High-temperature-resistant and salt-tolerant fracturing fluid and preparation method thereof

Abstract

The application discloses a high-temperature-resistant and salt-resistant fracturing fluid and a preparation method thereof, and relates to the technical field of oilfield fracturing fluids. In the preparation of the high-temperature-resistant and salt-resistant fracturing fluid, 3-chloro-2-hydroxypropane sulfonic acid sodium, N,N-dimethyl acrylamide and ethylene glycol are reacted to obtain a quaternary ammonium solid product, and the quaternary ammonium solid product is reacted with 1-bromooctadecane to obtain an amphoteric hydrophobic monomer; guar gum powder is reacted with 3-(1-naphthoxy)-1,2-epoxypropane to obtain naphthoxy functionalized guar gum, and then the naphthoxy functionalized guar gum is polymerized with acrylamide and the amphoteric hydrophobic monomer by using ammonium cerium nitrate as an initiator to obtain modified guar gum; zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine and glycerol are reacted to obtain an organic zirconium crosslinking agent; and finally, the modified guar gum, the organic zirconium crosslinking agent, sodium thiosulfate, sodium bromate, a surfactant and water are mixed to obtain the high-temperature-resistant and salt-resistant fracturing fluid. The high-temperature-resistant and salt-resistant fracturing fluid prepared by the application has excellent high-temperature resistance and salt resistance.

Description

Technical Field

[0001] This invention relates to the field of oilfield fracturing fluid technology, specifically to a high-temperature and salt-resistant fracturing fluid and its preparation method. Background Technology

[0002] Fracturing fluid is a key component of oil and gas well fracturing technology, and its performance directly affects the effectiveness of reservoir stimulation. Guar gum and its derivatives are often used as thickeners for water-based fracturing fluids due to their wide availability, low cost, and good thickening properties. Guar gum derivatives obtained through modification methods such as hydroxypropylation have improved temperature and salt resistance to a certain extent, meeting the fracturing requirements of conventional oil and gas reservoirs.

[0003] However, as unconventional oil and gas resource exploitation moves towards deeper and higher-temperature formations, the downhole environment is becoming increasingly complex, often facing severe challenges such as temperatures exceeding 150°C and formation water concentrations of tens of thousands of milligrams per cubic meter of high salinity. Under these extreme conditions, existing conventional modified guar gum fracturing fluids exhibit significant limitations: their molecular chains are prone to breakage and degradation at high temperatures, and in high-salt environments, the chains coil and hydration capacity decreases dramatically, leading to a sharp drop in solution viscosity, poor sand-suspending performance, and ultimately affecting the conductivity of the fracturing fractures, thus hindering the effective development of high-temperature and high-salt reservoirs. Therefore, there is an urgent need to develop a new type of high-temperature and salt-resistant fracturing fluid that can maintain structural stability and excellent rheological properties even under extreme conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature and salt-resistant fracturing fluid and its preparation method, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A high-temperature and salt-resistant fracturing fluid is prepared by mixing modified guar gum, organozirconium crosslinking agent, magnesium oxide, sodium citrate, calcium chloride, surfactant and water.

[0007] As an optimization, the modified guar gum is prepared by reacting guar gum powder with 3-(1-naphthoxy)-1,2-epoxypropane to obtain naphthoxy-functionalized guar gum, and then polymerizing it with acrylamide and an amphoteric hydrophobic monomer via cerium ammonium nitrate-initiated polymerization.

[0008] As an optimization, the amphoteric hydrophobic monomer is prepared by reacting sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethylacrylamide and ethylene glycol to obtain a quaternized solid product, which is then reacted with 1-bromooctadecane and the like.

[0009] As an optimization, the organozirconium crosslinking agent is prepared by reacting zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine and glycerol.

[0010] A method for preparing a high-temperature and salt-resistant fracturing fluid includes the following preparation steps:

[0011] (1) Weigh sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethylacrylamide, and ethylene glycol in a mass ratio of 1:(0.49~0.51):(2.5~3.5). Mix sodium 3-chloro-2-hydroxypropanesulfonate with ethylene glycol and stir at 60~80℃ and 200~400r / min for 20~30min. Add N,N-dimethylacrylamide dropwise within 30min and continue stirring for 5~7h. During this period, maintain the pH at 7.5~8.5 with 40wt% sodium hydroxide aqueous solution. Rotary evaporate to obtain the quaternized solid product. 1:(1.8~1.92):(0.4~0.6):(0.15~0.17):(2~2.5) Weigh the quaternized solid product, 1-bromooctadecane, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether. Mix the quaternized solid product, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether, stir at 80~90℃ and 200~400r / min for 20~30min, add 1-bromooctadecane dropwise, continue stirring for 2~4h, and evaporate under reduced pressure to obtain the amphoteric hydrophobic monomer;

[0012] (2) Weigh guar gum powder, 3-(1-naphthoxy)-1,2-epoxypropane, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol at a mass ratio of 1:(0.16~0.2):(0.28~0.32):(5.5~6.5). Mix the guar gum powder, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol, and stir at 25~30℃ and 400~600r / min for 3~4h. Add 3-(1-naphthoxy)-1,2-epoxypropane, raise the temperature to 40~50℃ and continue stirring for 1.5~2.5h. Adjust the pH to 6.5~7.5 with 10wt% hydrochloric acid aqueous solution. Collect the solid by suction filtration, wash with ethanol, and dry to obtain naphthoxy-functionalized guar gum. Add acrylamide, amphoteric hydrophobic monomer, and Span-8. 0. Tween-80 and deionized water were mixed and dissolved in a mass ratio of 1:(0.007~0.009):(1.2~1.4):(0.08~0.1):(1.6~2). The pH was adjusted to 6.5~7.5 with 45wt% sodium hydroxide aqueous solution to obtain a mixed emulsion. Naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water were mixed in a mass ratio of 1:(0.6~0.7):(500~550). The mixture was stirred at 25~30℃ and 400~600r / min for 20~30min. A mixed emulsion with a mass of 19~21 times that of naphthoxy-functionalized guar gum was added dropwise. The temperature was raised to 50~60℃ and stirring was continued for 20~28h. The solid was collected by acetone precipitation, washed with acetone, and post-treated to obtain modified guar gum.

