A method for preparing nano-silica sol grout suitable for high-temperature conditions

Abstract

This invention relates to the field of chemical grouting materials technology, and particularly to a method for preparing nano-silica sol grouting suitable for high-temperature conditions. The aim is to solve the problems of existing grouting materials being unusable at high temperatures, and the low gel strength and uncontrollable gel rate of single silica sols at high temperatures. This invention provides a method for preparing nano-silica sol grouting suitable for high-temperature conditions, comprising the following steps: Step 1: Surface modification of small-particle-size spherical nano-silica sol with vinylsilane to graft carbon-carbon double bonds onto its surface, obtaining modified nano-silica sol; Step 2: Adding water-soluble vinyl monomers and an initiator to the modified nano-silica sol; Step 3: Adding an appropriate amount of gelation promoter to obtain a high-strength grouting material with controllable gelation time at 70-120℃.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical grouting materials, and particularly relates to a preparation method of nano-silica sol grouting suitable for high-temperature conditions. BACKGROUND

[0002] With the development of oil exploration and development, the progress of drilling technology puts forward higher technical requirements for well cementing. Nano-silica sol is a new generation of grouting material, which has a small particle size (3-150 nm) and low viscosity (usually <10 mPa.S), and can easily penetrate the pore matrix of the formation, where it undergoes a physical transformation from a solid-free extrudable liquid to a high-viscosity or rigid material that blocks the water layer. The curing mechanism of silica sol is very clear. Because the surface of nano-silica particles is electronegative, there is a diffuse double electric layer in the alkaline solution. Due to the presence of electrostatic repulsion, nano-silica particles can be stably suspended and dispersed in the alkaline solution. Therefore, if the nano-silica particles are to be crosslinked with each other and form a stable three-dimensional network structure, metal ions with opposite charges are added to the alkaline solution to neutralize the negative charge on the particle surface, thereby compressing the thickness of the double electric layer and greatly reducing the electrostatic repulsion between the particles, so as to form a coherent siloxane (Si-O-Si) network, thereby causing the silica sol to gel and transforming the liquid into a gel-like solid. Invention patent CN109305777B discloses a grouting material using silica sol as the main raw material, but does not study its use under high-temperature conditions.

[0003] The formation in which the underground oil well is located often reaches a high temperature of 70-120 DEG C. The single silica sol cannot fully exert its potential when used at high temperature, mainly having two shortcomings: uncontrollable gelation rate and gel strength. First, the silica sol has a completely hydroxylated surface, which usually covalently bonds when induced by other cations to produce a gel. As the temperature rises, the gelation time accelerates, and the silica sol cannot penetrate to the desired grouting depth. The method to solve this problem is usually to modify the surface of the silica sol, so that the Si-OH on the surface is partially replaced by other groups. However, organic coating of the surface of nano-silica particles will cause the gel strength to decrease, because the surface silane modification covers the silicon hydroxyl group on the surface of nano-silica, reducing the binding force between the nano-silica particles. Therefore, it is necessary to find a preparation method of nano-silica sol grouting suitable for high-temperature conditions, which has controllable gelation time and high strength. SUMMARY

[0004] The present application relates to the technical field of chemical grouting materials, and particularly relates to a preparation method of nano-silica sol grouting suitable for high-temperature conditions.

[0005] To solve the above technical problems, the technical scheme provided by the present application is characterized in that:

[0006] A preparation method suitable for high-temperature nano-silica sol grouting, comprising the following steps:

[0007] Step 1: The small-particle-size spherical nano-silica sol is surface-modified with vinyl silane to graft carbon-carbon double bonds on the surface, obtaining modified nano-silica sol;

[0008] Step 2: Water-soluble vinyl monomers and initiators are added to the modified nano-silica sol;

[0009] Step 3: An appropriate amount of gelation accelerator is added to obtain a high-strength grouting material with controllable gelation time at 70-120℃.

[0010] Further,

[0011] In step 1, the small-particle-size spherical nano-silica sol has a particle size of 5-20 nm and a solid content of 20-40%.

