Film-coated particles and preparation method thereof, double-layer film-coated particle profile control agent and preparation method and application of double-layer film-coated particle profile control agent

Abstract

The invention provides coated particles and a preparation method thereof as well as a double-layer coated particle profile control agent as well as a preparation method and application thereof. The method comprises the following steps: mixing a film coating material and an organic solvent to obtain a film coating solution; in the film coating solution, the mass concentration of the film coating material is 30-50%; mixing the coating solution and the core particles according to the mass ratio of (1-3): 1 to obtain a mixed system, and then carrying out spray drying treatment on the mixed system to form coatings on the surfaces of the core particles to obtain the coated particles. The double-layer coated particle profile control agent provided by the invention 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 coated particle and a preparation method thereof, and a double-layer coated particle profile control agent and a preparation method and application thereof. Background Art

[0002] Low-permeability / ultra-low-permeability reservoirs have small pore throats and well-developed natural micro-fractures. The fracture scale is at the micron level and the pore throat scale is at the nanometer level. During water and gas injection development, the injected medium is prone to water and gas channeling along the fracture channel, resulting in low sweep efficiency; the displacement medium cannot effectively enter the nano-scale pore throats to replace crude oil, resulting in low oil washing efficiency. Deep profile control of low-permeability / ultra-low-permeability reservoirs requires profile control agents to have good injectivity, be able to smoothly enter deep formations, and effectively block channeling channels. However, profile control technologies and profile control agents suitable for conventional medium- and high-permeability reservoirs are not well matched with low-permeability / ultra-low-permeability reservoir conditions. Glue profile control agents are difficult to enter deep reservoirs, and contaminate the matrix end face during migration, causing irreversible damage to the reservoir. It is not advisable to completely block the fractures in low-permeability / ultra-low-permeability reservoirs by simply relying on strong glue to completely block the fractures and completely lose their contribution to production capacity. Ordinary granular plugging agents have good injectivity, but the plugging effect is limited by the matching relationship between particle size and fracture size. The coated particles form particle aggregates through self-adhesion, which can adapt to the size of the cracks and effectively block the escape channel. The coated particles themselves have good injectability of particle plugging agents, and also ensure the plugging effect. They have shown great application potential in the field of low permeability / ultra-low permeability reservoir profile control, but the existing technology still has problems that need to be solved.

[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 kernel 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, the fracture size of low-permeability / ultra-low-permeability reservoirs is often several or tens of microns, and the double-layer coated particles of 100 microns prepared by the above method cannot be effectively injected into the deep fractures. Double-layer coated particles with a particle size less than 100 microns have not been reported. Therefore, it is an urgent problem to provide a double-layer coated particle profile control agent with different types of cores of several or tens of microns suitable for low-permeability / ultra-low-permeability reservoirs. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention aims to provide a coated particle and a preparation method thereof and a double-layer coated particle profile control agent and a preparation method and application thereof. 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 coated particles is provided, which comprises:

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

[0008] The coating solution and the core particles are mixed at 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 realized by a spray drying method, which is applicable to a variety of core particles and has good effects. The preparation process of the present invention is simple, the operation 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 silicon dioxide (SiO 2 ), floating beads, calcium carbonate, barium sulfate, or a combination of two or more thereof.

[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] Wherein, 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 fruit 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 more than twice, and two or more layers of coating are sequentially formed on the surface of the core particles. By performing the spray drying process multiple times, different coating materials can be coated on the core particles in an orderly manner to form a composite material with a multi-layer core-shell structure. The composite material can be adapted to a variety of applications according to 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 temperature of the spray drying process is 5 to 20°C higher than the boiling point of the organic solvent, the feed rate is 20 to 50 ml / min, and the atomization pressure is 0.2 to 0.4 MPa. If the feed rate is too fast, the organic solvent will not have time to completely evaporate, and the particles will easily stick together; if the feed rate is slow, time and energy consumption will increase.

