A fracturing fluid crosslinking agent, its preparation method and application

Abstract

The present invention provides a fracturing fluid crosslinking agent, its preparation method and application. The fracturing fluid crosslinking agent is mainly prepared by mixing an organic aluminum-boron crosslinking agent and an organic titanium-boron crosslinking agent, and the volume ratio of the organic aluminum-boron crosslinking agent to the organic titanium-boron crosslinking agent is 1:0.5 to 2; wherein, the organic aluminum-boron crosslinking agent is mainly prepared from the following raw materials by weight: 0.5 to 0.7 parts of nano-aluminum oxide particles; 5.5 to 9 parts of borax; 0.004 to 0.005 parts of acetylacetone; 0.008 to 0.012 parts of sodium gluconate, 0.008 to 0.012 parts of ethylene glycol, 0.1 part of water; the organic titanium-boron crosslinking agent is mainly prepared from the following raw materials by weight: 0.4 to 0.6 parts of nano-titanium dioxide particles; 4 to 6 parts of borax; 0.0015 to 0.003 parts of acetylacetone; 1 to 3 parts of xylitol; 0.03 to 0.04 parts of glycerol; 0.1 part of water. The fracturing fluid crosslinking agent can enable the prepared fracturing fluid to simultaneously meet high temperature resistance and shear resistance, and the preparation process is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of fracturing fluid crosslinking agents, and specifically relates to a fracturing fluid crosslinking agent, a preparation method thereof, and an application thereof. Background Art

[0002] At present, deep low-permeability oil and gas fields have gradually become the main force in exploitation. In order to improve the fluidity of oil and gas flow in the formation, the hydraulic fracturing technology has gradually become a research hotspot for formation transformation. A fracturing fluid with high temperature resistance and shear resistance has important practical application value, and the high temperature resistance and shear resistance of the crosslinking agent are important factors directly affecting the quality of the fracturing fluid.

[0003] Currently, the common crosslinking agent for guar gum fracturing fluid is an organic boron crosslinking agent, which has advantages such as easy crosslinking, easy gel breaking and backflow, and low price. However, the organic boron crosslinking agent makes the prepared fracturing fluid have low properties such as high temperature resistance and shear resistance, and the high temperature resistance generally does not exceed 120°C. Therefore, it is of great significance to develop a fracturing fluid crosslinking agent that can endow the fracturing fluid with comprehensive properties of high temperature resistance and shear resistance. Summary of the Invention

[0004] The purpose of the present invention is to provide a fracturing fluid crosslinking agent, a preparation method thereof, and an application thereof, aiming at the problem that the existing fracturing fluid cannot simultaneously meet high high temperature resistance and shear resistance. The fracturing fluid crosslinking agent provided by the present invention can enable the prepared fracturing fluid to simultaneously meet high high temperature resistance and shear resistance, and the preparation process is simple, with high popularization value and economic value.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A fracturing fluid crosslinking agent is mainly prepared by mixing an organic aluminum boron crosslinking agent and an organic titanium boron crosslinking agent, and the volume ratio of the organic aluminum boron crosslinking agent to the organic titanium boron crosslinking agent is 1:0.5 - 2;

[0007] Among them, the organic aluminum boron crosslinking agent is mainly prepared from the following raw materials by weight:

[0008] 0.5 - 0.7 parts of nano-aluminum oxide particles; 5.5 - 9 parts of borax; 0.004 - 0.005 parts of acetylacetone; 0.008 - 0.012 parts of sodium gluconate, 0.008 - 0.012 parts of ethylene glycol, 0.1 part of water;

[0009] The organic titanium boron crosslinking agent is mainly prepared from the following raw materials by weight:

[0010] 0.4 to 0.6 parts of nano-titanium dioxide particles; 4 to 6 parts of borax; 0.0015 to 0.003 parts of acetylacetone; 1 to 3 parts of xylitol; 0.03 to 0.04 parts of glycerol; 0.1 part of water.

