Film covering method and device for film covering proppant

Abstract

The invention relates to the technical field of film-coated proppants, in particular to a film coating method and device of a film-coated proppant, and the film coating method of the film-coated proppant comprises the following steps: S1, material pretreatment: washing aggregate, soaking the aggregate in an aqueous solution of a silane coupling agent, filtering and then drying to obtain clean aggregate; s2, primary film covering is conducted, specifically, the clean aggregate is heated and then transferred into a powerful sand mixer, phenolic resin, oleophylic modified fumed silica, a phenolic resin curing agent and a lubricating agent are sequentially added in the stirring state, and first covered aggregate is obtained; s3, secondary coating: sequentially adding polyether polyol, a cross-linking agent, a polyether polyol curing agent and a metal catalyst into the first coated aggregate, finally adding oleophylic modified fumed silica, and fully stirring and mixing to obtain second coated aggregate; and S4, packaging to obtain the film-coated proppant. Wherein the phenolic resin and the oleophylic modified fumed silica are mixed and dispersed in advance.

Description

Technical Field

[0001] The invention relates to the technical field of film-coated proppants, and in particular to a film-coating method and device for a film-coated proppant. Background Art

[0002] Oil fracturing proppant is a supporting material used in the process of oil extraction. During the process of oil and natural gas extraction, the ore bed is treated by fracturing to create cracks in the oil and gas rock formation, forming a channel with high flow capacity. Oil fracturing proppant is used to fill the cracks to keep the cracks open and not close due to stress release, thereby maintaining high conductivity, allowing oil and gas to flow smoothly and increasing production.

[0003] At present, the commonly used petroleum fracturing proppants include quartz sand proppants, expanded clay proppants and coated proppants. Among them, the aggregates of the coated proppants are quartz sand and expanded clay. According to research, after coating, the resin film layer can limit the migration of proppant debris and prevent it from clogging the diversion channel. However, existing research is usually to improve the compressive strength and conductivity. After the proppant enters the crack, with the return of the sand-carrying fluid (Shang Yongbin et al., Analysis of Factors Affecting the Return of Proppant, Inner Mongolia Petrochemical, Issue 22, 2010, 66-68), the proppant may be affected, thereby affecting the opening of the crack and may also cause equipment damage. Therefore, many oil wells adopt the means of reducing pumping and reducing the pressure difference to avoid the return of the sand-carrying fluid. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a coating method and device for a coated proppant, improves the coating method for the coated proppant, reduces proppant flowback, and improves the compressive strength and hydrophobicity of the product.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A coating method for a coated proppant comprises the following steps:

[0007] Step S1: Material pretreatment, washing the aggregate with clean water and organic reagent in turn, then soaking it in an aqueous solution of silane coupling agent for more than 30 minutes, drying the aggregate after filtering, and storing it in a container at 200°C ± 10°C to obtain clean aggregate;

[0008] Step S2: First coating, the clean aggregate is transferred to a powerful sand mixer, phenolic resin and oleophilic modified fumed silica are added under stirring, stirred and mixed for a certain time, and then phenolic resin curing agent and lubricant are added and mixed for a certain time to obtain the first coated aggregate;

[0009] Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding polyether polyols to the first coated aggregate in sequence and mixing for a certain time, then adding a crosslinking agent, a polyether polyol curing agent and a metal catalyst and continuing to mix for a certain time, and finally adding oleophilic modified fumed silica, stirring and mixing thoroughly to obtain a second coated aggregate;

[0010] Step S4: packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant;

[0011] The phenolic resin and the lipophilic modified fumed silica are pre-mixed and dispersed, and the lipophilic modified fumed silica is dispersed in the phenolic resin.

[0012] Furthermore, the phenolic resin and the polyether polyol are both dissolved in industrial ethanol into a liquid with a viscosity of 500-1500 cps, the mixing time is 60s-75s after the resin is added, and the mixing time is 45s-55s after the curing agent component is added.

