A film-coated particle, a preparation method thereof, and a double-layer film-coated particle profile control agent, a preparation method thereof and application

Abstract

The application provides a coated particle, a preparation method of the coated particle, a double-layer coated particle profile control agent, a preparation method of the double-layer coated particle profile control agent and application. The method comprises the following steps: mixing a coating material and an organic solvent to obtain a coating solution; the mass concentration of the coating material in the coating solution is 30-50%; mixing the coating solution and core particles according to a mass ratio of 1-3:1 to obtain a mixed system; and then performing spray drying treatment on the mixed system to form a coating on the surface of the core particles, so as to obtain the coated particle. The double-layer coated particle profile control agent provided by the application has excellent injection performance and plugging performance in low-permeability / ultra-low-permeability oil reservoirs.

Description

Technical Field

[0001] The present invention relates to the technical field of oil reservoir development, and in particular to a film-coated particle and a preparation method thereof, and a double-layer film-coated particle profile control agent and a preparation method and application thereof. Background Art

[0002] Low- and ultra-low-permeability reservoirs have small pore throats and well-developed natural microfractures, with fractures measuring micrometers and pore throats at the nanometer level. During water and gas injection, the injected medium is prone to water and gas channeling along the fracture channels, resulting in low sweep efficiency. Displacement media cannot effectively penetrate the nanoscale pore throats to displace crude oil, resulting in low oil washing efficiency. Deep profile control in low- and ultra-low-permeability reservoirs requires profile control agents with excellent injectability, allowing them to penetrate deep into the formation and effectively block channeling channels. However, conventional profile control technologies and agents suitable for medium- and high-permeability reservoirs are poorly compatible with low- and ultra-low-permeability reservoir conditions. Gel-based profile control agents have difficulty penetrating deep into the reservoir and can contaminate the matrix during migration, causing irreversible damage to the reservoir. In low- and ultra-low-permeability reservoirs, relying solely on strong gels to completely block fractures, completely eliminating their contribution to production, is undesirable. Conventional granular plugging agents have good injectability, but their plugging effectiveness is limited by the matching relationship between particle size and fracture size. Coated particles self-adhere to form aggregates that adapt to fracture size, effectively blocking escape pathways. Coated particles inherently possess the excellent injectability of granular plugging agents, while also ensuring effective plugging. They demonstrate significant potential for profile control in low- and ultra-low-permeability reservoirs, but existing technologies still present challenges that need to be addressed.

[0003] CN105400503B provides a method for preparing a double-layer coated particle plugging agent by fluidized bed spraying, but the preparation method has limitations. When the particle size of the core particles is several or tens of microns, there are problems such as the particles cannot be effectively dispersed, resulting in the inability to evenly spray the particle surface, and serious particle agglomeration, especially for lightweight materials such as fruit shells. That is, the above method is still unable to effectively prepare coated particles with a particle size of several or tens of microns. In the literature, Cheng Tingting et al. also used the fluidized bed spraying method to prepare double-layer coated particles, but there are also limitations, that is, the particle size is all above 100 microns.

[0004] However, fractures in low-permeability / ultra-low-permeability reservoirs are often several or tens of microns in size. The hundreds-micron-sized double-layer coated particles prepared by the aforementioned method cannot be effectively injected deep into the fractures. Double-layer coated particles with a particle size less than 100 microns have not yet been reported. Therefore, providing a profile control agent with double-layer coated particles of varying core sizes, several or tens of microns in size, suitable for use in low-permeability / ultra-low-permeability reservoirs is an urgent need in the art. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, the present invention provides a coated particle and a preparation method thereof, and a double-layer coated particle profile control agent and its preparation method and application. The double-layer coated particle profile control agent has excellent injection performance and plugging performance in low-permeability / ultra-low-permeability reservoirs.

[0006] In order to achieve the above object, according to a first aspect of the present invention, a method for preparing film-coated particles is provided, which comprises:

[0007] Mixing a coating material and an organic solvent to obtain a coating solution; wherein the coating solution has a mass concentration of the coating material of 30 to 50%;

[0008] The coating solution and the core particles are mixed in a mass ratio of 3 to 5:1 to obtain a mixed system, and then the mixed system is spray-dried to form a coating on the surface of the core particles to obtain the coated particles.

