Temperature-controlled variable density high crush proppant and method of making

Abstract

The present application relates to the technical field of fracturing aids, and is a temperature-controlled variable-density high-pressure-resistant proppant and a preparation method thereof.The raw materials of the temperature-controlled variable-density high-pressure-resistant proppant include a proppant, a surface modifier, a temperature-controlled polymer, an initiator and an organic solvent.The temperature-controlled variable-density high-pressure-resistant proppant is prepared by first modifying the surface of the proppant to obtain a modified proppant, then grafting and polymerizing the modified proppant with the temperature-controlled polymer, and finally post-treating the final product.The temperature-controlled variable-density high-pressure-resistant proppant can reduce the density under the response of the bottom-hole temperature, so that it is more easily transported to the deep part of a complex fracture network and uniformly laid, has a low breakage rate, can well support the fractures and promote the flow of oil and gas in the fractures.Meanwhile, the temperature-controlled variable-density high-pressure-resistant proppant still has high pressure resistance after swelling, so as to avoid being crushed to reduce the fracture width and block the seepage channel and reduce the fracture conductivity.

Description

Technical Field

[0001] This invention relates to the field of fracturing additives, specifically a temperature-controlled variable density high compressive strength proppant and its preparation method. Background Technology

[0002] Currently, hydraulic fracturing is the most effective production enhancement measure in oil and gas extraction, especially for unconventional oil and gas resources such as tight oil and shale gas. A surface high-pressure pump truck pumps fracturing fluid into the formation to open fractures and delivers proppant into the reservoir fractures, forming flow channels that allow oil and gas to flow into the wellbore. Therefore, the quality of the proppant and its placement method directly determine the production enhancement effect after fracturing.

[0003] During reservoir stimulation, proppant is carried downhole by proppant-carrying fluid and enters the formation fractures through perforations. However, due to the high density of proppant, the limited flow rate of proppant-carrying fluid, and the reduced proppant-carrying capacity of existing conventional fracturing fluid systems at bottomhole temperatures, proppant tends to settle during transport. Its horizontal migration distance within the fractures is too short, making it difficult to reach the fracture edges or even penetrate micro-fractures. This results in limited oil and gas pathways, making it difficult to achieve the designed reservoir stimulation volume.

[0004] Currently, existing technologies reduce the density of proppant by modifying and coating it. However, because this type of proppant is suspended in fracturing fluid, it is prone to sand blockage, hindering its entry into fractures and the formation of effective sand. In addition, the reduced density of the proppant often leads to a decrease in compressive strength, making it more susceptible to crushing in the formation, blocking seepage channels, and resulting in reduced oil recovery. Summary of the Invention

[0005] This invention provides a temperature-controlled variable density high compressive strength proppant and its preparation method, which overcomes the shortcomings of the prior art and can effectively solve the problems of existing fracturing fluid proppants having high density, difficulty in entering micro-cracks and low compressive strength.

[0006] One of the technical solutions of the present invention is achieved through the following measures: a temperature-controlled variable density high compressive strength proppant, the raw materials comprising, by weight, 100 to 150 parts proppant, 12 to 25 parts surface modifier, 40 to 90 parts temperature-controlled polymer, 0.8 to 1.2 parts initiator, and 300 to 400 parts organic solvent, wherein the surface modifier is composed of a silane coupling agent and an accelerator in a mass ratio of 1:0.1 to 0.8, and the temperature-controlled polymer is composed of a temperature-controlled polymer main agent and a temperature-controlled polymer auxiliary agent in a mass ratio of 1:0.3 to 0.9.

[0007] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: The aforementioned temperature-controlled polymer main agent is one of polyamino acids and polypeptides, and the polyamino acid is one of polyα-amino acids and polylysine.

[0008] The aforementioned temperature-controlled polymer additives are one or more of poly(N-isopropylacrylamide), ethyl acrylate, polyimide, polybenzimidazole, polyvinylidene fluoride, and polyethersulfone.

[0009] The aforementioned silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, 3-(2-aminoethyl)-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)-aminopropylmethyldimethoxysilane.

[0010] The aforementioned accelerator is ferrocene.

[0011] The aforementioned proppant is one or more of the following: natural quartz sand, ceramsite, artificial glass spheres, rubber granules, and aluminum spheres.