[0013] Furthermore, in step S2, the weight of the phenolic resin accounts for 1.5%-2.5% of the weight of the clean aggregate; in step S3, the weight of the polyether polyol accounts for 1.5%-2% of the weight of the clean aggregate, and the mass of the polyether polyol is less than or equal to the mass of the phenolic resin.

[0014] Furthermore, in step S2, the amount of lipophilic modified fumed silica added is 2%-4% by weight of the phenolic resin.

[0015] Furthermore, the amount of lipophilic modified fumed silica added in step S3 is 5%-8% of the weight of the polyether polyol.

[0016] Furthermore, the preparation method of the oleophilic modified fumed silica is as follows: dispersing fumed silica in anhydrous ethanol to obtain a fumed silica mixed liquid, fully mixing a silane coupling agent with water to obtain a silane coupling agent hydrolyzate, fully mixing the fumed silica mixed liquid and the silane coupling agent hydrolyzate and condensing and refluxing at 70° C. for 1-2 hours under stirring, filtering, washing the filter cake with anhydrous ethanol, drying at 70° C. after suction filtration, and grinding into powder to obtain the oleophilic modified fumed silica.

[0017] A coating device for a coating proppant, comprising a shell, a lower stirring mechanism, an upper stirring mechanism and a solvent recovery mechanism, wherein the shell is provided with a feeding port, and the feeding port is provided with a closing device; the upper stirring mechanism is connected to the top surface of the shell, and the upper stirring mechanism comprises a driving motor located outside the shell, a stirring shaft extending into the shell, and a stirring blade connected to the stirring shaft; the lower stirring mechanism is connected to the center of the bottom surface of the shell, and the lower stirring mechanism has a central axis and a stirring blade, and the stirring blade comprises a connecting section and an upward section, and the connecting section and the upward section are both laterally inclined plates, wherein the upper end of the connecting section is lower than the lower end of the stirring shaft, the upper end of the upward section is higher than the lower end of the stirring shaft, and the rotation radius of the upward section is greater than the distance between the stirring shaft and the central axis;

[0018] The solvent recovery mechanism includes an air outlet pipe and a condensation box, one end of the air outlet pipe is connected to the upper end of the shell, and the other end is connected to the lower end of the condensation box. The condensation box is placed in a tank filled with water. There are multiple staggered guide plates inside the condensation box. The guide plates divide the space inside the condensation box into continuous "S"-shaped flow channels. The upper end of the condensation box is connected to the exhaust gas treatment pipeline.

[0019] Furthermore, a retaining ring is provided on the central axis, and the retaining ring is a circular ring. The inner wall of the retaining ring is connected to the central axis via a connecting piece. The upper end of the retaining ring is at the same height as the upper end of the rising section, and there is a gap between the lower end of the retaining ring and the upper end of the connecting section.

[0020] Furthermore, the stirring shaft is connected to a drying and cooling mechanism, which includes an air intake pipe, a positioning cylinder and fan blades. The positioning cylinder is sleeved outside the stirring shaft, and the stirring shaft corresponding to the positioning cylinder is connected to the fan blades. The positioning cylinder above the fan blades is connected to the air intake pipe, and the upper end of the air intake pipe passes through and extends out of the shell. A stop valve is provided on the air intake pipe outside the shell.

[0021] Beneficial Effects

[0022] 1. The present invention adopts double-layer coating, and the outer layer is polyether polyol, which can form elastic contact after the crack is closed. On the one hand, the contact area between the proppant particles is increased to increase the compressive strength. On the other hand, it also forms mutual adhesion to avoid proppant spitting back, and there is no need to reduce the means of pumping and reducing the pressure difference, thereby increasing the output. In addition, the addition of oleophilic modified fumed silica has both a reinforcing effect and an oleophilic and hydrophobic effect, which can improve the compressive strength and hydrophobicity of the product.

