Oil permeable and water blocking film coated quartz sand for fracturing and preparation method thereof

Abstract

The present application relates to a kind of oil-permeable water-blocking film-coated quartz sand for fracturing and its preparation method, and the oil-permeable water-blocking film-coated quartz sand for fracturing is three-layer core-shell structure, core is amino silane coupling agent modified quartz sand, middle layer is thermosetting epoxy resin, and outer layer is functional polymer layer;Preparation raw materials of middle layer include epoxy resin A, multifunctional epoxy resin, epoxy resin with double bond and amino resin, the epoxy resin A is selected from at least one in bisphenol type epoxy resin, phenolic epoxy resin;Preparation raw materials of outer layer include (Methyl) propenoic acid C6-C10 alkyl ester, fluorine-containing propenoic acid ester, isobornyl acrylate, dimethyl-diallyl ammonium chloride, bis (3-trimethoxysilylpropyl) fumarate.Solve the defect that the interface bonding force of resin layer and quartz sand matrix of film-coated quartz sand in prior art is insufficient, improve the interface bonding capacity, with excellent oil-permeable water-blocking performance and high temperature and high pressure resistance.

Description

Technical Field

[0001] This invention relates to the field of oil-permeable and water-blocking quartz sand technology, specifically to an oil-permeable and water-blocking coated quartz sand for fracturing and its preparation method. Background Technology

[0002] In oil production, fracturing is a method of creating fractures in oil and gas reservoirs using hydraulic pressure, also known as hydraulic fracturing. Fracturing improves the flow environment of oil in the formation, increasing well production. However, without modified proppant, both water and oil can pass through, leading to high water content in the produced wells, low oil production efficiency, and adverse effects on the formation. Water layers often exist near the fractured oil layer, especially in high water-cut, low-permeability reservoirs. Traditional control measures include varying the displacement or reducing the scale of operations to avoid water flooding during construction and preventing the fracture from connecting to the water layer. This approach has limitations: once the distance between the water layer and the oil layer is reduced to a certain range, fracture height control measures become ineffective. Using oil-permeable, water-blocking proppants to control the degree of water production after water layer penetration helps achieve the goal of post-fracturing water control and increased oil production. With the passage of time in oilfield development, the overall water cut of oilfields is increasing, with some major oilfields reaching as high as 90%. Hydraulic fracturing technology has become a major means of enhancing production.

[0003] A polymeric material is used to form a coating on the proppant surface, functioning through the following process: the polymeric coating proppant is transported to the fracturing fracture by fracturing fluid → the fracturing fracture closes → formation pressure compresses the polymeric coating material → capillary formation occurs between the material particles. Because the polymeric coating material is non-polar, it has oleophilic and hydrophobic properties. If the aqueous and oil phases pass through the capillary, the oil phase quickly wets the capillary wall, and the liquid surface inside the capillary is concave. The curved liquid surface generates additional pressure pointing towards the capillary, which promotes the oil phase to pass through the polymeric coating material and form capillaries. However, the aqueous phase does not wet the polymeric coating material capillary because the aqueous phase has a concave capillary surface, and the curved liquid surface generates additional pressure away from the capillary, hindering the water phase's passage. On the coating surface, the surface tension of water increases, causing it to aggregate into droplets, making it difficult to pass through the fracturing proppant, thus exhibiting a water-blocking effect. Therefore, oil-permeable and water-blocking proppants will facilitate the permeation of the oil phase while preventing the permeation of the water phase.