[0009] The present invention provides a coating preparation method that can be achieved by spray drying, which is applicable to a variety of core particles and has good effects. The preparation process of the present invention is simple, the operating cost is low, and it has good industrial application prospects.

[0010] In some preferred embodiments of the present invention, the particle size of the core particles is 0.5 to 50 microns.

[0011] In some preferred embodiments of the present invention, the core particles include inorganic core particles and / or biomass core particles. Preferably, the inorganic core particles include one or a combination of two or more of silicon dioxide (SiO2), floating beads, calcium carbonate, and barium sulfate.

[0012] In some preferred embodiments of the present invention, the inorganic core particles include metal oxide core particles; and the biomass core particles are obtained by ball milling of fruit shell materials.

[0013] The metal oxide core particles include iron oxide core particles, aluminum oxide core particles, and titanium oxide core particles.

[0014] The raw materials of the biomass kernel particles include hard fruit shells and cores, preferably, one or more of walnut shells, hawthorn cores, and jujube cores.

[0015] In some preferred embodiments of the present invention, the coating material includes one or a combination of two or more thermoplastic resins and thermosetting resins.

[0016] In some preferred embodiments of the present invention, the organic solvent comprises ethanol and / or acetone. More preferably, the organic solvent comprises ethanol.

[0017] In some preferred embodiments of the present invention, the spray drying process is performed two or more times, sequentially forming two or more coating layers on the surface of the core particles. By performing the spray drying process multiple times, different coating materials can be sequentially coated on the core particles to form a composite material having a multi-layer core-shell structure. This composite material can be adapted to a variety of applications depending on the different raw materials and structures, and has broad application prospects.

[0018] In some preferred embodiments of the present invention, the coating solution further comprises: a suspending dispersant, a surfactant, or a combination of two or more thereof.

[0019] In some preferred embodiments of the present invention, the spray drying temperature is 5-20°C higher than the boiling point of the organic solvent, the feed rate is 20-50 ml / min, and the atomization pressure is 0.2-0.4 MPa. If the feed rate is too fast, the organic solvent will not have enough time to completely evaporate, and the particles will tend to clumping together. If the feed rate is too slow, time and energy consumption will increase.

[0020] When spray drying coating is performed twice or more, when the second coating is performed and the coating material is a thermosetting resin, the spray drying temperature should be higher than the boiling point of the solvent and 50-100° C. higher than the curing temperature of the thermosetting resin.

[0021] According to another aspect of the present invention, there is provided a coated particle obtained according to the above method.

[0022] According to another aspect of the present invention, a method for preparing a double-layer coated particle profile control agent is provided, comprising:

[0023] S1, mixing a thermoplastic resin and an organic solvent to obtain a thermoplastic resin solution; mixing the thermoplastic resin solution with core particles to obtain a first mixed system; wherein the mass ratio of the thermoplastic resin, the organic solvent, and the core particles is 0.5-1:1-2:0.5-1; and the particle size of the core particles is 0.5-50 μm;

[0024] The first mixed system is subjected to a first spray drying process to form a first coating layer to obtain single-layer coated particles, wherein the thickness of the first coating layer is 300 to 500 nm;

[0025] S2, mixing a water-soluble thermosetting resin, water, and a surfactant to obtain a thermosetting resin dispersion, wherein the mass concentration of the thermosetting resin is 10-20%;

[0026] The thermosetting resin dispersion and the single-layer coated particles are mixed in a mass ratio of 3 to 5:1 to obtain a second mixed system; the second mixed system is subjected to a second spray drying process to form a second coating layer to obtain double-layer coated particles, wherein the thickness of the second coating layer is 500 to 1000 nm, and the particle size of the double-layer coated particles is 1.5 to 51.5 μm;

[0027] S3, mixing the double-layer coated particles and a suspending dispersant to obtain the double-layer coated particle profile control agent, wherein the mass concentration of the double-layer coated particles is 0.1-5%.

[0028] The double-layer coated particle profile control agent with different types of micron-sized cores of the present invention has a simple preparation process and low operating cost. It can efficiently prepare double-layer coated particles with cores of several or tens of microns in size. It has excellent injection performance and plugging performance in low permeability / ultra-low permeability oil reservoirs, plugs escape channels, improves the sweep efficiency of subsequent displacement media, and thus improves the recovery rate of low permeability / ultra-low permeability oil reservoirs.

