A type of coated sand, its preparation method and application

Abstract

This invention provides a coated abrasive grain, its preparation method, and its application. The coated abrasive grain comprises an outer layer, an intermediate layer, and a core material, from the outside to the inside, wherein the outer layer is a self-aggregating membrane, the intermediate layer is a resin membrane, and the core material is abrasive grain.

Description

Technical Field

[0001] This invention relates to the field of proppant, and in particular to a coated sand grain. Background Technology

[0002] Unconventional reservoirs such as tight oil and gas and shale oil and gas have extremely low permeability. With the continuous development of unconventional oil and gas resources, most unconventional reservoirs require reservoir stimulation through hydraulic fracturing. Fracturing proppant plays a crucial role in oil and gas extraction and is one of the key materials in hydraulic fracturing technology. Propane is pumped underground using surface pumping equipment to fill the fractures created by hydraulic fracturing. By supporting the fractures and preventing them from closing, it forms oil and gas transport channels with specific geometric dimensions and high conductivity, thereby increasing oil and gas production and extending well life, achieving the goal of increased production and injection.

[0003] Currently, the proppant used in hydraulic fracturing is mainly traditional proppant, which suffers from low strength, fragility, and poor conductivity. Furthermore, proppant backflow may occur during fracturing fluid flowback or oil production. In recent years, to improve fracturing efficiency, the sand ratio in hydraulic fracturing has been increasing year by year, leading to more frequent proppant backflow, sometimes exceeding 20% ​​of the total proppant volume. Proppant and formation sand brought to the surface can corrode nozzles, valves, and other equipment; they can also reduce fracture length and width, and decrease conductivity. All of these factors severely impact post-fracturing oil and gas well production, increasing unnecessary operational work (such as sand flushing and pump inspection) and operating costs. Therefore, controlling proppant backflow remains a challenging research area in hydraulic fracturing. Summary of the Invention

[0004] One aspect of the present invention provides a coated sand grain, which includes an outer layer, an intermediate layer and a core material from the outside to the inside, wherein the outer layer is a self-forming membrane, the intermediate layer is a resin membrane and the core material is sand grain.

[0005] In one specific embodiment, the material forming the self-aggregating membrane is at least one of sodium alginate, guar gum, and cellulose.

[0006] In one specific embodiment, the guar gum is selected from at least one of guar gum, hydroxypropyl guar gum, and carboxymethyl hydroxypropyl guar gum.

[0007] In one specific embodiment, the cellulose is selected from at least one of hydroxypropyl methylcellulose, hydroxyethyl cellulose, and carboxymethyl cellulose.

[0008] In one specific embodiment, the plasmid ratio of the outer layer, the intermediate layer and the core material is (5-15):(5-15):300.

[0009] In one specific embodiment, the particle ratio of the outer layer, the intermediate layer and the core material is (5-15):(4.9-14.3):(285.7-295).

[0010] In one specific embodiment, the plasmid ratio of the outer layer, the intermediate layer and the core material is 1:(1-2):(20-60).

[0011] In one specific embodiment, the particle ratio of the outer layer, the intermediate layer and the core material is 1:(0.95-1.94):(19-59).

[0012] In one specific embodiment, the material forming the resin film is phenolic resin and / or epoxy resin.

[0013] In one specific embodiment, the phenolic resin is a thermoplastic phenolic resin and / or a thermosetting phenolic resin.

[0014] In one specific embodiment, the epoxy resin is epoxy resin E51.

[0015] In one specific embodiment, the sand particles are at least one of quartz sand, ceramsite sand, kaolin, coal gangue, rock chips, fly ash, and walnut shells.

[0016] In one specific embodiment, the particle size of the coated sand particles is 20 to 40 mesh.

[0017] The second aspect of the present invention provides a method for preparing coated sand particles as described in any one of the first aspects of the present invention, comprising the following steps:

[0018] 1) Mix sand particles with silane coupling agent and treat them to obtain sand particles treated with silane coupling agent;

[0019] 2) Mix the sand particles treated with silane coupling agent with the intermediate layer material resin evenly to obtain sand particles coated with resin film.

[0020] 3) Before the resin solidifies, the sand particles coated with the resin film are mixed evenly with the outer layer material, then cured and ball-milled to obtain the coated sand particles.

[0021] In one specific embodiment, in step 1), sand particles are added to water, then the above-mentioned silane coupling agent is added, stirred, and dried to obtain sand particles treated with the silane coupling agent.

[0022] In one specific embodiment, in step 3), the product is cured at 80 to 120°C for 5 to 10 minutes.

[0023] In one specific embodiment, the mass ratio of the sand particles to the silane coupling agent is 300:(5-15).

