Micro-nano spherical modified silica acid liquid gelatinizer, its preparation method and application

Abstract

This invention provides a micro / nano-scale spherical modified silica acid gelling agent, its preparation method, and its application. The preparation method of this micro / nano-scale spherical modified silica acid gelling agent is as follows: nano-SiO2 and a silane coupling agent are reacted to obtain surface-modified nano-SiO2; the surface-modified nano-SiO2 is reacted with acrylic acid to obtain a macromolecular initiator; in the presence of an oxidant and a reducing agent, the macromolecular initiator is reacted with vinyl sulfonate, vinyl quaternary ammonium salt, and N-vinylpyrrolidone to obtain the micro / nano-scale spherical modified silica acid gelling agent. The micro / nano-scale spherical modified silica acid gelling agent of this invention is prepared by the above method. This invention also provides the application of this acid gelling agent in acid fracturing. The acid gelling agent of this invention can achieve a temperature resistance of 180℃, which can support oil and gas channels in specific formations, thereby improving oil recovery.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, specifically to a micro-nano spherical modified silica liquid gelling agent, its preparation method, and its application. Background Technology

[0002] Acid fracturing is one of the most important production enhancement technologies in oil and gas fields. It typically uses acid to dissolve or etch the target formation, creating pathways for oil and gas flow and increasing production. Studies show that the main influencing factors in acid fracturing operations are the conductivity of the fracture and the length of the dissolved fracture. Reducing the acid dissolution rate is crucial for ensuring successful acid fracturing operations. In field operations, increasing the acid viscosity is generally used to reduce the fracturing effect, as the molecular chain network structure reduces the diffusion rate of hydrogen ions, thereby decreasing the acid's corrosive effect on the rock surface. Therefore, the research on acid gelling agents has become one of the important topics in oil and gas field development.

[0003] In recent years, with the increasing difficulty of oil and gas well development, the number of deep and ultra-deep wells has gradually increased, leading to a rise in bottom-hole temperatures. At high temperatures, polymer molecules are susceptible to thermal degradation and thermo-oxidative degradation, resulting in polymer chain breakage. Simultaneously, the increased molecular thermal motion of hydrogen ions at high temperatures promotes chain degradation and impairs the thickening properties of drilling fluids. Product surveys indicate that some companies' gelling acids suffer from poor acid resistance and weak temperature resistance; while others have developed high-temperature acid-resistant slow-setting acids with superior temperature and acid resistance, but their higher prices negatively impact the production efficiency of oilfield enterprises.

[0004] Currently, there are several ways to improve the temperature resistance of polymer molecules: 1. Introducing rigid side chains of macromolecules; 2. Increasing the rigidity of the main chain; 3. Introducing monomers with hydrolysis-resistant functional groups; 4. Introducing hydrophobic associative monomers; 5. Introducing rigid framework structures. Most researchers generally improve the temperature resistance of acid gelling agents by introducing macromolecular side chains or hydrolysis-resistant functional groups, mainly because the polymerization mechanism is well-defined and easy to synthesize.

[0005] CN113563505A discloses a temperature-, acid-, and salt-resistant acid gelling agent and its preparation method. The acid gelling agent is synthesized from anionic monomers, cationic monomers, salt-resistant monomers, temperature-resistant monomers, and hydrophobic monomers under the action of coupling agents and other treatment agents. The acid gelling agent prepared by this invention has the characteristics of strong thickening ability, low shear resistance, acid stability, good temperature resistance, and minimal secondary damage to the formation. However, its reaction steps are relatively complicated, which is not conducive to large-scale production.

[0006] CN113321764A discloses an acid gelling agent, its preparation method, and its application. This acid gelling agent is synthesized from acrylamide, functional monomers, and methacryloyloxyethyltrimethylammonium chloride under the action of a chain control agent and an initiator. The acid gelling agent exhibits high thickening performance, good temperature resistance and shear strength, and can well meet the high-temperature acidizing requirements of deep formations. However, its reaction steps are relatively cumbersome, which is not conducive to large-scale production.

[0007] CN110982507A discloses an acid gelling agent for acid fracturing, its preparation method, and its application. It is synthesized from acrylamide, a bio-based cationic monomer, a temperature- and salt-resistant monomer, and a temperature-sensitive monomer. The acid gelling agent obtained by this invention exhibits good solubility and thickening properties in acid solutions. However, its temperature resistance is poor, and it cannot be used in high-temperature wells above 150°C.

[0008] CN108913119A discloses a fracturing gelling agent and its preparation method, which is synthesized from monomers such as modified hydroxypropyl guar gum, acid drag reducer, and acid corrosion inhibitor. This gelling agent has the advantages of high viscosity, low water insoluble matter, rapid solubility, and good fluidity, allowing for fast solution preparation during use. However, its temperature resistance is poor, and it cannot be used in high-temperature wells above 150℃.