[0029] The present invention first obtains core particles of several or tens of microns, disperses the core particles in a thermoplastic resin solution, stirs them evenly, and then spray-dries and granulates them to obtain particles with a single layer of film. The wet particles produced by the spray process have uniform particle size. After the wet particles are dried instantly, a layer of thermoplastic resin film is formed on the surface of the particles. When the particles come into contact with water in the stratum and reach the softening temperature, the thermoplastic resin film becomes sticky, and the particles are bonded together to form a mass, thereby sealing cracks. The coated particles with a single layer of adhesive film are dispersed in a thermosetting resin aqueous solution, and spray-dried and granulated to form micron-sized double-layer coated particles with both an adhesive film and a rigid protective film. The thermosetting resin aqueous solution is coated on the particle surface, and the wet particles are dried instantly at high temperature to form a layer of thermosetting resin film on the particle surface. At the same time, in a high temperature environment, the thermosetting resin film solidifies, i.e., a rigid protective shell is formed on the surface of the particle adhesive film, thereby obtaining micron-sized double-layer coated particles. After the water-soluble thermosetting resin is cured, it is no longer soluble in water. The double-layer coated particles can be dispersed again in the thermosetting resin aqueous solution and spray-dried repeatedly or the process parameters can be adjusted to improve the coating integrity and thickness of the rigid protective shell on the particle surface, so as to meet the deep profile control needs of low-permeability / ultra-low-permeability oil reservoirs with different migration distances.

[0030] In some preferred embodiments of the present invention, the core particles include inorganic core particles or biomass core particles.

[0031] In some preferred embodiments of the present invention, the material of the inorganic core particles is selected from silica or floating beads.

[0032] In some preferred embodiments of the present invention, the biomass core particles are obtained by ball milling fruit shell materials.

[0033] The silica core material has better compressive resistance, and the floating beads and fruit shell materials have better suspension performance.

[0034] Preferably, the husk material is selected from hawthorn seeds, walnut shells, etc., and the method for ball milling the husk material comprises:

[0035] The shell material is ground and crushed using a planetary ball mill to give the particles a certain sphericity, and then sieved to obtain kernel particles with a particle size that meets the requirements.

[0036] In some preferred embodiments of the present invention, the particle size of the silicon dioxide includes: 0.5 to 1 micron, 1 to 10 microns, 10 to 30 microns, or a combination of two or more thereof;

[0037] Preferably, the particle size of the floating beads is 30 to 50 microns.

[0038] In some preferred embodiments of the present invention, the particle size of the biomass core particles is 5 to 10 microns and / or 10 to 30 microns.

[0039] In some preferred embodiments of the present invention, the temperature of the first spray drying process is 85-95°C.

[0040] In some preferred embodiments of the present invention, the temperature of the second spray drying process is 150-200°C.

[0041] In some preferred embodiments of the present invention, the first spray-drying process is performed in a closed organic solvent spray dryer.

[0042] In some preferred embodiments of the present invention, the thermoplastic resin includes thermoplastic phenolic resin and / or modified thermoplastic phenolic resin;

[0043] Preferably, the organic solvent comprises ethanol and / or acetone; more preferably, the organic solvent comprises ethanol;

[0044] Preferably, the water-soluble thermosetting resin comprises a thermosetting phenolic resin and / or an epoxy resin. More preferably, the water-soluble thermosetting resin comprises a thermosetting phenolic resin.

[0045] In some preferred embodiments of the present invention, the mass concentration of the hexadecyltrimethylammonium bromide in the thermosetting resin dispersion is 0.1 to 0.3%.

[0046] In some preferred embodiments of the present invention, in the second mixed system, the mass concentration of the single-layer coated particles is 10-30%.

[0047] In some preferred embodiments of the present invention, the suspending dispersant includes guar gum, cetyltrimethylammonium bromide, and water; wherein, preferably, the mass concentration of the guar gum is 0.5-3%; preferably, the mass concentration of the cetyltrimethylammonium bromide is 0.1-0.5%.

[0048] According to another aspect of the present invention, a double-layer coated particle profile control agent prepared according to the above preparation method is also provided.