[0012] Further,

[0013] In step 1, the vinyl silane is one or more of vinyltrimethoxysilane, vinyltriethoxysilane, and other silanes containing vinyl groups.

[0014] Further,

[0015] In step 2, the water-soluble vinyl monomer is one or more of acrylamide and hydroxymethyl acrylamide.

[0016] Further,

[0017] In step 2, the amount of water-soluble vinyl monomer is 1-10% of the mass of the silica sol.

[0018] Further,

[0019] In step 2, the initiator is one of potassium persulfate and ammonium persulfate.

[0020] Further,

[0021] The amount of initiator is 0.3-3% of the water-soluble vinyl monomer.

[0022] Further,

[0023] In step 3, the gelation accelerator is one or more of potassium chloride, sodium chloride, potassium sulfate, sodium silicate, and potassium carbonate.

[0024] Further,

[0025] The amount of the gel promoter is 0.5-5% of the mass of the silica sol.

[0026] Further,

[0027] The preparation method comprises the following steps:

[0028] Step 1: 25g of vinyltrimethoxysilane is added into a mixed solvent of 80g of ethanol and 20g of water, and hydrolysis is carried out at room temperature for 1 hour to obtain a hydrolysis solution; 12g of the hydrolysis solution is slowly and uniformly added into 100g of silica sol with a particle size of 12nm and a solid content of 30% under stirring for 120 minutes, and then heating treatment is carried out at 90℃ for 1 hour to modify the surface of the nanosilica sol and reduce the temperature to 40℃;

[0029] Step 2: 5g of acrylamide, 0.05g of potassium persulfate and 20g of 10% sodium chloride aqueous solution are added into the product obtained in step 1, and stirring is carried out to uniformly mix them;

[0030] Step 3: the above system is treated at 70-120℃ to obtain a high-strength solidified gel body.

[0031] The technical effects that can be achieved by the present application in combination with the above technical solutions are as follows:

[0032] The present application first modifies the surface of small-particle-size spherical nanosilica sol with vinyl silane to graft carbon-carbon double bonds on the surface of the nanosilica sol to obtain modified nanosilica sol, then water-soluble vinyl monomers (acrylamide, hydroxymethyl acrylamide, etc.) and initiators (potassium persulfate, ammonium persulfate, etc.) are added into the nanosilica sol, and finally an appropriate amount of gel agent promoter is added; the solidified system will undergo two reactions under the condition of 70-120℃, the first reaction is that the vinyl monomers (acrylamide, hydroxymethyl acrylamide, etc.) will undergo free radical polymerization, and copolymerization with the vinyl on the surface of the nanosilica sol to form high molecular chains; the second reaction is that sodium chloride will promote the nanosilica to gel to form an inorganic network structure in which the nanosilica particles are linked to each other; under high-temperature conditions, the vinyl monomers undergo polymerization to form high molecular chains, and the gel agent promotes the nanosilica particles to gel, and finally an organic-inorganic hybrid gel system is formed, the gel time can be strictly controlled and the gel strength is greatly improved. DETAILED DESCRIPTION

[0033] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0034] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not considered critical for the invention. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, and to also disclose all values individualiy and in combination with intervening ranges between the stated values in the range that are also encompassed therein.

[0035] Accordingly, the following detailed description is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the inventions. Based upon the teachings provided herein, other embodiments apparent to those of ordinary skill in the art will be made in light of the above teachings and are to be within the scope of the claimed invention.

[0036] Example 1

[0037] (1) 25 g of vinyltrimethoxysilane was added to a mixed solvent of 80 g of ethanol and 20 g of water, and hydrolysis was performed at room temperature for 1 hour to obtain a hydrolysis solution. 12 g of the hydrolysis solution was slowly added to 100 g of silica sol having a particle size of 12 nm and a solid content of 30% at a uniform rate under stirring for 120 minutes, and then heating treatment was performed at 90°C for 1 hour to modify the surface of the nanosilica sol, and the temperature was lowered to 40°C.