[0023] 2. The present invention reduces the viscosity of the resin and improves production efficiency. The oleophilic modified fumed silica is used as an outer layer lubricant and distributed in the form of particles on the surface of the proppant. During storage and transportation, the outer layers of the proppant can be prevented from sticking together. When the proppant is input into the crack, the polyether polyol in the outer layer is not affected by the heat of the formation to form elastic deformation, and the proppant contacts and solidifies to form a bridge structure.

[0024] 3. The coating device of the coated proppant of the present invention is set to match the coating method of the coated proppant of the present invention. It completes ethanol recovery and reduces production costs through simple structural modification, and also has a positive promoting effect on the quality of the proppant produced by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The process flow chart of the coating method of the coating proppant of the present invention is

[0026] Figure 2 It is a structural schematic diagram of a coating device of a coated proppant of the present invention (partial cross-section);

[0027] Figure 3 is a top view of a coating device for a coated proppant of the present invention;

[0028] Figure 4 yes Figure 3 AA section view;

[0029] Figure 5 yes Figure 3 BB section view.

[0030] The numbers in the attached drawings are: 1. Shell; 2. Lower stirring mechanism; 3. Upper stirring mechanism; 4. Sand adding port; 5. Liquid adding port; 6. Sealing cover; 7. Sand adding pipe; 8. Butterfly valve; 9. Driving motor; 10. Stirring shaft; 11. Stirring blades; 12. Center axis; 13. Paddle blades; 14. Solvent recovery mechanism; 15. Exhaust pipe; 16. Condensation box; 17. Guide vane; 18. Baffle ring; 19. Connector; 20. Drying and cooling mechanism; 21. Inlet pipe; 22. Positioning cylinder; 23. Fan blades; 24. Stop valve. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0032] like Figure 1 As shown, a coating method for a coated proppant comprises the following steps:

[0033] Step S1: Material pretreatment, washing the aggregate with clean water and organic reagent in turn, then soaking it in an aqueous solution of silane coupling agent for more than 30 minutes, drying the aggregate after filtering, and storing it in a container at 200°C ± 10°C to obtain clean aggregate;

[0034] Step S2: First coating, the clean aggregate is transferred to a powerful sand mixer, phenolic resin and oleophilic modified fumed silica are added under stirring, stirred and mixed for a certain time, and then phenolic resin curing agent and lubricant are added and mixed for a certain time to obtain the first coated aggregate;

[0035] Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding polyether polyols to the first coated aggregate in sequence and mixing for a certain time, then adding a crosslinking agent, a polyether polyol curing agent and a metal catalyst and continuing to mix for a certain time, and finally adding oleophilic modified fumed silica, stirring and mixing thoroughly to obtain a second coated aggregate;

[0036] Step S4: packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant;

[0037] The phenolic resin and the lipophilic modified fumed silica are pre-mixed and dispersed, and the lipophilic modified fumed silica is dispersed in the phenolic resin.

[0038] In the first coating, the oleophilic modified fumed silica is pre-mixed and dispersed in the resin, which can improve the compressive strength of the resin. In the second coating, polyether polyol is used to make the second coating have a certain "face" and "face" contact between the proppants when the cracks are closed, which can effectively avoid the fragmentation of the proppants and form a larger contact surface between the proppants. The anti-scouring ability of the bridge arch formed by the proppant is enhanced, and it is not easy to be destroyed under a large pumping action, thereby preventing the proppant from flowing back. The oil-modified fumed silica is not pre-mixed and dispersed in the resin, but is added after the curing agent is added, which can make the oleophilic modified fumed silica evenly distributed on the outer surface of the resin coating layer of the proppant, and can produce physical separation during storage and transportation, reducing resin adhesion. However, when the proppant is located in the crack, due to the squeezing effect of the formation pressure, it does not affect the formation of a network structure between the proppants. At the same time, because the oleophilic modified fumed silica is located on the surface of the proppant, the oleophilic and hydrophobic properties of the proppant are improved in the crack, thereby improving the oil and gas recovery efficiency.