[0011] The present invention provides a fracturing fluid crosslinking agent, which is mainly prepared by mixing an organic aluminum-boron crosslinking agent and an organic titanium-boron crosslinking agent; the organic aluminum-boron crosslinking agent mainly uses nano-aluminum oxide particles and borax as the main raw materials, and acetylacetone, sodium gluconate and ethylene glycol as ligands, and is prepared by controlling the addition ratio of each raw material. The hydroxyl groups on the surface of nano-aluminum react with tetra-hydroxyborate ions to form borate compounds, and the borate compounds continue to react with the ligands to produce borate compounds with more complex structures. During use, the organic aluminum-boron crosslinking agent reacts with the ortho-cis hydroxyl groups on the molecular chain of guar gum under weak alkaline conditions to form a fracturing fluid with a spatial network structure in the microscopic morphology, effectively improving the high-temperature resistance and shear resistance of the fracturing fluid; the organic titanium-boron crosslinking agent mainly uses nano-titanium dioxide particles and borax as the main raw materials, and acetylacetone, xylitol and glycerol as ligands, and is prepared by selecting the type of ligand and the addition ratio between each raw material. The hydroxyl groups on the surface of nano-titanium react with tetra-hydroxyborate ions to form borate compounds, and the borate compounds continue to react with the ligands to produce an organic titanium-boron crosslinking agent with a more complex structure. The organic titanium-boron crosslinking agent reacts with the ortho-cis hydroxyl groups on the molecular chain of guar gum under weak alkaline conditions to form a fracturing fluid with a spatial network structure in the microscopic morphology, effectively improving the high-temperature resistance and shear resistance of the fracturing fluid. The organic aluminum-boron crosslinking agent and the organic titanium-boron crosslinking agent form a cross-body structure with a relatively stable structure under certain temperature conditions, so that the prepared fracturing fluid can simultaneously meet high high-temperature resistance and shear resistance, and has a low cost.

[0012] Further, the volume ratio of the organic aluminum-boron crosslinking agent to the organic titanium-boron crosslinking agent is 1:1 to 2. It is found that when the volume ratio of the two is 1:1 to 2, the fracturing fluid exhibits better shear resistance. More preferably, the volume ratio of the organic aluminum-boron crosslinking agent to the organic titanium-boron crosslinking agent is 1:1.5 to 2.

[0013] Further, in the raw materials of the organic aluminum-boron crosslinking agent, the weight ratio of the nano-aluminum oxide particles to the borax is 0.05 to 0.1:1. It is found that the weight ratio of nano-aluminum oxide to borax is an important influencing factor affecting the performance of the final crosslinking agent. Preferably, the weight ratio of the nano-aluminum oxide particles to the borax is 0.06 to 0.1:1. More preferably, the weight ratio of the nano-aluminum oxide particles to the borax is 0.08 to 0.1:1.

[0014] Further, in the raw materials of the organic titanium-boron crosslinking agent, the weight ratio of the nano-titanium dioxide particles to the borax is 0.08 - 0.12:1. It is found that the weight ratio of the nano-titanium dioxide particles to the borax is an important influencing factor for the performance of the final crosslinking agent. Preferably, the weight ratio of the nano-titanium dioxide particles to the borax is 0.08 - 0.12:1. More preferably, the weight ratio of the nano-titanium dioxide particles to the borax is 0.08 - 0.12:1.

[0015] Further, the particle size of the nano-aluminum oxide particles ≤ 10 nm; the particle size of the nano-titanium dioxide particles ≤ 10 nm. Different particle sizes of nanoparticles result in different nanoparticle properties such as specific surface area and application activity. Therefore, this study has certain requirements for the particle sizes of nano-aluminum oxide and titanium dioxide. Preferably, the particle size of the nano-aluminum oxide particles is 5 nm - 10 nm; the particle size of the nano-titanium dioxide particles is 5 nm - 10 nm. More preferably, the particle size of the nano-aluminum oxide particles is 5 nm - 8 nm; the particle size of the nano-titanium dioxide particles is 5 nm - 8 nm.

[0016] Further, the organic aluminum-boron crosslinking agent is mainly prepared by the following method: First, add the nano-aluminum oxide particles to water and stir to obtain a first solution; then adjust the pH of the first solution to 9 - 10 to obtain a second solution; thereafter, add borax, acetylacetone, sodium gluconate, and ethylene glycol to the second solution and react under stirring conditions to obtain the organic aluminum-boron crosslinking agent.

[0017] Further, the organic aluminum-boron crosslinking agent is mainly prepared by the following method: First, add the nano-aluminum oxide particles to water and stir to obtain a first solution; then adjust the pH of the first solution to 9 - 10 to obtain a second solution; thereafter, add borax, acetylacetone, sodium gluconate, and ethylene glycol to the second solution and stir and react at 50°C - 80°C for 3 h - 6 h to obtain the organic aluminum-boron crosslinking agent. The hydroxyl groups on the surface of nano-aluminum react with tetrahydroxyborate ions to form borate compounds, and the borate then continues to react with the ligand to produce borate compounds with a more complex structure, namely the organic aluminum-boron crosslinking agent.