[0004] CN119878099A discloses a water-controlling fracturing method based on modified superhydrophobic nanomaterials. This method involves dispersing nano-titanium dioxide and silica in an alcohol solvent, followed by modification with a titanate coupling agent to obtain modified superhydrophobic nanomaterials. This modification improves the dispersibility and stability of the nanomaterials in fracturing fluids and alters rock wettability. CN111607374A discloses a low-temperature curing permeable and water-blocking coated sand. This method uses thermosetting phenolic resin, thermosetting acrylic resin, and polyurethane resin layers in the coated sand, combined with a reaction with resorcinol, to achieve low-temperature, catalyst-free curing and high compressive strength. This solves the problems of poor sand control and insufficient water control in existing coated sand technologies and is suitable for high water-cut oil wells. However, it requires multiple reactions, making the process cumbersome and unsuitable for industrialization. CN108976366A discloses a hydrophobic coating support, which is prepared by heating and melting silica and silicone resin in a resin mixer until uniformly mixed. Then, acrylic acid, acrylamide, an alkyltrimethylammonium salt-type cationic surfactant, N,N-methylenebisacrylamide, methacryloxypropyltrimethoxysilane, an initiator, dibutyl phthalate, zinc stearate, and an alcohol solvent are added to initiate polymerization. The mixture is then filtered and dried to obtain the hydrophobic coating support. CN106883837A discloses a hydrophobic modified support, which is prepared by adding a small amount of hydrophobic resin adhesive to the support. The hydrophobic resin adhesive is a fluorinated acrylic resin adhesive, a fluorinated dopamine hydrophobic adhesive, an acrylate hydrophobic adhesive, a silicone hydrophobic adhesive, a polyurethane hydrophobic adhesive, an epoxy resin hydrophobic adhesive, or other hydrophobic adhesives with similar properties. The adhesive is shaken or stirred to wet the surface of the support, and then cured. CN107353888A discloses a water-blocking and oil-permeable proppant, wherein a hydrophobic polymer is coated on the surface of the proppant and cured; the mass ratio of the hydrophobic polymer to the proppant is 1:10 to 40; the hydrophobic polymer is polymerized from 2-acrylamido-2-methylpropanesulfonic acid, acrylamide and N-vinylpyrrolidone.

[0005] All of the above hydrophobic modified proppants use polymer resin to coat the proppant particles. Even with in-situ polymerization, there is still insufficient interfacial bonding between the resin coating layer and the core of the inorganic particles. Under the conditions of high temperature and high pressure downhole, the coating layer is prone to peeling and damage, which affects the long-term stability of oil permeability and water blocking.

[0006] CN117285924A discloses a method for preparing a nano-oil-permeable and water-blocking proppant, comprising the following steps: S1, pre-treating the surface of the proppant aggregate by immersion and etching with acid to make the surface of the proppant aggregate uneven; S2, adding nano-silica to ultrasonically disperse in an organic solvent, then adding a thickener, and stirring in an environment of 50-80°C until no obvious particles are present to obtain a mixture; the thickener is one of methylcellulose, carboxymethylcellulose, carbomer, xanthan gum, and gelatin; adding micron-sized silica to the mixture, stirring and mixing evenly, then ultrasonically dispersing for 10-20 min, then adding polysiloxane, and stirring and mixing evenly to obtain a modifier; S3, mixing the pre-treated proppant aggregate and the modifier evenly, placing it in an environment of 40-70°C for 2-4 h, then filtering out the proppant and drying it in an oven at 80-110°C to obtain an oil-permeable and water-blocking proppant. This patent uses acids, including hydrofluoric acid, to etch the proppant, creating an uneven surface—a pretreatment to increase roughness—in order to improve the affinity between the proppant and the resin coating layer. However, the effect is limited. Moreover, acid etching severely affects the strength of the proppant itself, increasing the breakage rate under high closing pressure and affecting backflow capability. Summary of the Invention

[0007] To overcome the problem of insufficient interfacial bonding between the resin coating layer and the quartz sand matrix in existing technologies, this invention provides a coated quartz sand with strong interfacial bonding, excellent oil permeability and water barrier properties, and resistance to high temperature and pressure, as well as its preparation method. This invention first modifies the proppant quartz sand using a silane coupling agent, then coats it with thermosetting epoxy resin as an intermediate layer, and finally performs in-situ free radical polymerization to obtain the outer layer. The final product is a three-layer core-shell structure for fracturing with oil permeability and water barrier properties: a core of quartz sand, an intermediate layer of thermosetting epoxy resin, and an outer layer of functional hydrophobic layer. To achieve the above objectives, this invention proposes the following technical solution:

[0008] A type of oil-permeable and water-blocking coated quartz sand for fracturing has a three-layer core-shell structure. The core is quartz sand modified with an aminosilane coupling agent, the middle layer is a thermosetting epoxy resin, and the outer layer is a functional polymer layer. The raw materials for preparing the middle layer include epoxy resin A, multifunctional epoxy resin, epoxy resin containing double bonds, and amino resin. The epoxy resin A is selected from at least one of bisphenol type epoxy resin and phenolic epoxy resin. The raw materials for preparing the outer layer include (meth)acrylate C6-C10 alkyl ester, fluorinated acrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate.

