High-strength low-density proppant as well as preparation method and in-situ generation method thereof

Abstract

The invention discloses a high-strength low-density proppant as well as a preparation method and an in-situ generation method thereof. The proppant is prepared by compounding recycled glass fiber reinforced plastic powder or glass fiber powder with different meshes and recycled glass fiber reinforced plastic powder in different proportions and blending a styrene system / unsaturated polyester resin system in different proportions. The glass fiber reinforced plastic powder as the filler can improve the mechanical properties of the proppant, such as strength and toughness. The matrix is made of polystyrene or unsaturated polyester or other high polymer materials and is low in density. Therefore, the proppant has the characteristics of high strength and low density. The invention discloses a preparation method of a high-strength and low-density proppant, which can produce the high-strength and low-density proppant with uniform particle size distribution on a large scale by adopting a suspension polymerization method, and can efficiently recover a large amount of glass fiber reinforced plastic wastes. The suspension polymerization method is simple to operate, the produced proppant is high in roundness and sphericity, the mining cost of a coal-bed gas well can be reduced, and the yield of coal-bed gas can be increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of proppants for coalbed methane and shale gas fracturing construction, and particularly relates to a high-strength low-density proppant, a preparation method thereof, and an in-situ generation method. Background Art

[0002] Hydraulic fracturing technology is an important new technology currently used for oil and gas extraction. It uses a surface high-pressure pump to inject a fracturing fluid with a relatively high viscosity into the oil reservoir through a wellbore to fracture the oil reservoir and generate fractures with strong conductivity. A proppant is a solid particle that can enter the fractured cracks during the hydraulic fracturing process and prevent them from closing again. It can help keep the cracks open and provide a seepage channel for oil and gas to flow from the formation to the wellbore, and is a key material in hydraulic fracturing construction. Usually, a fracturing fluid carrying proppants is pumped into the ground by a pump truck to make the proppants play their role.

[0003] Fracturing proppants are an important part of the drilling and completion cost. Currently, the proppants used at home and abroad are mainly divided into three categories: ceramsite, quartz sand, and porous resin-coated proppants, but they all have some problems. Ceramsite has the best conductivity and high strength, but the relative density of ceramsite is relatively large. The greater the volume density of the proppant, the higher the viscosity required for the fracturing fluid; Quartz sand has poor conductivity and low strength. Although it is cheap, it is only suitable for hydraulic fracturing of oil and gas reservoirs with low closure pressure and shallow wells; Porous resin-coated proppants: The life of the coated proppants is short, they can react with reagents such as fracturing fluid under certain conditions, and the cost is expensive. Currently, the research and development of high-strength low-density proppants is an important direction for future proppant research. As the reservoirs for oil and gas exploration and development become deeper and the formation closure stress increases, the requirements for the strength of proppants are getting higher and higher; at the same time, the density of proppants will affect the cost of the fracturing process. Usually, the greater the volume density of the proppant, the higher the viscosity required for the fracturing fluid, but high-viscosity fracturing fluid has high energy consumption, high machine cost, and great damage to the reservoir during construction. Therefore, it is necessary to carry out research and development of high-strength low-density proppants to ensure the strength of proppants while reducing the density of proppants. Summary of the Invention

[0004] In order to solve the deficiencies of existing proppant materials in the process of oil extraction by hydraulic fracturing, the purpose of the present invention is to provide a high-strength low-density proppant, a preparation method thereof, and an in-situ generation method.

[0005] According to the first aspect of the embodiments of the present application, a preparation method of a high-strength low-density proppant is provided, including:

[0006] S1. Prepare the oil phase: Prepare a styrene system / unsaturated polyester resin system, stir to mix them evenly, mix 50-99.9% by mass of the styrene system / unsaturated polyester resin system, 0-50% by mass of recycled fiberglass powder or a compound of recycled fiberglass powder with different mesh sizes of fiberglass powder and a coupling agent, and perform ultrasonic treatment and stirring in sequence to form an oil phase, wherein the coupling agent accounts for 0.1%-20% of the mass of the oil phase;

[0007] S2. Prepare the water phase: Determine the volume of the water phase according to the volume of the oil phase, and sequentially add an organic dispersant accounting for 0.1%-20% of the mass of the prepared oil phase, an inorganic dispersant accounting for 0.1%-20% of the mass of the prepared oil phase, a co-dispersant accounting for 0.1%-10% of the mass of the prepared oil phase, and a stabilizer accounting for 0.01%-1% of the mass of the prepared oil phase to water, and completely dissolve them by heating and stirring;

[0008] S3. Add an initiator accounting for 0.5%-3.5% of the mass of the oil phase to the oil phase and stir evenly, and add the oil phase to the water phase for pre-dispersion;

[0009] S4. Raise the temperature for reaction: (1) Styrene system: First, stir and raise the temperature to 65-70°C and react for 20-25 minutes; then stir and raise the temperature to 75-90°C and react for 25-35 minutes; finally, raise the temperature to 85-90°C and react for 10-12 hours; (2) Unsaturated polyester resin system: Stir and raise the temperature to 85-90°C, and react for one and a half to two and a half hours;

[0010] S5. Lower the temperature, and sequentially perform washing, draining, drying, and screening to obtain a high-strength and low-density proppant reinforced with recycled fiberglass powder.

[0011] Further, the styrene system includes at least one of styrene, α-methylstyrene, vinyltoluene, and divinylbenzene, and the unsaturated polyester resin system includes at least one of unsaturated polyester and the component compounds in the styrene system.

[0012] Further, after the styrene system / unsaturated polyester resin system is mixed with the recycled fiberglass powder in step S1, perform ultrasonic treatment for 20-30 minutes and stir for 12-24 hours. Stirring for 12-24 hours can fully decompose the silane coupling agent and play its role in bridging the organic phase and the inorganic phase.