[0009] CN106047333A discloses a high-temperature resistant acid gelling agent and its preparation method. The acid gelling agent is polymerized from three monomers: acrylamide monomer, acryloyloxyethyltrimethylammonium chloride monomer, and a third monomer. This invention's high-temperature resistant acid gelling agent is simple to synthesize and possesses high-temperature resistance, salt resistance, and slowing properties, making it effective for high-temperature carbonate rock acidification modification construction. However, this gelling agent only increases the molecular weight of the molecular chain and does not improve the rigidity and temperature resistance of the molecular chain structure.

[0010] CN104388075A discloses an acid gelling agent suitable for high-temperature carbonate rock acidification and its preparation method. The acid gelling agent is a cationic acid gelling agent synthesized by copolymerization of methacryloyloxyethyltrimethylammonium chloride and acrylamide monomers using an initiator. This acid gelling agent requires a small dosage, is simple to prepare, has low cost, and stable performance, meeting the construction requirements for high-temperature carbonate rock acidification. However, this gelling agent only increases the molecular weight of the molecular chain and does not improve the rigidity and temperature resistance of the molecular chain structure.

[0011] CN103923633A discloses a gelling acid solution suitable for high-temperature carbonate rock acidification, containing the following components: 0.6-0.8% acid gelling agent, 2-4% corrosion inhibitor, 1-2% drainage aid, 1-2% iron ion stabilizer, and 15-22% hydrochloric acid. This gelling acid solution can be applied in high-temperature carbonate rock acidification construction, exhibiting high-temperature resistance, salt resistance, and slowing effects, and can be effectively used in high-temperature carbonate rock acidification modification construction. However, this invention only involves simple compounding and does not include the development of molecular treatment agents.

[0012] US20100028434A1 discloses a biopolymer liquid-water composition for producing self-gelling systems and gels. The pH of the liquid composition is adjustable within the range of 5.8 to 7.4, and it forms a stable solid and a homogeneous gel at 10 to 70°C. The water-soluble molecules are polyol monophosphate disalts, monosulfonates, monosulfates, and monocarboxylates, etc. The composite gelling agent provided by this invention has not been explored in terms of temperature resistance, and its applicability is limited.

[0013] Therefore, how to prepare acid gelling agents resistant to high-temperature acid solutions is a current research focus and challenge. Summary of the Invention

[0014] To address the aforementioned technical problems, the present invention aims to provide a micro / nano-scale spherical modified silica acid gelling agent, its preparation method, and its application. The micro / nano-scale spherical modified SiO2 acid gelling agent provided by the present invention overcomes the problem of high-temperature degradation in existing acid gelling agents, exhibiting excellent acid and temperature resistance.

[0015] To achieve the above objectives, the present invention first provides a method for preparing micro / nano-scale spherical modified silica acid gelling agent, which includes the following steps:

[0016] (1) Nano-SiO2 and silane coupling agent are subjected to a first contact reaction in a first solvent, and after drying, surface-modified nano-SiO2 is obtained.

[0017] (2) The surface-modified nano-SiO2 and acrylic acid are subjected to a second contact reaction in a second solvent, and after drying, a macromolecular initiator is obtained;

[0018] (3) In the presence of an oxidant and a reducing agent, the macromolecular initiator is reacted with vinyl sulfonate, vinyl quaternary ammonium salt and N-vinylpyrrolidone in a third solvent to obtain the micro-nano spherical modified silica liquid gelling agent.

[0019] In the above preparation method, preferably, in step (1), the average particle size of the nano-SiO2 is 10-20 nm.

[0020] In the above preparation method, preferably, in step (1), the silane coupling agent includes one or a combination of several of γ-aminopropyltriethoxysilane (KH550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792), and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH602).

[0021] In the above preparation method, preferably, in step (1), the amount of the silane coupling agent added is 8 to 12 g relative to 100 mL of the first solvent (i.e., the amount of the silane coupling agent added is 80 to 120 g / L).

[0022] In the above preparation method, preferably, in step (1), the amount of nano-SiO2 added relative to 100mL of the first solvent is 1-5g (i.e., the amount of nano-SiO2 added is 10-50g / L), more preferably 1.5-3.5g.

[0023] In the above preparation method, preferably, in step (1), the first solvent may include water, such as deionized water or distilled water.

[0024] In the above preparation method, preferably, in step (1), the conditions for the first contact reaction are: a reaction temperature of 25-40℃ and a reaction time of 5-8h. More preferably, the first contact reaction can be carried out under stirring at a stirring speed of 200-1200 r / min. After the first contact reaction is completed, the reaction product can be subjected to conventional separation (e.g., filtration and / or centrifugation), washing, and other steps. After drying, the surface-modified nano-SiO2 is obtained.

[0025] In the above preparation method, preferably, in step (1), the drying is freeze drying, and the freeze drying conditions are: freezing with liquid nitrogen for 8 to 12 minutes, and freeze drying (vacuum drying) at -50°C and 9 Pa for 24 to 48 hours.

[0026] In step (1) of the preparation method of the present invention, the silane coupling agent used in the present invention can react on the surface of nano-SiO2 to prepare modified nano-SiO2 microspheres with contact sites on the surface.

[0027] In the above preparation method, preferably, in step (2), the amount of acrylic acid added relative to 100 mL of the second solvent is 0.05-0.5 mol (i.e., the amount of acrylic acid added is 0.5-5 mol / L), more preferably 0.1-0.3 mol.