[0009] Furthermore, the amino-coupled agent modified quartz sand is obtained by dispersing quartz sand in an alcohol aqueous solution and reacting it with an aminosilane coupling agent; even further, the quartz sand particle size is 40-100 mesh, the alcohol aqueous solution is a solution of C1-3 alcohol and water, the volume percentage of alcohol is 50-80%, and the C1-3 alcohol is selected from at least one of methanol, ethanol, and isopropanol; the aminosilane coupling agent is selected from at least one of γ-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, γ-diethylenetriaminepropylmethyldimethoxysilane, and N-2-aminoethyl-3-aminopropyltrimethoxysilane; preferably, the amount of aminosilane coupling agent used is 5-10 wt% of the mass of quartz sand.

[0010] Further, the bisphenol type epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; the phenolic epoxy resin is selected from at least one of phenol-formaldehyde epoxy resin, o-cresol-formaldehyde epoxy resin, resorcinol-formaldehyde epoxy resin, and bisphenol A type phenolic epoxy resin; the multifunctional epoxy resin is selected from at least one of AG-80, AG-70, AG-601, AG-602, AFG-90, and TDE-85; the double-bond-containing epoxy resin is selected from at least one of diallyl bisphenol A diglycidyl ether (CAS Registry No.: 13410-54-3) and itaconic acid diglycidyl ester (CAS Registry No.: 7748-43-8); and the amino resin is selected from at least one of methyl etherified melamine resin, melamine-formaldehyde resin, and urea / formaldehyde resin.

[0011] Furthermore, the mass ratio of epoxy resin A, multifunctional epoxy resin, double-bond epoxy resin, and amino resin is 40-55:6-10:2-3:5-8.

[0012] Further, the (meth)acrylate C6-C10 alkyl ester is selected from at least one of (meth)acrylate hexyl acrylate, (meth)acrylate heptyl acrylate, (meth)acrylate octyl acrylate, (meth)acrylate nonyl acrylate, and (meth)acrylate decyl acrylate; the fluorinated acrylate is selected from at least one of pentafluoropropyl acrylate, pentafluoropropyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, and perfluorohexylethyl acrylate.

[0013] Furthermore, the mass ratio of (meth)acrylate C6-C10 alkyl ester, fluorinated acrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate is 13-18:4-7:1.8-2.4:2.1-2.9:0.8-1.2.

[0014] Furthermore, the mass ratio of the raw materials for preparing the intermediate layer (epoxy resin A, multifunctional epoxy resin, epoxy resin containing double bonds, and amino resin) and the raw materials for preparing the outer layer ((meth)acrylate C6-C10 alkyl ester, fluorinated acrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate) is 100:30-40:65-80.

[0015] This invention also provides a method for preparing the above-mentioned oil-permeable and water-resistant coated quartz sand for fracturing, comprising the following steps:

[0016] (S1) Quartz sand is dispersed in an alcohol-water solution, an aminosilane coupling agent is added to react, washed, and dried to obtain amino-coupled agent modified quartz sand.

[0017] (S2) Epoxy resin A, multifunctional epoxy resin, double bond-containing epoxy resin and amino resin are mixed evenly according to the mass ratio to obtain a mixed resin; under an inert atmosphere, amino coupling agent modified quartz sand is added to a sand mixer, heated to 60-80℃, and sprayed with the mixed resin under stirring. After spraying, stirring is continued to complete the reaction, cooled, discharged, and cured at 90-120℃ to obtain epoxy resin-coated quartz sand.

[0018] (S3) Add epoxy resin-coated quartz sand and a mixed monomer solution to the reactor. The mixed monomer solution includes (meth)acrylate C6-C10 alkyl ester, fluorinated acrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, bis(3-trimethoxysilylpropyl) fumarate and an initiator. Initiate in-situ polymerization by heating. After polymerization, filter, wash the solid, and dry to obtain oil-permeable and water-resistant coated quartz sand for fracturing.

[0019] Furthermore, in step (S1), the reaction temperature is 50-70℃, the reaction time is 3-5h, and the washing is done with acetone.

[0020] Furthermore, in step (S2), the mixing speed of the sand mixer is 60-100 rpm, the time for spraying the mixed resin is 20-60 min, the time for continuing mixing to complete the reaction is 3-5 h, and the time for continuing curing is 1-2 h.