[0013] Further, the coupling agent added in step S1 is at least one selected from silane coupling agents, titanate coupling agents, and other types of coupling agents. The silane coupling agent is at least one selected from epoxy group silanes, vinyl silanes, and methacryloxy silanes. The titanate coupling agent is at least one selected from monoalkoxy type, coordination type, and chelating type. The other types of coupling agents are at least one of bimetallic coupling agents, lignin coupling agents, and tin coupling agents. The coupling agent can increase the binding ability between the resin organic phase and the glass fiber inorganic phase in the fiberglass powder, making the prepared proppant have higher strength.

[0014] Further, in step S2, the volume of the aqueous phase is determined according to the mass percentage of the recovered fiberglass powder in the oil phase. The ratio of the aqueous phase to the fiberglass powder will affect the product yield, and the mass percentage of the recovered fiberglass powder in the oil phase is directly proportional to the volume of the aqueous phase.

[0015] Further, in step S2, the organic dispersant is at least one of polyvinyl alcohol and water-soluble polymers, gelatin, and cellulose ethers. The inorganic dispersant is at least one of calcium carbonate, tricalcium phosphate, activated calcium phosphate, and talc powder. The co-dispersant is at least one of sodium stearate, calcium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate, and sodium petroleum sulfonate. The stabilizer is at least one of sodium sulfate, water-soluble black, nitroso R salt, and methylene blue.

[0016] Further, in step S3, the initiator added to the oil phase is at least one of organic peroxides, inorganic peroxides, and azo initiators. The organic peroxide initiators are at least one of methyl ethyl ketone peroxide, benzoyl peroxide, and tert-butyl peroxybenzoate. The inorganic peroxide initiators are at least one of potassium persulfate, ammonium persulfate, and sodium persulfate. The azo initiators are at least one of azobisisobutyronitrile and azobisisoheptonitrile.

[0017] Further, the pellet particle size of the high-strength and low-density dispersant obtained after screening in step S5 is 0.2 - 2 mm, that is, 10 - 70 mesh. In actual production requirements, the particle size of the fracturing proppant is generally between 20 - 70 mesh. If the proppant particle size is too large, it is difficult to migrate to the distal fracture. If the proppant particle size is too small, it is difficult to support the fracture.

[0018] According to the second aspect of the embodiments of the present application, a high-strength and low-density proppant is provided, and the high-strength and low-density proppant is prepared by the preparation method of the high-strength and low-density proppant described in the first aspect.

[0019] According to the third aspect of the embodiments of the present application, a method for in-situ generation of a high-strength and low-density proppant is provided. The aqueous phase and the oil phase are pumped into the fractures created by underground fracturing fluid. At the temperature and pressure at this position, the aqueous phase and the oil phase react to in-situ generate a high-strength and low-density proppant. The preparation processes of the aqueous phase and the oil phase include:

[0020] S11: Prepare the oil phase: Prepare an unsaturated polyester resin system and stir to mix it evenly. Mix an unsaturated polyester resin system with a mass percentage of 50-99.9%, recycled fiberglass powder with a mass percentage of 0.1-50%, a coupling agent, and an active agent, and perform ultrasonic treatment and stirring in sequence to form the oil phase. The mass percentage of the coupling agent in the oil phase is 0.1%-20% and the mass percentage of the active agent in the oil phase is 0.1%-20%. Styrene has a longer hardening temperature time and is prone to bonding during in-situ generation, so the styrene system is not used for in-situ generation;

[0021] S12: Prepare the aqueous phase: Determine the volume of the aqueous phase according to the volume of the oil phase. Sequentially add an organic dispersant with a mass percentage of 0.1%-20% of the prepared oil phase, an inorganic dispersant with a mass percentage of 0.1%-20%, a co-dispersant with a mass percentage of 0.1%-10%, and a stabilizer with a mass percentage of 0.01%-1% to the aqueous phase, and completely dissolve them by heating and stirring;

[0022] S13: Add a curing system to the oil phase. The curing system includes a curing agent A with a mass percentage of 0.5%-10% of the oil phase and a curing agent B with a mass percentage of 0.01%-5% of the oil phase. Add the curing agent A and B in sequence and stir well.

[0023] Further, the active agent is at least one of higher fatty acid salts, sulfonates, polyoxyethylene esters, fatty acid glycerol esters, and polyol esters.

[0024] Further, in step S12, the aqueous phase is a fracturing fluid, specifically a water-based fracturing fluid: including at least one of natural plant gum fracturing fluid, cellulose fracturing fluid, synthetic polymer fracturing fluid, and slickwater fracturing fluid system. The fracturing fluid simulates the liquid environment during on-site fracturing construction to make the preparation conditions more in line with the on-site construction environment.

[0025] Further, the forms of curing agent A and curing agent B added to the oil phase in step S13 are at least one of a compound or a microcapsule. The components of curing agent A or the microcapsules of curing agent A include at least one of organic peroxides, inorganic peroxides, and azo initiators. The organic peroxide initiators are at least one of methyl ethyl ketone peroxide, benzoyl peroxide, and tert-butyl peroxybenzoate. The inorganic peroxide initiators are at least one of potassium persulfate, ammonium persulfate, and sodium persulfate. The azo initiators are at least one of azobisisobutyronitrile and azodiisopentanenitrile. The components of curing agent B or the microcapsules of curing agent B include at least one of cobalt naphthenate, cobalt isooctanoate, zinc isooctanoate, N,N-dimethylaniline, N,N-diethylaniline, and vanadium phosphate.