[0020] When spray drying coating is performed more than twice, 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 and 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 to 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 inner cores of the present invention has a simple preparation process and low operating cost, and can efficiently prepare double-layer coated particles with inner cores of several or tens of microns in size. The double-layer coated particles have excellent injection performance and plugging performance in low permeability / ultra-low permeability oil reservoirs, plug the escape channel, improve the sweep efficiency of subsequent displacement media, and thus improve the recovery rate of low permeability / ultra-low permeability oil reservoirs.

[0029] The present invention first obtains several or tens of micron core particles, disperses the core particles in a thermoplastic resin solution, stirs evenly, and then spray-dries and granulates to obtain particles with a single layer of film. The wet particles produced by the spraying 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, so that after 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 into a mass to seal the 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-level double-layer coated particles with both an adhesive film and a rigid protective film. The thermosetting resin aqueous solution is coated on the surface of the particles, and the wet particles are dried instantly at high temperature to form a layer of thermosetting resin film on the surface of the particles. At the same time, in a high temperature environment, the thermosetting resin film is cured, that is, a rigid protective shell is formed on the surface of the particle adhesive film, thereby obtaining micron-level 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 in the thermosetting resin aqueous solution again and spray-dried or the process parameters can be adjusted repeatedly to improve the coating integrity and thickness of the rigid protective shell on the surface of the particles, so as to meet the deep profile control needs of low permeability / ultra-low permeability 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 silicon dioxide or floating beads.

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

[0033] The silica core material has better compression 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 husk material is ground and crushed using a planetary ball mill to give the particles a certain degree of 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 inner 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 carried out 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 thermosetting phenolic resin and / or epoxy resin. More preferably, the water-soluble thermosetting resin comprises thermosetting phenolic resin.

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

[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, hexadecyltrimethylammonium bromide and water; wherein, preferably, the mass concentration of the guar gum is 0.5-3%; preferably, the mass concentration of the hexadecyltrimethylammonium 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 inner 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 outer 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 a micron-sized inner core 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, softens and becomes sticky at the temperature of the reservoir, and adhesion occurs between the particles. According to the size of the cracks, adaptive bonding is performed to form particle clusters of corresponding sizes, which effectively seal the cracks. Due to the mutual bonding 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 inner 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 injection pressure variation of the 0.5-1 micron double-layer coated particles in Application Example 1 during the test is shown.

[0054] Figure 2 The injection pressure variation of the 1-10 micron double-layer coated particles in Application Example 1 during the test is shown.

[0055] Figure 3 The injection pressure variation of the 10-30 micron double-layer coated particles in Application Example 1 during the test is shown.

[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 microscope images of the core (left) and the double-layer coated particles (right) in Example 3 are shown.

[0061] Fig. 9 The dispersibility and suspension performance 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, purposes 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 construed as limiting the applicable scope of the present invention.

[0063] Embodiment 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 to 1 μm, 1 to 10 μm, and 10 to 30 μm were selected respectively as the core particles of double-layer coated particles with 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, and then 150 g of silica microspheres were added and fully stirred to obtain three first mixed systems respectively;

[0069] The three first mixed systems are 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 the surface;

[0070] 60 g of water-soluble thermosetting phenolic resin was dissolved in 130 g of water to form a thermosetting phenolic resin solution, and 10 g of hexadecyltrimethylammonium bromide was added and stirred evenly; 60 g of single-layer coated particles were added respectively and stirred sufficiently to make the particles evenly dispersed in the solution to obtain three second mixed systems respectively; the feed rate in 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 taken respectively, and spray-dried and granulated at 200° C. using a spray dryer, and the water-soluble thermosetting phenolic resin was cured on the surface of the particle adhesive film to form a rigid shell, thereby obtaining three different double-layer coated particles; the feed rate in 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] Take 0.5g of guar gum and dissolve it in 99.2g of water, add 0.3g of hexadecyltrimethylammonium bromide to obtain a suspension dispersant;

[0074] 5 g of double-layer coated particles were added to 95 g 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 to 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 and dissolve thoroughly to obtain a thermoplastic phenolic resin solution, then add 20g of floating beads, stir thoroughly to obtain a first mixed system;

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

[0082] 60 g of 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; 20 g of single-layer coated particles were added, and the mixture was stirred sufficiently to make the particles evenly dispersed in the solution to obtain a second mixed system;

[0083] 220 g of the second mixed system was taken and spray-dried and granulated at 200° C. using a spray dryer. The water-soluble thermosetting phenolic resin was cured on the surface of the particle adhesive film to form a rigid shell, thereby obtaining double-layer coated particles. The feed rate in the spray drying process was 20 ml / min and the atomization pressure was 0.2 MPa.