[0012] The mesh size of the aforementioned proppant is one of 20 to 40 mesh, 40 to 70 mesh, and 70 to 140 mesh.

[0013] The initiator mentioned above is azobisisobutyronitrile.

[0014] The organic solvent mentioned above is dimethyl sulfoxide.

[0015] The above-mentioned temperature-controlled variable density high compressive strength proppant is obtained by the following method: S1, add the required amount of surfactant to the ethanol aqueous solution, then add the required amount of proppant and stir to obtain a mixture; S2, after heating the mixture, the pH value of the mixture is adjusted, the mixture is stirred and allowed to stand to react, and the reaction product is obtained. After filtering and drying the reaction product, the modified proppant is obtained. S3, under a nitrogen atmosphere, the required amount of modified support agent, temperature-controlled polymer and initiator are added to an organic solvent and stirred to carry out a polymerization reaction. After the reaction is completed, the temperature is maintained to obtain the final product. S4. After soaking, filtering and drying the final product, a temperature-controlled variable density high compressive strength proppant is obtained.

[0016] In step S1 above, the amount of ethanol aqueous solution added is 5 to 8 times the mass of the silane coupling agent, and the mass concentration of the ethanol aqueous solution is 8% to 12%.

[0017] In step S1 above, the stirring time is 30 min to 60 min.

[0018] In step S2 above, the heating temperature is 80°C to 90°C, and the pH of the mixture is adjusted to 4.0 to 4.5 using acetic acid.

[0019] In step S2 above, the stirring speed is 500 r / min to 600 r / min, the stirring time is 3 h to 5 h, and the settling time is 8.0 h to 8.5 h.

[0020] In step S3 above, the stirring speed is 300 r / min to 350 r / min, the pH value during the reaction is 6 to 7, the reaction temperature is 60℃ to 80℃, the reaction time is 4h to 6h, and the heat preservation time is 2.0h to 2.5h.

[0021] In step S4 above, during soaking, the sample is first soaked in an ethanol aqueous solution at -30°C to -20°C for 4.0h to 4.5h, and then soaked in a sodium citrate aqueous solution with a mass concentration of 10% to 12% for 8.0h to 8.5h.

[0022] The second technical solution of the present invention is achieved through the following measures: a method for preparing a temperature-controlled variable density high compressive strength proppant, which is carried out according to the following method: S1, add the required amount of surfactant to the ethanol aqueous solution, then add the required amount of proppant and stir to obtain a mixture; S2, after heating the mixture, the pH value of the mixture is adjusted, the mixture is stirred and allowed to stand to react, and the reaction product is obtained. After filtering and drying the reaction product, the modified proppant is obtained. S3, under a nitrogen atmosphere, the required amount of modified support agent, temperature-controlled polymer and initiator are added to an organic solvent and stirred to carry out a polymerization reaction. After the reaction is completed, the temperature is maintained to obtain the final product. S4. After soaking, filtering and drying the final product, a temperature-controlled variable density high compressive strength proppant is obtained.

[0023] This invention relates to a temperature-controlled variable density high-compression-strength proppant. First, the surface of the proppant is modified to obtain a modified proppant. Then, the modified proppant is grafted and polymerized with a temperature-controlled polymer. Finally, the final product undergoes post-processing. This temperature-controlled variable density high-compression-strength proppant exhibits density reduction under bottom-hole temperature response, making it easier to migrate and uniformly deploy deep within complex fracture networks. It also has a low breakage rate, effectively supporting fractures and promoting oil and gas flow within them. Furthermore, after expansion, this temperature-controlled variable density high-compression-strength proppant retains high compressive strength, preventing crushing that would reduce fracture width and block seepage channels, thus reducing fracture conductivity. Attached Figure Description

[0024] Figure 1 This is a SEM image of the temperature-controlled variable density high compressive strength proppant prepared in Example 19 of the present invention. Detailed Implementation

[0025] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0026] The present invention will be further described below with reference to embodiments: Example 1: The temperature-controlled variable density high compressive strength proppant comprises, by weight, 100 to 150 parts proppant, 12 to 25 parts surface modifier, 40 to 90 parts temperature-controlled polymer, 0.8 to 1.2 parts initiator, and 300 to 400 parts organic solvent. The surface modifier is composed of a silane coupling agent and an accelerator in a mass ratio of 1:0.1 to 0.8. The temperature-controlled polymer is composed of a temperature-controlled polymer main agent and a temperature-controlled polymer auxiliary agent in a mass ratio of 1:0.3 to 0.9.

