Salt-tolerant hydrophobic association polymer, intermediate and preparation method thereof, and fracturing fluid preparation method

Abstract

The invention relates to a salt-tolerant hydrophobic association polymer, an intermediate, a preparation method and a fracturing fluid preparation method. Wherein the structural formula of the salt-tolerant hydrophobic associated polymer is as follows: # imgabs0 #, x, y, z and m are monomer molar ratios, x is 60%-80%, y is 10%-22%, z is 9%-15%, and m is 1%-3%; r1 is dodecyl, hexadecyl or octadecyl. The invention has the following effects: (1) the salt-tolerant hydrophobic association polymer prepared by the preparation method of the salt-tolerant hydrophobic association polymer is high in yield, low in cost and simple in production process; and (2) the prepared salt-tolerant hydrophobic associated polymer has excellent salt tolerance. And (3) the fracturing fluid prepared from the salt-tolerant hydrophobic association polymer has a good thickening effect in a saline solution, and can meet the engineering requirements of field construction of an oil field.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemical additives, and particularly relates to a salt-resistant hydrophobic associating polymer, an intermediate and a preparation method, and a fracturing fluid preparation method. Background Art

[0002] As the development of conventional oil and gas reservoirs gradually reaches the end stage, low-permeability, ultra-low-permeability, deep-layer high-temperature unconventional oil and gas resources such as tight sandstone gas, coalbed methane, and shale gas are in urgent need of development and utilization. Fracturing transformation is an important means of unconventional oil and gas development, and the performance of the fracturing fluid plays a decisive role in the success of the construction. At present, the water-based fracturing fluid based on guar gum is widely used in fracturing operations. This type of fracturing fluid has a good thickening effect, but it generally has the disadvantages of being easily biodegradable, high insoluble content, incomplete gel breaking, high residue content, and easy to damage the formation. In addition, the cost is increasing day by day, so there is an urgent need for the emergence of fracturing fluids with excellent performance.

[0003] Hydrophobic associating polymers refer to water-soluble polymers with a small amount of hydrophobic groups on the polymer macromolecular chains. In the polymer aqueous solution, due to the hydrophobic effect of the hydrophobic groups, the molecular chains aggregate to form intramolecular or intermolecular associations. When the solution concentration is less than the critical association concentration, the polymer will mainly form intramolecular associations, the macromolecular chains will curl, the fluid dynamics volume of the polymer will decrease, and the viscosity of the aqueous solution will be low; when the concentration is higher than the critical association concentration, the polymer will mainly form intermolecular associations, a network will be formed between the molecular chains, the fluid dynamics volume will increase sharply, and the viscosity will increase. Currently available hydrophobic associating polymer fracturing fluids have the disadvantages of poor salt resistance and severe performance loss during the preparation process of mineralized formation water. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a salt-tolerant hydrophobic associating polymer, an intermediate and a preparation method and a fracturing fluid preparation method.

[0005] In order to achieve the above object, the structural formula of the tricationic monomer TCWH for preparing the salt-tolerant hydrophobically associating polymer provided by the present invention is as follows:

[0006]

[0007] In the formula, R 1 It is dodecyl, hexadecyl or octadecyl.

[0008] The preparation method of the tricationic monomer TCWH provided by the present invention comprises the following steps performed in sequence:

[0009] 1) dissolving N,N-dimethyl-1,3-diaminopropane in ethanol, slowly adding epichlorohydrin dropwise, the molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin is 1:2-2.1, reacting at 25° C. for 12 hours to obtain a light yellow ethanol solution of intermediate A;

[0010] 2) heating the ethanol solution of the intermediate A to 40° C., adding allyl bromide, wherein the molar ratio of the ethanol solution of the intermediate A to allyl bromide is 1:1.1-1.2, and reacting under reflux at 40° C. for 24 hours. After the reaction is completed, cooling is performed, and the ethanol is removed by rotary evaporation using a rotary evaporator. A light yellow viscous liquid is obtained by suction filtration. Ethyl acetate is then added to soak for 1 day, the resultant is washed, and vacuum dried to constant weight to obtain an intermediate B;