[0021] Further, in step (S3), the initiator is selected from at least one of azo initiators and peroxide initiators. The azo initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate. The peroxide initiator is selected from at least one of benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, and di(4-tert-butylcyclohexyl) peroxide. The amount of initiator is 1-2 wt% of the mass of the mixed monomers, and the temperature for initiating in-situ polymerization is 60-80°C. The mixed monomers account for 20-30 wt% of the mixed monomer solution, and the solvent of the mixed monomer solution is selected from at least one of DMSO and DMF.

[0022] The present invention has the following technical advantages:

[0023] I. The fracturing oil-permeable and water-blocking coated quartz sand provided by this invention has a three-layer core-shell structure. The middle layer is epoxy resin, which provides high compressive strength and certain resistance to deformation. The outer layer has excellent oil permeability and water-blocking ability. The layers are connected by chemical bonds, which has good interfacial stability. It can still play a long-lasting and stable oil permeability and water-blocking role in the high temperature and high pressure environment of the formation.

[0024] II. The outer functional polymer layer plays multiple roles. The long-chain flexible alkyl groups reduce the interfacial tension between the polymer surface and the oil phase, promoting oil wetting and permeation. The fluorinated short-chain alkyl groups greatly increase the contact angle with water. The combined effect of these two elements significantly improves the oil permeability and hydrophobicity of the coated quartz sand. The polymer surface has a certain density of cationic quaternary ammonium salts, which adhere to the negatively charged rock surface, contributing to the stable function of the coated quartz sand.

[0025] Third, during the in-situ polymerization of the outer polymer layer, bis(3-trimethoxysilylpropyl) fumarate is added. The double bonds of fumarate participate in the polymerization, and the trimethoxysilane end groups at both ends undergo self-condensation after hydrolysis, enhancing its strength and durability. The inventors unexpectedly discovered that replacing bis(3-trimethoxysilylpropyl) fumarate with an alkenyl silane coupling agent with a siloxane alkyl group at one end did not yield satisfactory results. Attached Figure Description

[0026] Figure 1 This is an experiment on the water permeability of the water-blocking coated quartz sand and ordinary quartz sand prepared in Example 1. Detailed Implementation

[0027] The present invention will be described in detail below with specific embodiments. Example 1

[0028] (S1) 100 parts by mass of 60-mesh quartz sand were dispersed in an aqueous ethanol solution with a volume concentration of 60%, and 5 parts by mass of γ-diethylenetriaminepropylmethyldimethoxysilane were added. The mixture was heated to 70°C and reacted for 3 hours. The mixture was washed with ethanol and dried to obtain amino coupling agent modified quartz sand.

[0029] (S2) Bisphenol A epoxy resin E51, multifunctional epoxy resin AG-80, diallyl bisphenol A diglycidyl ether and amino resin CYMEL 325 are mixed evenly in a mass ratio of 40:10:2:5 to obtain a mixed resin. Under a nitrogen atmosphere, 100 parts by mass of amino coupling agent modified quartz sand are added to a sand mixer, heated to 60°C, and stirred at 100 rpm. Within 30 minutes, 30 parts by mass of the above mixed resin are evenly sprayed onto the surface of the amino coupling agent modified quartz sand. After spraying, stirring is continued for 3 hours to complete the reaction. After cooling, the material is discharged and cured at 110°C for 1 hour to obtain epoxy resin-coated quartz sand.

[0030] (S3) Hexyl acrylate, hexafluorobutyl methacrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate were mixed in a mass ratio of 18:4:2.4:2.9:0.8 as mixed monomers. 20 parts by mass of the mixed monomers, 79.8 parts by mass of solvent DMSO, and 0.2 parts by mass of initiator AIBN were mixed evenly to form a mixed monomer solution. The above-mentioned epoxy resin-coated quartz sand and 400 parts by mass of the mixed monomer solution (equivalent to a mass ratio of the mixed monomers to the amino coupling agent-modified quartz sand in the mixed monomer solution of 80:100) were added to the reactor. The temperature was raised to 80°C under stirring to initiate in-situ polymerization. After the polymerization reaction, the mixture was filtered, the solid was washed with ethanol, and dried to obtain oil-permeable and water-resistant coated quartz sand for fracturing.