[0024] In one specific embodiment, the mass ratio of the silane coupling agent-treated sand particles to the intermediate layer material resin is 300:(5-15).

[0025] In one specific embodiment, the mass ratio of the sand particles coated by the resin film to the outer layer material is 300:(5-15).

[0026] In one specific embodiment, the particle size of the sand is 20 to 40 mesh.

[0027] In one specific embodiment, the silane coupling agent is at least one of KH-550, KH-560, and KH-570.

[0028] The third aspect of the present invention provides the application of the coated sand particles prepared by the method according to any one of the first aspect of the present invention or the method according to any one of the second aspect of the present invention as a proppant.

[0029] The beneficial effects of this invention are:

[0030] 1) The proppant of the present invention can reduce the overall relative density and breakage rate of the proppant, and form better sphericity and chemical inertness. Furthermore, according to the breakage rate data of the proppant of the present invention, it can be determined that the proppant of the present invention is conducive to the discharge of oil and gas, so the reflux flow rate will be smaller, and the flow carrying capacity will be greatly improved.

[0031] 2) The proppant of the present invention can form a sand-like state, supporting cracks and constructing a stable channel network through point support in the cracks, thus solving the problem of proppant backflow.

[0032] 3) The sand particles and porous composite materials used in the preparation of the proppant of the present invention are all derived from industrial production, which are easy to obtain, inexpensive, and the preparation method is simple and time-saving. Attached Figure Description

[0033] Figure 1 This shows that uncoated quartz sand does not have self-aggregating properties.

[0034] Figure 2 This demonstrates that the coated sand particles prepared in Example 5 possess self-aggregating properties. Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0036] The thermoplastic phenolic resin was purchased from Aladdin, CA S number: 9003-35-4.

[0037] The thermosetting phenolic resin was purchased from Macklin, CA S number: 9003-35-4.

[0038] Epoxy resin E51 was purchased from Macklin, CA S number: 61788-97-4.

[0039] Guar gum was purchased from Aladdin, CA S number: 9000-30-0.

[0040] Example 1

[0041] 1) Add 300 parts by weight of deionized water to 300 parts by weight of 20 to 40 mesh quartz sand, then add 5 parts by weight of silane coupling agent KH-550, mechanically stir at 400 rpm for 10 min at 25°C, and dry at 100°C for 10 min to obtain 300 parts by weight of silane coupling agent treated quartz sand.

[0042] 2) Mix 300 parts by weight of silane coupling agent treated quartz sand with 5 parts by weight of thermoplastic phenolic resin, and mechanically stir at 400 rpm for 10 min at 25°C to make the thermoplastic phenolic resin evenly distributed on the surface of the quartz sand, so as to obtain sand particles coated with resin film.

[0043] 3) Before the thermoplastic phenolic resin solidifies, add 5 parts by weight of guar gum to 300 parts by weight of the resin film-coated sand particles, mechanically stir at 400 rpm for 10 min at 25°C, and then cure at 80°C for 10 min to obtain particles with an outer layer of self-aggregating film, an inner layer of resin film, and a core of sand particles.

[0044] 4) Place it in a ball mill and ball mill at 1000 rpm for 5 minutes. Then, sieve it through a 20 to 40 mesh screen and package it to obtain a self-agglomerating support agent.

[0045] Example 2

[0046] 1) Add 300 parts by weight of deionized water to 300 parts by weight of 20 to 40 mesh quartz sand, then add 5 parts by weight of silane coupling agent KH-560, mechanically stir at 600 rpm for 5 min at 25°C, and dry at 100°C for 10 min to obtain 300 parts by weight of silane coupling agent treated quartz sand.

[0047] 2) Mix 300 parts by weight of silane coupling agent treated quartz sand with 5 parts by weight of thermosetting phenolic resin, and mechanically stir at 600 rpm for 5 minutes at 25°C to make the thermosetting phenolic resin evenly distributed on the surface of the quartz sand, so as to obtain sand particles coated with resin film.

[0048] 3) Before the thermosetting phenolic resin solidifies, add 5 parts by weight of sodium alginate to 300 parts by weight of the resin film-coated sand particles, mechanically stir at 600 rpm for 5 min at 25℃, and then solidify at 100℃ for 10 min to obtain particles with an outer layer of self-aggregating film, an inner layer of resin film, and a core material of sand particles.

[0049] 4) Place it in a ball mill and ball mill at 2000 rpm for 2 minutes. Then, sieve it through a 20 to 40 mesh screen and package it to obtain a self-agglomerating support agent.

[0050] Example 3

[0051] 1) Add 300 parts by weight of deionized water to 300 parts by weight of 20 to 40 mesh quartz sand, then add 10 parts by weight of silane coupling agent KH-570, mechanically stir at 800 rpm for 5 min at 25°C, and dry at 120°C for 5 min to obtain 300 parts by weight of silane coupling agent treated quartz sand.