[0049] According to another aspect of the present invention, there is also provided a use of the above-mentioned double-layer coated particle profile control agent in profile control of low permeability / ultra-low permeability oil reservoirs.

[0050] The double-layer coated particles with different types of micron-sized cores of the present invention have excellent injection performance. The particle size is several or tens of microns and can be effectively injected into the crack escape channel. At the same time, under the protection of the rigid shell, the premature exposure of the inner adhesive film of the particles is avoided, thereby ensuring the injection performance and deep migration performance of the coated particles.

[0051] The double-layer coated particles with micron-sized inner cores of the present invention have strong sealing performance. The rigid outer shell of the double-layer coated particles is gradually worn during the migration of the stratum, so that the inner adhesive film of the particles is exposed to water, softened and becomes sticky at the reservoir temperature, and adhesion occurs between the particles. According to the size of the cracks, adaptive adhesion forms particle clusters of corresponding sizes, which effectively seal the cracks. Due to the mutual adhesion between the particles and between the particles and the cracks, the sealing strength is significantly improved compared with the rigid bridging sealing of ordinary particles, and the sealing effect is not limited to the size matching relationship between the particles and the cracks.

[0052] The double-layer coated particles with different types of micron-sized cores of the present invention achieve deep plugging in low-permeability / ultra-low-permeability oil reservoirs, significantly increase the sweep efficiency of subsequent displacement media, and improve the recovery rate of low-permeability / ultra-low-permeability oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The figure shows the injection pressure variation of 0.5-1 micron double-layer coated particles in the experiment in Application Example 1.

[0054] Figure 2 The figure shows the injection pressure variation of 1-10 micron double-layer coated particles in the experiment in Application Example 1.

[0055] Figure 3 The figure shows the injection pressure variation of 10-30 micron double-layer coated particles in the experiment in Application Example 1.

[0056] Figure 4 The pressure and recovery rate curve of the double-layer coated particles in Example 2 in Application Example 2 is shown.

[0057] Figure 5 The microscopic morphology of the 10-30 micron double-layer coated particles in Example 1 is shown.

[0058] Figure 6 The microscopic morphology of the double-layer coated particles in Example 2 is shown.

[0059] Figure 7 The microscopic morphology of the double-layer coated particles in Example 3 is shown.

[0060] Figure 8 Scanning electron micrographs of the core (left) and the double-layer coated particles (right) in Example 3 are shown.

[0061] Figure 9 The dispersion and suspension properties of the double-layer coated particles in Application Example 3 are shown. DETAILED DESCRIPTION

[0062] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0063] Example 1:

[0064] This embodiment provides a method for preparing a double-layer coated particle profile control agent, which specifically includes:

[0065] 1. Preparation of core particles:

[0066] 150 g, 150 g, and 150 g of silica microspheres with particle sizes of 0.5-1 μm, 1-10 μm, and 10-30 μm were selected as the core particles of double-layer coated particles of different particle sizes;

[0067] 2. Preparation of micron-sized double-layer coated particles:

[0068] 300 g of anhydrous ethanol was added to 150 g of thermoplastic phenolic resin powder, and after being fully stirred and dissolved, a thermoplastic phenolic resin solution was obtained. 150 g of silica microspheres was then added and fully stirred to obtain three first mixed systems respectively;

[0069] The three first mixed systems were spray-dried at 85° C. in a closed organic solvent spray dryer to obtain three single-layer coated particles with thermoplastic phenolic resin films on their surfaces.

[0070] 60 g of a water-soluble thermosetting phenolic resin was dissolved in 130 g of water to form a thermosetting phenolic resin solution, 10 g of cetyltrimethylammonium bromide was added, and the mixture was stirred evenly. 60 g of the single-layer coated particles were added separately and stirred thoroughly to uniformly disperse the particles in the solution, thereby obtaining three second mixed systems. The feed rate during the spray drying process was 20 ml / min, and the atomization pressure was 0.2 MPa.

[0071] 250 g of the second mixed system was spray dried and granulated at 200°C using a spray dryer. The water-soluble thermosetting phenolic resin solidified on the surface of the particle adhesive film to form a rigid shell, thereby obtaining three different double-layer coated particles. The feed rate during the spray drying process was 20 ml / min and the atomization pressure was 0.2 MPa.