[0026] The technical solutions provided by the embodiments of the present application may include the following beneficial effects:

[0027] The present invention provides a preparation method of a high-strength and low-density proppant. The method uses suspension polymerization to introduce recycled waste fiberglass powder into unsaturated polyester resin to synthesize the proppant product. While ensuring that the preparation process is simple, easy to implement, and convenient to operate, it can also mass-produce proppant particles with a uniform particle size distribution, greatly reducing the preparation cost of organic polymer proppants. In addition, different particle sizes of proppants can be produced by adjusting the formula to meet different actual production requirements.

[0028] The present invention provides a high-strength and low-density proppant. This type of proppant has high sphericity and roundness and strong conductivity. Using the high-strength and low-density proppant of the present invention can reduce the production cost of coalbed methane wells and increase the production of coalbed methane.

[0029] The present invention also provides an in-situ generation method of a high-strength and low-density proppant. The obtained proppant is also called a liquid proppant. By injecting an aqueous phase-free fracturing liquid underground, the liquid contains special chemical additives and is divided into oil and water phases. During pumping, the oil phase is dispersed into small droplets in the water phase through liquid-liquid multiphase flow. This fracturing fluid can form spherical solid particles through chemical reactions under formation conditions. Since the fracturing fluid itself can become a proppant, its strength continuously increases during the coalescence and curing process, which can maximize the effective support area and effectively support multi-scale fractures; it avoids the possibility of sand plugging caused by traditional proppant sand addition, and the return flow rate of the fracturing liquid is also very small. Since only liquid is injected during the entire fracturing process, it can be evenly injected into the fractured cracks, thereby maximizing the effective support area and the reservoir stimulation volume. At the same time, the in-situ produced proppant still has the characteristics of high strength, low density, high sphericity and roundness, and strong conductivity.

[0030] The present invention uses recycled fiberglass powder, which is low-cost and easy to obtain as a filler to modify styrene systems / unsaturated polyester systems, not only achieving the efficient recycling of fiberglass waste and improving environmental pollution, but also the prepared high-strength and low-density proppants meet the technical standards of SY / T5108-2014.

[0031] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments in accordance with this application, and are used together with the specification to explain the principles of this application.

[0033] Figure 1 It is a diagram of the proppant product prepared by the present invention based on the styrene system.

[0034] Figure 2 It is a diagram of the proppant product prepared by the present invention based on the unsaturated polyester system.

[0035] Figure 3 It is a schematic diagram of the reaction process and products inside the visualization box-type substation material analyzer, where (a) is the diagram of the reaction for 40 minutes, (b) is the diagram of the reaction for 1 hour, (c) is the schematic diagram of the product, and (d) is the diagram of the product under the microscope.

[0036] Figure 4 It is the schematic diagram of the in-situ generation of high-strength and low-density proppants by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0038] The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms of "a", "the" and "said" used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0039] It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to a determination".

[0040] The reagents such as styrene system, unsaturated polyester resin system, coupling agent, initiator, etc. used in each embodiment are all industrial grade, and the dispersant and other additives are all CP or AR grade.

[0041] The waste scraps or waste fiberglass materials generated during the production process of fiberglass enterprises are processed into powders with a micron size (below 60 μm), and this kind of powder is called recycled fiberglass powder. Currently, there are mainly two categories of recycling methods for fiberglass waste: chemical method and physical method. The chemical method requires first crushing the fiberglass waste to a certain specified particle size, and then dissolving the pulverized fine powder. Under the action of high temperature and alkali catalyst, the resin is decomposed to separate the glass fiber and unsaturated polyester molecules. The physical method is to directly use the fiberglass waste crushed into a certain particle size as a filler, that is, the powder filling method. Although the chemical regeneration method can decompose fiberglass into raw materials for reuse, the cost is too high and it cannot be adopted on a large scale; while the physical method has a low cost and can process fiberglass waste on a large scale. Therefore, the powder filling method is used to process the recycled fiberglass powder, and the recycled fiberglass powder or the fiberglass powder with different mesh numbers is compounded with the recycled fiberglass powder in different proportions, and it is used as a filler to be mixed with the styrene system and the unsaturated polyester system to prepare a high-strength and low-density proppant.

[0042] Suspension polymerization, also known as bead polymerization, refers to the polymerization process in which monomers are dispersed into droplets, usually suspended in water, under the action of mechanical stirring or oscillation and a dispersant. Suspension polymerization is particularly suitable for large-scale industrial production and has many advantages such as a simple process, easy removal of polymerization heat, convenient operation and control, easy separation and washing of polymers, and can be directly used for molding processing.

[0043] Example 1

[0044] The preparation steps of the high-strength and low-density proppant are as follows:

[0045] S1. Prepare the oil phase: First, prepare a styrene system (α-methylstyrene: vinyltoluene = 1:1 (volume ratio)), stir to mix it evenly, then mix 85% by mass of the styrene system and 25% of the recycled fiberglass powder, ultrasonicate for 20 minutes first, and then stir for 12 hours. At the same time, add an epoxy group silane coupling agent accounting for 0.5% of the mass of the oil phase.

[0046] S2. Prepare the water phase: Determine the volume of water added according to the oil-water ratio of 1:3. Sequentially add gelatin, an organic dispersant accounting for 0.1% of the mass of the prepared oil phase, calcium carbonate, an inorganic dispersant accounting for 0.1%, sodium stearate, a co-dispersant accounting for 0.5%, and water-soluble black, a stabilizer accounting for 0.5% into the water. While stirring, slowly heat it in an oil bath to about 70 °C until it is completely dissolved.