[0039] The phenolic resin and polyether polyol are both dissolved in industrial ethanol into a liquid with a viscosity of 500-1500 cps. The mixing time is 60s-75s after the resin is added, and the mixing time is 45s-55s after the curing agent component is added.

[0040] Dissolving both phenolic resin and polyether polyol into a liquid with a viscosity of 500-1500cps using industrial ethanol can greatly enhance the fluidity of the resin, reduce the stirring and mixing time, complete the coating of the proppant aggregate in a shorter time, simplify the feeding and stirring process, and improve production efficiency.

[0041] In step S2, the weight of the phenolic resin accounts for 1.5%-2.5% of the weight of the clean aggregate; in step S3, the weight of the polyether polyol accounts for 1.5%-2% of the weight of the clean aggregate, and the mass of the polyether polyol is less than or equal to the mass of the phenolic resin.

[0042] In the step S2, the amount of lipophilic modified fumed silica added is 2% to 4% of the weight of the phenolic resin.

[0043] The amount of lipophilic modified fumed silica added in step S3 accounts for 5% to 8% of the weight of the polyether polyol.

[0044] The preparation method of the oleophilic modified fumed silica is as follows: dispersing fumed silica in anhydrous ethanol to obtain a fumed silica mixed liquid, fully mixing a silane coupling agent with water to obtain a silane coupling agent hydrolyzate, fully mixing the fumed silica mixed liquid and the silane coupling agent hydrolyzate and condensing and refluxing under stirring at 70° C. for 1-2 hours, filtering, washing the filter cake with anhydrous ethanol, drying at 70° C. after suction filtration, and grinding into powder to obtain the oleophilic modified fumed silica.

[0045] Sources:

[0046] Ceramic proppant: 40-80 mesh, homemade; Silane coupling agent KH550: purchased from outside; Phenolic resin and its curing agent: taken from the factory inventory; Polyether polyol and its curing agent: purchased from outside; Oleophilic modified fumed silica: homemade

[0047] The experimental process is as follows:

[0048] 10 kg of the material was pretreated in step S1 and divided into 10 portions, each of 1000 g; coated proppants with different proportions of resin and oleophilic modified fumed silica addition were prepared and tested respectively.

[0049] Embodiment 1:

[0050] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 15.3 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 2% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 2.25 g of hexamethylenetetramine and 0.045 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0051] Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding 10g of polyether polyol to the first coated aggregate in sequence and mixing for 75s, then adding 0.7g of DV-125 crosslinking agent, 0.8g of diethylenetriamine and 0.03g of metal catalyst and continuing to mix for 45s, and finally adding 0.75g of oleophilic modified fumed silica, and mixing thoroughly to obtain the second coated aggregate;

[0052] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0053] Embodiment 2:

[0054] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 20.6 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 3% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 3 g of hexamethylenetetramine and 0.06 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0055] Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding 18g of polyether polyol to the first coated aggregate in sequence and mixing for 75s, then adding 0.9g of DV-125 crosslinking agent, 1.4g of diethylenetriamine and 0.06g of metal catalyst and continuing to mix for 45s, finally adding 1.2g of oleophilic modified fumed silica, and fully stirring and mixing to obtain the second coated aggregate;

[0056] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0057] Embodiment three:

[0058] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 26 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 4% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 3.75 g of hexamethylenetetramine and 0.075 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0059] Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding 20g of polyether polyol to the first coated aggregate in sequence and mixing for 75s, then adding 1g of DV-125 crosslinking agent, 1.6g of diethylenetriamine and 0.07g of metal catalyst and continuing to mix for 45s, and finally adding 1.6g of oleophilic modified fumed silica, stirring and mixing thoroughly to obtain the second coated aggregate;

[0060] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0061] Embodiment 4:

[0062] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 15.45 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 3% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 2.25 g of hexamethylenetetramine and 0.045 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0063] Step S3: Second coating, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C ± 5°C, add 15g of polyether polyol to the first coated aggregate in sequence and mix for 75s, then add 0.7g of DV-125 crosslinking agent, 1.2g of diethylenetriamine and 0.05g of metal catalyst and continue mixing for 45s, finally add 1g of oleophilic modified fumed silica, and stir and mix thoroughly to obtain the second coated aggregate;

[0064] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0065] Embodiment five:

[0066] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 20.4 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 2% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 3 g of hexamethylenetetramine and 0.06 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0067] Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding 18g of polyether polyol to the first coated aggregate in sequence and mixing for 75s, then adding 0.9g of DV-125 crosslinking agent, 1.4g of diethylenetriamine and 0.06g of metal catalyst and continuing to mix for 45s, finally adding 1.4g of oleophilic modified fumed silica, and fully stirring and mixing to obtain the second coated aggregate;

[0068] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0069] Embodiment six:

[0070] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 25.5 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 2% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 3.75 g of hexamethylenetetramine and 0.075 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0071] Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding 20g of polyether polyol to the first coated aggregate in sequence and mixing for 75s, then adding 1g of DV-125 crosslinking agent, 1.6g of diethylenetriamine and 0.07g of metal catalyst and continuing to mix for 45s, and finally adding 1.6g of oleophilic modified fumed silica, stirring and mixing thoroughly to obtain the second coated aggregate;

[0072] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0073] Embodiment seven:

[0074] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 15.45 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 3% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 2.25 g of hexamethylenetetramine and 0.045 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0075] Step S3: second coating, maintaining the stirring state of the sand mixer, when the first coated aggregate is cooled to 120°C ± 5°C, 20g of polyether polyol is added to the first coated aggregate in sequence and mixed for 75s, then 1g of DV-125 crosslinking agent, 1.6g of diethylenetriamine and 0.07g of metal catalyst are added and mixed for 45s, and finally 1g of oleophilic modified fumed silica is added, and the second coated aggregate is obtained after sufficient stirring and mixing;

[0076] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0077] Embodiment eight:

[0078] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 20.8 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 4% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 3 g of hexamethylenetetramine and 0.06 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0079] Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding 18g of polyether polyol to the first coated aggregate in sequence and mixing for 75s, then adding 0.9g of DV-125 crosslinking agent, 1.4g of diethylenetriamine and 0.06g of metal catalyst and continuing to mix for 45s, and finally adding 1.6g of oleophilic modified fumed silica, stirring and mixing thoroughly to obtain the second coated aggregate;

[0080] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0081] Embodiment nine:

[0082] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 25.75 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 3% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 3.75 g of hexamethylenetetramine and 0.075 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0083] Step S3: Second coating, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C ± 5°C, add 15g of polyether polyol to the first coated aggregate in sequence and mix for 75s, then add 0.5g of DV-125 crosslinking agent, 1.2g of diethylenetriamine and 0.05g of metal catalyst and continue mixing for 45s, finally add 1.2g of oleophilic modified fumed silica, and stir and mix thoroughly to obtain the second coated aggregate;

[0084] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0085] Embodiment ten:

[0086] Step S2: First coating, 1000 g of clean aggregate is transferred to a powerful sand mixer, and 25.75 g of a mixture of phenolic resin and oleophilic modified fumed silica is added under stirring, wherein the amount of oleophilic modified fumed silica added accounts for 3% of the weight of the phenolic resin, and the mixture is stirred and mixed for 60 seconds, and then 3.75 g of hexamethylenetetramine and 0.075 g of lubricant are added and the mixture is mixed for 45 seconds to obtain the first coated aggregate;

[0087] Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding 20g of polyether polyol to the first coated aggregate in sequence and mixing for 75s, then adding 1g of DV-125 crosslinking agent, 1.6g of diethylenetriamine and 0.07g of metal catalyst and continuing to mix for 45s, and finally adding 1.6g of oleophilic modified fumed silica, stirring and mixing thoroughly to obtain the second coated aggregate;

[0088] Step S4: Packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant.