[0072] 3. Preparation of micron-sized double-layer coated particle profile control agent:

[0073] Dissolve 0.5 g of guar gum in 99.2 g of water and add 0.3 g of hexadecyltrimethylammonium bromide to obtain a suspending dispersant.

[0074] 5g of double-layer coated particles were added to 95g of suspending dispersant and mixed evenly to obtain three types of micron-sized double-layer coated particle profile control agents, which were recorded as 0.5-1 micron type, 1-10 micron type and 10-30 micron type.

[0075] Example 2

[0076] This embodiment provides a method for preparing a double-layer coated particle profile control agent, which specifically includes:

[0077] 1. Preparation of core particles:

[0078] 20g of floating beads with a particle size of 40-50 microns were selected as the core particles of the double-layer coated particles;

[0079] 2. Preparation of micron-sized double-layer coated particles:

[0080] Take 200g of anhydrous ethanol, add 100g of thermoplastic phenolic resin powder, stir thoroughly to dissolve, obtain thermoplastic phenolic resin solution, then add 20g of floating beads, stir thoroughly to obtain a first mixed system;

[0081] The first mixed system was spray-dried in a closed organic solvent spray dryer at 85° C. to obtain single-layer coated particles with a thermoplastic phenolic resin film on the surface; the feed rate during the spray drying process was 20 ml / min and the atomization pressure was 0.2 MPa;

[0082] Take 60g water-soluble thermosetting phenolic resin dissolved in 130g water, form thermosetting phenolic resin solution, add 10g of cetyl trimethyl ammonium bromide, stirring uniform; Add 20g single layer coated particles, fully stirred, make the particles evenly dispersed in the solution, get the second mixed system;

[0083] Take 220g of the second mixed system, using spray dryer at 200℃ for spray drying granulation, water-soluble thermosetting phenolic resin in the surface of the particle bonding film solidification form rigid shell, and then get double layer coated particles; The feeding speed in the spray drying process is 20ml / min, and the atomization pressure is 0.2MPa;

[0084] 3, micron double layer coated particle profile control agent preparation:

[0085] Take 0.5g of guar gum dissolved in 99.2g of water, add 0.3g of cetyl trimethyl ammonium bromide, get suspended dispersant;

[0086] Take 5g double layer coated particles into 95g suspended dispersant, mix evenly, get double layer coated particle profile control agent.

[0087] Example 3

[0088] The embodiment provides a kind of double layer coated particle profile control agent preparation method, specifically including:

[0089] 1, the preparation of core particle:

[0090] Take 1000g hawthorn seed shell material, dry, and preliminary broken, further using planetary ball mill, grinding broken hawthorn seed particles, so that its particle has certain sphericity, sieve, get 150g core particle with particle size of 10-30 microns;

[0091] 2, micron double layer coated particle preparation:

[0092] Take 300g of anhydrous ethanol, add 150g of thermoplastic phenolic resin powder, after fully stirring and dissolving, get thermoplastic phenolic resin solution, respectively add 150g of hawthorn seed particles, fully stirred, get the first mixed system;

[0093] The first mixed system is sprayed and dried by closed organic solvent spray dryer at 85 DEG C, to obtain single layer coated particles coated with thermoplastic phenolic resin film; The feeding speed in the spray drying process is 20ml / min, and the atomization pressure is 0.2MPa;

[0094] 60 g of a water-soluble thermosetting phenolic resin was dissolved in 130 g of water to form a thermosetting phenolic resin solution, 10 g of hexadecyltrimethylammonium bromide was added, and the mixture was stirred evenly; 60 g of the single-layer coated particles were added and stirred thoroughly to uniformly disperse the particles in the solution to obtain a second mixed system;

[0095] 250 g of the second mixed system was spray dried and granulated at 200°C using a spray dryer. The water-soluble thermosetting phenolic resin solidified on the surface of the particle adhesive film to form a rigid shell, thereby obtaining double-layer coated particles. The feed rate during the spray drying process was 20 ml / min, and the atomization pressure was 0.2 MPa.

[0096] 3. Preparation of micron-sized double-layer coated particle profile control agent:

[0097] Dissolve 0.5 g of guar gum in 99.2 g of water and add 0.3 g of hexadecyltrimethylammonium bromide to obtain a suspending dispersant.