[0018] Further, the organic titanium-boron crosslinking agent is mainly prepared by the following method: First, add the nano-titanium dioxide particles to water and stir to obtain a first solution; then adjust the pH of the first solution to 9 - 10 to obtain a second solution; thereafter, add borax, acetylacetone, xylitol, and glycerol to the second solution and react under stirring conditions to obtain the organic titanium-boron crosslinking agent.

[0019] Further, the organic titanium boron crosslinking agent is mainly prepared by the following method: First, add nano-titanium dioxide particles into water and stir to obtain a first solution; then adjust the pH of the first solution to 9-10 to obtain a second solution; thereafter, add borax, acetylacetone, xylitol and glycerol into the second solution, and stir and react at 60°C-90°C for 3h-6h to obtain the organic titanium boron crosslinking agent. The hydroxyl groups on the surface of nano-titanium react with tetra-hydroxyborate ions to form borate compounds, and the borate compounds continue to react with ligands to produce borate compounds with more complex structures, namely the organic titanium boron crosslinking agent.

[0020] Another object of the present invention is to provide a preparation method of the above fracturing fluid crosslinking agent.

[0021] A preparation method of the above fracturing fluid crosslinking agent includes the following steps: Mix the organic aluminum boron crosslinking agent and the organic titanium boron crosslinking agent according to the volume ratio of the raw materials, and stir for 30 min-1 h to obtain the fracturing fluid crosslinking agent.

[0022] The preparation method of the fracturing fluid crosslinking agent provided by the present invention fully mixes the organic aluminum boron crosslinking agent and the organic titanium boron crosslinking agent, and the two crosslinking agents form a cross-integral structure. The preparation process is simple and easy to control.

[0023] Further, mix the organic aluminum boron crosslinking agent and the organic titanium boron crosslinking agent at 60°C-80°C according to the volume ratio of the raw materials, and stir for 30 min-1 h to obtain the fracturing fluid crosslinking agent.

[0024] Another object of the present invention is to provide an application of the above fracturing fluid crosslinking agent.

[0025] An application of the above fracturing fluid crosslinking agent in the preparation of guar gum fracturing fluid.

[0026] The fracturing fluid crosslinking agent provided by the present invention can make the prepared fracturing fluid simultaneously meet the high temperature resistance and shear resistance, the preparation process is simple, and it has high application value.

[0027] Another object of the present invention is to provide a guar gum fracturing fluid prepared by the above fracturing fluid crosslinking agent.

[0028] A guar gum fracturing fluid is mainly prepared by the following method: First, adjust the pH value of the guar gum solution to 9-10, and then add the above-mentioned fracturing fluid crosslinking agent and mix to obtain the guar gum fracturing fluid.

[0029] Further, the mass concentration of the guar gum solution is 0.4%-0.8%, and the volume ratio of the fracturing fluid crosslinking agent to the guar gum solution is: 0.2-0.8:100.

[0030] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are:

[0031] 1. The present invention provides a fracturing fluid crosslinking agent, which is mainly prepared by mixing an organic aluminum-boron crosslinking agent and an organic titanium-boron crosslinking agent; the organic aluminum-boron crosslinking agent mainly uses nano-aluminum oxide particles and borax as the main raw materials, and acetylacetone, sodium gluconate and ethylene glycol as ligands, and is prepared by controlling the addition ratio of each raw material. The hydroxyl groups on the surface of nano-aluminum react with tetrahydroxyborate ions to form borate compounds, and the borate then continues to react with the ligands to produce borate compounds with more complex structures. During use, the organic aluminum-boron crosslinking agent reacts with the ortho-cis hydroxyl groups on the guar gum molecular chain under weak alkaline conditions to form a fracturing fluid with a spatial network structure in the microscopic morphology, effectively improving the high-temperature resistance and shear resistance of the fracturing fluid; the organic titanium-boron crosslinking agent mainly uses nano-titanium dioxide particles and borax as the main raw materials, and acetylacetone, xylitol and glycerol as ligands, and is prepared by selecting the types of ligands and the addition ratio between each raw material. The hydroxyl groups on the surface of nano-titanium react with tetrahydroxyborate ions to form borate compounds, and the borate then continues to react with the ligands to produce an organic titanium-boron crosslinking agent with a more complex structure. The organic titanium-boron crosslinking agent reacts with the ortho-cis hydroxyl groups on the guar gum molecular chain under weak alkaline conditions to form a fracturing fluid with a spatial network structure in the microscopic morphology, effectively improving the high-temperature resistance and shear resistance of the fracturing fluid. The organic aluminum-boron crosslinking agent and the organic titanium-boron crosslinking agent form a cross-body structure with a relatively stable structure under certain temperature conditions, so that the prepared fracturing fluid can simultaneously meet high high-temperature resistance and shear resistance, and has a low cost.