[0027] Example 2: As an optimization of the above example, the temperature-controlled polymer main agent is one of polyamino acids and polypeptides, and the polyamino acid is one of polyα-amino acids and polylysine.

[0028] Example 3: As an optimization of the above examples, the temperature-controlled polymer adjuvant is one or more of poly(N-isopropylacrylamide), ethyl acrylate, polyimide, polybenzimidazole, polyvinylidene fluoride and polyethersulfone.

[0029] Example 4: As an optimization of the above examples, the silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, 3-(2-aminoethyl)-aminopropyltrimethoxysilane and 3-(2-aminoethyl)-aminopropylmethyldimethoxysilane.

[0030] Example 5: As an optimization of the above examples, the accelerator is ferrocene.

[0031] In this invention, ferrocene can increase solubility and improve modification effect through coordination, and the rigid groups in ferrocene can improve the compressive strength of temperature-controlled variable density high compressive proppant.

[0032] Example 6: As an optimization of the above examples, the proppant is one or more of natural quartz sand, ceramsite, artificial glass spheres, rubber granules and aluminum spheres.

[0033] Example 7: As an optimization of the above embodiment, the mesh size of the proppant is one of 20 to 40 mesh, 40 to 70 mesh, and 70 to 140 mesh, preferably 70 to 140 mesh.

[0034] In this invention, the proppant is preferably made of 70 to 140 mesh, as smaller particle size allows for easier transport to the distal end, supporting secondary and tertiary fractures and increasing the effective fracturing volume; the apparent density of the proppant is in the range of 1.0 g / cm³. 3 Up to 2.8 g / cm 3 The compressive strength of the proppant is 28 MPa to 103 MPa, preferably 64 MPa to 103 MPa, and it has a high compressive strength after absorbing water and swelling.

[0035] Example 8: As an optimization of the above examples, the initiator is azobisisobutyronitrile.

[0036] Example 9: As an optimization of the above examples, the organic solvent is dimethyl sulfoxide.

[0037] Example 10: As an optimization of the above examples, a temperature-controlled variable density high compressive strength proppant was obtained by the following method: S1, add the required amount of surfactant to the ethanol aqueous solution, then add the required amount of proppant and stir to obtain a mixture; S2, after heating the mixture, the pH value of the mixture is adjusted, the mixture is stirred and allowed to stand to react, and the reaction product is obtained. After filtering and drying the reaction product, the modified proppant is obtained. S3, under a nitrogen atmosphere, the required amount of modified support agent, temperature-controlled polymer and initiator are added to an organic solvent and stirred to carry out a polymerization reaction. After the reaction is completed, the temperature is maintained to obtain the final product. S4. After soaking, filtering and drying the final product, a temperature-controlled variable density high compressive strength proppant is obtained.

[0038] Example 11: As an optimization of the above example, in step S1, the amount of ethanol aqueous solution added is 5 to 8 times the mass of the silane coupling agent, and the mass concentration of the ethanol aqueous solution is 8% to 12%.

[0039] Example 12: As an optimization of the above example, in step S1, the stirring time is 30 min to 60 min.

[0040] Example 13: As an optimization of the above example, in step S2, the heating temperature is 80°C to 90°C, and the pH of the mixture is adjusted to 4.0 to 4.5 with acetic acid.

[0041] Example 14: As an optimization of the above example, in step S2, the stirring speed is 500 r / min to 600 r / min, the stirring time is 3 h to 5 h, and the settling time is 8.0 h to 8.5 h.

[0042] Example 15: As an optimization of the above example, in step S3, the stirring speed is 300 r / min to 350 r / min, the pH value is 6 to 7, the reaction temperature is 60°C to 80°C, the reaction time is 4 h to 6 h, and the heat preservation time is 2.0 h to 2.5 h.