[0028] In the above preparation method, preferably, in step (2), the amount of surface-modified nano-SiO2 added relative to 100 mL of the second solvent is 5-30 g, more preferably 10-20 g.

[0029] In the above preparation method, preferably, in step (2), the second solvent may include water, such as deionized water or distilled water.

[0030] In the above preparation method, preferably, in step (2), the conditions for the second contact reaction are: reaction temperature 25-40℃, reaction time 5-8h. More preferably, the second contact reaction can be carried out under stirring at a stirring speed of 600-1000 r / min. After the second contact reaction is completed, the reaction product can be subjected to conventional separation (e.g., filtration and / or centrifugation), washing, and other steps. After drying, the macromolecular initiator is obtained.

[0031] In the above preparation method, preferably, in step (2), the drying is freeze drying, and the freeze drying conditions are: freezing with liquid nitrogen for 8 to 12 minutes, and freeze drying (vacuum drying) at -50°C and 9 Pa for 24 to 48 hours.

[0032] In step (2) of the preparation method of the present invention, the surface-modified nano-SiO2 can serve as a framework. Its surface has highly active reaction sites that can react with acrylic acid on the surface, thereby increasing the activity of the reaction sites and further improving the reactivity of the modified nano-SiO2. After subsequent addition reactions, a polymer film can be formed on the surface of the modified nano-SiO2 spheres, thereby improving the temperature and acid resistance of the prepared acid gelling agent.

[0033] In the above preparation method, preferably, in step (3), the vinyl sulfonate (i.e., the vinyl-containing sulfonate) includes one or a combination of several of sodium 2-acrylamido-2-methylpropanesulfonate, sodium allyl sulfonate, sodium styrene sulfonate and sodium vinyl sulfonate.

[0034] In the above preparation method, preferably, in step (3), the vinyl quaternary ammonium salt includes one or a combination of several of the following: dimethyl diallyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, trimethyl vinyl ammonium bromide, and 4-vinylbenzyl trimethyl ammonium chloride.

[0035] In the above preparation method, preferably, in step (3), the amount of the macromolecular initiator added is 10-20g relative to 100mL of the third solvent (i.e., the amount of the macromolecular initiator added is 100-200g / L).

[0036] In the above preparation method, preferably, in step (3), the amount of vinyl sulfonate added relative to 100 mL of the third solvent is 0.05-0.5 mol (i.e., the amount of vinyl sulfonate added is 0.5-5.0 mol / L), more preferably 0.1-0.3 mol.

[0037] In the above preparation method, preferably, in step (3), the molar ratio of the vinyl sulfonate, the vinyl quaternary ammonium salt and the N-vinylpyrrolidone is 1:(1-3):(0.5-1.5), more preferably 1:(1.2-2.3):(0.7-1.3).

[0038] In the above preparation method, preferably, in step (3), the oxidant includes ammonium persulfate and / or potassium persulfate, etc.

[0039] In the above preparation method, preferably, in step (3), the reducing agent includes sodium bisulfite.

[0040] In the above preparation method, preferably, in step (3), the amount of oxidant added relative to 100 mL of the third solvent is 0.001-0.005 mol (i.e., the amount of oxidant added is 0.01-0.05 mol / L).

[0041] In the above preparation method, preferably, in step (3), the molar ratio of the oxidant to the reducing agent is 1:(0.5-1.5), more preferably 1:(0.8-1.3).

[0042] In the above preparation method, preferably, in step (3), the third solvent may include water, such as deionized water or distilled water.

[0043] In the above preparation method, preferably, in step (3), the conditions for the third contact reaction are: reaction temperature 65-80℃, reaction time 3-6h, and the third contact reaction is carried out under a nitrogen atmosphere. More preferably, the third contact reaction can be carried out under stirring at a stirring speed of 600-800 r / min. After the third contact reaction is completed, the reaction product can be subjected to conventional separation (e.g., filtration and / or centrifugation), washing, and other steps. After drying, micro-nano spherical modified silica liquid gelling agent is obtained.

[0044] In the above preparation method, preferably, in step (3), the drying is vacuum drying, the drying temperature is 60°C, the drying time is 24h, and the vacuum degree is 9Pa.

[0045] In this invention, the vinyl quaternary ammonium salt monomer, vinyl sulfonate monomer, and N-vinylpyrrolidone monomer all react by opening the C=C double bond. The vinyl sulfonate monomer, vinyl quaternary ammonium salt monomer, and N-vinylpyrrolidone monomer can all undergo polymerization via atom transfer radicals in the presence of an oxidizing agent and a reducing agent. The resulting polymer reacts with the highly active reaction sites on the modified nano-SiO2 surface. The steric hindrance provided by the macromolecular functional groups on its surface effectively prevents the polymers from entangled and adsorbing, thereby improving the temperature resistance of the prepared acid gelling agent.