[0013] (3) Weigh zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine, glycerol, and deionized water in a mass ratio of 1:(0.148~0.152):(0.4~0.6):(1.2~1.3):(3~5):(4~5). Mix the water and glycerol, heat to 50~60℃, add zirconium oxychloride octahydrate and titanium chloride while stirring at 200~400 r / min, react for 2~4 h, then add lactic acid and ethylenediamine dropwise and continue the reaction for 4~6 h to obtain the organozirconium crosslinking agent; prepare fracturing fluid according to the following mass ratio: 0.5% ~0.8% modified guar gum, 0.02%~0.04% organozirconium crosslinking agent, 0.8%~1% sodium thiosulfate, 0.06%~0.1% sodium bromate, 0.04%~0.08% surfactant FS-1120, and the balance is water; mix the polymer emulsion with water, stir at 25~30℃ and 1000~1400 r / min for 20~40 min, add organozirconium crosslinking agent, continue stirring for 20~30 min, and then add sodium bromate, sodium thiosulfate and surfactant in sequence to prepare high temperature and salt resistant fracturing fluid.

[0014] As an optimization, the reaction process of the amphoteric hydrophobic monomer in step (1) is as follows:

[0015] .

[0016] As an optimization, the guar gum powder in step (2) is industrial grade and manufactured by Renqiu Shuoda Chemical Co., Ltd.

[0017] As an optimization, the reaction process of the modified guar gum in step (2) is as follows:

[0018] .

[0019] As an optimization, the post-processing process in step (2) is as follows: after washing with acetone, the mixture of glacial acetic acid and N,N-dimethylformamide in a volume ratio of 1:1 is refluxed at 75~85℃, the solvent is added to acetone for precipitation, the filtrate is collected by filtration and dried to constant weight to obtain modified guar gum.

[0020] As an optimization, the active ingredient content of surfactant FS-1120 in step (3) is 100%, and the manufacturer is Hunan Nonferrous Chenzhou Fluorochemical Co., Ltd.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0022] In preparing a high-temperature and salt-resistant fracturing fluid, this invention involves reacting sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethylacrylamide, and ethylene glycol to obtain a quaternized solid product, which is then reacted with 1-bromooctadecane to obtain an amphoteric hydrophobic monomer. Guar gum powder is reacted with 3-(1-naphthoxy)-1,2-epoxypropane to obtain naphthoxy-functionalized guar gum, which is then polymerized with acrylamide and the amphoteric hydrophobic monomer via cerium ammonium nitrate-initiated polymerization to obtain modified guar gum. Zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine, and glycerol are reacted to obtain an organozinc crosslinking agent. Finally, the modified guar gum, organozinc crosslinking agent, magnesium oxide, sodium citrate, calcium chloride, surfactant, and water are mixed to obtain the high-temperature and salt-resistant fracturing fluid.

[0023] First, an amphoteric hydrophobic monomer integrating sulfonic acid groups, quaternary ammonium salts, and long-chain alkyl groups was synthesized by stepwise reaction of sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethylacrylamide, and 1-bromooctadecane. This monomer was then grafted and copolymerized with acrylamide onto a naphthoxy-functionalized guar gum backbone to obtain modified guar gum that simultaneously incorporates rigid naphthalene rings, anionic sulfonic acid groups, cationic quaternary ammonium salts, and hydrophobic long chains. The rigid naphthalene rings effectively enhance the rigidity of the polymer backbone, resisting chain curling and degradation caused by high temperatures. The copolymer side chains simultaneously incorporate sulfonic acid groups, quaternary ammonium salt zwitterionic groups, and long-chain alkyl groups. The zwitterionic groups maintain the extended state of the molecular chains in salt solutions through strong hydration, while the hydrophobic long chains can form a dynamically reversible hydrophobic association physical cross-linking network in water, thereby synergistically endowing the fracturing fluid base with excellent thickening ability, temperature resistance, and salt resistance.

[0024] Secondly, the prepared organozirconium crosslinking agent and modified guar gum constitute a highly synergistic crosslinking system. This organozirconium crosslinking agent is a polynuclear organometallic compound with zirconium and titanium as its core. The metal ions in its molecules can efficiently coordinate with the abundant hydroxyl and sulfonic acid groups on the modified guar gum molecular chain, rapidly constructing a dense and stable "metal-organic" three-dimensional network structure. This transforms the linear chain structure of the polymer into a spatial network structure, greatly improving the viscoelasticity, shear resistance, and sand-suspending capacity of the fracturing fluid. This stable crosslinking network formed by the synergistic effect of the polymer with a specific structure and the polynuclear metal crosslinking agent is the fundamental reason why the fracturing fluid's performance does not degrade under extreme high-temperature and high-salt conditions. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] To more clearly illustrate the method provided by the present invention, the following embodiments will be described in detail.

[0027] Example 1:

[0028] A method for preparing a high-temperature and salt-resistant fracturing fluid includes the following preparation steps:

[0029] (1) Weigh sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethylacrylamide and ethylene glycol in a mass ratio of 1:0.49:2.5. Mix sodium 3-chloro-2-hydroxypropanesulfonate with ethylene glycol and stir at 60°C and 200 r / min for 20 min. Add N,N-dimethylacrylamide dropwise over 30 min and continue stirring for 5 h. During this period, maintain the pH at 7.5 with 40 wt% sodium hydroxide aqueous solution. Rotary evaporate to obtain the quaternized solid product. Weigh the quaternized solid product, 1-bromooctadecane, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether according to the mass ratio 1:1.8:0.4:0.15:2. Mix the quaternized solid product, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether, stir at 80℃ and 200r / min for 20min, add 1-bromooctadecane dropwise, continue stirring for 2h, and evaporate under reduced pressure to obtain the amphoteric hydrophobic monomer.