[0011] 3) The intermediate B is dissolved in ethanol, heated to 60° C., and dodecyl dimethyl tertiary amine is added dropwise using a constant pressure funnel, the molar ratio of the intermediate B to dodecyl dimethyl tertiary amine is 1:2.1-2.2, and the reaction is carried out for 22-24 hours. After the reaction is completed, the mixture is cooled and rotary evaporated using a rotary evaporator to remove the ethanol. A light yellow paste is obtained by suction filtration, and then acetone is added to soak for 1 day, the resultant is washed, and vacuum dried to constant weight to finally obtain the tricationic monomer TCWH;

[0012] The reaction formula is as follows:

[0013]

[0014]

[0015] In step 3), the dodecyldimethyl tertiary amine can be replaced by hexadecyldimethyl tertiary amine or octadecyldimethyl tertiary amine.

[0016] The structural formula of the salt-tolerant hydrophobic associating polymer HTCWM prepared by using the above-mentioned tricationic monomer TCWH provided by the present invention is as follows:

[0017]

[0018] Among them, x, y, z, and m are the molar ratios of monomers, x is 60%-80%, y is 10%-22%, z is 9%-15%, and m is 1%-3%.

[0019] The preparation method of the salt-tolerant hydrophobically associating polymer HTCWM provided by the present invention comprises the following steps performed in sequence:

[0020] 1) adding acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and the above-mentioned tricationic monomer TCWH as monomers into deionized water, wherein the molar percentages of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and the above-mentioned tricationic monomer TCWH are 60%-80%, 10%-22%, 9%-15% and 1%-3%, respectively, to prepare an aqueous solution with a monomer concentration of 25%-30%;

[0021] 2) After the aqueous solution is fully mixed, sodium hydroxide is added to adjust the pH to 7.0, and nitrogen is passed through for 30 minutes to remove dissolved oxygen in the water;

[0022] 3) using 2,2-azobisisobutylamidine dihydrochloride as an initiator, the initiator accounting for 0.1%-0.3% of the total monomer amount, the initial reaction temperature being 25° C., using an ultraviolet lamp for irradiation, and conducting free radical aqueous solution polymerization under ultraviolet light photoinitiation conditions with a wavelength of 365 nm, and reacting for 6-8 hours to prepare the salt-resistant hydrophobic associating polymer HTCWM;

[0023] The polymerization process is as follows:

[0024]

[0025] The method for preparing fracturing fluid by using salt-tolerant hydrophobic associating polymer HTCWM provided by the present invention comprises the following steps: cutting the hydrophobic associating polymer HTCWM into pieces, soaking and drying the polymer in anhydrous ethanol, grinding the powder into powder, and then adding the powder into mineralized water at a mass fraction of 0.3% to 0.6% to prepare the fracturing fluid.

[0026] The salt-resistant hydrophobic associating polymer, intermediate, preparation method and fracturing fluid preparation method provided by the present invention have the following beneficial effects:

[0027] (1) The salt-tolerant hydrophobically associating polymer prepared by the salt-tolerant hydrophobically associating polymer preparation method has high yield, low cost and simple production process.

[0028] (2) The prepared salt-tolerant hydrophobic associating polymer has excellent salt tolerance.