[0031] Wetting tests were conducted using the water-resistant coated quartz sand from Example 1 and ordinary quartz sand. The results of the simple wetting test are as follows: Figure 1 As shown. Figure 1 On the left is the water-resistant coated quartz sand from Example 1, and on the right is ordinary quartz sand. It can be observed that the coated quartz sand turns brown, and water forms droplets on its surface that do not disappear for a long time. In contrast, water immediately penetrates the ordinary quartz sand, leaving penetration marks on its surface. Example 2

[0032] (S1) 100 parts by mass of 100 mesh quartz sand were dispersed in an 80% volume concentration ethanol aqueous solution, 10 parts by mass of 3-aminopropyltriethoxysilane were added, the temperature was raised to 50℃ and reacted for 5 hours, washed with ethanol and dried to obtain amino coupling agent modified quartz sand.

[0033] (S2) Mix o-cresol epoxy resin CYDCN-200, multifunctional epoxy resin AFG-90, itaconic acid diglycidyl ester and amino resin CYMEL 323 in a mass ratio of 55:6:3:8 to obtain a mixed resin. Under a nitrogen atmosphere, add 100 parts by mass of amino coupling agent modified quartz sand to a sand mixer, heat to 60°C, and under stirring at 100 rpm, spray 40 parts by mass of the above mixed resin onto the surface of the amino coupling agent modified quartz sand evenly within 30 minutes. After spraying, continue stirring for 3 hours to complete the reaction, cool, discharge, and continue curing at 110°C for 1 hour to obtain epoxy resin coated quartz sand.

[0034] (S3) Decyl acrylate, pentafluoropropyl methacrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate were mixed in a mass ratio of 18:4:2.4:2.9:0.8 as mixed monomers. 20 parts by mass of the mixed monomers, 79.8 parts by mass of solvent DMF, and 0.2 parts by mass of initiator BPO were mixed evenly to form a mixed monomer solution. The above-mentioned epoxy resin-coated quartz sand and 325 parts by mass of the mixed monomer solution (equivalent to a mass ratio of the mixed monomers to the amino coupling agent-modified quartz sand in the mixed monomer solution of 65:100) were added to the reactor. The temperature was raised to 80°C under stirring to initiate in-situ polymerization. After the polymerization reaction, the mixture was filtered, the solid was washed with ethanol, and dried to obtain oil-permeable and water-resistant coated quartz sand for fracturing. Example 3

[0035] (S1) 100 parts by mass of 80-mesh quartz sand were dispersed in an aqueous ethanol solution with a volume concentration of 60%, and 7 parts by mass of γ-diethylenetriaminepropylmethyldimethoxysilane were added. The mixture was heated to 70°C and reacted for 3 hours. The mixture was washed with ethanol and dried to obtain amino coupling agent modified quartz sand.

[0036] (S2) Mix o-cresol epoxy resin CYDCN-200, multifunctional epoxy resin AG-601, diallyl bisphenol A diglycidyl ether and amino resin CYMEL 325 in a mass ratio of 50:8:2:6 to obtain a mixed resin. Under a nitrogen atmosphere, add 100 parts by mass of amino coupling agent modified quartz sand to a sand mixer, heat to 60°C, and under stirring at 100 rpm, uniformly spray 37 parts by mass of the above mixed resin onto the surface of the amino coupling agent modified quartz sand within 30 minutes. After spraying, continue stirring for 3 hours to complete the reaction, cool, discharge, and continue curing at 110°C for 1 hour to obtain epoxy resin coated quartz sand.

[0037] (S3) Hexyl acrylate, hexafluorobutyl methacrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate were mixed in a mass ratio of 15:5:2:2.3:1 as mixed monomers. 20 parts by mass of the mixed monomers, 79.8 parts by mass of solvent DMSO, and 0.1 parts by mass of initiator AIBN and 0.1 parts by mass of initiator BPO were mixed evenly to form a mixed monomer solution. The above-mentioned epoxy resin-coated quartz sand and 400 parts by mass of the mixed monomer solution (equivalent to a mass ratio of the mixed monomers to the amino coupling agent-modified quartz sand in the mixed monomer solution of 70:100) were added to the reactor. The temperature was raised to 80°C under stirring to initiate in-situ polymerization. After the polymerization reaction, the mixture was filtered, the solid was washed with ethanol, and dried to obtain oil-permeable and water-resistant coated quartz sand for fracturing. Comparative Example 1