[0046] Figure 1 This diagram illustrates the preparation process and molecular structure design of the micro / nano-scale spherical modified SiO2 acid gelling agent of the present invention. Figure 1 As shown, the preparation method of the micro / nano-scale spherical modified silica acid gelling agent provided by the present invention firstly increases the active reaction sites on the surface of nano-SiO2 through a silane coupling agent, and then reacts with acrylic acid to further increase the activity of the reaction sites, thereby improving the reactivity of the modified nano-SiO2. Then, C=C is introduced through the reaction between the amine and carboxyl groups in the vinyl quaternary ammonium salt monomer, vinyl sulfonate monomer, and N-vinylpyrrolidone monomer, which can effectively reduce the steric hindrance effect caused by the presence of solid particles, thus reducing the problem of low monomer grafting rate on the surface of solid particles. Simultaneously, the vinyl quaternary ammonium salt monomer and vinyl sulfonate monomer used in the present invention can provide macromolecular side chains, improving the steric hindrance of the prepared polymer; on the other hand, the anti-polyelectrolyte effect of the anions and cations can also better maintain the stability of the polymer molecular chain; and the N-vinylpyrrolidone monomer used in the present invention further improves the branch rigidity of the prepared polymer molecular chain.

[0047] The second aspect of the present invention provides a micro / nano-scale spherical modified silica liquid gelling agent, which is prepared by the above-described preparation method.

[0048] According to a specific embodiment of the present invention, preferably, the average particle size of the micro-nano spherical modified silica gel is 500-2000 nm, more preferably 500-900 nm.

[0049] According to a specific embodiment of the present invention, preferably, the micro-nano-sized spherical modified silica acid gelling agent is dissolved in a 20% (w / w) HCl aqueous solution at 180°C for 170 seconds. -1 Under shearing conditions for 1 hour, its apparent viscosity is greater than 45 mPa·s.

[0050] A third aspect of the present invention provides the application of the above-mentioned micro / nano-scale spherical modified silica acid gelling agent in acid fracturing.

[0051] In the above applications, preferably, the target reservoir temperature for acid fracturing is above 150°C, more preferably above 180°C.

[0052] The micro / nano-scale spherical modified silica acid gelling agent of this invention is composed of micro / nano-scale spherical SiO2 and an organic polymer loaded on the micro / nano-scale spherical SiO2. This invention uses micro / nano-scale spherical modified SiO2 as an excellent template, coating the surface with a polymer layer, introducing macromolecular side chains and a rigid main chain, thus improving the temperature and acid resistance of the acid gelling agent. The gelling acid system formed by the acid gelling agent of this invention can be applied in high-temperature reservoirs (180°C or even higher), its apparent viscosity is less affected by high temperature, and it maintains a high apparent viscosity even under high shear rate conditions, thereby delaying H2O degradation. + The purpose of this invention is to improve the acidification effect in high-temperature carbonate reservoirs by reducing the release rate, decreasing the acid-rock reaction rate, increasing the effective action distance of the acid, and thus enhancing the acidification effect. Therefore, the micro-nano-sized spherical modified silica acid gelling agent of this invention possesses excellent temperature and acid resistance, overcoming the problem of high-temperature degradation in existing acid gelling agents. This acid gelling agent can support oil and gas channels in specific formations, thereby improving oil recovery.

[0053] In summary, the micro / nano-scale spherical modified SiO2 acid gelling agent provided by this invention has the following excellent technical effects:

[0054] (1) Compared with traditional acid gelling agents, the micro-nano spherical modified SiO2 acid gelling agent of the present invention has rigid skeleton particles that can enter the pores of the target formation and support the oil and gas channels.

[0055] (2) Compared with traditional acid gelling agents, the polymer molecular chains of the micro-nano spherical modified SiO2 acid gelling agent of the present invention have macromolecular side chains and functional groups, which can improve its temperature resistance.

[0056] (3) Compared with traditional acid gelling agents, the reaction conditions of the micro-nano spherical modified SiO2 acid gelling agent of the present invention are easy to control, the reaction process is relatively stable, and it is easy to industrialize. Attached Figure Description

[0057] Figure 1 This is a flowchart and molecular structure design diagram of the preparation process of the micro / nano-scale spherical modified SiO2 acid gelling agent of the present invention. Detailed Implementation

[0058] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0059] The present invention will be described in detail below through embodiments.

[0060] In the following examples and comparative examples:

[0061] The nano-silica used was provided by Beijing Deco Island Gold Technology Co., Ltd.

[0062] The silane coupling agent, N-vinylpyrrolidone, vinyl sulfonate, and vinyl quaternary ammonium salt used were all provided by Sinopharm Shanghai Test Group.

[0063] The potassium persulfate, ammonium persulfate, and sodium bisulfite used were all supplied by Aladdin Reagent Co., Ltd.

[0064] The average particle size of the acid gelling agent was measured using a Malvern Zetasizer 3000 potentiometric particle size analyzer.