[0047] S3. Before the reaction, add tert-butyl peroxybenzoate, an initiator accounting for 0.5% of the mass of the oil phase, to the oil phase and stir evenly. Transfer the water phase to a three-necked flask or a reaction kettle, and then add the oil phase to the water phase and pre-disperse for about 15 minutes.

[0048] S4. Heat in an oil bath: (1) Styrene system: First, stir and heat up to 70 °C and react for about 20 minutes; then stir and heat up to 80 °C. The viscosity of the droplets increases and the heat release increases. To prevent aggregation and caking, increase the stirring speed and react for about 30 minutes; finally, raise the temperature to 85 °C and react for about 10 hours.

[0049] S5. After the reaction is completed, turn off the heating and stirring device. After cooling to room temperature, successively wash, drain, dry, and sieve to obtain a high-strength and low-density proppant reinforced with recycled fiberglass powder with a pellet particle size of 0.9 mm (20 mesh).

[0050] Example 2

[0051] The preparation steps of the high-strength and low-density proppant are as follows:

[0052] S1. Prepare the oil phase: First, prepare a styrene system (styrene: vinyltoluene: α-methylstyrene = 2:1:1 (volume ratio)), stir to mix it evenly, then mix 65% by mass of the styrene system and 35% of the glass fiber powder compounded recycled fiberglass powder (300-mesh glass fiber powder: recycled fiberglass powder = 3:1 (mass ratio)), ultrasonicate for 25 minutes first, and then stir for 20 hours. At the same time, add a monoalkoxy type titanate coupling agent accounting for 5% of the mass of the oil phase.

[0053] S2. Prepare the aqueous phase: Determine the volume of water to be added according to an oil-water ratio of 1:5. Sequentially add to the water an organic dispersant, hydroxymethyl cellulose (a cellulose ether), accounting for 8% by mass of the prepared oil phase, an inorganic dispersant, activated calcium phosphate, accounting for 3% by mass, a co-dispersant, calcium dodecylbenzenesulfonate, accounting for 1% by mass, and a stabilizer, sodium sulfate, accounting for 0.8% by mass. While stirring, slowly heat it in an oil bath to about 70 °C until it is completely dissolved.

[0054] S3. Before the reaction, add an initiator, azobisisobutyronitrile, accounting for 1.5% by mass of the oil phase, to the oil phase and stir evenly. Transfer the aqueous phase to a three-necked flask or a reaction kettle, and then add the oil phase to the aqueous phase and pre-disperse for about 15 minutes.

[0055] S4. Heat in an oil bath: (1) Styrene system: First, stir and heat up to 70 °C and react for about 20 minutes; then stir and heat up to 80 °C. The viscosity of the droplets increases and the heat release increases. To prevent aggregation and caking, increase the stirring speed and react for about 30 minutes; finally, raise the temperature to 85 °C and react for about 12 hours.

[0056] S5. After the reaction is completed, turn off the heating and stirring device. After cooling to room temperature, sequentially wash with water, drain, dry, and screen to obtain a high-strength and low-density proppant reinforced with recycled fiberglass powder with a pellet particle size of 0.5 mm (35 mesh).

[0057] Example 3

[0058] The preparation steps of the high-strength and low-density proppant are as follows:

[0059] S1. Prepare the oil phase: First, prepare an unsaturated polyester system (unsaturated polyester resin: α-methylstyrene = 1:1.5 (volume ratio)), stir to mix it evenly, and then mix 80% by mass of the unsaturated polyester system and 20% by mass of the recycled fiberglass powder. First, ultrasonicate for 20 minutes and then stir for 16 hours. At the same time, add a lignin coupling agent accounting for 2% by mass of the oil phase.

[0060] S2. Prepare the aqueous phase: Determine the volume of water to be added according to an oil-water ratio of 1:4. Sequentially add to the water an organic dispersant, ethyl cellulose (a cellulose ether), accounting for 6% by mass of the prepared oil phase, an inorganic dispersant, tricalcium phosphate, accounting for 0.8% by mass, a co-dispersant, sodium dodecylbenzenesulfonate, accounting for 1.2% by mass, and a stabilizer, methylene blue, accounting for 0.2% by mass. While stirring, slowly heat it in an oil bath to about 70 °C until it is completely dissolved.

[0061] S3. Before the reaction, add an initiator, ammonium persulfate, accounting for 1% by mass of the oil phase, to the oil phase and stir evenly. Transfer the aqueous phase to a three-necked flask or a reaction kettle, and then add the oil phase to the aqueous phase and pre-disperse for about 15 minutes.

[0062] S4. Oil bath heating: (2) Unsaturated polyester resin system: Heat it up to 85 °C while stirring, and react for about one and a half hours.

[0063] S5. After the reaction is completed, turn off the heating and stirring device. After cooling to room temperature, successively wash with water, drain, dry, and screen to obtain high-strength and low-density proppants reinforced with recycled fiberglass powder with a pellet diameter of 1 mm (18 mesh).

[0064] Example 4

[0065] The preparation steps of the high-strength and low-density proppants are as follows:

[0066] S1. Prepare the oil phase: First, prepare an unsaturated polyester system (unsaturated polyester resin: vinyltoluene: divinylbenzene = 1:1:1 (volume ratio)), stir to mix it evenly, then mix 65% of the unsaturated polyester system by mass and 35% of the recycled fiberglass powder, ultrasonicate for 25 minutes first, and then stir for 24 hours. At the same time, add a methacryloyloxy silane coupling agent accounting for 6% of the mass of the oil phase.