[0030] (2) Weigh guar gum powder, 3-(1-naphthoxy)-1,2-epoxypropane, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol in a mass ratio of 1:0.16:0.28:5.5. Mix the guar gum powder, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol, stir at 25℃ and 400r / min for 3h, add 3-(1-naphthoxy)-1,2-epoxypropane, heat to 40℃ and continue stirring for 1.5h, adjust the pH to 6.5 with 10wt% hydrochloric acid aqueous solution, filter to collect the solid, wash with ethanol, dry to obtain naphthoxy-functionalized guar gum; add acrylamide, Amphoteric hydrophobic monomers, Span-80, Tween-80, and deionized water were mixed and dissolved in a mass ratio of 1:0.007:1.2:0.08:1.6. The pH was adjusted to 6.5 with 45wt% sodium hydroxide aqueous solution to obtain a mixed emulsion. Naphthoxy-functionalized guar gum, cerium ammonium nitrate, and deionized water were mixed in a mass ratio of 1:0.65:500 and stirred at 25℃ and 400r / min for 20min. A mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum was added dropwise. The temperature was raised to 55℃ and stirring was continued for 20h. The solid was collected by acetone precipitation and washed with acetone to obtain modified guar gum.

[0031] (3) Weigh zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine, glycerol and deionized water in a mass ratio of 1:0.148:0.4:1.2:3:4. Mix water and glycerol, heat to 50°C, add zirconium oxychloride octahydrate and titanium chloride while stirring at 200 r / min, react for 2 h, then add lactic acid and ethylenediamine dropwise and continue the reaction for 4 h to obtain organozirconium crosslinking agent. Prepare fracturing fluid according to the following mass ratio: 0.5% modified guar gum, 0.03% organozirconium crosslinking agent, 0.8% sodium thiosulfate, 0.06% sodium bromate, 0.04% surfactant FS-1120, and the remainder is water. Mix the polymer emulsion with water, stir at 25°C and 1000 r / min for 20 min, add organozirconium crosslinking agent, continue stirring for 20 min, then add sodium bromate, sodium thiosulfate and surfactant in sequence to obtain high temperature and salt resistant fracturing fluid.

[0032] Example 2:

[0033] A method for preparing a high-temperature and salt-resistant fracturing fluid includes the following preparation steps:

[0034] (1) Weigh sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethylacrylamide, and ethylene glycol in a mass ratio of 1:0.5:3. Mix sodium 3-chloro-2-hydroxypropanesulfonate with ethylene glycol and stir at 70°C and 300 r / min for 25 min. Add N,N-dimethylacrylamide dropwise over 30 min and continue stirring for 6 h. During this period, maintain the pH at 8 with 40 wt% sodium hydroxide aqueous solution. Rotary evaporate to obtain the quaternized solid product. Weigh out the quaternized solid product, 1-bromooctadecane, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether in a ratio of 1:1.86:0.5:0.16:2.3. Mix the quaternized solid product, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether, stir at 85℃ and 300r / min for 25min, add 1-bromooctadecane dropwise, continue stirring for 3h, and evaporate under reduced pressure to obtain the amphoteric hydrophobic monomer.

[0035] (2) Weigh guar gum powder, 3-(1-naphthoxy)-1,2-epoxypropane, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol according to a mass ratio of 1:0.18:0.3:6. Mix the guar gum powder, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol, stir at 27℃ and 500r / min for 3.5h, add 3-(1-naphthoxy)-1,2-epoxypropane, heat to 45℃ and continue stirring for 2h, adjust the pH to 7 with 10wt% hydrochloric acid aqueous solution, filter to collect the solid, wash with ethanol, dry, and obtain naphthoxy-functionalized guar gum; add acrylamide, amphoteric hydrochloride... Aqueous monomers, Span-80, Tween-80, and deionized water were mixed and dissolved in a mass ratio of 1:0.008:1.3:0.09:1.8. The pH was adjusted to 7 with a 45wt% sodium hydroxide aqueous solution to obtain a mixed emulsion. Naphthoxy-functionalized guar gum, cerium ammonium nitrate, and deionized water were mixed in a mass ratio of 1:0.65:530 and stirred at 27℃ and 500r / min for 25min. A mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum was added dropwise. The temperature was raised to 55℃ and stirring was continued for 24h. The solid was collected by acetone precipitation, washed with acetone, and post-treated to obtain modified guar gum.

[0036] (3) Weigh zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine, glycerol and deionized water in a mass ratio of 1:0.15:0.5:1.25:4:4.5. Mix water and glycerol, heat to 55°C, add zirconium oxychloride octahydrate and titanium chloride while stirring at 300 r / min, react for 3 h, add lactic acid and ethylenediamine dropwise and continue the reaction for 5 h to obtain organozirconium crosslinking agent; prepare fracturing fluid according to the following mass ratio: 0.7% modified guar gum, 0.03% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the remainder is water; mix polymer emulsion with water, stir at 27°C and 1200 r / min for 30 min, add organozirconium crosslinking agent, continue stirring for 25 min, and then add sodium bromate, sodium thiosulfate and surfactant in sequence to obtain high temperature and salt resistant fracturing fluid.