[0043] Example 16: As an optimization of the above embodiment, in step S4, during soaking, the sample is first soaked in an ethanol aqueous solution at -30°C to -20°C for 4.0h to 4.5h, and then soaked in a sodium citrate aqueous solution with a mass concentration of 10% to 12% for 8.0h to 8.5h.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the temperature-controlled variable density high-compression-strength proppant of this invention mainly consists of a proppant, a surface modifier (silane coupling agent and accelerator), and a temperature-controlled polymer (temperature-controlled polymer main agent and temperature-controlled polymer auxiliary agent). Its structure is divided into three layers from the inside out: an inner proppant layer, a surface modifier layer, and an outer temperature-controlled layer (temperature-controlled polymer). Among them, the outer temperature-controlled layer mainly uses a temperature-controlled polymer, which has stable physicochemical properties at room temperature and pressure. At a specific temperature, it can undergo a change in molecular conformation, causing the outer temperature-controlled layer to absorb water and swell, reducing its density, floating in the fracturing fluid, and migrating to the distal end of the fracture or secondary and tertiary fractures for support.

[0045] Specifically, temperature-controlled polymers consist of a temperature-controlled polymer master and a temperature-controlled polymer auxiliaries. The master is selected from polyamino acids or peptides, which, due to their chiral backbone and abundant side chain structures, can form various secondary structures (such as α-helices and β-sheets). These secondary structures can be interconverted through external stimulation. The responsiveness of polyamino acid or peptide polymers largely depends on the polymer's secondary structure and the length of its side chains. Therefore, their temperature-controlled performance is mainly achieved through the effective design of side chain groups. Thus, temperature-controlled polymer auxiliaries can be introduced into the master to provide specific groups to facilitate conformational changes or enhance certain functions. For example, rigid groups can improve temperature and pressure resistance; flexible chains can increase molecular activity; hydrogen bonds can regulate the hydrophilicity of the material; and longer alkyl chains (such as poly-N-n-octylglycine) provide hydrophobicity and crystallinity. Therefore, in this invention, the transition temperature, hydrophilicity / hydrophobicity, and density of the temperature-controlled variable density high compressive strength proppant are controlled by selecting the preferred temperature-controlled polymer main agent and temperature-controlled polymer auxiliary agent, so that the activation temperature of the temperature-controlled variable density high compressive strength proppant is 32°C to 85°C. At this temperature, a change in molecular conformation can occur, causing the outer temperature-controlled layer to absorb water and expand, reduce its density, float in the fracturing fluid, and migrate to the far end of the fracture or the second and third order fractures for support. Secondly, in the preparation method of the temperature-controlled variable density high compressive strength proppant of the present invention, step S4 specifically involves cold treatment and salt impregnation of the final product to form anisotropic microcrystalline regions inside, which can greatly improve the compressive strength of the temperature-controlled variable density high compressive strength proppant. Under 100MPa pressure, it also has a low breakage rate, which can effectively support the fracture and promote the flow of oil and gas in the fracture.

[0046] Example 17: This temperature-controlled variable density high compressive strength proppant is made from the following raw materials: 100g proppant (20-40 mesh ceramsite, Henan Zhengnai New Materials Co., Ltd.), 10g silane coupling agent (γ-aminopropyltriethoxysilane), 2g accelerator (ferrocene), 30g temperature-controlled polymer main agent (poly-α-amino acid, Xi'an Qiyue Biotechnology Co., Ltd.), 10g temperature-controlled polymer auxiliary agent (5g poly(N-isopropylacrylamide) and 5g ethyl acrylate), 0.8g initiator (azobisisobutyronitrile), and 300mL organic solvent (dimethyl sulfoxide). It is obtained according to the following method: S1. Add the required amount of silane coupling agent and accelerator to 50 mL of 10% ethanol aqueous solution, then add the required amount of support agent and stir magnetically for 30 min to disperse it evenly to obtain a mixture. S2, after heating the mixture to 85℃, the pH of the mixture was adjusted to 4.5 with acetic acid. The mixture was stirred at a constant temperature of 500 r / min for 3 h and then allowed to stand for 8.0 h to obtain the reaction product. The reaction product was filtered and vacuum dried to obtain the modified proppant. S3, under a nitrogen atmosphere, the required amount of modified support agent, temperature-controlled polymer and initiator are added to the organic solvent. Under the conditions of 60℃, 300 r / min and pH 6, the mixture is stirred and polymerization begins for 4 h. After the reaction is completed, the temperature is maintained for another 2.0 h to obtain the final product. S4. The final product is soaked in an ethanol aqueous solution at -20℃ for 4.0h, and then soaked in a sodium citrate aqueous solution with a mass concentration of 10% for 8.0h. After filtration and drying, a temperature-controlled variable density high compressive strength proppant is obtained.