[0032] 2. The fracturing fluid crosslinking agent provided by the present invention enables the prepared fracturing fluid to simultaneously meet high high-temperature resistance and shear resistance, has a simple preparation process, and has high application value. Detailed Embodiments

[0033] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Example 1

[0035] Preparation of fracturing fluid crosslinking agent

[0036] (1) Take 0.58 g of aluminum oxide particles with a particle size of 10 nm and disperse them into a three-necked flask containing 100 mL of deionized water. Stir magnetically for 10 min to fully disperse them. Adjust the pH to 9 - 10 with a 10% sodium hydroxide solution by mass. Add 7 g of borax, 4.9 mg of acetylacetone, 10 mg of sodium gluconate, and 11.13 mg of ethylene glycol. Stir and react at 60 °C for 5 h to obtain an organic aluminum-boron crosslinking agent.

[0037] (2) Preparation of an organic titanium-boron crosslinking agent

[0038] Take 0.5 g of titanium dioxide particles with a particle size of 8 nm and disperse them into a three-necked flask containing 100 mL of deionized water. Stir magnetically for 10 min to fully disperse them. Adjust the pH to 9 - 10 with a 10% sodium hydroxide solution by mass. Add 5 g of borax, 2.94 mg of acetylacetone, 2 g of xylitol, and 37.83 mg of glycerol. Stir and react at 70 °C for 5 h to obtain an organic titanium-boron crosslinking agent.

[0039] (3) Preparation of an organic aluminum-titanium-boron crosslinking agent

[0040] Mix the organic aluminum-boron crosslinking agent and the organic titanium-boron crosslinking agent in a volume ratio of 1:2 and stir magnetically for 30 min to obtain an organic aluminum-titanium-boron crosslinking agent.

[0041] Preparation of guar gum fracturing fluid

[0042] Take 100 mL of a guar gum solution with a mass fraction of 0.6%. Adjust the pH of the guar gum fracturing fluid to 9 - 10 with a 20% NaOH solution by mass. Add 0.5 mL of the organic aluminum-titanium-boron crosslinking agent to prepare a guar gum fracturing fluid.

[0043] Take the guar gum fracturing fluid prepared in Example 1 and put it into the test cup of a rheometer to conduct heat resistance and shear resistance experiments. The experimenter records the change in the viscosity of the fracturing fluid over time.

[0044] The test results are as follows:

[0045] Heat resistance: When the viscosity reaches the node above 50 mPa, the corresponding temperature is 160 °C.

[0046] Shear resistance: At 160 °C, shear for 4 h under the condition of 170 s -1 and the viscosity remains at 100 mPa.

[0047] The research results show that the guar gum fracturing fluid prepared in Example 1 can simultaneously meet good high-temperature resistance and shear resistance.

[0048] Example 2

[0049] Preparation of fracturing fluid crosslinking agent

[0050] (1) Disperse 0.7 g of aluminum oxide particles with a particle size of 5 nm into a three-necked flask containing 100 mL of deionized water, stir magnetically for 10 min to disperse them fully, adjust the pH to 9 - 10 with a 10% sodium hydroxide solution by mass, add 7 g of borax, 4.0 mg of acetylacetone, 8 mg of sodium gluconate, and 8 mg of ethylene glycol, and stir and react at 50 °C for 4 h to obtain an organic aluminum-boron crosslinking agent.

[0051] (2) Preparation of organic titanium-boron crosslinking agent

[0052] Disperse 0.6 g of titanium dioxide particles with a particle size of 8 nm into a three-necked flask containing 100 mL of deionized water, stir magnetically for 10 min to disperse them fully, adjust the pH to 9 - 10 with a 10% sodium hydroxide solution by mass, add 5 g of borax, 1.51 mg of acetylacetone, 1 g of xylitol, and 30.05 mg of glycerol, and stir and react at 60 °C for 5 h to obtain an organic titanium-boron crosslinking agent.

[0053] (3) Preparation of organic aluminum-titanium-boron crosslinking agent

[0054] Mix the organic aluminum-boron crosslinking agent and the organic titanium-boron crosslinking agent according to a volume ratio of 1:0.5, stir magnetically for 45 min to obtain an organic aluminum-titanium-boron crosslinking agent.

[0055] Preparation of guar gum fracturing fluid

[0056] Take 100 mL of a guar gum solution with a mass fraction of 0.6%, adjust the pH of the guar gum fracturing fluid to 9 - 10 with a 20% NaOH solution by mass, and add 0.5 mL of the organic aluminum-titanium-boron crosslinking agent to prepare a guar gum fracturing fluid.