[0037] Example 3:

[0038] A method for preparing a high-temperature and salt-resistant fracturing fluid includes the following preparation steps:

[0039] (1) Weigh sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethylacrylamide, and ethylene glycol in a mass ratio of 1:0.5:1:3.5. Mix sodium 3-chloro-2-hydroxypropanesulfonate with ethylene glycol and stir at 80°C and 400 r / min for 30 min. Add N,N-dimethylacrylamide dropwise within 30 min and continue stirring for 7 h. During this period, maintain the pH at 8.5 with 40 wt% sodium hydroxide aqueous solution. Rotary evaporate to obtain the quaternized solid product. Weigh out the quaternized solid product, 1-bromooctadecane, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether in a mass ratio of 1:1.92:0.6:0.17:2.5. Mix the quaternized solid product, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether, stir at 80℃ and 200r / min for 20min, add 1-bromooctadecane dropwise, continue stirring for 2h, and evaporate under reduced pressure to obtain the amphoteric hydrophobic monomer.

[0040] (2) Weigh guar gum powder, 3-(1-naphthoxy)-1,2-epoxypropane, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol in a mass ratio of 1:0.16:0.28:5.5. Mix the guar gum powder, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol, stir at 30℃ and 600r / min for 4h, add 3-(1-naphthoxy)-1,2-epoxypropane, heat to 50℃ and continue stirring for 2.5h, adjust the pH to 7.5 with 10wt% hydrochloric acid aqueous solution, filter to collect the solid, wash with ethanol, dry to obtain naphthoxy-functionalized guar gum; add acrylamide, Amphoteric hydrophobic monomers, Span-80, Tween-80, and deionized water were mixed and dissolved in a mass ratio of 1:0.009:1.4:0.1:2. The pH was adjusted to 7.5 with 45wt% sodium hydroxide aqueous solution to obtain a mixed emulsion. Naphthoxy-functionalized guar gum, cerium ammonium nitrate, and deionized water were mixed in a mass ratio of 1:0.65:550 and stirred at 30℃ and 600r / min for 30min. A mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum was added dropwise. The temperature was raised to 55℃ and stirring was continued for 28h. The solid was collected by acetone precipitation, washed with acetone, and post-treated to obtain modified guar gum.

[0041] (3) Weigh zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine, glycerol and deionized water in a mass ratio of 1:0.148:0.4:1.2:3:4. Mix water and glycerol, heat to 60°C, add zirconium oxychloride octahydrate and titanium chloride while stirring at 400 r / min, react for 4 h, add lactic acid and ethylenediamine dropwise and continue the reaction for 6 h to obtain organozirconium crosslinking agent; prepare fracturing fluid according to the following mass ratio: 0.8% modified guar gum, 0.03% organozirconium crosslinking agent, 1% sodium thiosulfate, 0.1% sodium bromate, 0.08% surfactant FS-1120, and the remainder is water; mix polymer emulsion with water, stir at 30°C and 1400 r / min for 40 min, add organozirconium crosslinking agent, continue stirring for 30 min, and then add sodium bromate, sodium thiosulfate and surfactant in sequence to obtain high temperature and salt resistant fracturing fluid.

[0042] Comparative Example 1:

[0043] The only difference from Example 2 is the step (2), where “mixing naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water in a mass ratio of 1:0.65:530” is changed to “mixing naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water in a mass ratio of 1:0.5:530”.

[0044] Comparative Example 2:

[0045] The only difference from Example 2 is the step (2), where “mixing naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water in a mass ratio of 1:0.65:530” is changed to “mixing naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water in a mass ratio of 1:0.6:530”.

[0046] Comparative Example 3:

[0047] The only difference from Example 2 is the step (2), which changes "mixing naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water in a mass ratio of 1:0.65:530" to "mixing naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water in a mass ratio of 1:0.7:530".

[0048] Comparative Example 4:

[0049] The only difference from Example 2 is the step (2), where “mixing naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water in a mass ratio of 1:0.65:530” is changed to “mixing naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water in a mass ratio of 1:0.8:530”.

[0050] Comparative Example 5:

[0051] The only difference from Example 2 is step (2), where “adding a mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum” is changed to “adding a mixed emulsion with a mass of 18 times that of naphthoxy-functionalized guar gum”.

[0052] Comparative Example 6:

[0053] The only difference from Example 2 is step (2), where “adding a mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum” is changed to “adding a mixed emulsion with a mass of 19 times that of naphthoxy-functionalized guar gum”.

[0054] Comparative Example 7:

[0055] The only difference from Example 2 is step (2), where “adding a mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum” is changed to “adding a mixed emulsion with a mass of 21 times that of naphthoxy-functionalized guar gum”.

[0056] Comparative Example 8:

[0057] The only difference from Example 2 is step (2), where “adding a mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum” is changed to “adding a mixed emulsion with a mass of 22 times that of naphthoxy-functionalized guar gum”.

[0058] Comparative Example 9:

[0059] The only difference from Example 2 is the difference in step (2). In step (2), "mix naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water at a mass ratio of 1:0.65:530, stir at 27°C and 500 r / min for 25 min, add dropwise a mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum, raise the temperature to 55°C, continue stirring for 24 h, collect the solid by acetone precipitation, wash with acetone, and perform post-treatment to obtain modified guar gum", the "raise the temperature to 55°C" is changed to "raise the temperature to 40°C".

[0060] Comparative Example 10:

[0061] The only difference from Example 2 is step (2), where “heating to 55°C” is changed to “heating to 50°C”.

[0062] Comparative Example 11:

[0063] The only difference from Example 2 is step (2), where “heating to 55°C” is changed to “heating to 60°C”.

[0064] Comparative Example 12:

[0065] The only difference from Example 2 is step (2), where “heating to 55°C” is changed to “heating to 70°C”.

[0066] Comparative Example 13:

[0067] The only difference from Example 2 is step (3), where “the fracturing fluid is prepared according to the following mass ratio: 0.7% modified guar gum, 0.03% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the balance is water” is changed to “the fracturing fluid is prepared according to the following mass ratio: 0.7% modified guar gum, 0.01% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the balance is water”.