[0052] 2) Mix 300 parts by weight of silane coupling agent treated quartz sand with 10 parts by weight of thermosetting phenolic resin, and mechanically stir at 800 rpm for 5 minutes at 25°C to make the thermosetting phenolic resin uniformly distributed on the surface of the quartz sand, so as to obtain sand particles coated with resin film.

[0053] 3) Before the thermosetting phenolic resin solidifies, add 5 parts by weight of sodium alginate to 300 parts by weight of the resin film-coated sand particles, mechanically stir at 800 rpm for 5 minutes at 25°C, and then solidify at 120°C for 5 minutes to obtain particles with an outer layer of self-aggregating film, an inner layer of resin film, and a core material of sand particles.

[0054] 4) Place it in a ball mill and ball mill at 2000 rpm for 2 minutes. Then, sieve it through a 20 to 40 mesh screen and package it to obtain a self-agglomerating support agent.

[0055] Example 4

[0056] 1) Add 300 parts by weight of deionized water to 300 parts by weight of 20 to 40 mesh quartz sand, then add 5 parts by weight of silane coupling agent KH-560, mechanically stir at 600 rpm for 5 min at 25°C, and dry at 100°C for 10 min to obtain 300 parts by weight of silane coupling agent treated quartz sand.

[0057] 2) Mix 300 parts by weight of silane coupling agent treated quartz sand with 5 parts by weight of epoxy resin E51, and mechanically stir at 600 rpm for 5 minutes at 25°C to make the epoxy resin evenly distributed on the surface of the quartz sand, thus obtaining resin-coated sand particles.

[0058] 3) Before the epoxy resin solidifies, add 5 parts by weight of sodium alginate to 300 parts by weight of the resin film-coated sand particles, mechanically stir at 600 rpm for 5 minutes at 25°C, and then cure at 100°C for 10 minutes to obtain particles with an outer layer of self-aggregating film, an inner layer of resin film, and a core material of sand particles.

[0059] 4) Place it in a ball mill and ball mill at 1000 rpm for 5 minutes. Then, sieve it through a 20 to 40 mesh screen and package it to obtain a self-agglomerating support agent.

[0060] Example 5

[0061] 1) Add 300 parts by weight of deionized water to 300 parts by weight of 20 to 40 mesh quartz sand, then add 10 parts by weight of silane coupling agent KH-560, mechanically stir at 800 rpm for 5 min at 25°C, and dry at 100°C for 10 min to obtain 300 parts by weight of silane coupling agent treated quartz sand.

[0062] 2) Mix 300 parts by weight of silane coupling agent treated quartz sand with 10 parts by weight of epoxy resin E51, and mechanically stir at 800 rpm for 5 minutes at 25°C to make epoxy resin E51 evenly distributed on the surface of quartz sand, thus obtaining resin-coated sand particles.

[0063] 3) Before the epoxy resin E51 solidifies, add 5 parts by weight of carboxymethyl hydroxypropyl guanidine gum to 300 parts by weight of the resin film-coated sand particles, mechanically stir at 800 rpm for 5 min at 25°C, and then cure at 80°C for 10 min to obtain particles with an outer layer of self-aggregating film, an inner layer of resin film, and a core material of sand particles.

[0064] 4) Place it in a ball mill and ball mill at 2000 rpm for 2 minutes. Then, sieve it through a 20 to 40 mesh screen and package it to obtain a self-agglomerating support agent.

[0065] Example 6

[0066] 1) Add 300 parts by weight of deionized water to 300 parts by weight of 20 to 40 mesh quartz sand, then add 15 parts by weight of silane coupling agent KH-560, mechanically stir at 400 rpm for 10 min at 25°C, and dry at 100°C for 10 min to obtain 300 parts by weight of silane coupling agent treated quartz sand.

[0067] 2) Mix 300 parts by weight of silane coupling agent treated quartz sand with 15 parts by weight of epoxy resin E51, and mechanically stir at 400 rpm for 10 min at 25°C to make epoxy resin E51 evenly distributed on the surface of quartz sand, thus obtaining resin-coated sand particles.

[0068] 3) Before the epoxy resin E51 solidifies, add 15 parts by weight of carboxymethyl hydroxypropyl guanidine gum to 300 parts by weight of sand particles coated with resin film, mechanically stir at 400 rpm for 10 min at 25°C, and then cure at 80°C for 10 min to obtain particles with an outer layer of self-aggregating film, an inner layer of resin film, and a core of sand particles.

[0069] 4) Place it in a ball mill and ball mill at 2000 rpm for 2 minutes. Then, sieve it through a 20 to 40 mesh screen and package it to obtain a self-agglomerating support agent.