[0057] Using the same test method as in Example 1, test the temperature resistance and shear resistance of the guar gum fracturing fluid prepared in Example 2;

[0058] The test results are as follows:

[0059] Temperature resistance: When the viscosity reaches the node above 50 mPa, the corresponding temperature is 140 °C.

[0060] Shear resistance: At 160 °C, shear for 2 h under the condition of 170 s -1 , and the viscosity remains at 60 mPa.

[0061] The research results show that the guar gum fracturing fluid prepared in Example 2 can simultaneously meet good high-temperature resistance and shear resistance.

[0062] Example 3

[0063] Preparation of fracturing fluid crosslinking agent

[0064] (1) Disperse 0.5 g of aluminum oxide particles with a particle size of 8 nm into a three-necked flask containing 100 mL of deionized water, and stir magnetically for 10 min to fully disperse them. Adjust the pH to 9 - 10 with a 10% sodium hydroxide solution by mass. Add 9 g of borax, 4.5 mg of acetylacetone, 9 mg of sodium gluconate, and 10 mg of ethylene glycol, and stir and react at 50 °C for 6 h to obtain an organic aluminum-boron crosslinking agent.

[0065] (2) Preparation of organic titanium-boron crosslinking agent

[0066] Disperse 0.4 g of titanium dioxide particles with a particle size of 5 nm into a three-necked flask containing 100 mL of deionized water, and stir magnetically for 10 min to fully disperse them. Adjust the pH to 9 - 10 with a 10% sodium hydroxide solution by mass. Add 4 g of borax, 2.11 mg of acetylacetone, 1.5 g of xylitol, and 33.3 mg of glycerol, and stir and react at 90 °C for 3 h to obtain an organic titanium-boron crosslinking agent.

[0067] (3) Preparation of organic aluminum-titanium-boron crosslinking agent

[0068] Mix the organic aluminum-boron crosslinking agent and the organic titanium-boron crosslinking agent in a volume ratio of 1:1, and stir magnetically for 30 min to obtain an organic aluminum-titanium-boron crosslinking agent.

[0069] Preparation of guar gum fracturing fluid

[0070] Take 100 mL of a guar gum solution with a mass fraction of 0.6%, adjust the pH of the guar gum fracturing fluid to 9 - 10 with a 20% NaOH solution by mass, and add 0.5 mL of the organic aluminum-titanium-boron crosslinking agent to prepare the guar gum fracturing fluid.

[0071] Using the same test method as in Example 1, test the temperature resistance and shear resistance of the guar gum fracturing fluid prepared in Example 3;

[0072] The test results are as follows:

[0073] Temperature resistance: When the viscosity reaches the node above 50 mPa, the corresponding temperature is 150 °C.

[0074] Shear resistance: At 160 °C, for 170 s -1 Under the condition of shearing for 2.5 h, the viscosity remains at 80 mPa.

[0075] The research results show that the guar gum fracturing fluid prepared in Example 2 can simultaneously meet good high-temperature resistance and shear resistance.

[0076] Example 4

[0077] Preparation of fracturing fluid crosslinking agent

[0078] (1) 0.5 g of aluminum oxide particles with a particle size of 10 nm were dispersed in a three-necked flask filled with 100 mL of deionized water, and magnetic stirring was performed for 10 min to fully disperse them. The pH was adjusted to 9-10 with a 10% sodium hydroxide solution, and 5.5 g of borax, 5.0 mg of acetylacetone, 12 mg of sodium gluconate, and 12 mg of ethylene glycol were added. The mixture was stirred at 80° C. for 3 h to obtain an organic aluminum boron crosslinking agent.

[0079] (2) Preparation of organic titanium boron crosslinking agent

[0080] Take 0.48g of titanium dioxide particles with a particle size of 10nm and disperse them in a three-necked flask filled with 100mL of deionized water. Stir magnetically for 10min to fully disperse them. Adjust the pH to 9-10 with 10% by mass sodium hydroxide solution. Add 6g of borax, 3.00mg of acetylacetone, 3g of xylitol, and 40mg of glycerol. Stir and react at 60℃ for 6h to obtain an organic titanium boron crosslinker.

[0081] (3) Preparation of organic aluminum-titanium-boron crosslinking agent

[0082] The organic aluminum-boron crosslinking agent and the organic titanium-boron crosslinking agent were mixed in a volume ratio of 1:1.5, and magnetically stirred for 60 minutes to obtain an organic aluminum-titanium-boron crosslinking agent.