[0038] (2) 5 g of acrylamide, 0.05 g of potassium persulfate, and 20 g of a 10% sodium chloride aqueous solution were added to the product obtained in step (1) and stirred to mix uniformly.

[0039] (3) The solution of step (2) was placed in an environment of 80°C, and the gelation time was observed and the gel strength was measured.

[0040] Example 2

[0041] (1) 25 g of vinyltrimethoxysilane was added to a mixed solvent of 80 g of ethanol and 20 g of water, and hydrolysis was performed at room temperature for 1 hour to obtain a hydrolysis solution. 12 g of the hydrolysis solution was slowly added to 100 g of silica sol having a particle size of 12 nm and a solid content of 30% at a uniform rate under stirring for 120 minutes, and then heating treatment was performed at 90°C for 1 hour to modify the surface of the nanosilica sol, and the temperature was lowered to 40°C.

[0042] (2) 5 g of acrylamide, 0.05 g of potassium persulfate, and 20 g of a 10% sodium chloride aqueous solution were added to the product obtained in step (1) and stirred to mix uniformly.

[0043] (3) The solution of step (2) was placed in an environment of 80°C, and the gelation time was observed and the gel strength was measured.

[0044] Example 3

[0045] (1) 25 g of vinyltrimethoxysilane was added to a mixed solvent of 80 g of ethanol and 20 g of water, and hydrolysis was performed at room temperature for 1 hour to obtain a hydrolysis solution. 2 g of the hydrolysis solution was slowly added to 100 g of silica sol having a particle size of 12 nm and a solid content of 30% at a constant rate for 120 minutes under stirring, and then heated at 90°C for 1 hour to perform surface modification of the nanosilica sol, and then cooled to 40°C.

[0046] (2) 5 g of acrylamide, 0.05 g of potassium persulfate, and 20 g of 10% sodium chloride aqueous solution were added to the product obtained in step (1) and stirred to mix uniformly.

[0047] (3) The solution in step (2) was placed in an environment of 80°C, and the gelation time and the gel strength were measured.

[0048] Example 4

[0049] (1) 25 g of vinyltrimethoxysilane was added to a mixed solvent of 80 g of ethanol and 20 g of water, and hydrolysis was performed at room temperature for 1 hour to obtain a hydrolysis solution. 2 g of the hydrolysis solution was slowly added to 100 g of silica sol having a particle size of 12 nm and a solid content of 30% at a constant rate for 120 minutes under stirring, and then heated at 90°C for 1 hour to perform surface modification of the nanosilica sol, and then cooled to 40°C.

[0050] (2) 5 g of acrylamide, 0.05 g of potassium persulfate, and 20 g of 10% sodium chloride aqueous solution were added to the product obtained in step (1) and stirred to mix uniformly.

[0051] (3) The solution in step (2) was placed in an environment of 80°C, and the gelation time and the gel strength were measured.

[0052] Example 5

[0053] (1) 25 g of vinyltrimethoxysilane was added to a mixed solvent of 80 g of ethanol and 20 g of water, and hydrolysis was performed at room temperature for 1 hour to obtain a hydrolysis solution. 2 g of the hydrolysis solution was slowly added to 100 g of silica sol having a particle size of 12 nm and a solid content of 30% at a constant rate for 120 minutes under stirring, and then heated at 90°C for 1 hour to perform surface modification of the nanosilica sol, and then cooled to 40°C.

[0054] (2) 5 g of acrylamide, 0.05 g of potassium persulfate, and 20 g of 10% sodium chloride aqueous solution were added to the product obtained in step (1) and stirred to mix uniformly.

[0055] (3) The solution in step (2) was placed in an environment of 80°C, and the gelation time and the gel strength were measured.

[0056] Example 6

[0057] (1) Add 25g of vinyltrimethoxysilane to a mixed solvent of 80g of ethanol and 20g of water, and stir at room temperature for 1 hour to obtain a hydrolysate. Take 12g of the above hydrolysate and slowly add it to 100g of silica sol with a particle size of 12nm and a solid content of 30% over a period of 120 minutes under stirring. Then heat the mixture to 90℃ for 1 hour to modify the surface of the nano-silica sol, and then cool it down to 40℃.