[0067] S2. Prepare the water phase: Determine the volume of water added according to the oil-water ratio of 1:6. Successively add polyvinyl alcohol, an organic dispersant accounting for 10% of the mass of the prepared oil phase, talc powder, an inorganic dispersant of 1%, sodium petroleum sulfonate, a co-dispersant of 1%, and nitroso R salt, a stabilizer of 0.3% to the water. Slowly heat it to about 70 °C in an oil bath while stirring until it is completely dissolved.

[0068] S3. Before the reaction, add benzoyl peroxide, an initiator accounting for 2% of the mass of the oil phase, to the oil phase and stir evenly. Transfer the water phase to a three-necked flask or a reaction kettle, and then add the oil phase to the water phase and pre-disperse for about 15 minutes.

[0069] S4. Oil bath heating: (2) Unsaturated polyester resin system: Heat it up to 85 °C while stirring, and react for about 2 hours.

[0070] S5. After the reaction is completed, turn off the heating and stirring device. After cooling to room temperature, successively wash with water, drain, dry, and screen to obtain high-strength and low-density proppants reinforced with recycled fiberglass powder with a pellet diameter of 0.6 mm (30 mesh).

[0071] Example 5

[0072] The preparation steps of the high-strength and low-density proppants are as follows:

[0073] S1. Prepare the oil phase: First, prepare an unsaturated polyester system (unsaturated polyester resin: α-methylstyrene: styrene = 2:2:1 (volume ratio)), stir to mix it evenly, and then mix 55% by mass of the unsaturated polyester system and 45% of glass fiber powder-reclaimed FRP powder (3000-mesh glass fiber powder: reclaimed FRP powder = 2:1 (mass ratio)). First, ultrasonicate for 25 minutes, and then stir for 22 hours. At the same time, add a coordination-type titanate coupling agent accounting for 8% of the mass of the oil phase.

[0074] S2. Prepare the water phase: Determine the volume of water added according to the oil-water ratio of 1:8. Sequentially add gelatin, an organic dispersant accounting for 8% of the mass of the prepared oil phase, 1.5% of calcium carbonate, an inorganic dispersant, 2% of sodium stearate, an auxiliary dispersant, and 0.8% of water-soluble black, a stabilizer, to the water. While stirring, slowly heat it in an oil bath to about 70 °C until it is completely dissolved.

[0075] S3. Before the reaction, add methyl ethyl ketone peroxide, an initiator accounting for 2.5% of the mass of the oil phase, to the oil phase and stir evenly. Transfer the water phase to a three-necked flask or a reaction kettle, and then add the oil phase to the water phase and pre-disperse for about 15 minutes.

[0076] S4. Oil bath heating: (2) Unsaturated polyester resin system: While stirring, raise the temperature to 85 °C, and react for about two and a half hours.

[0077] S5. After the reaction is completed, turn off the heating and stirring device. After cooling to room temperature, successively wash, drain, dry, and screen to obtain a high-strength and low-density proppant reinforced with reclaimed FRP powder with a pellet particle size of 0.5 mm (35 mesh).

[0078] The proppant product prepared in this application based on the styrene system and the unsaturated polyester system is as Figure 1 and Figure 2 shown. The high-strength and low-density proppants prepared in Examples 1 to 5 were subjected to tests on bulk density, apparent density, crushing stress, and sphericity. The test process was carried out strictly in accordance with the test method for proppant performance in SY / T5108-2014 Hydraulic Fracturing and Gravel Packing Operations. The test results are shown in Table 1

[0079] Table 1

[0080] Test content Industry standard Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[Body density (g / cm 3 )]]> ≤1.5 0.589 0.641 0.648 0.670 0.684 <![CDATA[Apparent density (g / cm 3 )]]> ≤2.8 1.035 1.125 1.137 1.176 1.2 Crushing rate at 69 MPa (%) ≤9％ 2.15 1.94 2.21 2.09 1.96 Roundness ≥0.7 0.9 0.9 0.9 0.9 0.9 Sphericity ≥0.7 0.9 0.9 0.9 0.9 0.9

[0081] As can be seen from Table 1, the proppants obtained in Examples 1 to 5 of the present invention have the characteristics of high strength, low density, and high sphericity. As the percentage of reclaimed FRP powder in the oil phase increases, the strength gradually increases, while the density slightly increases and the sphericity changes little.

[0082] Example 6

[0083] The in-situ generation steps of the high-strength and low-density proppant are as follows:

[0084] S11. Prepare the oil phase: First, prepare an unsaturated polyester system (unsaturated polyester resin: vinyltoluene: divinylbenzene = 2:1:1 (volume ratio)), stir to mix it evenly, then mix 80% by mass of the unsaturated polyester system and 20% of recycled fiberglass powder, ultrasonicate for 20 minutes first, and then stir for 12 hours. At the same time, an epoxy-based silane coupling agent accounting for 1% of the mass of the oil phase and an active agent higher fatty acid salt of 0.5% also need to be added.

[0085] S12. Prepare the water phase: Determine the volume of the fracturing fluid to be pressurized according to the oil-water ratio of 1:5. Sequentially add polyvinyl alcohol, an organic dispersant accounting for 5% of the mass of the prepared oil phase, calcium carbonate, an inorganic dispersant of 1%, sodium petroleum sulfonate, an auxiliary dispersant of 0.5%, and water-soluble black, a stabilizer of 0.1% to the fracturing fluid. Slowly heat it to about 70 °C in an oil bath while stirring until it is completely dissolved.

[0086] S13. Before the reaction, sequentially add methyl ethyl ketone peroxide, a curing agent A accounting for 1.5% of the mass of the oil phase, and N-N diethylaniline, a curing agent B of 0.5% to the oil phase, and stir for 1 - 2 minutes to make it uniform. Transfer the water phase to a three-necked flask or a reaction kettle, and then add the oil phase to the water phase, and pre-disperse for about 8 - 10 minutes.