[0083] Preparation of guar gum fracturing fluid

[0084] 100 mL of 0.6% guar solution was taken, the pH of the guar fracturing fluid was adjusted to 9-10 with 20% NaOH solution, and 0.5 mL of organic aluminum-titanium-boron crosslinking agent was added to prepare guar fracturing fluid.

[0085] The same test method as in Example 1 was used to test the temperature resistance and shear resistance of the guar gum fracturing fluid prepared in Example 4;

[0086] The test results are:

[0087] Temperature resistance: When the viscosity reaches above 50mPa, the corresponding temperature is 140℃.

[0088] Shear resistance: at 160℃, 170s -1 The viscosity was maintained at 90 mPa under shearing conditions for 3 h.

[0089] The research results show that the guar gum fracturing fluid prepared in Example 4 can simultaneously meet good high temperature resistance and shear resistance.

[0090] Comparative Example 1

[0091] Comparative Example 1 prepared an organoaluminum boron crosslinking agent using the same method as in Example 1.

[0092] Preparation of guar gum fracturing fluid

[0093] Take 100 mL of a guar gum solution with a mass fraction of 0.6%, adjust the pH of the guar gum fracturing fluid to 9 - 10 with a 20% NaOH solution by mass, and add 0.5 mL of the organoaluminum boron crosslinking agent to prepare a guar gum fracturing fluid.

[0094] Using the same test method as in Example 1, the temperature resistance and shear resistance of the guar gum fracturing fluid prepared in Comparative Example 1 were tested;

[0095] The test results were:

[0096] Temperature resistance: When the viscosity reached the node above 50 mPa, the corresponding temperature was 105 °C.

[0097] Shear resistance: Sheared for 1 h under the conditions of 160 °C and 170 s -1 The viscosity remained at 50 mPa.

[0098] The research results showed that it was difficult for the guar gum fracturing fluid prepared with a single organoaluminum boron crosslinking agent to simultaneously meet good high-temperature resistance and shear resistance.

[0099] Comparative Example 2

[0100] Comparative Example 2 prepared an organotitanium boron crosslinking agent using the same method as in Example 1.

[0101] Preparation of guar gum fracturing fluid

[0102] Take 100 mL of a guar gum solution with a mass fraction of 0.6%, adjust the pH of the guar gum fracturing fluid to 9 - 10 with a 20% NaOH solution by mass, and add 0.5 mL of the organotitanium boron crosslinking agent to prepare a guar gum fracturing fluid.

[0103] Using the same test method as in Example 1, the temperature resistance and shear resistance of the guar gum fracturing fluid prepared in Comparative Example 2 were tested;

[0104] The test results were:

[0105] Temperature resistance: When the viscosity reached the node above 50 mPa, the corresponding temperature was 100 °C.

[0106] Shear resistance: Sheared for 1 h under the conditions of 160 °C and 170 s -1 The viscosity remained at 60 mPa.

[0107] The research results showed that it was difficult for the guar gum fracturing fluid prepared with a single organotitanium boron crosslinking agent to simultaneously meet good high-temperature resistance and shear resistance.

[0108] Comparative Example 3

[0109] In Comparative Example 3, the fracturing fluid crosslinking agent, organoaluminum boron, organotitanium boron crosslinking agent and guar gum fracturing fluid were prepared by the same preparation method as in Example 1. The difference is that in Comparative Example 3, the addition of three ligands (acetylacetone, sodium gluconate and ethylene glycol) in the preparation process of the organoaluminum boron crosslinking agent was changed. For other preparation processes, process parameters, raw material ratios and raw material sources were exactly the same as those in Example 1. And the same test method as in Example 1 was used to test the performance of the guar gum fracturing fluid prepared in Comparative Example 3. The addition of ligands in the preparation process of the organoaluminum boron crosslinking agent in Comparative Example 3 and the test results are shown in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] Through a large amount of data research by the inventors, it was found that in the process of the organoaluminum boron crosslinking agent, not using ligands, using a single ligand or lacking one ligand would greatly reduce the temperature resistance and shear resistance of the guar gum fracturing fluid. Even if sodium gluconate was converted to the same molar amount of xylitol, the fracturing fluid crosslinking agent prepared with the same molar amount of glycerol would also greatly reduce the temperature resistance and shear resistance of the fracturing fluid.

[0114] Comparative Example 4

[0115] In Comparative Example 4, the fracturing fluid crosslinking agent, organoaluminum boron, organotitanium boron crosslinking agent and guar gum fracturing fluid were prepared by the same preparation method as in Example 1. The difference is that in Comparative Example 4, the addition of three ligands (acetylacetone, xylitol and glycerol) in the preparation process of the organotitanium boron crosslinking agent was changed. For other preparation processes, process parameters, raw material ratios and raw material sources were exactly the same as those in Example 1. And the same test method as in Example 1 was used to test the performance of the guar gum fracturing fluid prepared in Comparative Example 4. The addition of ligands in the preparation process of the organotitanium boron crosslinking agent in Comparative Example 4 and the test results are shown in Table 2.

