Salt-tolerant hydrophobically associating polymers, intermediates and methods of making and methods of making fracturing fluids

Abstract

A salt-resistant hydrophobic associating polymer, an intermediate, a preparation method, and a fracturing fluid preparation method are disclosed. The structural formula of the salt-resistant hydrophobic associating polymer is as follows: where x, y, z, and m are the 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 advantages of this invention are: (1) The salt-resistant hydrophobic associating polymer prepared by the method has high yield, low cost, and a simple production process. (2) The obtained salt-resistant hydrophobic associating polymer exhibits excellent salt tolerance. (3) The fracturing fluid prepared using the salt-resistant hydrophobic associating polymer has a good thickening effect in salt solutions, which can meet the engineering needs of oilfield field construction.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical additives technology, and specifically relates to a salt-resistant hydrophobic associative polymer, an intermediate, a preparation method, and a fracturing fluid preparation method. Background Technology

[0002] As conventional oil and gas reservoirs reach the end of their development phase, unconventional oil and gas resources such as tight sandstone gas, coalbed methane, and shale gas—characterized by low permeability and ultra-low permeability, and high temperature in deep formations—urgently need to be developed and utilized. Fracturing is a crucial method in unconventional oil and gas development, and the performance of fracturing fluids plays a decisive role in the success or failure of the operation. Currently, water-based fracturing fluids based on guar gum are widely used in fracturing operations. While these fluids have good thickening effects, they generally suffer from drawbacks such as easy biodegradability, high insoluble content, incomplete gel breaking, high residue content, and potential formation damage. Furthermore, their costs are escalating rapidly. Therefore, there is an urgent need for fracturing fluids with superior performance.

[0003] Hydrophobic associating polymers are water-soluble polymers with a small number of hydrophobic groups on their macromolecular chains. In aqueous solutions, due to the hydrophobic interactions of these groups, the molecular chains aggregate, forming intramolecular or intermolecular associations. When the solution concentration is below the critical association concentration, the polymer primarily forms intramolecular associations, the macromolecular chains coil, the polymer's hydrodynamic volume decreases, and the aqueous solution viscosity is low. Above the critical association concentration, intermolecular associations dominate, the molecular chains form a network, the hydrodynamic volume increases sharply, and the viscosity increases. Currently available hydrophobic associating polymer fracturing fluids suffer from poor salt tolerance and significant performance loss during preparation with highly saline formation water. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a salt-resistant hydrophobic associative polymer, an intermediate, a preparation method thereof, and a fracturing fluid preparation method.

[0005] To achieve the above objectives, the present invention provides the following structural formula for the tricationic monomer TCWH used in the preparation of salt-resistant hydrophobic associative polymers:

[0006]

[0007] In the formula, R1 is dodecyl, hexadecyl, or octadecyl.

[0008] The method for preparing the tricationic monomer TCWH provided by this invention includes the following steps performed in sequence:

[0009] 1) Dissolve N,N-dimethyl-1,3-diaminopropane in ethanol, and slowly add epichlorohydrin. The molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin is 1:2-2.1. React at 25°C for 12 hours to obtain a pale yellow ethanol solution of intermediate A.

[0010] 2) The ethanol solution of intermediate A was heated to 40°C, and bromopropylene was added. The molar ratio of the ethanol solution of intermediate A to bromopropylene was 1:1.1-1.2. The mixture was refluxed at 40°C for 24 hours. After the reaction was completed, the mixture was cooled and the ethanol was removed by rotary evaporation. The mixture was filtered to obtain a pale yellow viscous liquid. Ethyl acetate was then added and the mixture was soaked for 1 day. The product was washed and dried under vacuum to constant weight to obtain intermediate B.

[0011] 3) Dissolve the above intermediate B in ethanol, heat to 60°C, and then add dodecyl dimethyl tertiary amine dropwise using a constant pressure funnel. The molar ratio of intermediate B to dodecyl dimethyl tertiary amine is 1:2.1-2.2. React for 22-24 hours. After the reaction is completed, cool and remove ethanol by rotary evaporation. Filter to obtain a pale yellow paste. Then add acetone to soak for 1 day, wash the product, and vacuum dry to constant weight to finally obtain the tricationic monomer TCWH.

[0012] The reaction formula is as follows:

[0013]

[0014]

[0015] In step 3), the dodecyl dimethyl tertiary amine can be replaced by hexadecyl dimethyl tertiary amine or octadecyl dimethyl tertiary amine.

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

[0017]

[0018] Where 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 method for preparing the salt-resistant hydrophobic associative polymer HTCWM provided by this invention includes the following steps performed in sequence:

[0020] 1) Add acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and the above-mentioned tricationic monomer TCWH as monomers to 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 above aqueous solution is thoroughly mixed, add sodium hydroxide to adjust the pH to 7.0, and purge with nitrogen for 30 minutes to remove dissolved oxygen from the water;

[0022] 3) Using 2,2-azobisisobutylamidine dihydrochloride as an initiator, the initiator accounts for 0.1%-0.3% of the total monomer. The initial reaction temperature is 25°C. Under ultraviolet light initiation conditions with a wavelength of 365nm, free radical aqueous solution polymerization is carried out. The salt-resistant hydrophobic associative polymer HTCWM can be prepared by reacting for 6-8 hours.