[0089] The addition amount of the above phenolic resin and polyether polyol is measured in terms of solid content. The bulk density and crushing rate are tested according to SY_T 5108-2006 performance indicators and test recommended methods for fracturing proppants. The conductivity of the proppant is tested according to the SY / T6302-2019 test method for conductivity of fracturing proppants.

[0090] The test results are as follows:

[0091]

[0092]

[0093] like Figure 2 and Figure 3As shown, a coating device for a coated proppant comprises a shell 1, a lower stirring mechanism 2 and an upper stirring mechanism 3. The shell 1 is provided with a feeding port, and the feeding port comprises a sand feeding port 4 and a liquid feeding port 5. The sand feeding port 4 is used to add ceramsite, and the liquid feeding port 5 is used to add resin and additives. The feeding port is provided with a sealing device, such as Figure 3 As shown, the closing device on the liquid adding port 5 is a sealing cover 6 that is rotatably connected to the liquid adding port 5 and can be quickly closed to prevent ethanol vapor from overflowing. The closing device on the sand adding port 4 is a sand adding pipe 7 and a butterfly valve 8. The lower end of the sand adding pipe 7 is connected to the sand adding port 4, and the upper end is connected to the ceramsite storage mechanism. The butterfly valve 8 is connected to the sand adding pipe 7. When the butterfly valve 8 is opened, the ceramsite enters the sand adding port 4 from the sand adding pipe 7. When the butterfly valve 8 is closed, the sand adding pipe 7 is closed; the upper stirring mechanism 3 is connected to the top surface of the shell 1. There are at least two upper stirring mechanisms 3, and the two upper stirring mechanisms 3 both include a driving mechanism located outside the shell 1. A motor 9, a stirring shaft 10 extending into the housing 1, and a stirring blade 11 connected to the stirring shaft 10; the lower stirring mechanism 2 is connected to the center of the bottom surface of the housing 1, the lower stirring mechanism 2 has a central axis 12 and a stirring blade 13, the stirring blade 13 includes a connecting section and an upward section, the connecting section and the upward section are both laterally inclined plates, wherein the upper end of the connecting section is lower than the lower end of the stirring shaft 10, the upper end of the upward section is higher than the lower end of the stirring shaft 10, and the rotation radius of the upward section is greater than the distance between the stirring shaft 10 and the central axis 12, and a solvent recovery mechanism 14 is provided on the housing 1;

[0094] like Figure 4 As shown, the solvent recovery mechanism 14 includes an air outlet pipe 15 and a condensation box 16. One end of the air outlet pipe 15 is connected to the upper end of the shell 1, and the other end is connected to the lower end of the condensation box 16. The condensation box 16 is made of metal. The condensation box 16 is placed in a tank filled with water. There are multiple staggered guide plates 17 inside the condensation box 16. The guide plates 17 divide the space inside the condensation box into continuous "S"-shaped flow channels. The upper end of the condensation box 16 is connected to the exhaust gas treatment pipeline.

[0095] The solvent recovery mechanism 14 is used to recover the ethanol solvent. The recovered ethanol solvent can be reused to reduce production costs.

[0096] The condensation tank 16 is placed obliquely, and the end of the guide plate 17 is inclined upward.

[0097] like Figure 2 and Figure 4 As shown, a retaining ring 18 is provided on the central shaft 12. The retaining ring 18 is a circular ring. The inner wall of the retaining ring 18 is connected to the central shaft 12 via a connecting piece 19. The upper end of the retaining ring 18 is at the same height as the upper end of the rising section, and there is a gap between the lower end of the retaining ring 18 and the upper end of the connecting section.