[0116] Table 2

[0117]

[0118]

[0119] Through extensive data research by the inventors, it has been found that during the process of organic titanium-boron crosslinking agents, the absence of ligands, the use of a single ligand, or the lack of one ligand will significantly reduce the temperature resistance and shear resistance of the guar gum fracturing fluid. Even when xylitol is converted into the same molar amount of sodium gluconate and the fracturing fluid crosslinking agent is prepared using the same molar amount of ethylene glycol, the temperature resistance and shear resistance of the fracturing fluid will be significantly reduced.

[0120] Comparative Example 5

[0121] In Comparative Example 5, the organic aluminum-boron crosslinking agent, organic titanium-boron crosslinking agent, fracturing fluid crosslinking agent, and guar gum fracturing fluid were prepared using the same method as in Example 1. The difference from Example 1 was that in Comparative Example 5, the particle sizes of the nano-aluminum oxide particles and nano-titanium dioxide particles were changed, and both particle sizes were 15 nm. The other experimental procedures and experimental materials were exactly the same as those in Example 1.

[0122] Using the same test method as in Example 1, the temperature resistance and shear resistance of the guar gum fracturing fluid prepared in Comparative Example 5 were measured;

[0123] The test results were as follows:

[0124] Temperature resistance: When the viscosity reached the node above 50 mPa, the corresponding temperature was 115 °C.

[0125] Shear resistance: Sheared for 1 h under the conditions of 160 °C and 170 s -1 , and the viscosity remained at 60 mPa.

[0126] The research results show that nanoparticles with appropriate particle sizes have a close relationship with the performance of the fracturing fluid. The guar gum fracturing fluid prepared with crosslinking agents made from nanoparticles with too large particle sizes is difficult to simultaneously meet good high-temperature resistance and shear resistance.

[0127] Comparative Example 6

[0128] Preparation of organic boron crosslinking agent

[0129] Take 100 mL of deionized water into a three-necked flask, stir magnetically for 10 min to disperse it fully, adjust the pH to 9 - 10 with a 10% mass fraction sodium hydroxide solution, add 7 g of borax, 4.9 mg of acetylacetone, 10 mg of sodium gluconate, 11.13 mg of ethylene glycol, and stir and react at 60 °C for 5 h to obtain an organic aluminum-boron crosslinking agent.

[0130] Preparation of guar gum fracturing fluid

[0131] Take 100 mL of a 0.6% mass fraction guar gum solution, adjust the pH of the guar gum fracturing fluid to 9 - 10 with a 20% mass fraction NaOH solution, and add 0.5 mL of the organic boron crosslinking agent to prepare the guar gum fracturing fluid.

[0132] Test results:

[0133] Using the same test method as in Example 1, the temperature resistance and shear resistance of the guar gum fracturing fluid prepared in Comparative Example 6 were tested;

[0134] The test results were as follows:

[0135] Temperature resistance: When the viscosity reached the node above 50 mPa, the corresponding temperature was 80 °C.

[0136] Shear resistance: At 160 °C and 170 s -1 under the condition of shearing for 0.5 h, the viscosity remained at 50 mPa.

[0137] The research results show that it is difficult for the guar gum fracturing fluid prepared by common organic boron crosslinking agents to simultaneously meet good high-temperature resistance and shear resistance.

[0138] The present invention provides a fracturing fluid crosslinking agent, which is mainly prepared by mixing an organic aluminum boron crosslinking agent and an organic titanium boron crosslinking agent. The two crosslinking agents form a cross-linked structure with relatively stable structure under certain temperature conditions, so that the prepared fracturing fluid can simultaneously meet high high-temperature resistance and shear resistance. Among them, the organic aluminum boron crosslinking agent mainly uses nano-aluminum oxide particles and borax as the main raw materials, and acetylacetone, sodium gluconate and ethylene glycol as ligands, and is prepared by controlling the addition ratio of each raw material. The hydroxyl groups on the surface of nano-aluminum react with tetra-hydroxyborate ions to form borate compounds, and the borate reacts with the ligand to produce borate compounds with more complex structures. The organic aluminum boron crosslinking agent reacts with the ortho-cis hydroxyl groups on the guar gum molecular chain under weak alkaline conditions to form a fracturing fluid with a spatial network structure in micro-morphology. The thickness of this network structure determines the temperature and shear resistance of the fracturing fluid. The organic titanium boron crosslinking agent mainly uses nano-titanium dioxide particles and borax as the main raw materials, and acetylacetone, xylitol and glycerol as ligands, and is prepared by selecting the type of ligand and the addition ratio between each raw material. The hydroxyl groups on the surface of nano-titanium react with tetra-hydroxyborate ions to form borate compounds, and the borate reacts with the ligand to produce an organic titanium boron crosslinking agent with a more complex structure. The organic titanium boron crosslinking agent reacts with the ortho-cis hydroxyl groups on the guar gum molecular chain under weak alkaline conditions to form a fracturing fluid with a spatial network structure in micro-morphology. The thickness of this network structure determines the temperature and shear resistance of the fracturing fluid.