[0038] The other conditions are the same as in Example 3, except that step (S1) is omitted and step (S2) uses 80-mesh quartz sand as raw material, that is, the quartz sand is not modified by amino coupling agent. Comparative Example 2

[0039] The other conditions are the same as in Example 3, except that in step (S2), the multifunctional epoxy resin AG-601 is not added. Comparative Example 3

[0040] The other conditions are the same as in Example 3, except that diallyl bisphenol A diglycidyl ether is not added in step (S2). Comparative Example 4

[0041] The other conditions are the same as in Example 3, except that in step (S3), the mixed monomers are a mixture of hexyl acrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate in a mass ratio of 20:2:2.3:1. That is, hexafluorobutyl methacrylate is replaced with an equal mass of hexyl acrylate. Comparative Example 5

[0042] The other conditions are the same as in Example 3, except that in step (S3), the mixed monomers are a mixture of hexyl acrylate, hexafluorobutyl methacrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate in a mass ratio of 15:5:2.3:1, i.e., isobornyl acrylate is not added. Comparative Example 6

[0043] The other conditions are the same as in Example 3, except that in step (S3), the mixed monomers are a mixture of hexyl acrylate, hexafluorobutyl methacrylate, isobornyl acrylate, and bis(3-trimethoxysilylpropyl)fumarate in a mass ratio of 15:5:2:1. That is, dimethyl diallyl ammonium chloride is not added. Comparative Example 7

[0044] The other conditions are the same as in Example 3, except that in step (S3), the mixed monomers are a mixture of hexyl acrylate, hexafluorobutyl methacrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate in a mass ratio of 15:5:2:2.3:1. That is, bis(3-trimethoxysilylpropyl) fumarate is replaced with an equal mass of vinyltriethoxysilane.

[0045] Application examples

[0046] The performance of the fracturing oil-permeable and water-blocking coated quartz sand obtained in the above embodiments and preparation examples was tested, and the results are shown in Table 1.

[0047] The breakage rate test was conducted according to SY / T 5108-2014, with a hydraulic press test pressure of 60 MPa. The flowability test was conducted according to SY / T6302-2019, with a proppant placement area of ​​64.5 cm². 2 The closing pressure is 60 MPa. High-temperature aging involves aging the coated quartz sand at 120°C for 16 hours and then retesting its conductivity.

[0048] Table 1 Performance Tests of Oil-Permeable and Water-Barrier Coated Quartz Sand for Fracturing

[0049]

[0050] As can be seen from the data in Table 1, the fracturing-grade oil-permeable and water-blocking coated quartz sand provided by this invention has excellent oil permeability and water-blocking capabilities. Furthermore, it maintains a stable and long-lasting oil permeability and water-blocking effect even under high-temperature and high-pressure formation conditions. After high-temperature aging, it still retains a high oil-water ratio (≥1.60) and kerosene conductivity (≥43.5μm). 2 The fracturing oil-permeable and water-blocking coated quartz sand of this invention exhibits low breakage rate (≤1.7%) under a high closure pressure of 60 MPa. The superior performance of this invention is achieved through the rational formulation of its components; the absence of any core component or raw material would prevent the attainment of these superior effects.

Claims

1. A type of oil-permeable and water-barrier coated quartz sand for fracturing, characterized in that, It has a three-layer core-shell structure, with the core being quartz sand modified with an aminosilane coupling agent, the middle layer being a thermosetting epoxy resin, and the outer layer being a functional polymer layer. The raw materials for preparing the middle layer include epoxy resin A, multifunctional epoxy resin, double-bond epoxy resin, and amino resin. Epoxy resin A is selected from at least one of bisphenol-type epoxy resin and phenolic epoxy resin. The raw materials for preparing the outer layer include (meth)acrylate C6-C10 alkyl ester, fluorinated acrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, and bis(3-trimethoxysilylpropyl) fumarate. The amount of aminosilane coupling agent is 5-10 wt% of the quartz sand mass. The multifunctional epoxy resin is selected from at least one of AG-80, AG-70, AG-601, AG-602, AFG-90, and TDE-85. The double-bond epoxy resin... The resin is selected from at least one of diallyl bisphenol A diglycidyl ether and itaconic acid diglycidyl ester; the amino resin is selected from at least one of methyl etherified melamine resin, melamine-formaldehyde resin, and urea / formaldehyde resin; the mass ratio of epoxy resin A, multifunctional epoxy resin, double-bonded epoxy resin and amino resin is 40-55:6-10:2-3:5-8; the mass ratio of (meth)acrylate C6-C10 alkyl ester, fluorinated acrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride and bis(3-trimethoxysilylpropyl) fumarate is 15-18:4-5:2-2.4:2.3-2.9:0.8-1; the mass ratio of aminosilane coupling agent modified quartz sand, the raw material for preparing the intermediate layer and the raw material for preparing the outer layer is 100:30-40:65-80.