[0023] The polymerization process is as follows:

[0024]

[0025] The method for preparing fracturing fluid using salt-resistant hydrophobic associating polymer HTCWM provided by the present invention is to cut the hydrophobic associating polymer HTCWM into small pieces, soak it in anhydrous ethanol, dry it, grind it into powder, and then add it to mineralized water at a mass fraction of 0.3%-0.6% to prepare fracturing fluid.

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

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

[0028] (2) The salt-resistant hydrophobic associative polymer obtained has excellent salt tolerance.

[0029] (3) The fracturing fluid made of salt-resistant hydrophobic associative polymer has a good thickening effect in salt solution and can meet the engineering needs of oilfield field construction. Attached Figure Description

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

[0031] Figure 2 This is a graph showing the viscosity variation of the fracturing fluid obtained in Example 6 of the present invention under different degrees of calcium chloride salinity.

[0032] Figure 3 This is a graph showing the viscosity variation of the fracturing fluid obtained in Example 7 of the present invention under standard brine with different salinity. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0034] Example 1: Preparation of the tricationic monomer TCWH

[0035] The method for preparing the tricationic monomer TCWH provided in this embodiment includes the following steps performed in sequence:

[0036] 1) Dissolve N,N-dimethyl-1,3-diaminopropane in ethanol, slowly add epichlorohydrin, the molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin is 1:2, react at 25°C for 12 hours to obtain a pale yellow ethanol solution of intermediate A.

[0037] 2) The ethanol solution of intermediate A was heated to 40°C, and bromopropylene was added. The molar ratio of the ethanol solution of intermediate A to bromopropylene was 1:1.1. The mixture was refluxed at 40°C for 24 hours. After the reaction was completed, the mixture was cooled and the ethanol was removed by rotary evaporation. The mixture was filtered to obtain a pale yellow viscous liquid. Ethyl acetate was then added and the mixture was soaked for 1 day. The product was washed and dried under vacuum to constant weight to obtain intermediate B.

[0038] 3) Dissolve the above intermediate B in ethanol, heat to 60°C, and then add dodecyl dimethyl tertiary amine dropwise using a constant pressure funnel. The molar ratio of intermediate B to dodecyl dimethyl tertiary amine is 1:2.1. React for 24 hours. After the reaction is completed, cool and remove ethanol by rotary evaporation. Filter to obtain a pale yellow paste. Then, add acetone to soak for 1 day, wash the product, and vacuum dry to constant weight to finally obtain the tricationic monomer TCWH with a yield of 90%.

[0039] Example 2: Preparation of the tricationic monomer TCWH

[0040] The method for preparing the tricationic monomer TCWH provided in this embodiment includes the following steps performed in sequence:

[0041] 1) Dissolve N,N-dimethyl-1,3-diaminopropane in ethanol, and slowly add epichlorohydrin. The molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin is 1:2.1. React at 25°C for 12 hours to obtain a pale yellow ethanol solution of intermediate A.

[0042] 2) The ethanol solution of intermediate A was heated to 40°C, and bromopropylene was added. The molar ratio of the ethanol solution of intermediate A to bromopropylene was 1:1.2. The mixture was refluxed at 40°C for 24 hours. After the reaction was completed, the mixture was cooled and the ethanol was removed by rotary evaporation. The mixture was filtered to obtain a pale yellow viscous liquid. Ethyl acetate was then added and the mixture was soaked for 1 day. The product was washed and dried under vacuum to constant weight to obtain intermediate B.

[0043] 3) Dissolve the above intermediate B in ethanol, heat to 60°C, and then add dodecyl dimethyl tertiary amine dropwise using a constant pressure funnel. The molar ratio of intermediate B to dodecyl dimethyl tertiary amine is 1:2.2. React for 24 hours. After the reaction is complete, cool and remove ethanol by rotary evaporation. Filter to obtain a pale yellow paste. Then, soak in acetone for 1 day, wash the product, and vacuum dry to constant weight to finally obtain the tricationic monomer TCWH; the yield is 94%.

[0044] Example 3: Preparation of the tricationic monomer TCWH

[0045] The method for preparing the tricationic monomer TCWH provided in this embodiment includes the following steps performed in sequence:

[0046] 1) Dissolve N,N-dimethyl-1,3-diaminopropane in ethanol, and slowly add epichlorohydrin. The molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin is 1:2.05. React at 25°C for 12 hours to obtain an ethanol solution of pale yellow intermediate A.

[0047] 2) The ethanol solution of intermediate A was heated to 40°C, and bromopropylene was added. The molar ratio of the ethanol solution of intermediate A to bromopropylene was 1:1.15. The mixture was refluxed at 40°C for 24 hours. After the reaction was completed, the mixture was cooled and the ethanol was removed by rotary evaporation. The mixture was filtered to obtain a pale yellow viscous liquid. Ethyl acetate was then added and the mixture was soaked for 1 day. The product was washed and dried under vacuum to constant weight to obtain intermediate B.

