

[0013] Furthermore, in step 3), the final concentrations of the amino acid-modified Prussian blue nanozyme aqueous solution and hydrogen peroxide in the guar gum-based fracturing fluid are 25 μM and 30 mM, respectively.

[0014] Natural enzyme degradation of guar gum is limited by temperature and pH conditions, easily leading to inactivation, and is also costly, hindering large-scale application. This invention synthesizes an amino acid-stabilized copper-cobalt-based Prussian blue-like nanozyme using potassium cobalt cyanide as a reactant precursor, amino acids as stabilizers and modifiers, and copper sulfate as a precipitant. Adding this nanozyme simultaneously with hydrogen peroxide to a guar gum aqueous solution enables rapid degradation of guar gum even at low temperatures. The amino acid-modified Prussian blue-like nanozyme synthesized in this invention exhibits a significantly improved low-temperature degradation rate compared to unmodified copper-cobalt-based Prussian blue-like nanozymes.

[0015] The beneficial effects of this invention are:

[0016] 1. The preparation method of amino acid-modified Prussian blue-like nanozymes is simple, safe, easy to operate, and suitable for mass production.

[0017] 2. It exhibits high peroxidase-like activity under neutral and low-temperature conditions, and can rapidly degrade guar gum aqueous solutions in the presence of hydrogen peroxide. The reaction conditions are mild, require less equipment investment, and have good reproducibility.

[0018] 3. Guar gum is not only widely used in petroleum, but also in food, agriculture, textiles, papermaking, pharmaceuticals, water treatment and cosmetics. Therefore, this invention has important value and significance. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a TEM image of the histidine-modified Prussian blue-like nanozyme of experimental sample 1.

[0021] Figure 2 This is a graph showing the degradation curves of guar gum catalyzed by experimental sample 1 at different temperatures.

[0022] Figure 3 These are the degradation curves of guar gum catalyzed by experimental samples 1-3 and the control sample at 20℃. Detailed Implementation

[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] I. Preparation of amino acid-modified Prussian blue-like nanozymes

[0026] Experimental Sample 1: Histidine-modified Prussian blue-like nanozyme

[0027] The first step involves dispersing 10 mM amino acid powder (15.5 mg histidine powder) in 8 mL of ultrapure water at 25 °C and stirring until the histidine is completely dissolved.

[0028] The second step is to slowly add 1 mL of freshly prepared 50 mM potassium cobalt cyanide aqueous solution to the histidine solution, and stir continuously at 800 r / min for 10 min.

[0029] In the third step, 1 mL of freshly prepared 100 mM copper sulfate solution was slowly added dropwise to the solution from the second step, and the reaction was continuously stirred at 800 r / min for 0.5 h. Finally, the mixture was aged at room temperature for 24 h, centrifuged and washed, and then dissolved in ultrapure water to prepare histidine-modified Prussian blue nanozyme, which was then stored at 4 °C for later use.

[0030] like Figure 1 The image shows a TEM image of the histidine-modified Prussian blue nanozyme prepared in Example 1. The image shows that the nanozyme has a chain network structure.

[0031] Experimental Sample 2: Lysine-modified Prussian blue-like nanozyme

[0032] The preparation steps are the same as in Example 1, except that 15.5 mg of histidine powder is replaced with 14.6 mg of lysine powder.

[0033] Experimental Sample 3: Arginine-modified Prussian blue-like nanozyme

[0034] The preparation steps are the same as in Example 1, except that 17.4 mg of histidine powder is replaced with 17.4 mg of arginine powder.

[0035] Comparison Sample 1: Prussian blue-like nanozymes without amino acid modification

[0036] In the first step, at 25°C, 1 mL of freshly prepared 40 mM potassium cobalt cyanide aqueous solution was slowly added dropwise to 8 mL of ultrapure water, and the mixture was stirred continuously at 900 r / min for 10 min. In the second step, 1 mL of freshly prepared 80 mM copper sulfate solution was slowly added dropwise to the solution from the second step, and the mixture was stirred continuously at 900 r / min for 1 h. Finally, the mixture was aged at room temperature for 24 h, centrifuged and washed, and then dissolved in ultrapure water to prepare an amino acid-free Prussian blue-like nanozyme, which was then stored at 4°C for later use.

[0037] II. Catalytic Degradation of Guar Gum

[0038] Experiment 1:

[0039] Preparation of guar gum aqueous solution to simulate guar gum-based fracturing fluid: Add 30 mg / mL guar gum powder to 9.8 mL of ultrapure water to prepare a guar gum solution with a mass fraction of 0.3%, and stir at 40 °C until completely hydrated.