[0047] Comparative Example 1: The difference from Embodiment 17 of the present invention is that the raw material "accelerator (ferrocene)" is missing, while the rest of the steps are the same.

[0048] Example 18: This temperature-controlled variable density high compressive strength proppant is made from the following raw materials: 120g proppant (ceramsite with a mesh size of 40-70 mesh, Henan Zhengnai New Materials Co., Ltd.), 12g silane coupling agent (γ-aminopropyltriethoxysilane), 7g accelerator (ferrocene), 30g temperature-controlled polymer main agent (polymer peptide, Xi'an Qiyue Biotechnology Co., Ltd.), 20g temperature-controlled polymer auxiliary agent (10g poly(N-isopropylacrylamide) and 10g polyvinylidene fluoride), 1.0g initiator (azobisisobutyronitrile), and 300mL organic solvent (dimethyl sulfoxide). It is obtained according to the following method: S1. Add the required amount of silane coupling agent and accelerator to 50 mL of 10% ethanol aqueous solution, then add the required amount of support agent and stir magnetically for 60 min to disperse it evenly to obtain a mixture. S2, after heating the mixture to 85℃, the pH of the mixture was adjusted to 4.5 with acetic acid. The mixture was stirred at a constant temperature of 500 r / min for 3 h and then allowed to stand for 8.0 h to obtain the reaction product. The reaction product was filtered and vacuum dried to obtain the modified proppant. S3, under a nitrogen atmosphere, the required amount of modified support agent, temperature-controlled polymer and initiator are added to the organic solvent. Under the conditions of 70℃, 350 r / min and pH 6, the mixture is stirred and polymerization begins for 4 h. After the reaction is completed, the temperature is maintained for another 2.0 h to obtain the final product. S4. The final product is soaked in an ethanol aqueous solution at -20℃ for 4.0h, and then soaked in a sodium citrate aqueous solution with a mass concentration of 10% for 8.0h. After filtration and drying, a temperature-controlled variable density high compressive strength proppant is obtained.

[0049] Comparative Example 2: The difference from Example 18 of this invention is that the raw material "temperature-controlled polymer auxiliaries (poly(N-isopropylacrylamide) and polyvinylidene fluoride)" is missing, while the rest of the steps are the same.

[0050] Example 19: This temperature-controlled variable density high compressive strength proppant comprises, by weight, 150g proppant (ceramsite with a mesh size of 70-140 mesh, Henan Zhengnai New Materials Co., Ltd.), 15g silane coupling agent (γ-aminopropyltriethoxysilane), 10g accelerator (ferrocene), 60g temperature-controlled polymer main agent (polylysine, Xi'an Qiyue Biotechnology Co., Ltd.), 20g temperature-controlled polymer auxiliary agent (15g poly(N-isopropylacrylamide) and 5g polyethersulfone), 1.2g initiator (azobisisobutyronitrile), and 300mL organic solvent (dimethyl sulfoxide), obtained by the following method: S1. Add the required amount of silane coupling agent and accelerator to 80 mL of 10% ethanol aqueous solution, then add the required amount of support agent and stir magnetically for 60 min to disperse it evenly to obtain a mixture. S2, after heating the mixture to 85℃, the pH of the mixture was adjusted to 4.5 with acetic acid. The mixture was stirred at a constant temperature of 600 r / min for 3 h and then allowed to stand for 8.0 h to obtain the reaction product. The reaction product was filtered and vacuum dried to obtain the modified proppant. S3, under a nitrogen atmosphere, the required amount of modified support agent, temperature-controlled polymer and initiator are added to the organic solvent. Under the conditions of 80℃, 350 r / min and pH 7, the mixture is stirred and polymerization begins for 6 h. After the reaction is completed, the temperature is maintained for another 2.0 h to obtain the final product. S4. The final product is soaked in an ethanol aqueous solution at -30℃ for 4.0h, and then soaked in a sodium citrate aqueous solution with a mass concentration of 10% for 8.0h. After filtration and drying, a temperature-controlled variable density high compressive strength proppant is obtained.