[0065] Example 1

[0066] This embodiment provides a micro / nano-scale spherical modified silica acid gelling agent, which is prepared by the following method:

[0067] (1) Add 68g of nano-SiO2 (20nm) to 2000mL of deionized water and stir magnetically for 20min to disperse it evenly in the deionized water to obtain a nano-SiO2 suspension; slowly add 200g of silane coupling agent KH550 to the nano-SiO2 suspension and stir at 1200r / min to dissolve it; then continue stirring and react at 40℃ for 8h, filter, freeze in liquid nitrogen for 10min, and vacuum dry at -50℃ and 9Pa for 24h to obtain surface-modified nano-SiO2;

[0068] (2) Add 0.6 mol of acrylic acid (AA) to 200 mL of deionized water to obtain AA solution; add 39.2 g of surface-modified nano SiO2 obtained in step (1) to the AA solution; react at 40 °C and 1000 r / min for 8 h, filter, freeze in liquid nitrogen for 10 min, and vacuum dry at -50 °C and 9 Pa for 24 h to obtain macromolecular initiator;

[0069] (3) In a 500 mL three-necked round-bottom flask equipped with a thermometer, stirring rod, and nitrogen inlet tube, 38.6 g of the macromolecular initiator obtained in step (2), 137.54 g (0.6 mol) of sodium 2-acrylamide-2-methylpropanesulfonate, 213.41 g (1.32 mol) of dimethyldiallyl ammonium chloride, and 86.58 g (0.78 mol) of N-vinylpyrrolidone were dispersed in 200 mL of deionized water. The temperature was raised to 80 °C, and 2.7 g (0.01 mol) of potassium persulfate and 1.35 g (0.013 mol) of sodium bisulfite were added sequentially. The mixture was stirred at 800 r / min for 6 h. After the reaction was completed, the mixture was filtered, washed, and dried (drying was done under vacuum at 60 °C for 24 h at a vacuum of 9 Pa) to obtain the micro / nano-scale spherical modified silica liquid gelling agent, named NSGA-1 (Nano Spheres of Gelling Agent-1).

[0070] The average particle size of NSGA-1 was measured to be 532.95 nm.

[0071] Example 2

[0072] This embodiment provides a micro / nano-scale spherical modified silica acid gelling agent, which is prepared by the following method:

[0073] (1) Add 32g of nano-SiO2 to 2000mL of deionized water and stir magnetically for 20min to disperse it evenly in the deionized water to obtain a nano-SiO2 suspension; slowly add 160g of silane coupling agent KH792 to the nano-SiO2 suspension and stir at 200r / min to dissolve it; then continue stirring and react at 40℃ for 8h, filter, freeze in liquid nitrogen for 8min, and vacuum dry at -50℃ and 9Pa for 48h to obtain surface-modified nano-SiO2;

[0074] (2) Add 0.2 mol of acrylic acid (AA) to 200 mL of deionized water to obtain AA solution; add 39.2 g of surface-modified nano SiO2 obtained in step (1) to the AA solution; react at 40 °C and 1000 r / min for 8 h, filter, freeze in liquid nitrogen for 10 min, and vacuum dry at -50 °C and 9 Pa for 24 h to obtain macromolecular initiator;

[0075] (3) In a 500 mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 29.48 g of the macromolecular initiator obtained in step (2), 57.64 g (0.4 mol) sodium allyl sulfonate, 191.08 g (0.92 mol) methacryloyloxyethyltrimethylammonium chloride and 44.4 g (0.4 mol) N-vinylpyrrolidone were dispersed into 200 mL of deionized water, heated to 80 °C, and 2.7 g (0.01 mol) potassium persulfate and 1.35 g (0.013 mol) sodium bisulfite were added sequentially. The mixture was stirred at 800 r / min for 6 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain the micro-nano spherical modified silica acid gelling agent, named NSGA-2 (Nano Spheres of Gelling Agent-2).

[0076] The average particle size of NSGA-2 was measured to be 732.95 nm.

[0077] Example 3

[0078] This embodiment provides a micro / nano-scale spherical modified silica acid gelling agent, which is prepared by the following method:

[0079] (1) Add 50g of nano-SiO2 to 2000mL of deionized water and stir magnetically for 20min to disperse it evenly in the deionized water to obtain a nano-SiO2 suspension; slowly add 240g of silane coupling agent KH602 to the nano-SiO2 suspension and stir at 1000r / min to dissolve it; then continue stirring and react at 40℃ for 8h, filter, freeze in liquid nitrogen for 12min, and vacuum dry at -50℃ and 9Pa for 24h to obtain surface-modified nano-SiO2;

[0080] (2) Add 0.4 mol of acrylic acid (AA) to 200 mL of deionized water to obtain AA solution; add 39.2 g of surface-modified nano SiO2 obtained in step (1) to the AA solution; react at 40 °C and 1000 r / min for 8 h, filter, freeze in liquid nitrogen for 12 min, and vacuum dry at -50 °C and 9 Pa for 36 h to obtain macromolecular initiator;

[0081] (3) In a 500 mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 22.4 g of the macromolecular initiator obtained in step (2), 41.23 g (0.2 mol) sodium styrene sulfonate, 41.52 g (0.25 mol) trimethylvinyl ammonium bromide and 15.54 g (0.14 mol) N-vinylpyrrolidone were dispersed into 200 mL of deionized water, heated to 80 °C, and 2.7 g (0.01 mol) potassium persulfate and 1.35 g (0.013 mol) sodium bisulfite were added in sequence. The mixture was stirred at 800 r / min for 6 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain the micro-nano spherical modified silica acid gelling agent, named NSGA-3 (Nano Spheres of Gelling Agent-3).