[0087] S14. Place the water phase and the oil phase in a visualization box variable material analyzer to simulate the underground construction environment, and carry out the reaction under the conditions of 80 °C, a displacement pressure of 0.01 MPa, a water linear velocity of 0.57 cm / s, and an oil linear velocity of 2.29 cm / s to obtain the high-strength and low-density proppant. The reaction process and products are as Figure 3 shown.

[0088] Example 7

[0089] The in-situ generation steps of the high-strength and low-density proppant are as follows:

[0090] S11. Prepare the oil phase: First, prepare an unsaturated polyester system (unsaturated polyester resin: α-methylstyrene: styrene = 2:2:1), stir to mix it evenly, then mix 70% by mass of the styrene system and 30% of recycled fiberglass powder, ultrasonicate for 22 minutes first, and then stir for 14 hours. At the same time, a monoalkoxy-type titanate coupling agent accounting for 3% of the mass of the oil phase and a polyoxyethylene-type ester of 1% as an active agent also need to be added.

[0091] S12. Prepare the aqueous phase: Determine the volume of the fracturing fluid according to the oil-water ratio of 1:6. Sequentially add gelatin, an organic dispersant accounting for 8% of the mass of the prepared oil phase, calcium phosphate, an inorganic dispersant of 0.8%, sodium stearate, a co-dispersant of 0.8%, and sodium sulfate, a stabilizer of 0.2% into the fracturing fluid. While stirring, slowly heat it in an oil bath to about 70 °C until it is completely dissolved.

[0092] S13. Before the reaction, add tert-butyl peroxybenzoate microcapsule, a curing agent A accounting for 2% of the mass of the oil phase, and zinc isooctanoate, a curing agent B of 0.6% into the oil phase, and stir for 1 - 2 minutes to make it uniform. Transfer the aqueous phase to a three-necked flask or a reaction kettle, and then add the oil phase to the aqueous phase, and pre-disperse for about 8 - 10 minutes.

[0093] S14. Place the aqueous phase and the oil phase in a visualization box variable material analyzer to simulate the underground construction environment, and carry out the reaction under the conditions of 80 °C, a displacement pressure of 0.03 MPa, a water linear velocity of 0.98 cm / s, and an oil linear velocity of 1.88 cm / s to obtain a high-strength and low-density proppant.

[0094] Example 8

[0095] The in-situ generation steps of the high-strength and low-density proppant are as follows:

[0096] S11. Prepare the oil phase: First, prepare an unsaturated polyester system (unsaturated polyester resin: α-methylstyrene = 1:2 (volume ratio)), stir to make it evenly mixed, and then mix 85% of the unsaturated polyester system and 15% of the glass fiber powder compound recycled fiberglass powder (300-mesh glass fiber powder: recycled fiberglass powder = 4:1 (mass ratio)), ultrasonicate for 25 minutes first, and then stir for 16 hours. At the same time, add a coordination type titanate coupling agent accounting for 3% of the mass of the oil phase and a surfactant fatty acid glyceride of 1.5%.

[0097] S12. Prepare the aqueous phase: Determine the volume of the fracturing fluid according to the oil-water ratio of 1:8. Sequentially add methyl cellulose (cellulose ether), an organic dispersant accounting for 6% of the mass of the prepared oil phase, tricalcium phosphate, an inorganic dispersant of 0.5%, calcium dodecylbenzenesulfonate, a co-dispersant of 0.6%, and methylene blue, a stabilizer of 0.2% into the fracturing fluid. While stirring, slowly heat it in an oil bath to about 70 °C until it is completely dissolved.

[0098] S13. Before the reaction, add tert-butyl peroxybenzoate microcapsule, a curing agent A accounting for 3% of the mass of the oil phase, and zinc isooctanoate, a curing agent B of 0.2% into the oil phase, and stir for 1 - 2 minutes to make it uniform. Transfer the aqueous phase to a three-necked flask or a reaction kettle, and then add the oil phase to the aqueous phase, and pre-disperse for about 8 - 10 minutes.

[0099] S14. Place the aqueous phase and the oil phase in a visual box-type material analyzer to simulate the underground construction environment, and carry out the reaction under the conditions of 80 °C, a displacement pressure of 0.05 MPa, a water linear velocity of 1.56 cm / s, and an oil linear velocity of 3.12 cm / s to obtain a high-strength and low-density proppant.

[0100] Example 9

[0101] The in-situ generation steps of the high-strength and low-density proppant are as follows:

[0102] S11. Prepare the oil phase: First, prepare an unsaturated polyester system (unsaturated polyester resin: vinyl toluene = 1:4), stir to mix it evenly, and then mix 75% of the unsaturated polyester system by mass and 25% of the glass fiber powder compounded recycled fiberglass powder (800-mesh glass fiber powder: recycled fiberglass powder = 2:1 (mass ratio)). Ultrasonic for 25 minutes first, and then stir for 18 hours. At the same time, add a vinyl silane coupling agent accounting for 5% of the mass of the oil phase and an active agent polyol ester accounting for 2%.

[0103] S12. Prepare the aqueous phase: Determine the volume of the fracturing fluid to be pressurized according to the oil-water ratio of 1:9. Sequentially add an organic dispersant hydroxypropyl cellulose (cellulose ether) accounting for 10% of the mass of the prepared oil phase, an inorganic dispersant talc powder accounting for 2%, a co-dispersant sodium dodecylbenzenesulfonate accounting for 0.9%, and a stabilizer nitrosyl R salt accounting for 0.3% to the fracturing fluid. Slowly heat it to about 70 °C in an oil bath while stirring until it is completely dissolved.