[0070] Experimental Example 1

[0071] The roundness, sphericity, bulk density, and 28MPa breakage rate of uncoated quartz sand and the self-agglomerated proppant prepared in Examples 1 to 5 above were tested according to the standard SY / T5108-2006 fracturing proppant performance test method. The proppant performance is shown in Table 1.

[0072] The suspension time in Table 1 is the longest time that the proppant can remain freely suspended in the guar gum solution.

[0073] As can be seen from Table 1, the proppant with epoxy resin added during coating has a sphericity close to 1 and a lower bulk density than the proppant used in general resin coating.

[0074] Table 1

[0075]

[0076] Experimental Example 2

[0077] 20g of the self-agglomerating support prepared in Examples 1 to 5 and uncoated quartz sand were respectively poured into 100mL bottles, which were filled with a 2wt% guar gum aqueous solution. After mechanical stirring at 25℃ and 400rpm for 5min, the bottles were inverted. The result was that the uncoated quartz sand remained loose and immediately fell to the bottom within 10s. Figure 1 After coating, the proppant initially descended in small, continuous pieces, then completely settled within one minute. The results using the self-agglomerating proppant prepared in Example 5 are shown below. Figure 2 The above experimental results show that the treated sand particles have self-aggregating properties and can aggregate into proppant clusters.

[0078] While the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to the subject, spirit, and scope of the invention to suit specific situations, materials, material compositions, and methods. All such modifications are included within the scope of the claims of the present invention.

Claims

1. A type of coated abrasive grain, comprising an outer layer, an intermediate layer, and a core material from the outside to the inside, wherein, The outer layer is a self-aggregating membrane, the middle layer is a resin membrane, and the core material is sand particles; The material forming the self-aggregating membrane is at least one of sodium alginate, guar gum, and cellulose; The material forming the resin film is phenolic resin and / or epoxy resin; The mass ratio of the outer layer, the middle layer and the core material is 1:(0.95-1.94):(19-59).

2. The coated sand particles according to claim 1, characterized in that, The guar gum is selected from at least one of guar gum, hydroxypropyl guar gum, and carboxymethyl hydroxypropyl guar gum; The cellulose is selected from at least one of hydroxypropyl methylcellulose, hydroxyethyl cellulose, and carboxymethyl cellulose.

3. The coated sand particles according to claim 1, characterized in that, The mass ratio of the outer layer, the middle layer and the core material is (5-15):(5-15):

300.

4. The coated sand particles according to claim 1, characterized in that, The mass ratio of the outer layer, the intermediate layer and the core material is (5-15):(4.9-14.3):(285.7-295).

5. The coated sand particles according to claim 1, characterized in that, The mass ratio of the outer layer, the middle layer and the core material is 1:(1-2):(20-60).

6. The coated sand particles according to claim 1, characterized in that, The phenolic resin is a thermoplastic phenolic resin and / or a thermosetting phenolic resin. The epoxy resin is epoxy resin E51.

7. The coated sand particles according to claim 1, characterized in that, The sand particles are at least one of the following: quartz sand, ceramsite sand, kaolin, coal gangue, rock chips, fly ash, and walnut shells.

8. The coated sand particles according to claim 1, characterized in that, The particle size of the coated sand is 20 to 40 mesh.

9. A method for preparing coated sand particles as described in any one of claims 1 to 8, comprising the following steps: 1) Mix sand particles with silane coupling agent and treat them to obtain sand particles treated with silane coupling agent; 2) Mix the sand particles treated with silane coupling agent with the intermediate layer material resin evenly to obtain sand particles coated with resin film. 3) Before the resin solidifies, the sand particles coated with the resin film are mixed evenly with the outer layer material, then cured and ball-milled to obtain the coated sand particles.

10. The method according to claim 9, characterized in that, In step 1), sand particles are added to water, then the aforementioned silane coupling agent is added, stirred, and dried to obtain sand particles treated with the silane coupling agent; and / or In step 3), cure at 80 to 120°C for 5 to 10 minutes.

11. The method according to claim 10, characterized in that, The mass ratio of the sand particles to the silane coupling agent is 300:(5-15); and / or The mass ratio of the silane coupling agent-treated sand particles to the intermediate layer material resin is 300:(5-15); and / or The mass ratio of the sand particles coated by the resin film to the outer material is 300:(5-15).

12. The method according to claim 9, characterized in that, The particle size of the sand is 20 to 40 mesh; and / or The silane coupling agent is at least one of KH-550, KH-560, and KH-570.

13. The use of the coated sand particles according to any one of claims 1 to 8 or the coated sand particles prepared by the method according to any one of claims 9 to 12 as a proppant.

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