[0098] 5 g of double-layer coated particles were added to 95 g of suspending dispersant and mixed evenly to obtain a double-layer coated particle profile control agent.

[0099] Application Example 1

[0100] In this application example, the 0.5-1 micron, 1-10 micron, and 10-30 micron double-layer coated particle profile control agents prepared in Example 1 were used to conduct core plugging performance evaluation experiments, and the core inlet pressure was recorded during the experiment.

[0101] Double-layer coated particles of varying sizes are selected based on the fracture size range of low-permeability reservoirs. For fracture widths of 1 to 10 microns, 0.5 to 1 micron double-layer coated particles are used; for fracture widths of 10 to 50 microns, 10 to 30 micron double-layer coated particles are used; and for fracture widths of 50 to 100 microns, 30 to 50 micron double-layer coated particles are used. Double-layer coated particles smaller than the fracture size ensure the injectability of the particle profile control agent, enabling it to migrate deep into the fracture. Subsequently, the particles adaptively bond to form clusters based on the fracture size, sealing the fracture and achieving deep-seated profile control and flooding capabilities.

[0102] 1. Prepare a cylindrical core with a fracture width of 10 microns and a length of 10 cm. The core diameter is 2.5 cm and the matrix permeability is 5 mD to simulate a fractured, ultra-low permeability reservoir (fracture width 10 microns). Place the core in a core holder, evacuate the core, saturate it with water, and calculate the core pore volume (PV).

[0103] Carry out water flooding at a constant rate of 0.5 mL / min. When the pressure stabilizes, stop water flooding. Start injecting 0.5-1 micron double-layer coated particle profile control agent at a constant rate of 0.5 mL / min and an injection volume of 0.5 PV.

[0104] After the double-layer coated particle profile control agent was injected, it was placed in a high temperature (95°C) oven for 12 hours, and then subsequent water flooding was carried out at a constant rate of 0.5 mL / min until the pressure stabilized, and the plugging rate was calculated. The changes in the core inlet pressure during the experiment were as follows: Figure 1 shown.

[0105] 2. Prepare a cylindrical core with a fracture width of 50 microns and a length of 10 cm. The core diameter is 2.5 cm and the matrix permeability is 30 mD to simulate a fractured low-permeability reservoir (fracture width 50 microns). Place the core in a core holder, evacuate the core, saturate it with water, and calculate the core pore volume (PV).

[0106] Carry out water flooding at a constant rate of 0.5 mL / min. When the pressure stabilizes, stop water flooding. Start injecting 1-10 micron double-layer coated particle profile control agent at a constant rate of 0.5 mL / min and an injection volume of 0.5 PV.

[0107] After the double-layer coated particle profile control agent was injected, it was placed in a high temperature (95°C) oven for 12 hours, and then subsequent water flooding was carried out at a constant rate of 0.5 mL / min until the pressure stabilized. The changes in the core inlet pressure during the experiment are shown in Figure 2. Figure 2 shown.

[0108] 3. Prepare a cylindrical core with a fracture width of 100 microns and a length of 10 cm. The core diameter is 2.5 cm and the matrix permeability is 50 mD to simulate a fractured low-permeability reservoir (fracture width 100 microns). Place the core in a core holder, evacuate the core, saturate it with water, and calculate the core pore volume (PV).

[0109] Carry out water flooding at a constant rate of 0.5 mL / min. When the pressure stabilizes, stop water flooding. Start injecting 10-30 micron double-layer coated particle profile control agent at a constant rate of 0.5 mL / min and an injection volume of 0.5 PV.

[0110] After the double-layer coated particle profile control agent was injected, it was placed in a high temperature (95°C) oven for 12 hours, and then subsequent water flooding was carried out at a constant rate of 0.5 mL / min until the pressure stabilized, and the plugging rate was calculated. The changes in the core inlet pressure during the experiment were as follows: Figure 3 shown.

[0111] Depend on Figures 1 to 3It can be seen that double-layer coated particles of different particle sizes have good injection performance and plugging performance. In the first water flooding stage, the injected water escapes along the cracks and the injection pressure is low; after the double-layer coated particles are injected, the pressure rises rapidly, indicating that the micron-sized double-layer coated particles adaptively bond to form particle clusters according to the crack size, blocking the crack channel; in the subsequent water flooding stage, the micron-sized double-layer coated particle profile adjustment system effectively blocks the cracks, forcing the subsequent injected water to enter the low-permeability matrix, significantly expanding the water flooding sweep efficiency. The present invention overcomes the limitation that conventional rigid particle-type adjustment and displacement agents cannot take into account both injectability and plugging properties at the same time.