[0068] Comparative Example 14:

[0069] The only difference from Example 2 is step (3), where “the fracturing fluid is prepared according to the following mass ratio: 0.7% modified guar gum, 0.03% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the balance is water” is changed to “the fracturing fluid is prepared according to the following mass ratio: 0.7% modified guar gum, 0.02% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the balance is water”.

[0070] Comparative Example 15:

[0071] The only difference from Example 2 is step (3), where “the fracturing fluid is prepared according to the following mass ratio: 0.7% modified guar gum, 0.03% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the balance is water” is changed to “the fracturing fluid is prepared according to the following mass ratio: 0.7% modified guar gum, 0.04% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the balance is water”.

[0072] Comparative Example 16:

[0073] The only difference from Example 2 is step (3), where “the fracturing fluid is prepared according to the following mass ratio: 0.7% modified guar gum, 0.03% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the balance is water” is changed to “the fracturing fluid is prepared according to the following mass ratio: 0.7% modified guar gum, 0.05% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the balance is water”.

[0074] Comparative Example 17:

[0075] A method for preparing a high-temperature and salt-resistant fracturing fluid includes the following preparation steps:

[0076] (1) Weigh sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethylacrylamide, and ethylene glycol in a mass ratio of 1:0.5:3. Mix sodium 3-chloro-2-hydroxypropanesulfonate with ethylene glycol and stir at 70°C and 300 r / min for 25 min. Add N,N-dimethylacrylamide dropwise over 30 min and continue stirring for 6 h. During this period, maintain the pH at 8 with 40 wt% sodium hydroxide aqueous solution. Rotary evaporate to obtain the quaternized solid product. Weigh out the quaternized solid product, 1-bromooctadecane, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether in a ratio of 1:1.86:0.5:0.16:2.3. Mix the quaternized solid product, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether, stir at 85℃ and 300r / min for 25min, add 1-bromooctadecane dropwise, continue stirring for 3h, and evaporate under reduced pressure to obtain the amphoteric hydrophobic monomer.

[0077] (2) Acrylamide, amphoteric hydrophobic monomer, Span-80, Tween-80 and deionized water were mixed and dissolved in a mass ratio of 1:0.008:1.3:0.09:1.8. The pH was adjusted to 7 with 45wt% sodium hydroxide aqueous solution to obtain a mixed emulsion. Guar gum powder, cerium ammonium nitrate and deionized water were mixed in a mass ratio of 1:0.65:530. The mixture was stirred at 27℃ and 500r / min for 25min. A mixed emulsion with a mass of 20 times that of guar gum powder was added dropwise. The temperature was raised to 55℃ and stirring was continued for 24h. The solid was collected by acetone precipitation, washed with acetone, and post-treated to obtain modified guar gum.

[0078] (3) Weigh zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine, glycerol and deionized water in a mass ratio of 1:0.15:0.5:1.25:4:4.5. Mix water and glycerol, heat to 55°C, add zirconium oxychloride octahydrate and titanium chloride while stirring at 300 r / min, react for 3 h, add lactic acid and ethylenediamine dropwise and continue the reaction for 5 h to obtain organozirconium crosslinking agent; prepare fracturing fluid according to the following mass ratio: 0.7% modified guar gum, 0.03% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the remainder is water; mix polymer emulsion with water, stir at 27°C and 1200 r / min for 30 min, add organozirconium crosslinking agent, continue stirring for 25 min, and then add sodium bromate, sodium thiosulfate and surfactant in sequence to obtain high temperature and salt resistant fracturing fluid.

[0079] Comparative Example 18:

[0080] A method for preparing a high-temperature and salt-resistant fracturing fluid includes the following preparation steps:

[0081] (1) Weigh guar gum powder, 3-(1-naphthoxy)-1,2-epoxypropane, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol according to a mass ratio of 1:0.18:0.3:6. Mix the guar gum powder, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol, stir at 27℃ and 500r / min for 3.5h, add 3-(1-naphthoxy)-1,2-epoxypropane, heat to 45℃ and continue stirring for 2h, adjust the pH to 7 with 10wt% hydrochloric acid aqueous solution, filter to collect the solid, wash with ethanol, dry and obtain naphthoxy Functionalized guar gum: Acrylamide and deionized water were mixed and dissolved at a mass ratio of 1:1.8, and the pH was adjusted to 7 with 45wt% sodium hydroxide aqueous solution to obtain a mixed emulsion; Naphthoxy-functionalized guar gum, cerium ammonium nitrate and deionized water were mixed at a mass ratio of 1:0.65:530, stirred at 27℃ and 500r / min for 25min, and a mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum was added dropwise, the temperature was raised to 55℃, and stirring was continued for 24h. The solid was collected by acetone precipitation, washed with acetone, and post-treated to obtain modified guar gum;

[0082] (2) Weigh zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine, glycerol and deionized water in a mass ratio of 1:0.15:0.5:1.25:4:4.5. Mix water and glycerol, heat to 55°C, add zirconium oxychloride octahydrate and titanium chloride while stirring at 300 r / min, react for 3 h, add lactic acid and ethylenediamine dropwise and continue the reaction for 5 h to obtain organozirconium crosslinking agent; prepare fracturing fluid according to the following mass ratio: 0.7% modified guar gum, 0.03% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the remainder is water; mix polymer emulsion with water, stir at 27°C and 1200 r / min for 30 min, add organozirconium crosslinking agent, continue stirring for 25 min, and then add sodium bromate, sodium thiosulfate and surfactant in sequence to obtain high temperature and salt resistant fracturing fluid.