[0029] (3) The fracturing fluid made of salt-resistant hydrophobic associating polymer has a good thickening effect in salt solution and can meet the engineering requirements of oil field on-site construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a graph showing the viscosity change of the fracturing fluid obtained in Example 5 of the present invention under sodium chloride with different salinities;

[0031] Figure 2 This is a graph showing the viscosity change of the fracturing fluid obtained in Example 6 of the present invention under different mineralizations of calcium chloride;

[0032] Figure 3 This is a graph showing the viscosity change of the fracturing fluid obtained in Example 7 of the present invention in standard brine with different salinities. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Example 1: Preparation of tricationic monomer TCWH

[0035] The preparation method of the tricationic monomer TCWH provided in this embodiment comprises the following steps performed in sequence:

[0036] 1) dissolving N,N-dimethyl-1,3-diaminopropane in ethanol, slowly adding epichlorohydrin dropwise, the molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin is 1:2, reacting at 25° C. for 12 hours to obtain a light yellow ethanol solution of intermediate A;

[0037] 2) heating the ethanol solution of the intermediate A to 40° C., adding allyl bromide, wherein the molar ratio of the ethanol solution of the intermediate A to allyl bromide is 1:1.1, and reacting under reflux at 40° C. for 24 hours. After the reaction is completed, cooling is performed, and the ethanol is removed by rotary evaporation using a rotary evaporator. A light yellow viscous liquid is obtained by suction filtration. Ethyl acetate is then added to soak for 1 day, the resultant is washed, and vacuum dried to constant weight to obtain an intermediate B;

[0038] 3) The intermediate B was dissolved in ethanol, heated to 60° C., and dodecyl dimethyl tertiary amine was added dropwise using a constant pressure funnel. The molar ratio of intermediate B to dodecyl dimethyl tertiary amine was 1:2.1. The reaction was continued for 24 hours. After the reaction was completed, the mixture was cooled and evaporated using a rotary evaporator to remove the ethanol. A light yellow paste was obtained by suction filtration. Acetone was then added to soak the mixture for 1 day. The resultant was washed and dried under vacuum to constant weight. Finally, the tricationic monomer TCWH was obtained with a yield of 90%.

[0039] Example 2: Preparation of tricationic monomer TCWH

[0040] The preparation method of the tricationic monomer TCWH provided in this embodiment comprises the following steps performed in sequence:

[0041] 1) dissolving N,N-dimethyl-1,3-diaminopropane in ethanol, slowly adding epichlorohydrin dropwise, the molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin is 1:2.1, reacting at 25° C. for 12 hours to obtain a light yellow ethanol solution of intermediate A;

[0042] 2) heating the ethanol solution of the intermediate A to 40° C., adding propylene bromide, wherein the molar ratio of the ethanol solution of the intermediate A to propylene bromide is 1:1.2, and reacting under reflux at 40° C. for 24 hours. After the reaction is completed, cooling is performed, and ethanol is removed by rotary evaporation using a rotary evaporator. A light yellow viscous liquid is obtained by suction filtration. Ethyl acetate is then added to soak for 1 day, the resultant is washed, and vacuum dried to constant weight to obtain an intermediate B;

[0043] 3) The intermediate B was dissolved in ethanol, heated to 60° C., and then dodecyl dimethyl tertiary amine was added dropwise using a constant pressure funnel, the molar ratio of intermediate B to dodecyl dimethyl tertiary amine was 1:2.2, and the reaction was continued for 24 hours. After the reaction was completed, the mixture was cooled and evaporated using a rotary evaporator to remove the ethanol. A light yellow paste was obtained by suction filtration, and then acetone was added to soak the mixture for 1 day. The resultant was washed and vacuum dried to constant weight to finally obtain the tricationic monomer TCWH. The yield was 94%.

[0044] Example 3: Preparation of tricationic monomer TCWH

[0045] The preparation method of the tricationic monomer TCWH provided in this embodiment comprises the following steps performed in sequence:

[0046] 1) dissolving N,N-dimethyl-1,3-diaminopropane in ethanol, slowly adding epichlorohydrin dropwise, the molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin is 1:2.05, reacting at 25° C. for 12 hours to obtain a light yellow ethanol solution of intermediate A;