[0098] When the central shaft 12 rotates, the proppant is pushed toward the periphery of the shell 1 by the paddle 13, so that it is fully stirred and dispersed by the stirring blades 11 on the stirring shaft 10. The retaining ring 18 can keep the proppant close to the outer area of ​​the shell to enhance the stirring effect, and can also be used as a counter-attack plate of the proppant during stirring to improve the mixing effect.

[0099] like Figure 2 and Figure 5 As shown, the stirring shaft 10 is connected to a drying and cooling mechanism 20, and the drying and cooling mechanism 20 includes an air inlet pipe 21, a positioning cylinder 22 and a fan blade 23. The positioning cylinder 22 is sleeved on the outside of the stirring shaft 10, and the upper end of the positioning cylinder 22 is connected to the limiting mechanism of the stirring shaft 10. The stirring shaft 10 corresponding to the positioning cylinder 22 is connected to the fan blade 23. The positioning cylinder 22 above the fan blade 23 is connected to the air inlet pipe 21, and the upper end of the air inlet pipe 21 passes through and extends out of the shell 1. A stop valve 24 is provided on the air inlet pipe 21 outside the shell 1.

[0100] When the stirring shaft 10 rotates, the fan blades 23 are driven to rotate. When the stop valve 24 is opened, the fan blades 23 rotate to introduce air from outside the shell 1 into the shell 1. When the stop valve 24 is closed, the fan blades 23 rotate and cannot introduce air into the shell 1.

[0101] When the stop valve 24 is closed, the present invention promotes ethanol vapor to enter the condensation box 16 through the pressure generated by the evaporation of ethanol in the resin, thereby realizing ethanol recovery. At this time, the temperature in the shell 1 drops slowly, and maintaining a certain temperature is conducive to better mixing and coating of the resin. When the evaporation of ethanol is nearing the end, the pressure in the shell 1 decreases, and the stop valve 24 is opened. At this time, the air inlet pipe 21 is connected to the shell 1. When the fan blades 23 rotate, air is introduced into the shell 1 through the air inlet pipe 21, and the ethanol vapor in the shell 1 is discharged into the condensation box 16, which is conducive to fully recovering ethanol, reducing ethanol volatilization in the workshop, and protecting the production environment. At the same time, the temperature drop in the shell 1 is accelerated, which is conducive to quickly completing the temperature drop and improving production efficiency.

[0102] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

Claims

1. A coating method for a coated proppant, characterized in that: The following steps are involved: Step S1: Material pretreatment, washing the aggregate with clean water and organic reagent in turn, then soaking it in an aqueous solution of silane coupling agent for more than 30 minutes, drying the aggregate after filtering, and storing it in a container at 200°C ± 10°C to obtain clean aggregate; Step S2: First coating, the clean aggregate is transferred to a powerful sand mixer, phenolic resin and oleophilic modified fumed silica are added under stirring, stirred and mixed for a certain time, and then phenolic resin curing agent and lubricant are added and mixed for a certain time to obtain the first coated aggregate; Step S3: coating for the second time, maintaining the stirring state of the sand mixer, when the temperature of the first coated aggregate drops to 120°C±5°C, adding polyether polyols to the first coated aggregate in sequence and mixing for a certain time, then adding a crosslinking agent, a polyether polyol curing agent and a metal catalyst and continuing to mix for a certain time, and finally adding oleophilic modified fumed silica, stirring and mixing thoroughly to obtain a second coated aggregate; Step S4: packaging, cooling to below 50° C. under stirring, discharging and packaging to obtain the coated proppant; The phenolic resin and the lipophilic modified fumed silica are pre-mixed and dispersed, and the lipophilic modified fumed silica is dispersed in the phenolic resin.

2. A coating method for a coated proppant according to claim 1, characterized in that: The phenolic resin and polyether polyol are both dissolved in industrial ethanol into a liquid with a viscosity of 500-1500 cps. The mixing time is 60s-75s after the resin is added, and the mixing time is 45s-55s after the curing agent component is added.