[0083] Comparative Example 19:

[0084] A method for preparing a high-temperature and salt-resistant fracturing fluid includes the following preparation steps:

[0085] (1) Weigh sodium 3-chloro-2-hydroxypropanesulfonate, N,N-dimethylacrylamide, and ethylene glycol in a mass ratio of 1:0.5:3. Mix sodium 3-chloro-2-hydroxypropanesulfonate with ethylene glycol and stir at 70°C and 300 r / min for 25 min. Add N,N-dimethylacrylamide dropwise over 30 min and continue stirring for 6 h. During this period, maintain the pH at 8 with 40 wt% sodium hydroxide aqueous solution. Rotary evaporate to obtain the quaternized solid product. Weigh out the quaternized solid product, 1-bromooctadecane, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether in a ratio of 1:1.86:0.5:0.16:2.3. Mix the quaternized solid product, 40wt% sodium hydroxide aqueous solution, benzyltriethylammonium chloride and ethylene glycol monoethyl ether, stir at 85℃ and 300r / min for 25min, add 1-bromooctadecane dropwise, continue stirring for 3h, and evaporate under reduced pressure to obtain the amphoteric hydrophobic monomer.

[0086] (2) Weigh guar gum powder, 3-(1-naphthoxy)-1,2-epoxypropane, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol according to a mass ratio of 1:0.18:0.3:6. Mix the guar gum powder, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol, stir at 27℃ and 500r / min for 3.5h, add 3-(1-naphthoxy)-1,2-epoxypropane, heat to 45℃ and continue stirring for 2h, adjust the pH to 7 with 10wt% hydrochloric acid aqueous solution, filter to collect the solid, wash with ethanol, dry, and obtain naphthoxy-functionalized guar gum; add acrylamide, amphoteric hydrochloride... Aqueous monomers, Span-80, Tween-80, and deionized water were mixed and dissolved in a mass ratio of 1:0.008:1.3:0.09:1.8. The pH was adjusted to 7 with a 45wt% sodium hydroxide aqueous solution to obtain a mixed emulsion. Naphthoxy-functionalized guar gum, cerium ammonium nitrate, and deionized water were mixed in a mass ratio of 1:0.65:530 and stirred at 27℃ and 500r / min for 25min. A mixed emulsion with a mass of 20 times that of naphthoxy-functionalized guar gum was added dropwise. The temperature was raised to 55℃ and stirring was continued for 24h. The solid was collected by acetone precipitation, washed with acetone, and post-treated to obtain modified guar gum.

[0087] (3) Weigh zirconium oxychloride octahydrate, lactic acid, ethylenediamine, glycerol and deionized water in a mass ratio of 1:0.5:1.25:4:4.5. Mix water and glycerol, heat to 55°C, add zirconium oxychloride octahydrate and titanium chloride while stirring at 300 r / min, react for 3 h, add lactic acid and ethylenediamine dropwise and continue the reaction for 5 h to obtain organozirconium crosslinking agent; prepare fracturing fluid according to the following mass ratio: 0.7% modified guar gum, 0.03% organozirconium crosslinking agent, 0.9% sodium thiosulfate, 0.08% sodium bromate, 0.06% surfactant FS-1120, and the remainder is water; mix polymer emulsion with water, stir at 27°C and 1200 r / min for 30 min, add organozirconium crosslinking agent, continue stirring for 25 min, and then add sodium bromate, sodium thiosulfate and surfactant in sequence to obtain high temperature and salt resistant fracturing fluid.

[0088] Experimental Example 1:

[0089] Determination of optimal conditions for modified guar gum (addition amount of cerium ammonium nitrate, addition amount of mixed emulsion, reaction temperature)

[0090] Test method: Analysis was performed using apparent viscosity. Referring to SY / T5107-2016 "Performance Evaluation Method for Water-Based Fracturing Fluids", a rheometer was used at 170s... -1 The apparent viscosity was measured at the shear rate and at a temperature of 25°C to assess its high-temperature and salt-resistance properties.

[0091] The results are shown in Table 1.

[0092] Table 1

[0093] ;

[0094] By comparing Example 2 with Comparative Examples 1-4, it can be found that there is an optimal range for the amount of cerium ammonium nitrate added. When the amount of cerium ammonium nitrate is too low, the number of active free radicals generated is insufficient, resulting in shorter graft chains of acrylamide and amphoteric hydrophobic monomers on the guar gum backbone, thus resulting in lower fracturing fluid viscosity. When the amount of cerium ammonium nitrate is too high, the excess free radicals will intensify the chain termination reaction, causing the polymer molecular chain growth process to end prematurely. In addition, the excess initiator significantly increases the number of macromolecular free radicals generated on the guar gum molecular backbone. With a relatively fixed total amount of monomers participating in the chain growth reaction, the increase in the number of grafting points will inevitably lead to a decrease in the amount of monomers that can be allocated to each grafting point, thereby shortening the average length of the grafted side chains and reducing the kinetic chain length.

[0095] A comparison of Examples 2 and Comparative Examples 5-8 reveals that the viscosity of the fracturing fluid initially increases rapidly with increasing monomer content, then gradually stabilizes. When the monomer content is insufficient, the active sites on the guar gum skeleton cannot fully graft to form long-chain branched structures, resulting in limited thickening effect. As the monomer content increases, the length and density of the grafted branches significantly increase, forming a stronger spatial network structure through hydrophobic association and other interactions, thereby greatly increasing the viscosity. However, when the monomer content exceeds the maximum grafting capacity of the guar gum skeleton, the excess free monomer can only generate homopolymers with low thickening efficiency, failing to further effectively increase the system viscosity, thus exhibiting a plateau in viscosity growth.

[0096] A comparison of Example 2 and Comparative Examples 10-12 reveals that the viscosity of the fracturing fluid initially increases and then decreases with increasing temperature. When the temperature is below 55°C, the reaction system lacks sufficient energy, resulting in a slow decomposition rate of cerium ammonium nitrate and low monomer grafting efficiency. When the temperature exceeds 60°C, the excessively high thermal energy intensifies the chain termination reaction, and the rapid decomposition of the initiator easily leads to the oxidative degradation of the guar gum backbone, causing a decrease in polymer molecular weight and ultimately resulting in a significant reduction in the viscosity of the fracturing fluid.