[0082] The average particle size of NSGA-3 was measured to be 892.43 nm.

[0083] Example 4

[0084] This embodiment provides a micro / nano-scale spherical modified silica acid gelling agent, which is prepared by the following method:

[0085] (1) Add 96g of nano-SiO2 to 2000mL of deionized water and stir magnetically for 20min to disperse it evenly in the deionized water to obtain a nano-SiO2 suspension; slowly add 190g of silane coupling agent KH550 to the nano-SiO2 suspension and stir at 800r / min to dissolve it; then continue stirring and react at 40℃ for 8h, filter, freeze in liquid nitrogen for 12min, and vacuum dry at -50℃ and 9Pa for 30h to obtain surface-modified nano-SiO2;

[0086] (2) Add 1.0 mol of acrylic acid (AA) to 200 mL of deionized water to obtain AA solution; add 39.2 g of surface-modified nano SiO2 obtained in step (1) to the AA solution; react at 40 °C and 1000 r / min for 8 h, filter, freeze in liquid nitrogen for 12 min, and vacuum dry at -50 °C and 9 Pa for 30 h to obtain macromolecular initiator;

[0087] (3) In a 500 mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 37.2 g of the macromolecular initiator obtained in step (2), 110.58 g (0.85 mol) of sodium vinyl sulfonate, 451.98 g (2.13 mol) of 4-vinylbenzyltrimethylammonium chloride and 133.2 g (1.2 mol) of N-vinylpyrrolidone were dispersed into 200 mL of deionized water, heated to 80 °C, and 2.7 g (0.01 mol) of potassium persulfate and 1.35 g (0.013 mol) of sodium bisulfite were added in sequence. The mixture was stirred at 800 r / min for 6 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain the micro-nano spherical modified silica acid gelling agent, named NSGA-4 (Nano Spheres of Gelling Agent-4).

[0088] The average particle size of NSGA-4 was measured to be 1035.28 nm.

[0089] Example 5

[0090] This embodiment provides a micro / nano-scale spherical modified silica acid gelling agent, which is prepared by the following method:

[0091] (1) Add 24g of nano-SiO2 to 2000mL of deionized water and stir magnetically for 20min to disperse it evenly in the deionized water to obtain a nano-SiO2 suspension; slowly add 210g of silane coupling agent KH792 to the nano-SiO2 suspension and stir at 400r / min to dissolve it; then continue stirring and react at 40℃ for 8h, filter, freeze in liquid nitrogen for 11min, and vacuum dry at -50℃ and 9Pa for 33h to obtain surface-modified nano-SiO2;

[0092] (2) Add 0.12 mol of acrylic acid (AA) to 200 mL of deionized water to obtain AA solution; add 39.2 g of surface-modified nano SiO2 obtained in step (1) to the AA solution; react at 40 °C and 1000 r / min for 8 h, filter, freeze in liquid nitrogen for 11 min, and vacuum dry at -50 °C and 9 Pa for 33 h to obtain macromolecular initiator;

[0093] (3) In a 500 mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 31.64 g of the macromolecular initiator obtained in step (2), 160.46 g (0.7 mol) of sodium 2-acrylamide-2-methylpropanesulfonate, 124.49 g (0.77 mol) of dimethyl diallyl ammonium chloride and 38.85 g (0.35 mol) of N-vinylpyrrolidone were dispersed into 200 mL of deionized water, heated to 80 °C, and 2.7 g (0.01 mol) of potassium persulfate and 1.35 g (0.013 mol) of sodium bisulfite were added sequentially. The mixture was stirred at 800 r / min for 6 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain the micro-nano spherical modified silica acid gelling agent, named NSGA-5 (Nano Spheres of Gelling Agent-5).

[0094] The average particle size of NSGA-5 was measured to be 1486.38 nm.

[0095] Example 6

[0096] This embodiment provides a micro / nano-scale spherical modified silica acid gelling agent, which is prepared by the following method:

[0097] (1) Add 60g of nano-SiO2 to 2000mL of deionized water and stir magnetically for 20min to disperse it evenly in the deionized water to obtain a nano-SiO2 suspension; slowly add 220g of silane coupling agent KH602 to the nano-SiO2 suspension and stir at 300r / min to dissolve it; then continue stirring and react at 40℃ for 8h, filter, freeze in liquid nitrogen for 10min, and vacuum dry at -50℃ and 9Pa for 44h to obtain surface-modified nano-SiO2;

[0098] (2) Add 0.5 mol of acrylic acid (AA) to 200 mL of deionized water to obtain AA solution; add 39.2 g of surface-modified nano SiO2 obtained in step (1) to the AA solution; react at 40 °C and 1000 r / min for 8 h, filter, freeze in liquid nitrogen for 10 min, and vacuum dry at -50 °C and 9 Pa for 44 h to obtain macromolecular initiator;