3. The coating method of a coated proppant according to claim 1, characterized in that: In step S2, the weight of the phenolic resin accounts for 1.5%-2.5% of the weight of the clean aggregate; in step S3, the weight of the polyether polyol accounts for 1.5%-2% of the weight of the clean aggregate, and the mass of the polyether polyol is less than or equal to the mass of the phenolic resin.

4. The coating method of a coated proppant according to claim 1, characterized in that: In the step S2, the amount of lipophilic modified fumed silica added is 2% to 4% of the weight of the phenolic resin.

5. The coating method of a coated proppant according to claim 1, characterized in that: The amount of lipophilic modified fumed silica added in step S3 accounts for 5% to 8% of the weight of the polyether polyol.

6. The coating method of a coated proppant according to claim 1, characterized in that: The preparation method of the oleophilic modified fumed silica is as follows: dispersing fumed silica in anhydrous ethanol to obtain a fumed silica mixed liquid, fully mixing a silane coupling agent with water to obtain a silane coupling agent hydrolyzate, fully mixing the fumed silica mixed liquid and the silane coupling agent hydrolyzate and condensing and refluxing under stirring at 70° C. for 1-2 hours, filtering, washing the filter cake with anhydrous ethanol, drying at 70° C. after suction filtration, and grinding into powder to obtain the oleophilic modified fumed silica.

7. A coating device for a coated proppant, characterized in that: The invention comprises a shell (1), a lower stirring mechanism (2), an upper stirring mechanism (3) and a solvent recovery mechanism (14), wherein the shell (1) is provided with a feeding port, and the feeding port is provided with a sealing device; the upper stirring mechanism (3) is connected to the top surface of the shell (1), and comprises a driving motor (9) located outside the shell (1), a stirring shaft (10) extending into the shell (1), and a stirring blade (11) connected to the stirring shaft (10); the lower stirring mechanism (2) is connected to the center of the bottom surface of the shell (1), and the lower stirring mechanism (2) has a central axis (12) and a stirring blade (13), and the stirring blade (13) comprises a connecting section and an upward section, wherein the connecting section and the upward section are both laterally inclined plates, wherein the upper end of the connecting section is lower than the lower end of the stirring shaft (10), the upper end of the upward section is higher than the lower end of the stirring shaft (10), and the rotation radius of the upward section is greater than the distance between the stirring shaft (10) and the central axis (12); The solvent recovery mechanism (14) comprises an air outlet pipe (15) and a condensation box (16); one end of the air outlet pipe (15) is connected to the upper end of the shell (1), and the other end is connected to the lower end of the condensation box (16); the condensation box (16) is placed in a tank filled with water; a plurality of staggered guide plates (17) are arranged inside the condensation box (16); the guide plates divide the space inside the condensation box (16) into continuous "S"-shaped flow channels; the upper end of the condensation box (16) is connected to an exhaust gas treatment pipeline.

8. A coating device for coating a coating proppant according to claim 7, characterized in that: A retaining ring (18) is provided on the central shaft (12). The retaining ring (18) is a circular ring. The inner wall of the retaining ring (18) is connected to the central shaft (12) via a connecting piece (19). The upper end of the retaining ring (18) is at the same height as the upper end of the rising section. There is a gap between the lower end of the retaining ring (18) and the upper end of the connecting section.

9. A coating device for coating a coating proppant according to claim 7, characterized in that: The stirring shaft (10) is connected to a drying and cooling mechanism (20), the drying and cooling mechanism (20) comprising an air intake pipe (21), a positioning cylinder (22) and a fan blade (23), the positioning cylinder (22) being sleeved outside the stirring shaft (10), the fan blade (23) being connected to the stirring shaft (10) corresponding to the positioning cylinder (22), the positioning cylinder (22) above the fan blade (23) being connected to the air intake pipe (21), the upper end of the air intake pipe (21) passing through and extending outside the shell (1), and a stop valve (24) being provided on the air intake pipe (21) outside the shell (1).

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