[0058] (2) Add 0.5g acrylamide, 0.05g potassium persulfate and 20g 10% sodium chloride aqueous solution to the product obtained in step (1) and stir to mix evenly.

[0059] (3) Place the solution from step (2) in an environment of 80°C, observe the gelation time and measure the gel strength.

[0060] Example 7

[0061] (1) Add 25g of vinyltriethoxysilane to a mixed solvent of 80g of ethanol and 20g of water, and stir at room temperature for 1 hour to obtain a hydrolysate. Take 12g of the above hydrolysate and slowly add it to 100g of silica sol with a particle size of 12nm and a solid content of 30% over a period of 120 minutes under stirring. Then heat the mixture to 90℃ for 1 hour to modify the surface of the nano-silica sol, and then cool it down to 40℃.

[0062] (2) Add 5g of hydroxymethylacrylamide, 0.05g of potassium persulfate and 20g of 10% sodium chloride aqueous solution to the product obtained in step (1) and stir to mix evenly.

[0063] (3) Place the solution from step (2) in an environment of 80°C, observe the gelation time and measure the gel strength.

[0064] Comparative Example 1

[0065] (1) Heat 100g of silica sol with a particle size of 12nm and a solid content of 30% to 90℃ for 1 hour, and then cool it down to 40℃.

[0066] (2) Add 20g of 10% sodium chloride aqueous solution to the product obtained in step (1) and stir to mix evenly.

[0067] (3) Place the solution from step (2) in an environment of 80°C, observe the gelation time and measure the gel strength.

[0068] Comparative Example 2

[0069] (1) Add 25g of vinyltrimethoxysilane to a mixed solvent of 80g of ethanol and 20g of water, and stir at room temperature for 1 hour to obtain a hydrolysate. Take 12g of the above hydrolysate and slowly add it to 100g of silica sol with a particle size of 12nm and a solid content of 30% over a period of 120 minutes under stirring. Then heat the mixture to 90℃ for 1 hour to modify the surface of the nano-silica sol, and then cool it down to 40℃.

[0070] (2) Add 20g of 10% sodium chloride aqueous solution to the product obtained in step (1) and stir to mix evenly.

[0071] (3) Place the solution from step (2) in an environment of 80°C, observe the gelation time and measure the gel strength.

[0072] Comparative Example 3

[0073] (1) Heat 100g of silica sol with a particle size of 12nm and a solid content of 30% to 90℃ for 1 hour, and then cool it down to 40℃.

[0074] (2) Add 5g of acrylamide, 0.05g of potassium persulfate and 20g of 10% sodium chloride aqueous solution to the product obtained in step (1) and stir to mix evenly.

[0075] (3) Place the solution from step (2) in an environment of 80°C, observe the gelation time and measure the gel strength.

[0076] The strength of the gel was determined using a universal testing machine with a cylindrical flat-head punch of 12.7 mm in diameter; punching speed: 0.5 mm / s; punching depth: 20 mm; the sample was prepared... A cylindrical sample was pressed to a diameter of 20 mm, and the force required for the gel to rupture was recorded. The gel time of the silica sol was determined using the static test tube method.

[0077] The experimental conditions and gel strengths obtained from the various embodiments described above are summarized in the table below:

[0078] Gel strength (N) Gel time (h) Example 1 312.56 7.5 Example 2 261.82 5.3 Example 3 157.23 0.8 Example 4 295.15 6.7 Example 5 193.77 6.8 Example 6 106.13 7.9 Example 7 195.62 9.5 Comparative Example 1 105.35 0.2 Comparative Example 2 35.62 6.5 Comparative Example 3 Flocculation occurred --

[0079] As shown in the table, compared to the comparative example, the grouting material prepared by the method provided in this embodiment has higher gel strength and its gelation time is controllable. Examples 1-3 show that the gelation time decreases with decreasing degree of silica sol modification. Comparative Example 1 shows that the gelation time of unmodified silica sol is only 0.2 h. Therefore, the gelation time can be controlled by adjusting the degree of silica sol modification. This is because silica sol has a fully hydroxylated surface, which usually undergoes covalent bonding and gelation when induced by other cations. Surface modification of silica sol, causing the Si-OH groups on its surface to be partially replaced by other groups to varying degrees, effectively improves surface properties and reactivity.