[0051] Comparative Example 3: The difference from Embodiment 19 of the present invention is that step S4 is omitted, and the final product obtained in step S3 is obtained by filtration and drying, while the remaining steps are the same.

[0052] Experimental Example 1: To investigate the performance of the temperature-controlled variable density high compressive strength proppant of the present invention.

[0053] Experimental Methods: The performance of the temperature-controlled variable density high-compression-strength proppants prepared in Examples 17 to 19 of this invention was investigated according to the methods specified in SY / T 5108-2014 "Performance of Proppants for Hydraulic Fracturing and Gravel Packing Operations". Meanwhile, the temperature-controlled variable density high-compression-strength proppants prepared in Comparative Examples 1 to 3 of this invention and the original ceramsite were used as controls. The investigated performance included apparent density (g / cm³). 3 Before modification), apparent density (g / cm³) 3 25℃, g / cm 3 The temperature-controlled variable density high compressive strength proppant prepared in Example 19 of this invention was subjected to SEM testing, and the breakage rates (69 MPa and 103 MPa) were measured at 80℃.

[0054] Experimental results: SEM images of the temperature-controlled variable density high compressive strength proppant prepared in Example 19 of this invention are shown below. Figure 1 As shown, from Figure 1 It can be seen that the temperature-controlled variable density high compressive strength proppant of the present invention has a uniform overall particle size and a high degree of sphericity.

[0055] The performance of the temperature-controlled variable density high compressive strength proppant of the present invention is shown in Table 1. As can be seen from Table 1, compared with the untreated proppant (original ceramsite), the temperature-controlled variable density high compressive strength proppant prepared in Examples 17 to 19 of the present invention can reduce the apparent density in response to temperature, making it easier to migrate to the depth of complex fracture networks and be evenly laid. It also has a low breakage rate and can support the fracture well and promote the flow of oil and gas in the fracture. As can be seen from Example 17 and Comparative Example 1, the addition of an accelerator (ferrocene) to the raw materials can enhance the adhesion between the temperature-controlled polymer and the modified proppant, thereby improving the overall performance of the temperature-controlled variable density high compressive strength proppant, such as low apparent density and low breakage rate, i.e., high compressive strength. As can be seen from Example 18 and Comparative Example 2, the temperature-controlled polymer is composed of a temperature-controlled polymer main agent and a temperature-controlled polymer auxiliary agent. The introduction of rigid groups into the temperature-controlled polymer auxiliary agent and the chemical interaction between the temperature-controlled polymer main agent molecules are more conducive to improving the temperature control response sensitivity and compressive strength of the temperature-controlled variable density high compressive strength proppant. As can be seen from Example 19 and Comparative Example 3, step S4 specifically involves cold treatment and salt impregnation of the final product to form anisotropic microcrystalline regions inside, which can significantly improve the compressive strength of the temperature-controlled variable density high compressive strength proppant and also has a low breakage rate under 100MPa pressure.

[0056] In summary, the temperature-controlled variable density high-compression-strength proppant of this invention first involves surface modification of the proppant to obtain a modified proppant, then grafting and polymerizing the modified proppant with a temperature-controlled polymer, and finally post-processing the final product. Under the same bottom-hole temperature response, this temperature-controlled variable density high-compression-strength proppant can reduce apparent density, making it easier to migrate to deep, complex fracture networks and distribute evenly. It also has a low breakage rate and can effectively support fractures, promoting oil and gas flow within them. Furthermore, after expansion, the temperature-controlled variable density high-compression-strength proppant of this invention retains high compressive strength, preventing crushing that would reduce fracture width and block seepage channels, thus reducing fracture conductivity.

[0057] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A temperature-controlled variable density high compressive strength proppant, characterized in that... The raw materials, by weight, include 100 to 150 parts of proppant, 12 to 25 parts of surface modifier, 40 to 90 parts of temperature-controlled polymer, 0.8 to 1.2 parts of initiator, and 300 to 400 parts of organic solvent. The surface modifier consists of a silane coupling agent and an accelerator in a mass ratio of 1:0.1 to 0.

8. The temperature-controlled polymer consists of a temperature-controlled polymer main agent and a temperature-controlled polymer auxiliary agent in a mass ratio of 1:0.3 to 0.