[0104] S13. Before the reaction, add potassium persulfate as curing agent A accounting for 3.5% of the mass of the oil phase and N,N-dimethylaniline microcapsule as curing agent B accounting for 0.5% to the oil phase, and stir for 1 - 2 minutes to make it uniform. Transfer the aqueous phase to a three-necked flask or a reaction kettle, and then add the oil phase to the aqueous phase, and pre-disperse for about 8 - 10 minutes.

[0105] S14. Place the aqueous phase and the oil phase in a visual box-type material analyzer to simulate the underground construction environment, and carry out the reaction under the conditions of 80 °C, a displacement pressure of 0.07 MPa, a water linear velocity of 2.24 cm / s, and an oil linear velocity of 4.47 cm / s to obtain a high-strength and low-density proppant.

[0106] Example 10

[0107] The in-situ generation steps of the high-strength and low-density proppant are as follows:

[0108] S11. Prepare the oil phase: First, prepare an unsaturated polyester system (unsaturated polyester resin: vinyl toluene: styrene: divinylbenzene = 3:1:1:1), stir to mix it evenly, and then mix 65% by mass of the unsaturated polyester system with 35% of glass fiber powder-recovered fiberglass powder (3000-mesh glass fiber powder: recovered fiberglass powder = 1:5 (mass ratio)). First, ultrasonicate for 25 minutes, and then stir for 22 hours. At the same time, add 6% by mass of lignin coupling agent and 1.5% of surfactant sulfonate to the oil phase.

[0109] S12. Prepare the aqueous phase: Determine the volume of the fracturing fluid according to the oil-water ratio of 1:10. Sequentially add 8% by mass of organic dispersant gelatin, 1.5% of inorganic dispersant tricalcium phosphate, 1.2% of co-dispersant petroleum sulfonate, and 0.3% of stabilizer methylene blue to the fracturing fluid. Slowly heat it to about 70 °C in an oil bath while stirring until it is completely dissolved.

[0110] S13. Before the reaction, add 4% by mass of curing agent A azobisisoheptonitrile microcapsules and 0.6% of curing agent B vanadium phosphate to the oil phase, and stir for 1 - 2 minutes to make it uniform. Transfer the aqueous phase to a three-necked flask or reaction kettle, and then add the oil phase to the aqueous phase, and pre-disperse for about 8 - 10 minutes.

[0111] S14. Place the aqueous phase and the oil phase in a visualization box variable material analyzer to simulate the underground construction environment, and carry out the reaction under the conditions of 80 °C, a displacement pressure of 0.09 MPa, a water linear velocity of 2.89 cm / s, and an oil linear velocity of 5.61 cm / s to obtain a high-strength low-density proppant.

[0112] In the actual production and implementation process, the principle of in-situ generation of the proppant is as Figure 4 shown.

[0113] Carry out volume density, apparent density, crushing stress, and sphericity performance tests on the high-strength low-density proppants prepared in Examples 6 to 10. The test process is carried out strictly in accordance with SY / T5108-2014 Test Method for Proppant Performance in Hydraulic Fracturing and Gravel Packing Operations. The test results are shown in Table 2

[0114] Table 2

[0115] Test content Industry standard Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[Apparent density (g / cm 3 )]]> ≤1.5 0.608 0.631 0.648 0.670 0.684 <![CDATA[Apparent density (g / cm 3 )]]> ≤2.8 1.068 1.107 1.137 1.176 1.2 Crushing rate at 69 MPa (%) ≤9％ 2.52 2.36 2.21 2.09 1.96 Roundness ≥0.7 0.9 0.9 0.9 0.9 0.9 Sphericity ≥0.7 0.9 0.9 0.9 0.9 0.9

[0116] In order to further deeply understand the diversion ability of the phase change material, select the high-strength low-density proppants prepared in Examples 6 to 10, and carry out a diversion ability experiment in accordance with SY / T6302—2009 Recommended Method for Evaluating Short-Term Diversion Ability of Fracture Proppant Packing Layers.

[0117] Experimental temperature: 25 °C

[0118] Experimental liquid: distilled water

[0119] Table 3 Conductivity under different closing pressures

[0120]

[0121] The above embodiments are only preferred embodiments of the present invention, and the scope of protection of the present invention cannot be limited thereby. Any non-substantive changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for preparing a high-strength, low-density proppant, characterized in that: include: S1. preparing an oil phase: preparing a styrene system / unsaturated polyester resin system, stirring to make it uniformly mixed, mixing 50-99.9% by mass of the styrene system / unsaturated polyester resin system, 0-50% by mass of recycled glass fiber reinforced plastic powder or glass fiber powder of different mesh sizes, recycled glass fiber reinforced plastic powder and a coupling agent, and sequentially performing ultrasonic treatment and stirring to form an oil phase, wherein the coupling agent accounts for 0.1% to 20% by mass of the oil phase; S2. Prepare the water phase: determine the volume of the water phase according to the volume of the oil phase, add 0.1% to 20% of the mass percentage of the prepared oil phase of an organic dispersant, 0.1% to 20% of an inorganic dispersant, 0.1% to 10% of a dispersant aid, and 0.01% to 1% of a stabilizer into the water, and completely dissolve them by heating and stirring; S3, adding 0.5% to 3.5% of the initiator by mass percentage to the oil phase and stirring evenly, adding the oil phase to the water phase and pre-dispersing; S4, heating reaction: (1) Styrene system: first stir and heat to 65-70°C, react for 20-25 minutes; then stir and heat to 75-90°C, react for 25-35 minutes; finally heat to 85-90°C, react for 10-12 hours; (2) Unsaturated polyester resin system: stir and heat to 85-90°C, react for 1.5 to 2.5 hours; S5, cooling, washing, draining, drying, and screening in sequence to obtain a high-strength and low-density proppant reinforced with recycled glass fiber reinforced plastic powder.