2. The oil-permeable and water-blocking coated quartz sand for fracturing according to claim 1, characterized in that, Amino-coupled agent modified quartz sand is obtained by dispersing quartz sand in an alcohol aqueous solution and reacting it with an aminosilane coupling agent. The quartz sand has a particle size of 40-100 mesh. The alcohol aqueous solution is a solution of C1-3 alcohol and water, with the alcohol having a volume percentage of 50-80%. The C1-3 alcohol is selected from at least one of methanol, ethanol, and isopropanol. The aminosilane coupling agent is selected from at least one of γ-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, γ-diethylenetriaminepropylmethyldimethoxysilane, and N-2-aminoethyl-3-aminopropyltrimethoxysilane.

3. The oil-permeable and water-blocking coated quartz sand for fracturing according to claim 1, characterized in that, The bisphenol type epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; the phenolic epoxy resin is selected from at least one of phenol formaldehyde epoxy resin, o-cresol formaldehyde epoxy resin, resorcinol formaldehyde epoxy resin, and bisphenol A type phenolic epoxy resin.

4. The oil-permeable and water-blocking coated quartz sand for fracturing according to claim 1, characterized in that, The (meth)acrylate C6-C10 alkyl ester is selected from at least one of (meth)acrylate hexyl acrylate, (meth)acrylate heptyl acrylate, (meth)acrylate octyl acrylate, (meth)acrylate nonyl acrylate, and (meth)acrylate decyl acrylate; the fluorinated acrylate is selected from at least one of pentafluoropropyl acrylate, pentafluoropropyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, and perfluorohexylethyl acrylate.

5. The method for preparing the oil-permeable and water-blocking coated quartz sand for fracturing according to any one of claims 1-4, characterized in that, Includes the following steps: (S1) Quartz sand is dispersed in an alcohol-water solution, an aminosilane coupling agent is added to react, washed, and dried to obtain amino-coupled agent modified quartz sand. (S2) Epoxy resin A, multifunctional epoxy resin, double bond-containing epoxy resin and amino resin are mixed evenly according to the mass ratio to obtain a mixed resin; under an inert atmosphere, amino coupling agent modified quartz sand is added to a sand mixer, heated to 60-80℃, and sprayed with the mixed resin under stirring. After spraying, stirring is continued to complete the reaction, cooled, discharged, and cured at 90-120℃ to obtain epoxy resin-coated quartz sand. (S3) Add epoxy resin-coated quartz sand and a mixed monomer solution to the reactor. The mixed monomer solution includes (meth)acrylate C6-C10 alkyl ester, fluorinated acrylate, isobornyl acrylate, dimethyl diallyl ammonium chloride, bis(3-trimethoxysilylpropyl) fumarate and an initiator. Initiate in-situ polymerization by heating. After polymerization, filter, wash the solid, and dry to obtain oil-permeable and water-resistant coated quartz sand for fracturing.

6. The preparation method according to claim 5, characterized in that, In step (S1), the reaction temperature is 50-70℃, the reaction time is 3-5 hours, and the washing is done with acetone; and / or In step (S2), the mixing speed of the sand mixer is 60-100 rpm, the time for spraying the mixed resin is 20-60 min, the time for continuing mixing to complete the reaction is 3-5 h, and the time for continuing curing is 1-2 h.

7. The preparation method according to claim 5, characterized in that, In step (S3), the initiator is selected from at least one of azo initiators and peroxide initiators. The azo initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate. The peroxide initiator is selected from at least one of benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, and di(4-tert-butylcyclohexyl) peroxide. The amount of initiator is 1-2 wt% of the mass of the mixed monomers, and the temperature for initiating in-situ polymerization is 60-80°C. The mixed monomers account for 20-30 wt% of the mixed monomer solution, and the solvent of the mixed monomer solution is selected from at least one of DMSO and DMF.

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