[0112] Application Example 2

[0113] In this application example, the double-layer coated particle profile control agent prepared in Example 2 was used to conduct a core displacement experiment, and the inlet pressure and outlet liquid production were recorded during the experiment.

[0114] A cylindrical core with a fracture width of 100 μm and a length of 10 cm was prepared. The core had a diameter of 2.5 cm, was placed in a core holder, evacuated, and saturated with oil, and the pore volume (PV) of the core was calculated.

[0115] A water flooding was performed at a constant rate of 0.5 mL / min. When no oil came out of the outlet, the water flooding was stopped. The micron-sized double-layer coated particle profile control agent was injected at a constant rate of 0.5 mL / min and an injection volume of 0.5 PV.

[0116] After injecting the micron-sized double-layer coated particle profile control agent, the mixture was placed in a high-temperature (95°C) oven for 12 hours, and then subsequent water flooding was carried out at a constant rate of 0.5 mL / min until the pressure stabilized and no oil was discharged from the outlet. The pressure and recovery rate curves during the experiment are shown in Figure 2. Figure 4 shown.

[0117] Depend on Figure 4 It can be seen that in the first water drive stage, the injected water escapes quickly along the fracture channel, and the recovery rate of the first water drive is low. After the micron-sized double-layer coated particle profile control agent is injected, the pressure rises rapidly, indicating that the micron-sized double-layer coated particles adaptively bond to form particle clusters according to the fracture size, blocking the fracture channel; in the subsequent water drive stage, since the micron-sized double-layer coated particle profile control system effectively blocks the fracture, the subsequent injected water is forced to enter the low-permeability matrix, the crude oil in the matrix is ​​activated, and the recovery rate increases. After the water forms a fixed seepage channel in the matrix, the water drive pressure gradually flattens, and the recovery rate basically no longer changes. The stability of the plugging section in the fracture is good during the whole process. In summary, the micron-sized double-layer coated particle profile control agent of this embodiment has excellent injection performance and strong blocking effect in low-permeability / ultra-low-permeability oil reservoirs, and has a significant effect on improving the recovery rate.

[0118] Application Example 3

[0119] Microscopic morphology tests were conducted on the 10-30 micron double-layer coated particles in Example 1 and the double-layer coated particles prepared in Example 2 and Example 3. The dispersibility and suspension performance of the double-layer coated particles prepared in Example 3 were evaluated.

[0120] The microscopic appearance of the 10-30 μm double-layer coated particles in Example 1 and the double-layer coated particles prepared in Example 2 and 3 under an optical microscope is as follows: Figure 5 、 Figure 6 and Figure 7 ,Depend on Figures 5 to 7 It can be seen that the double-layer coated particles are evenly dispersed without obvious agglomeration. Figure 8 The scanning electron microscope images of the core (left) and the double-layer coated particles (right) of Example 3 are shown. Figure 8 It can be seen that before coating, the hawthorn seed particles showed a distinct hierarchical structure composed of layers of plant fibers. After coating, the hawthorn seed particles had a smooth surface, indicating that the coating was successful and uniform, with no agglomeration.

[0121] Prepare guar gum suspensions with mass concentrations of 0.1%, 0.2%, 0.3%, 0.4% and 0.5% respectively. That is, prepare 100g of suspension dispersant respectively, of which guar gum is 0.1, 0.2, 0.3, 0.4 and 0.5g respectively, hexadecyltrimethylammonium bromide is 0.3g, and the rest is water. Take 5g of double-layer coated particles and add them to 95g of guar gum suspension dispersant with different mass concentrations, mix them evenly, place them in a test tube, and observe them. Figure 9 .Depend on Figure 9 It can be seen that at the initial moment, the particles are evenly dispersed in the dispersant, with good dispersibility. After standing for 6 hours, the suspension dispersant with a guar gum concentration of 0.1% to 0.4% has poor suspension performance and obvious precipitation. The guar gum concentration of 0.5% has excellent suspension performance and no obvious precipitation. Therefore, the preferred guar gum concentration in the suspension dispersant is 0.5%.