[0097] Therefore, the optimal selection was chosen as follows: the mass of cerium ammonium nitrate was 0.65 times the mass of naphthoxy-functionalized guar gum, the mass of the mixed emulsion was 20 times the mass of naphthoxy-functionalized guar gum, and the reaction temperature was 55℃, which is the reaction condition of Example 2.

[0098] Experimental Example 2:

[0099] Determination of the optimal addition amount of organozirconium crosslinking agent

[0100] Test method: Determined by temperature resistance performance. The high-temperature and salt-resistant fracturing fluid was heated starting at 30℃, then at a heating rate of 5℃ / min. During this process, a rheometer was used to measure the temperature over 170 seconds.-1 Viscosity was measured at a shear rate of [value missing]. According to SY / T5107-2016 "Evaluation Method for Performance of Water-Based Fracturing Fluids", when the apparent viscosity is less than 50 mPa·s, it indicates that the fracturing fluid has reached its temperature resistance limit.

[0101] The results are shown in Table 2.

[0102] Table 2

[0103] ;

[0104] A comparison of Example 2 and Comparative Examples 13-16 reveals an optimal range for the addition amount of organic zirconium crosslinking agent to affect the temperature resistance of fracturing fluid. When the amount of crosslinking agent is too low, there are insufficient crosslinking sites on the zirconium and titanium ions and the modified guar gum molecular chains, preventing the formation of a complete three-dimensional network structure. This loose structure is easily destroyed by thermal motion during heating. When the amount is too high, excessive crosslinking leads to excessive rigidity and decreased elasticity in the network structure, making it more prone to brittle fracture at high temperatures. Simultaneously, too many crosslinking points may cause localized network shrinkage, weakening its ability to bind water molecules and resist shear, resulting in a decrease in the viscosity retention capacity of the fracturing fluid at high temperatures and a reduction in its temperature resistance limit.

[0105] Experimental Example 3:

[0106] Temperature resistance and salt resistance testing

[0107] Temperature resistance test method: The high-temperature and salt-resistant fracturing fluids obtained in each example and the fracturing fluids of Comparative Examples 17-20 were heated at a starting temperature of 30°C at a heating rate of 5°C / min. During this period, a rheometer was used to measure the temperature over 170 seconds. -1 Viscosity was measured at a shear rate of [value missing]. According to SY / T5107-2016 "Evaluation Method for Performance of Water-Based Fracturing Fluids", when the apparent viscosity is less than 50 mPa·s, it indicates that the fracturing fluid has reached its temperature resistance limit.

[0108] Salt resistance test method: The deionized water in the preparation process of the high-temperature and salt-resistant fracturing fluids obtained in each example and the fracturing fluids of Comparative Examples 17-20 was replaced with a salt solution, including inorganic salts such as sodium chloride, calcium chloride, and magnesium chloride; a rheometer was used to test the salt resistance at 170s. -1 The shear rate and viscosity were measured at 25°C.

[0109] The results are shown in Table 3.

[0110] Table 3

[0111] ;

[0112] A comparison of the experimental data from Examples 1-3 and Comparative Examples 17-19 in Table 3 shows that the high-temperature and salt-resistant fracturing fluid prepared by this invention has good high-temperature and salt-resistant properties.

[0113] A comparison of Examples 1-3 and Comparative Example 17 reveals that grafting 3-(1-naphthoxy)-1,2-epoxypropane onto the guar gum backbone to introduce a rigid naphthalene ring enhances the temperature resistance of the fracturing fluid. The large, rigid naphthalene ring, acting as a side group, attaches to the guar gum molecular chain, creating a significant steric hindrance effect that restricts the free rotation of single bonds and the intense thermal motion of chain segments on the polymer backbone. Due to the support of its rigid side groups, the naphthoxy-functionalized guar gum molecular chain maintains a relatively extended conformation at high temperatures, effectively resisting hydrolysis and chain coiling caused by high temperatures, thus significantly improving the temperature resistance limit of the fracturing fluid.

[0114] A comparison of Examples 1-3 and Comparative Example 18 reveals that copolymerizing the synthesized amphoteric hydrophobic monomer with acrylamide and grafting it onto the guar gum backbone significantly improves the temperature and salt resistance of the fracturing fluid. The sulfonic acid groups in the monomer possess strong hydration capabilities and anionic properties; their hydration is minimally affected by temperature, maintaining an effective hydrated layer at high temperatures. Furthermore, the electrostatic repulsion between anions maintains the extended state of the polymer molecular chains at high temperatures, resisting chain coiling. Secondly, the quaternary ammonium salt cationic groups not only form internal salts with sulfonate groups, enhancing structural stability, but also shield the polymer backbone from attack by anions in formation water through electrostatic interactions. The long-chain octadecyl groups can form a dynamic physical cross-linked network in water through hydrophobic association. This network strengthens with increasing temperature, effectively compensating for hydrogen bonds and other forces damaged by high temperatures, thus maintaining excellent viscosity and structural strength under high temperature and high salt conditions, resulting in superior temperature and salt resistance for the fracturing fluid system.

[0115] A comparison of Examples 1-3 and Comparative Example 19 reveals that introducing titanium ions to form a zirconium-titanium composite crosslinking agent during the preparation of the organic zirconium crosslinking agent significantly enhances the temperature and salt resistance of the fracturing fluid. Zirconium ions tend to form crosslinking bonds with higher bond energy and better stability, providing a solid basic structure and initial strength for the crosslinking network. While the crosslinking bonds formed by titanium ions have slightly lower bond energy, their bonding exhibits stronger dynamic reversibility, allowing for faster reformation after breakage under high-temperature shear, thus endowing the crosslinking network with excellent self-healing capabilities. Furthermore, under high-temperature conditions, titanium ions are less prone to hydrolysis and precipitation. Their good stability complements that of zirconium ions, jointly ensuring that the crosslinking network does not collapse during long-term high-temperature aging, thereby raising the temperature resistance limit of the fracturing fluid to a higher level and maintaining excellent viscosity retention in high-salinity brine.