[0139] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fracturing fluid crosslinking agent, characterized in that, it is mainly prepared by mixing an organic aluminum-boron crosslinking agent and an organic titanium-boron crosslinking agent, and the volume ratio of the organic aluminum-boron crosslinking agent to the organic titanium-boron crosslinking agent is 1:0.5 - 2; wherein, the organic aluminum-boron crosslinking agent is mainly prepared from the following raw materials by weight: 0.5 parts - 0.7 parts of nano-aluminum trioxide particles; 5.5 parts - 9 parts of borax; 0.004 parts - 0.005 parts of acetylacetone; 0.008 parts - 0.012 parts of sodium gluconate, 0.008 parts - 0.012 parts of ethylene glycol, 0.1 part of water; The organic titanium-boron crosslinking agent is mainly prepared from the following raw materials by weight: 0.4 parts - 0.6 parts of nano-titanium dioxide particles; 4 parts - 6 parts of borax; 0.0015 parts - 0.003 parts of acetylacetone; 1 part - 3 parts of xylitol; 0.03 parts - 0.04 parts of glycerol; 0.1 part of water; The particle size of the nano-aluminum trioxide particles ≤ 10 nm; the particle size of the nano-titanium dioxide particles ≤ 10 nm.

2. The fracturing fluid crosslinking agent according to claim 1, characterized in that, the volume ratio of the organic aluminum-boron crosslinking agent to the organic titanium-boron crosslinking agent is 1:1 - 2.

3. The fracturing fluid crosslinking agent according to claim 1, characterized in that, in the raw materials of the organic titanium-boron crosslinking agent, the weight ratio of the nano-aluminum trioxide particles to the borax is 0.05 - 0.1:

1.

4. The fracturing fluid crosslinking agent according to claim 1, characterized in that, in the raw materials of the organic titanium-boron crosslinking agent, the weight ratio of the nano-titanium dioxide particles to the borax is 0.08 - 0.12:

1.

5. The fracturing fluid crosslinking agent according to claim 1, characterized in that, the particle size of the nano-aluminum trioxide particles is 5 nm - 10 nm; the particle size of the nano-titanium dioxide particles is 5 nm - 10 nm.

6. The fracturing fluid crosslinking agent according to claim 1, characterized in that, the organic aluminum-boron crosslinking agent is mainly prepared by the following method: First, add nano-aluminum trioxide particles to water and stir to obtain a first solution; then adjust the pH of the first solution to 9 - 10 to obtain a second solution; thereafter, add borax, acetylacetone, sodium gluconate, and ethylene glycol to the second solution and stir and react at 50°C - 80°C for 3 h - 6 h to obtain the organic aluminum-boron crosslinking agent; the organic titanium-boron crosslinking agent is mainly prepared by the following method: First, add nano-titanium dioxide particles to water and stir to obtain a first solution; then adjust the pH of the first solution to 9 - 10 to obtain a second solution; thereafter, add borax, acetylacetone, xylitol, and glycerol to the second solution and stir and react at 60°C - 90°C for 3 h - 6 h to obtain the organic titanium-boron crosslinking agent.

7. A preparation method of the fracturing fluid crosslinking agent according to any one of claims 1 - 6, characterized in that, it includes the following steps: Mix the organic aluminum-boron crosslinking agent and the organic titanium-boron crosslinking agent according to the volume ratio of the raw materials, and stir for 30 min - 1 h to obtain the fracturing fluid crosslinking agent.

8. Use of a fracturing fluid crosslinking agent according to any one of claims 1-6 in the preparation of a guar gum fracturing fluid.

9. A guar gum fracturing fluid, characterized in that it is mainly prepared by the following method: First, adjust the pH value of the guar gum solution to 9-10, and then add a fracturing fluid crosslinking agent according to any one of claims 1-6 and mix to obtain a guar gum fracturing fluid.

Images