[0080] The preparation method provided in this embodiment is easy to operate, has simple components, controllable gelation time, high gel strength, and is suitable for use in high-temperature environments.

[0081] This embodiment uses spherical nano-silica sol as the main agent. Through surface modification with vinyl silane and the addition of vinyl monomers, polymerization initiators, and gelling agents, the vinyl monomers undergo polymerization at high temperature to form polymer chains. Simultaneously, the gelling agent promotes the gelation of the nano-silica particles, ultimately forming an organic-inorganic hybrid gel system. By controlling the degree of modification, the gelation time can be controlled, and the polymer chains formed under high temperature conditions significantly improve the gel strength.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a nanosilica sol grout suitable for use under high temperature conditions, characterized in that, It comprises the following steps: Step 1: the small particle size spherical nanometer silica sol is surface modified with vinyl silane to graft carbon-carbon double bond on the surface, obtaining modified nanometer silica sol; the small particle size spherical nanometer silica sol has a particle size of 5-20 nm and a solid content of 20-40%; Step 2: water-soluble vinyl monomer and initiator are added to the modified nanometer silica sol; Step 3: an appropriate amount of gel promoter is added to obtain high-strength grouting material with controllable gel time at 70-120℃.

2. The preparation method of nanometer silica sol grouting suitable for high temperature conditions according to claim 1, wherein in step 1, the vinyl silane is one or more of vinyl trimethoxysilane, vinyl triethoxysilane and other silanes containing vinyl groups.

3. The preparation method of nanometer silica sol grouting suitable for high temperature conditions according to claim 1, wherein in step 2, the water-soluble vinyl monomer is one or more of acrylamide and hydroxymethyl acrylamide.

4. The preparation method of nanometer silica sol grouting suitable for high temperature conditions according to claim 1, wherein in step 2, the amount of water-soluble vinyl monomer is 1-10% of the mass of silica sol.

5. The preparation method of nanometer silica sol grouting suitable for high temperature conditions according to claim 1, wherein in step 2, the initiator is one of potassium persulfate and ammonium persulfate.

6. The preparation method of nanometer silica sol grouting suitable for high temperature conditions according to claim 1, wherein the amount of initiator is 0.3-3% of the water-soluble vinyl monomer.

7. The preparation method of nanometer silica sol grouting suitable for high temperature conditions according to claim 1, wherein in step 3, the gel promoter is one or more of potassium chloride, sodium chloride, potassium sulfate, sodium silicate and potassium carbonate.

8. The preparation method of nanometer silica sol grouting suitable for high temperature conditions according to claim 1, wherein the amount of gel promoter is 0.5-5% of the mass of silica sol. It comprises the following steps: Step 1: 25g of vinyl trimethoxysilane is added to a mixture of 80g of ethanol and 20g of water, and hydrolysis is carried out at room temperature for 1 hour to obtain a hydrolysis solution; 12g of the hydrolysis solution is slowly and uniformly added to 100g of silica sol with a particle size of 12nm and a solid content of 30% under stirring conditions within 120 minutes, and then heated to 90℃ for 1 hour for surface modification of the nanometer silica sol, and cooled to 40℃; Step 2: 50g of acrylamide, 0.5g of potassium persulfate and 20g of 10% sodium chloride aqueous solution are added to the product obtained in step 1, and stirred and mixed uniformly; Step 3: the above system is treated at 70-120℃ to obtain a high-strength solidified gel. ​ ​ ​ 9. The process for the preparation of nanosilica sol slurry suitable for high temperature conditions according to claim 1, characterized in that, ​ ​ ​ ​