[0099] (3) In a 500mL three-necked round-bottom flask equipped with a thermometer, a stirring rod and a nitrogen inlet tube, 20.5g of the macromolecular initiator obtained in step (2), 20.17g (0.14mol) sodium allyl sulfonate, 78.93g (0.38mol) methacryloyloxyethyltrimethylammonium chloride and 9.32g (0.084mol) N-vinylpyrrolidone were dispersed in 200mL of deionized water, heated to 80℃, and 2.7g (0.01mol) potassium persulfate and 1.35g (0.013mol) sodium bisulfite were added in sequence. The mixture was stirred at 800r / min for 6h. After the reaction was completed, the mixture was filtered, washed and dried to obtain the micro-nano spherical modified silica acid gelling agent, named NSGA-6 (Nano Spheres of Gelling Agent-6).

[0100] The average particle size of NSGA-6 was measured to be 1967.47 nm.

[0101] Comparative Example 1

[0102] This comparative example provides an acid gelling agent, which is basically prepared according to the method of Example 1. The difference is that in step (1), the silane coupling agent KH550 is not added. Other raw materials and dosages and preparation process are the same as in Example 1, and acid gelling agent D1 is obtained, with an average particle size of 3.28 μm.

[0103] Comparative Example 2

[0104] This comparative example provides an acid gelling agent, which is basically prepared according to the method of Example 1. The difference is that in step (2), acrylic acid (AA) is not added. Other raw materials and amounts and preparation process are the same as in Example 1, and acid gelling agent D2 is obtained, with an average particle size of 15.28 μm.

[0105] Comparative Example 3

[0106] This comparative example provides an acid gelling agent, which is basically prepared according to the method of Example 1. The difference is that in step (3), the amount of sodium 2-acrylamide-2-methylpropanesulfonate added is changed to 0.48g. Other raw materials, dosages and preparation processes are the same as in Example 1, and acid gelling agent D3 is obtained, with an average particle size of 1.52μm.

[0107] Comparative Example 4

[0108] This comparative example provides an acid gelling agent, which is basically prepared according to the method of Example 1. The difference is that in step (3), the amount of N-vinylpyrrolidone added is changed to 1.16g. Other raw materials and amounts and preparation process are the same as in Example 1. Acid gelling agent D4 is obtained, and its average particle size is measured to be 1.24μm.

[0109] Comparative Example 5

[0110] This comparative example provides an acid gelling agent, which is basically prepared according to the method of Example 1. The difference is that in step (3), dimethyl diallyl ammonium chloride is not added. Other raw materials and dosages and preparation process are the same as in Example 1. Acid gelling agent D5 is obtained, and its average particle size is measured to be 1.12 μm.

[0111] Comparative Example 6

[0112] This comparative example provides an acid gelling agent, which is basically prepared according to the method of Example 1. The difference is that in step (3), dimethyl diallyl ammonium chloride is replaced with 1.32 mol of acrylamide. Other raw materials and amounts and preparation process are the same as in Example 1. Acid gelling agent D6 is obtained, and its average particle size is measured to be 0.98 μm.

[0113] Comparative Example 7

[0114] This comparative example provides an acid gelling agent, which is basically prepared according to the method of Example 1. The difference is that in step (3), N-vinylpyrrolidone is replaced with 0.78 mol of styrene. Other raw materials and amounts and preparation process are the same as in Example 1, and acid gelling agent D7 is obtained, with an average particle size of 2.26 μm.

[0115] Comparative Example 8

[0116] This comparative example provides an acid gelling agent, which is basically prepared according to the method of Example 1. The difference is that in step (3), sodium 2-acrylamide-2-methylpropanesulfonate is replaced with 0.6 mol of styrene. Other raw materials and dosages and preparation process are the same as in Example 1, and acid gelling agent D8 is obtained, with an average particle size of 2.46 μm.

[0117] Test case

[0118] This test example conducted experiments on the acid gelling agents provided in Examples 1-6 and Comparative Examples 1-8, and tested their apparent viscosity at room temperature and 180°C in a 20% HCl aqueous solution. The results are shown in Table 1.

[0119] Table 1 Performance parameters of different types of acid gelling agents

[0120]

[0121]

[0122] The ambient temperature is 25℃.

[0123] As can be clearly seen from Table 1, the micro-nano-sized spherical modified silica liquid gelling agent prepared in the embodiments of the present invention exhibits good performance at 180℃ and 170s. -1 Under shear conditions for 1 hour, the apparent viscosity is greater than 45 mPa·s, thus exhibiting excellent temperature and acid resistance.