Claims

1. A method for preparing coated particles, characterized in that: include: mixing a thermoplastic resin and an organic solvent to obtain a thermoplastic resin solution; Mixing a water-soluble thermosetting resin, water, and a surfactant to obtain a thermosetting resin dispersion; wherein the mass concentration of the thermoplastic resin is 33.3% and the mass concentration of the water-soluble thermosetting resin is 30%; The thermoplastic resin solution is subjected to a first spray drying treatment on the surface of the core particles to form a first coating layer, thereby obtaining single-layer coated particles; the mass ratio of the thermoplastic resin, the organic solvent, and the core particles is 0.5-1:1-2:0.5-1; The thermosetting resin dispersion is subjected to a second spray drying process on the surface of the single-layer film-coated particles to obtain the film-coated particles; the mass ratio of the thermosetting resin dispersion to the single-layer film-coated particles is 3 to 5:1; The particle size of the core particles is 0.5 to 50 microns.

2. The preparation method according to claim 1, characterized in that The core particles include inorganic core particles and / or biomass core particles.

3. The preparation method according to claim 2, characterized in that The inorganic core particles include metal oxide core particles; the biomass core particles are obtained by ball milling of fruit shell materials.

4. The preparation method according to claim 1, characterized in that The organic solvent includes ethanol and / or acetone.

5. The preparation method according to claim 1, characterized in that The temperature of the spray drying process is 5-20° C. higher than the boiling point of the organic solvent, the feed rate is 20-50 ml / min, and the atomization pressure is 0.2-0.4 MPa.

6. A film-coated particle, characterized in that: The coated particles are prepared according to the method for preparing the coated particles according to any one of claims 1 to 4.

7. A method for preparing a double-layer coated particle profile control agent, characterized in that: include: S1, mixing a thermoplastic resin and an organic solvent to obtain a thermoplastic resin solution; mixing the thermoplastic resin solution with core particles to obtain a first mixed system; wherein the mass ratio of the thermoplastic resin, the organic solvent, and the core particles is 0.5-1:1-2:0.5-1; and the particle size of the core particles is 0.5-50 μm; The first mixed system is subjected to a first spray drying process to form a first coating layer to obtain single-layer coated particles, wherein the thickness of the first coating layer is 300-500 nm; S2, mixing a water-soluble thermosetting resin, water, and a surfactant to obtain a thermosetting resin dispersion, wherein the mass concentration of the thermosetting resin is 30%; The thermosetting resin dispersion and the single-layer coated particles are mixed in a mass ratio of 3 to 5:1 to obtain a second mixed system; the second mixed system is subjected to a second spray drying process to form a second coating layer to obtain double-layer coated particles, wherein the thickness of the second coating layer is 500 to 1000 nm, and the particle size of the double-layer coated particles is 1.5 to 51.5 μm; S3, mixing the double-layer coated particles and a suspending dispersant to obtain the double-layer coated particle profile control agent, wherein the mass concentration of the double-layer coated particles is 0.1-5%.

8. The preparation method according to claim 7, characterized in that The core particles include inorganic core particles and / or biomass core particles.

9. The preparation method according to claim 8, characterized in that The material of the inorganic core particles is selected from silicon dioxide or floating beads.

10. The preparation method according to claim 9, characterized in that The particle size of the silicon dioxide includes: 0.5-1 micron, 1-10 micron, 10-30 micron, or a combination of two or more thereof.

11. The preparation method according to claim 10, characterized in that: The particle size of the floating beads is 30 to 50 microns.

12. The preparation method according to claim 8, characterized in that The biomass core particles are obtained by ball milling fruit shell materials.

13. The preparation method according to claim 12, characterized in that The particle size of the biomass core particles includes 5-10 microns and / or 10-30 microns.

14. The preparation method according to claim 7, characterized in that The temperature of the first spray drying process is 85-95°C; and / or, The temperature of the second spray drying process is 150-200°C.

15. A double-layer coated particle profile control agent, characterized in that: Prepared according to the preparation method according to any one of claims 7 to 14.

16. Use of the double-layer coated particle profile control agent according to claim 15 in profile control of low permeability / ultra-low permeability oil reservoirs.

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