[0047] 2) heating the ethanol solution of the intermediate A to 40° C., adding allyl bromide, wherein the molar ratio of the ethanol solution of the intermediate A to allyl bromide is 1:1.15, and reacting under reflux at 40° C. for 24 hours. After the reaction is completed, cooling is performed, and the ethanol is removed by rotary evaporation using a rotary evaporator. A light yellow viscous liquid is obtained by suction filtration. Ethyl acetate is then added to soak for 1 day, the resultant is washed, and vacuum dried to constant weight to obtain an intermediate B;

[0048] 3) The intermediate B was dissolved in ethanol, heated to 60° C., and then dodecyl dimethyl tertiary amine was added dropwise using a constant pressure funnel, the molar ratio of intermediate B to dodecyl dimethyl tertiary amine was 1:2.15, and the reaction was continued for 24 hours. After the reaction was completed, the mixture was cooled and evaporated using a rotary evaporator to remove the ethanol. A light yellow paste was obtained by suction filtration, and then acetone was added to soak the mixture for 1 day. The resultant was washed and vacuum dried to constant weight to finally obtain the tricationic monomer TCWH. The yield was 96%.

[0049] Example 4: Preparation of salt-tolerant hydrophobic associating polymer HTCWM

[0050] The preparation method of the salt-tolerant hydrophobically associating polymer HTCWM provided in this embodiment comprises the following steps performed in sequence:

[0051] 1) adding 9 g of acrylamide, 3 g of acrylic acid, 1.8 g of 2-acrylamido-2-methylpropanesulfonic acid and 0.3 g of tricationic monomer TCWH as monomers into deionized water to prepare an aqueous solution with a monomer concentration of 30%;

[0052] 2) After the aqueous solution is fully mixed, sodium hydroxide is added to adjust the pH to 7.0, and nitrogen is passed through for 30 minutes to remove dissolved oxygen in the water;

[0053] 3) Using 2,2-azobisisobutylamidine dihydrochloride (V50) as an initiator, the initiator accounts for 0.3% of the total monomer amount, the initial reaction temperature is 25° C., an ultraviolet lamp is used for irradiation, and free radical aqueous solution polymerization is carried out under the condition of ultraviolet light photoinitiation with a wavelength of 365 nm. The reaction is carried out for 8 hours to prepare the salt-resistant hydrophobic associating polymer HTCWM.

[0054] Embodiment 5:

[0055] The salt-resistant hydrophobic associating polymer HTCWM in Example 4 was taken and cut into pieces, soaked in anhydrous ethanol and dried, and ground into powder. Then, sodium chloride solutions with different mineralizations were used to prepare a water-based fracturing fluid with a mass fraction of 0.4%. The viscosity of the fracturing fluid was tested using a HAAKEMARS III (006-1322) rheometer at 25°C. At a higher mineralization, the viscosity of the fracturing fluid was higher than 180 mPa·s, indicating good thickening properties and tolerance to sodium chloride.

[0056] Embodiment 6:

[0057] The salt-resistant hydrophobic associating polymer HTCWM in Example 4 was taken and cut into pieces, soaked in anhydrous ethanol and dried, and ground into powder. Then, calcium chloride solutions with different mineralizations were used to prepare a water-based fracturing fluid with a mass fraction of 0.4%. The viscosity of the fracturing fluid was tested using a HAAKEMARS III (006-1322) rheometer at 25°C. At a higher mineralization, the viscosity of the fracturing fluid was higher than 80 mPa·s, indicating good thickening properties and tolerance to calcium chloride.

[0058] Embodiment 7:

[0059] The salt-resistant hydrophobic associating polymer HTCWM in Example 4 was taken and cut into pieces, soaked in anhydrous ethanol and dried, and ground into powder. Then, standard brine with different mineralization degrees was used to prepare a water-based fracturing fluid with a mass fraction of 0.4%. The viscosity of the fracturing fluid was tested using a HAAKEMARS III (006-1322) rheometer at 25°C. At a higher mineralization degree, the viscosity of the fracturing fluid was higher than 140 mPa·s, and the fracturing fluid had good thickening properties and tolerance to standard salt.