[0040] Gum breaking: Add 100 μL or more of the Prussian blue nanozyme prepared in Example 1 and 100 μL of 3M hydrogen peroxide to the above-mentioned 0.3% guar gum solution to form a solution with a total volume of 10 mL.

[0041] After stirring evenly, add 10 mL of the above solution to the Ubbelohde viscometer. Place the Ubbelohde viscometer in a 40°C constant temperature bath and let it stand for 3 minutes. Measure the relative viscosity based on the time it takes for the liquid to flow through the bath and plot the relationship between time and relative viscosity. If the guar gum viscosity is less than 5 mPa·s, the guar gum aqueous solution is considered to have been degraded and broken down.

[0042] Experiment 2:

[0043] Similar to Experiment 1, except that the temperature condition was set to 30℃.

[0044] Experiment 3:

[0045] Similar to Experiment 1, except that the temperature condition was set to 20℃.

[0046] Depend on Figure 2 As can be seen, the ability of histidine-modified copper-cobalt-based Prussian blue nanozymes to catalyze the degradation of guar gum increases with increasing temperature. At 40℃, it only takes 10 minutes to catalyze the degradation of guar gum to a relative viscosity of less than 5 mPa·s, and even at a lower temperature of 20℃, it only takes 110 minutes to catalyze the degradation of guar gum to a relative viscosity of less than 5 mPa·s.

[0047] Experiment 4:

[0048] Similar to Experiment 3, except that the histidine-modified Prussian blue nanozyme was replaced with the lysine-modified Prussian blue nanozyme from Experiment 2.

[0049] Experiment 5:

[0050] Similar to Experiment 3, except that the histidine-modified Prussian blue-like nanozyme was replaced with the arginine-modified Prussian blue-like nanozyme of Experiment 3.

[0051] Experiment 6:

[0052] Similar to Experiment 3, except that the histidine-modified Prussian blue nanozyme was replaced with the unmodified Prussian blue nanozyme of control sample 1.

[0053] Depend on Figure 3 The results show that lysine- or arginine-modified copper-cobalt-based Prussian blue nanozymes reduced the relative viscosity of guar gum aqueous solutions to below 5 mPa·s at 20°C in approximately 4 h and 6 h, respectively. Compared to the unmodified copper-cobalt-based Prussian blue nanozymes, which required 17 h at 20°C to reduce the relative viscosity of guar gum aqueous solutions to below 5 mPa·s, this demonstrates that lysine- or histidine-modified copper-cobalt-based Prussian blue nanozymes can also be used for the decomposition and degradation of guar gum at low temperatures.

[0054] This invention is the first to combine nanozymes with petroleum extraction technology, developing a method that, under neutral and low-temperature conditions, catalyzes the generation of free radicals from hydrogen peroxide to oxidize and break the acetal bonds in plant gums, including guar gum, and their derivatives, thereby achieving degradation and gum breakdown. Since guar gum is widely used not only in petroleum but also in food, agriculture, textiles, papermaking, pharmaceuticals, water treatment, and cosmetics, this invention has significant value and importance.

[0055] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for low-temperature gel breaking of guar gum-based fracturing fluid using amino acid-modified Prussian blue-like nanozymes, characterized in that, Includes the following steps: 1) Add the freshly prepared potassium cobalt cyanide solution dropwise into the amino acid aqueous solution, and then stir at room temperature for 10-30 minutes; 2) Slowly add freshly prepared copper sulfate solution to the mixed solution in step 1), stir at room temperature for 0.5 to 2 h, and then age at room temperature for 24 h to obtain an amino acid-modified Prussian blue nanozyme aqueous solution; 3) The obtained amino acid-modified Prussian blue nanozyme aqueous solution and hydrogen peroxide were added simultaneously to the guar gum-based fracturing fluid, and the gel was broken up at 10~40 ℃ for 10~110 min; The amino acids used are lysine, histidine, or arginine. The molar ratio of the amino acid to potassium cobalt cyanide is 1 to 2:1; the concentration of the amino acid aqueous solution is 10 mM, and the concentration of the potassium cobalt cyanide solution is 50 mM.

2. The method for low-temperature gel breaking of guar gum-based fracturing fluid using amino acid-modified Prussian blue nanozymes as described in claim 1, characterized in that, The concentration of the copper sulfate solution is 7.5 mM.

3. The method for low-temperature gel breaking of guar gum-based fracturing fluid using amino acid-modified Prussian blue nanozymes as described in claim 1, characterized in that... In step 3), the final concentrations of the amino acid-modified Prussian blue nanozyme aqueous solution and hydrogen peroxide in the guar gum-based fracturing fluid are 25 μM and 30 mM, respectively.

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