[0116] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A high temperature and salt resistant fracturing fluid, characterized in that, The high-temperature-resistant and salt-resistant fracturing fluid is prepared by mixing modified guar gum, organic zirconium crosslinking agent, sodium thiosulfate, sodium bromate, surfactant and water; The modified guar gum is prepared by reacting guar gum powder with 3-(1-naphthoxy)-1,2-epoxypropane to obtain naphthoxy-functionalized guar gum, and then by polymerizing with acrylamide and amphoteric hydrophobic monomer through ammonium nitrate initiation; The amphoteric hydrophobic monomer is prepared by reacting 3-chloro-2-hydroxypropane sulfonic acid sodium, N,N-dimethyl acrylamide and ethylene glycol to obtain quaternary ammonium solid product, and then by reacting with 1-bromooctadecane. 2.The high-temperature and salt-tolerant fracturing fluid of claim 1, characterized in that, The organic zirconium crosslinking agent is prepared by reacting zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine and glycerol.

3. A method for preparing a high-temperature and salt-tolerant fracturing fluid, characterized in that, The preparation steps include: (1) 3-chloro-2-hydroxypropane sulfonic acid sodium, N,N-dimethyl acrylamide and ethylene glycol are weighed according to the mass ratio of 1:(0.49-0.51):(2.5-3.5), 3-chloro-2-hydroxypropane sulfonic acid sodium and ethylene glycol are mixed, stirred at 60-80°C and 200-400 r / min for 20-30 min, N,N-dimethyl acrylamide is added dropwise within 30 min, and stirring is continued for 5-7 h, during which 40wt% sodium hydroxide aqueous solution is continuously used to maintain pH at 7.5-8.5, and rotary evaporation is performed to obtain quaternary ammonium solid product; the quaternary ammonium solid product, 1-bromooctadecane, 40wt% sodium hydroxide aqueous solution, benzyl triethyl ammonium chloride and ethylene glycol monoethyl ether are weighed according to the mass ratio of 1:(1.8-1.92):(0.4-0.6):(0.15-0.17):(2-2.5), the quaternary ammonium solid product, 40wt% sodium hydroxide aqueous solution, benzyl triethyl ammonium chloride and ethylene glycol monoethyl ether are mixed, stirred at 80-90°C and 200-400 r / min for 20-30 min, 1-bromooctadecane is added dropwise, and stirring is continued for 2-4 h, and rotary evaporation is performed under reduced pressure to obtain amphoteric hydrophobic monomer; (2) Guar gum powder, 3-(1-naphthoxy)-1,2-epoxypropane, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol are weighed according to the mass ratio of 1:(0.16-0.2):(0.28-0.32):(5.5-6.5), the guar gum powder, 20wt% sodium hydroxide aqueous solution and anhydrous ethanol are mixed, stirred at 25-30℃ and 400-600r / min for 3-4h, 3-(1-naphthoxy)-1,2-epoxypropane is added, the temperature is raised to 40-50℃ and stirring is continued for 1.5-2.5h, 10wt% hydrochloric acid aqueous solution is used to adjust the pH to 6.5-7.5, the solid is collected by suction filtration, washed with ethanol and dried to obtain naphthoxy functionalized guar gum; acrylamide, amphiphilic hydrophobic monomer, span-80, tween-80 and deionized water are mixed and dissolved according to the mass ratio of 1:(0.007-0.009):(1.2-1.4):(0.08-0.1):(1.6-2), 45wt% sodium hydroxide aqueous solution is used to adjust the pH to 6.5-7.5 to obtain a mixed emulsion; naphthoxy functionalized guar gum, cerium nitrate and deionized water are mixed according to the mass ratio of 1:(0.6-0.7):(500-550), stirred at 25-30℃ and 400-600r / min for 20-30min, the mixed emulsion is added dropwise, the mass of which is 19-21 times the mass of the naphthoxy functionalized guar gum, the temperature is raised to 50-60℃ and stirring is continued for 20-28h, the solid is precipitated with acetone, washed with acetone and post-treated to obtain modified guar gum; (3) Zirconium oxychloride octahydrate, titanium chloride, lactic acid, ethylenediamine, glycerol and deionized water are weighed according to the mass ratio of 1:(0.148-0.152):(0.4-0.6):(1.2-1.3):(3-5):(4-5), the water and glycerol are mixed, heated to 50-60℃, zirconium oxychloride octahydrate and titanium chloride are added under stirring at 200-400r / min, lactic acid and ethylenediamine are added dropwise after 2-4h of reaction and the reaction is continued for 4-6h to obtain an organic zirconium crosslinking agent; The fracturing fluid is prepared according to the following mass proportions: 0.5%-0.8% modified guar gum, 0.02%-0.04% organic zirconium crosslinking agent, 0.8%-1% sodium thiosulfate, 0.06%-0.1% sodium bromate, 0.04%-0.08% surfactant FS-1120 and the balance is water; the polymer emulsion is mixed with water, stirred at 25-30℃ and 1000-1400r / min for 20-40min, the organic zirconium crosslinking agent is added and stirring is continued for 20-30min, then sodium bromate, sodium thiosulfate and surfactant are added in sequence to obtain a high-temperature and salt-resistant fracturing fluid.

4. The method according to claim 3, characterized in that, The guar gum powder in step (2) is an industrial grade.

5. The method according to claim 3, characterized in that, The post-treatment process in step (2) is as follows: after acetone washing, the mixture of glacial acetic acid and N,N-dimethylformamide (volume ratio 1:1) is refluxed and dissolved at 75-85℃, the solvent is precipitated with acetone, the filtrate is collected by filtration and dried to constant weight to obtain modified guar gum.

6. The method according to claim 3, characterized in that, The active ingredient content of the surfactant FS-1120 in step (3) is 100%.