Claims

1. A method for preparing a micro / nano-sized spherical modified silica acid liquid gelling agent, comprising the following steps: (1) The nano-SiO2 and the silane coupling agent are subjected to a first contact reaction in the first solvent, and after drying, the surface-modified nano-SiO2 is obtained. (2) The surface-modified nano-SiO2 and acrylic acid are subjected to a second contact reaction in a second solvent, and after drying, a macromolecular initiator is obtained; (3) In the presence of an oxidant and a reducing agent, the macromolecular initiator is reacted with vinyl sulfonate, vinyl quaternary ammonium salt and N-vinylpyrrolidone in a third solvent to obtain the micro-nano spherical modified silica acid gelling agent. The silane coupling agent includes one or a combination of several of γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane; The amount of the silane coupling agent added relative to 100 mL of the first solvent is 8-12 g, and the amount of the nano-SiO2 added is 1-5 g; The amount of acrylic acid added relative to 100 mL of the second solvent is 0.05-0.5 mol, and the amount of surface-modified nano-SiO2 added is 5-30 g; The vinyl sulfonate includes one or a combination of several of sodium 2-acrylamido-2-methylpropanesulfonate, sodium allyl sulfonate, sodium styrene sulfonate, and sodium vinyl sulfonate; The vinyl quaternary ammonium salt includes one or a combination of several of dimethyl diallyl ammonium chloride, methacryloyloxyethyltrimethyl ammonium chloride, trimethylvinyl ammonium bromide, and 4-vinylbenzyltrimethyl ammonium chloride; The amount of the macromolecular initiator added relative to 100 mL of the third solvent is 10-20 g, and the amount of the vinyl sulfonate added is 0.05-0.5 mol; the molar ratio of the vinyl sulfonate, the vinyl quaternary ammonium salt and the N-vinylpyrrolidone is 1:(1-3):(0.5-1.5).

2. The preparation method according to claim 1, wherein, In step (1), the average particle size of the nano-SiO2 is 10-20 nm.

3. The preparation method according to claim 1, wherein, In step (1), the first solvent includes water.

4. The preparation method according to claim 1, wherein, In step (1), the conditions for the first contact reaction are: reaction temperature 25-40 ℃, reaction time 5-8 h.

5. The preparation method according to claim 1, wherein, In step (1), the first contact reaction is carried out under stirring at a speed of 200-1200 r / min.

6. The preparation method according to claim 1, wherein, In step (1), the drying is freeze drying, and the freeze drying conditions are: freezing with liquid nitrogen for 8-12 min, and freeze drying at -50℃ and 9Pa for 24-48 h.

7. The preparation method according to claim 1, wherein, In step (2), the second solvent includes water.

8. The preparation method according to claim 1, wherein, In step (2), the conditions for the second contact reaction are: reaction temperature 25-40 ℃, reaction time 5-8 h.

9. The preparation method according to claim 1, wherein, In step (2), the second contact reaction is carried out under stirring at a speed of 600-1000 r / min.

10. The preparation method according to claim 1, wherein, In step (2), the drying is freeze drying, and the freeze drying conditions are: freezing with liquid nitrogen for 8-12 min, and freeze drying at -50℃ and 9Pa for 24-48 h.

11. The preparation method according to claim 1, wherein, In step (3), the molar ratio of the vinyl sulfonate, the vinyl quaternary ammonium salt and the N-vinylpyrrolidone is 1:(1.2-2.3):(0.7-1.3).

12. The preparation method according to claim 1, wherein, In step (3), the oxidant includes ammonium persulfate and / or potassium persulfate.

13. The preparation method according to claim 1, wherein, In step (3), the reducing agent includes sodium bisulfite.

14. The preparation method according to claim 1, wherein, In step (3), the amount of oxidant added is 0.001-0.005 mol relative to 100 mL of the third solvent.

15. The preparation method according to claim 1, wherein, In step (3), the molar ratio of the oxidant to the reducing agent is 1:(0.5-1.5).

16. The preparation method according to claim 15, wherein, In step (3), the molar ratio of the oxidant to the reducing agent is 1:(0.8-1.3).

17. The preparation method according to claim 1, wherein, In step (3), the third solvent includes water.

18. The preparation method according to claim 1, wherein, In step (3), the conditions for the third contact reaction are: reaction temperature 65-80℃, reaction time 3-6h, and the third contact reaction is carried out under a nitrogen atmosphere.

19. The preparation method according to claim 1, wherein, In step (3), the third contact reaction is carried out under stirring at a speed of 600-800 r / min.

20. A micro / nano-scale spherical modified silica liquid gelling agent, which is prepared by the preparation method according to any one of claims 1-19.

21. The micro / nano-scale spherical modified silica acid gelling agent according to claim 20, wherein, The average particle size of the micro-nano spherical modified silica gel is 500-2000 nm.

22. The micro / nano-scale spherical modified silica acid gelling agent according to claim 21, wherein, The average particle size of the micro-nano spherical modified silica gel is 500-900 nm.

23. The micro / nano-scale spherical modified silica acid gelling agent according to claim 20, wherein, The micro / nano-sized spherical modified silica acid gelling agent was dissolved in a 20% HCl aqueous solution at 180 °C for 170 s. -1 Under shearing conditions for 1 h, its apparent viscosity is greater than 45 mPa·s.

24. The application of the micro / nano-sized spherical modified silica acid gelling agent according to any one of claims 20-23 in acid fracturing.

25. The application according to claim 24, wherein, The target reservoir temperature for acid fracturing is above 150°C.

26. The application according to claim 25, wherein, The target reservoir temperature for acid fracturing is above 180°C.

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