2. The method for preparing a high-strength, low-density proppant according to claim 1, characterized in that: The styrene system includes at least one of styrene, α-methylstyrene, vinyltoluene and divinylbenzene, and the unsaturated polyester resin system includes at least one type of constituent compounds of unsaturated polyester and styrene system; The coupling agent added in step S1 is at least one selected from silane coupling agent, titanate coupling agent, and other coupling agents, the silane coupling agent is at least one selected from epoxy silane, vinyl silane, and methacryloxy silane, the titanate coupling agent is at least one selected from monoalkoxy type, coordination type, and chelate type, and the other coupling agent is at least one selected from bimetallic coupling agent, lignin coupling agent, and tin coupling agent; In step S2, the organic dispersant is at least one of polyvinyl alcohol, water-soluble polymers, gelatin, and cellulose ethers; the inorganic dispersant is at least one of calcium carbonate, tricalcium phosphate, activated calcium phosphate, and talcum powder; the auxiliary dispersant is at least one of sodium stearate, calcium dodecylbenzene sulfonate, sodium dodecylbenzene sulfonate, and sodium petroleum sulfonate; and the stabilizer is at least one of sodium sulfate, water-soluble black, nitroso R salt, and methylene blue; The initiator added to the oil phase in step S3 is at least one of organic peroxides, inorganic peroxides, and azo initiators, the organic peroxide initiator is at least one of methyl ethyl ketone peroxide, benzoyl peroxide, and tert-butyl perbenzoate, the inorganic peroxide initiator is at least one of potassium persulfate, ammonium persulfate, and sodium persulfate, and the azo initiator is at least one of azobisisobutyronitrile and azobisisoheptylnitrile.

3. The method for preparing a high-strength, low-density proppant according to claim 1, characterized in that: In step S1, after the styrene system / unsaturated polyester resin system is mixed with the recycled glass fiber reinforced plastic powder, ultrasonic treatment is performed for 20 to 30 minutes and stirring is performed for 12 to 24 hours.

4. The method for preparing a high-strength, low-density proppant according to claim 1, characterized in that: In step S2, the volume of the water phase is determined according to the mass percentage of the recovered FRP powder in the oil phase, and the mass percentage of the recovered FRP powder in the oil phase is proportional to the volume of the water phase.

5. The method for preparing a high-strength, low-density proppant according to claim 1, characterized in that: The particle size of the spherical particles of the high-strength and low-density dispersant obtained after screening in step S5 is 0.2 to 2 mm, that is, 10 to 70 meshes.

6. A high-strength, low-density proppant, characterized in that: The high-strength, low-density proppant is prepared by the preparation method of the high-strength, low-density proppant according to any one of claims 1-5.

7. A method for in-situ generation of high-strength, low-density proppant, characterized in that: The water phase and the oil phase are pumped into the underground hydraulic fracture, and the water phase and the oil phase react at the temperature and pressure at the location to generate high-strength and low-density proppants in situ, wherein the preparation process of the water phase and the oil phase includes: S11: preparing the oil phase: preparing an unsaturated polyester resin system, stirring to make it uniformly mixed, mixing 50-99.9% by mass of the unsaturated polyester resin system, 0.1-50% of the recycled glass fiber reinforced plastic powder, a coupling agent and an active agent, and sequentially performing ultrasonication and stirring to form an oil phase, wherein the coupling agent accounts for 0.1%-20% by mass of the oil phase and the active agent accounts for 0.1%-20% by mass of the oil phase; S12: preparing the water phase: determining the volume of the water phase according to the volume of the oil phase, sequentially adding 0.1% to 20% of an organic dispersant, 0.1% to 20% of an inorganic dispersant, 0.1% to 10% of a dispersant aid, and 0.01% to 1% of a stabilizer to the water phase in the mass percentage of the prepared oil phase, and completely dissolving them by heating and stirring; S13: Add a curing system to the oil phase, wherein the curing system includes 0.5% to 10% by mass of curing agent A and 0.01% to 5% by mass of curing agent B in the oil phase, and add curing agents A and B in sequence and stir thoroughly.

8. The in-situ generation method of high-strength and low-density proppant according to claim 7, characterized in that: The active agent is at least one of higher fatty acid salts, sulfonates, polyoxyethylene esters, fatty acid glycerides, and polyol esters.

9. The in-situ generation method of high-strength and low-density proppant according to claim 7, characterized in that: The aqueous phase in step S12 is a fracturing fluid, specifically a water-based fracturing fluid: including at least one of a natural plant gum fracturing fluid, a cellulose fracturing fluid, a synthetic polymer fracturing fluid and a slick water fracturing fluid system.

10. The in-situ generation method of high-strength and low-density proppant according to claim 7, characterized in that: In step S13, the curing agent A and the curing agent B added to the oil phase are in the form of at least one compound or microcapsule, the components of the curing agent A or the microcapsules of the curing agent A include at least one of organic peroxides, inorganic peroxides, and azo initiators, the organic peroxide initiator is at least one of methyl ethyl ketone peroxide, benzoyl peroxide, and tert-butyl perbenzoate, the inorganic peroxide initiator is at least one of potassium persulfate, ammonium persulfate, and sodium persulfate, the azo initiator is at least one of azobisisobutyronitrile and azobisisoheptylnitrile, and the components of the curing agent B or the microcapsules of the curing agent B include at least one of cobalt cyclohexaneate, cobalt isooctanoate, zinc isooctanoate, NN dimethylaniline, NN diethylaniline, and vanadium phosphate.

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