[0048] 3) Dissolve the above intermediate B in ethanol, heat to 60°C, and then add dodecyl dimethyl tertiary amine dropwise using a constant pressure funnel. The molar ratio of intermediate B to dodecyl dimethyl tertiary amine is 1:2.15. React for 24 hours. After the reaction is complete, cool and remove ethanol by rotary evaporation. Filter to obtain a pale yellow paste. Then, soak in acetone for 1 day, wash the product, and vacuum dry to constant weight to finally obtain the tricationic monomer TCWH; the yield is 96%.

[0049] Example 4: Preparation of salt-resistant hydrophobic associative polymer HTCWM

[0050] The method for preparing the salt-resistant hydrophobic associative polymer HTCWM provided in this embodiment includes the following steps performed in sequence:

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

[0052] 2) After the above aqueous solution is thoroughly mixed, add sodium hydroxide to adjust the pH to 7.0, and purge with nitrogen for 30 minutes to remove dissolved oxygen from the water;

[0053] 3) Using 2,2-azobisisobutylamidine dihydrochloride (V50) as an initiator, which accounts for 0.3% of the total monomer, the initial reaction temperature is 25°C, and the reaction is carried out under ultraviolet light initiation conditions with a wavelength of 365nm. Free radical aqueous solution polymerization is carried out, and the salt-resistant hydrophobic associative polymer HTCWM can be prepared after 8 hours of reaction.

[0054] Example 5:

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

[0056] Example 6:

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

[0058] Example 7:

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

[0060] While specific embodiments of the present invention have been described in detail, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. A trication monomer TCWH for preparing salt-tolerant hydrophobic associating polymer, having the following structural formula: wherein R1 is dodecyl, hexadecyl or octadecyl. The preparation method comprises the following steps in sequence:

2. A method for preparing the tricationic monomer TCWH according to claim 1, characterized by: 1) dissolving N,N-dimethyl-1,3-diaminopropane in ethanol, slowly adding epichlorohydrin, the molar ratio of N,N-dimethyl-1,3-diaminopropane to epichlorohydrin being 1:2-2.1, and reacting at 25℃ for 12 hours to obtain a yellowish ethanol solution of intermediate A; 2) heating the ethanol solution of intermediate A to 40℃, adding bromopropylene, the molar ratio of the ethanol solution of intermediate A to bromopropylene being 1:1.1-1.2, refluxing at 40℃ for 24 hours, cooling after the reaction, rotary evaporation to remove ethanol, and suction filtration to obtain a yellowish viscous liquid, then soaking in ethyl acetate for 1 day, washing the product, and vacuum drying to constant weight to obtain intermediate B; 3) dissolving intermediate B in ethanol, heating to 60℃, then adding dodecyldimethyl tertiary amine through a constant pressure funnel, the molar ratio of intermediate B to dodecyldimethyl tertiary amine being 1:2.1-2.2, and reacting for 22-24 hours, cooling after the reaction, rotary evaporation to remove ethanol, and suction filtration to obtain a yellowish paste, then soaking in acetone for 1 day, washing the product, and vacuum drying to constant weight to finally obtain the trication monomer TCWH; The reaction formula is as follows: In step 3), the dodecyldimethyl tertiary amine can be replaced by hexadecyldimethyl tertiary amine or octadecyldimethyl tertiary amine.

3. The method for preparing the tricationic monomer TCWH according to claim 2, characterized in that:

4. A salt-tolerant hydrophobic associating polymer HTCWM prepared by using the trication monomer TCWH of claim 1, having the following structural formula: x, y, z and m are molar ratios of monomers, x is 60%-80%, y is 10%-22%, z is 9%-15%, and m is 1%-3%. wherein The preparation method comprises the following steps in sequence:

5. A process for the preparation of the hydrophobically associating polymer of claim 4, which is characterized by: 1) adding acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and the trication monomer TCWH as monomers in deionized water, the molar percentages of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and the trication monomer TCWH being 60%-80%, 10%-22%, 9%-15% and 1%-3% respectively, and preparing an aqueous solution with a monomer concentration of 25%-30%; 2) after the aqueous solution is fully mixed and uniform, adding sodium hydroxide to adjust the pH to 7.0, and removing dissolved oxygen in water by nitrogen blowing for 30 minutes; 3) using 2,2-azobisdimethylamide dihydrochloride as an initiator, the initiator accounting for 0.1%-0.3% of the total monomers, and using a UV lamp to irradiate at an initial temperature of 25℃, and under the condition of UV light with a wavelength of 365 nm, the salt-tolerant hydrophobic associating polymer HTCWM is prepared by free radical aqueous solution polymerization for 6-8 hours; The polymerization process is as follows: ​ 6. A method for preparing a fracturing fluid using the salt-tolerant hydrophobically associating polymer HTCWM of claim 4, characterized in that: The method is to cut the hydrophobic associated polymer, soak in anhydrous ethanol, dry, beat into powder, then add into water of mineralization according to 0.3%-0.6% mass fraction to make the fracturing fluid.

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