9.

2. The temperature-controlled variable density high compressive strength proppant according to claim 1, characterized in that... The temperature-controlled polymer main agent is one of polyamino acids and polypeptides, and the polyamino acid is one of poly-α-amino acids and polylysine; or / and the temperature-controlled polymer auxiliary agent is one or more of poly(N-isopropylacrylamide), ethyl acrylate, polyimide, polybenzimidazole, polyvinylidene fluoride and polyethersulfone.

3. The temperature-controlled variable density high compressive strength proppant according to claim 1 or 2, characterized in that... The silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, 3-(2-aminoethyl)-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)-aminopropylmethyldimethoxysilane; or / and the accelerator is ferrocene.

4. The temperature-controlled variable density high compressive strength proppant according to claim 1, 2, or 3, characterized in that... The proppant is one or more of natural quartz sand, ceramsite, artificial glass spheres, rubber granules and aluminum spheres; or / and the mesh size of the proppant is one of 20 to 40 mesh, 40 to 70 mesh and 70 to 140 mesh.

5. The temperature-controlled variable density high compressive strength proppant according to any one of claims 1 to 4, characterized in that... The initiator is azobisisobutyronitrile; or / and the organic solvent is dimethyl sulfoxide.

6. The temperature-controlled variable density high compressive strength proppant according to any one of claims 1 to 5, characterized in that... Obtained using the following method: S1, add the required amount of surfactant to the ethanol aqueous solution, then add the required amount of proppant and stir to obtain a mixture; S2, after heating the mixture, the pH value of the mixture is adjusted, the mixture is stirred and allowed to stand to react, and the reaction product is obtained. After filtering and drying the reaction product, the modified proppant is obtained. S3, under a nitrogen atmosphere, the required amount of modified support agent, temperature-controlled polymer and initiator are added to an organic solvent and stirred to carry out a polymerization reaction. After the reaction is completed, the temperature is maintained to obtain the final product. S4. After soaking, filtering and drying the final product, a temperature-controlled variable density high compressive strength proppant is obtained.

7. The temperature-controlled variable density high compressive strength proppant according to claim 6, characterized in that... In step S1, the amount of ethanol aqueous solution added is 5 to 8 times the mass of the silane coupling agent, and the mass concentration of the ethanol aqueous solution is 8% to 12%; or / and, in step S1, the stirring time is 30 min to 60 min.

8. The temperature-controlled variable density high compressive strength proppant according to claim 6 or 7, characterized in that... In step S2, the heating temperature is 80°C to 90°C, and the pH of the mixture is adjusted to 4.0 to 4.5 with acetic acid; or / and, in step S2, the stirring speed is 500 r / min to 600 r / min, the stirring time is 3 h to 5 h, and the standing time is 8.0 h to 8.5 h.

9. The temperature-controlled variable density high compressive strength proppant according to claim 6, 7, or 8, characterized in that... In step S3, the stirring speed is 300 r / min to 350 r / min, the pH value during the reaction is 6 to 7, the reaction temperature is 60℃ to 80℃, the reaction time is 4h to 6h, and the holding time is 2.0h to 2.5h; or / and, in step S4, during soaking, the sample is first soaked in an ethanol aqueous solution at -30℃ to -20℃ for 4.0h to 4.5h, and then soaked in a sodium citrate aqueous solution with a mass concentration of 10% to 12% for 8.0h to 8.5h.

10. A method for preparing a temperature-controlled variable density high compressive strength proppant according to any one of claims 1 to 5, 7 to 9, characterized in that... Perform it as follows: S1, add the required amount of surfactant to the ethanol aqueous solution, then add the required amount of proppant and stir to obtain a mixture; S2, after heating the mixture, the pH value of the mixture is adjusted, the mixture is stirred and allowed to stand to react, and the reaction product is obtained. After filtering and drying the reaction product, the modified proppant is obtained. S3, under a nitrogen atmosphere, the required amount of modified support agent, temperature-controlled polymer and initiator are added to an organic solvent and stirred to carry out a polymerization reaction. After the reaction is completed, the temperature is maintained to obtain the final product. S4. After soaking, filtering and drying the final product, a temperature-controlled variable density high compressive strength proppant is obtained.

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