[0060] Although the specific implementation of the present invention has been described in detail, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A tricationic monomer TCWH for preparing a salt-tolerant hydrophobic associating polymer, the structural formula of which is as follows: In the formula, R1 is dodecyl, hexadecyl or octadecyl.

2. A method for preparing the tricationic monomer TCWH according to claim 1, characterized in that: The preparation method comprises the following steps performed in sequence: 1) dissolving N,N-dimethyl-1,3-diaminopropane in ethanol, slowly adding epichlorohydrin dropwise, the molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin is 1:2-2.1, reacting at 25° C. for 12 hours to obtain a light yellow ethanol solution of intermediate A; 2) heating the ethanol solution of the intermediate A to 40° C., adding allyl bromide, wherein the molar ratio of the ethanol solution of the intermediate A to allyl bromide is 1:1.1-1.2, and reacting under reflux at 40° C. for 24 hours. After the reaction is completed, cooling is performed, and the ethanol is removed by rotary evaporation using a rotary evaporator. A light yellow viscous liquid is obtained by suction filtration. Ethyl acetate is then added to soak for 1 day, the resultant is washed, and vacuum dried to constant weight to obtain an intermediate B; 3) The intermediate B is dissolved in ethanol, heated to 60° C., and dodecyl dimethyl tertiary amine is added dropwise using a constant pressure funnel, the molar ratio of the intermediate B to dodecyl dimethyl tertiary amine is 1:2.1-2.2, and the reaction is carried out for 22-24 hours. After the reaction is completed, the mixture is cooled and rotary evaporated using a rotary evaporator to remove the ethanol. A light yellow paste is obtained by suction filtration, and then acetone is added to soak for 1 day, the resultant is washed, and vacuum dried to constant weight to finally obtain the tricationic monomer TCWH; The reaction formula is as follows:

3. The method for preparing the tricationic monomer TCWH according to claim 2, characterized in that: In step 3), the dodecyldimethyl tertiary amine can be replaced by hexadecyldimethyl tertiary amine or octadecyldimethyl tertiary amine.

4. A salt-tolerant hydrophobic associating polymer HTCWM prepared using the tricationic monomer TCWH according to claim 1, having the following structural formula: in, x, y, z, and m are the molar ratios of monomers, x is 60%-80%, y is 10%-22%, z is 9%-15%, and m is 1%-3%.

5. A method for preparing the salt-tolerant hydrophobically associating polymer HTCWM according to claim 4, characterized in that: The preparation method comprises the following steps performed in sequence: 1) adding acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and the above-mentioned tricationic monomer TCWH as monomers into deionized water, wherein the molar percentages of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and the above-mentioned tricationic monomer TCWH are 60%-80%, 10%-22%, 9%-15% and 1%-3%, respectively, to prepare an aqueous solution with a monomer concentration of 25%-30%; 2) After the aqueous solution is fully mixed, sodium hydroxide is added to adjust the pH to 7.0, and nitrogen is passed through for 30 minutes to remove dissolved oxygen in the water; 3) using 2,2-azobisisobutylamidine dihydrochloride as an initiator, the initiator accounting for 0.1%-0.3% of the total monomer amount, the initial reaction temperature being 25° C., using an ultraviolet lamp for irradiation, and conducting free radical aqueous solution polymerization under ultraviolet light photoinitiation conditions with a wavelength of 365 nm, and reacting for 6-8 hours to prepare the salt-resistant hydrophobic associating polymer HTCWM; The polymerization process is as follows:

6. A method for preparing a fracturing fluid using the salt-tolerant hydrophobically associating polymer HTCWM according to claim 4, characterized in that: The method comprises the following steps: cutting the hydrophobic associating polymer into pieces, soaking and drying the polymer in anhydrous ethanol, grinding the polymer into powder, and then adding the powder into mineralized water at a mass fraction of 0.3% to 0.6% to prepare a fracturing fluid.

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