[0084] 3. Preparation of micron-sized double-layer coated particle profile control agent:

[0085] Take 0.5g of guar gum and dissolve it in 99.2g of water, add 0.3g of hexadecyltrimethylammonium bromide to obtain a suspension dispersant;

[0086] 5 g of double-layer coated particles were added into 95 g of suspending dispersant and mixed evenly to obtain a double-layer coated particle profile control agent.

[0087] Example 3

[0088] This embodiment provides a method for preparing a double-layer coated particle profile control agent, which specifically includes:

[0089] 1. Preparation of core particles:

[0090] 1000g of hawthorn seed and other shell materials were taken, dried, and preliminarily crushed, and the crushed hawthorn seed particles were further ground using a planetary ball mill to make the particles have a certain sphericity, and sieved to obtain 150g of kernel particles with a particle size of 10 to 30 microns;

[0091] 2. Preparation of micron-sized double-layer coated particles:

[0092] Take 300g of anhydrous ethanol, add 150g of thermoplastic phenolic resin powder, stir and dissolve thoroughly to obtain a thermoplastic phenolic resin solution, add 150g of hawthorn seed particles respectively, stir thoroughly to obtain a first mixed system;

[0093] The first mixed system is spray dried at 85° C. in a closed organic solvent spray dryer to obtain single-layer coated particles with a thermoplastic phenolic resin film on the surface; the feed rate in the spray drying process is 20 ml / min, and the atomization pressure is 0.2 MPa;

[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 the mixture was stirred sufficiently to make the particles evenly dispersed in the solution to obtain a second mixed system;

[0095] 250 g of the second mixed system was taken and spray-dried and granulated at 200° C. using a spray dryer. The water-soluble thermosetting phenolic resin was cured on the surface of the particle adhesive film to form a rigid shell, thereby obtaining double-layer coated particles. The feed rate in 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] Take 0.5g of guar gum and dissolve it in 99.2g of water, add 0.3g of hexadecyltrimethylammonium bromide to obtain a suspension dispersant;

[0098] 5 g of double-layer coated particles were added into 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] According to the fracture size range of low permeability reservoirs, double-layer coated particles of different particle sizes are selected. For fracture widths of 1 to 10 microns, 0.5 to 1 micron double-layer coated particles are selected; for fracture widths of 10 to 50 microns, 10 to 30 micron double-layer coated particles are selected; for fracture widths of 50 to 100 microns, 30 to 50 micron double-layer coated particles are selected. Double-layer coated particles smaller than the fracture size ensure the injectability of the particle profile control agent, which can migrate to the deep fractures. Subsequently, according to the fracture size, the particle clusters are formed by adaptive bonding to plug the fractures and realize the deep profile control function.

[0102] 1. Prepare a cylindrical core with a crack 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 (crack width 10 microns). Place the core in a core holder, evacuate it, saturate it with water, and calculate the core pore volume (PV);

[0103] Carry out water flooding at a constant rate of 0.5mL / 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 0.5mL / min and an injection volume of 0.5PV.

[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 are shown in Figure 2. 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 it, saturate it with water, and calculate the core pore volume (PV);

[0106] Carry out water flooding at a constant rate of 0.5mL / 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 0.5mL / min and an injection volume of 0.5PV.

[0107] After the double-layer coated particle profile control agent was injected, it was placed in a high temperature (95°C) oven for 12 h, 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 it, saturate it with water, and calculate the core pore volume (PV);

[0109] Carry out water flooding at a constant rate of 0.5mL / 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 0.5mL / min and an injection volume of 0.5PV.

[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 are shown in Figure 2. 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 drive stage, the injected water escapes along the cracks and the injection pressure is relatively 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, plugging the crack channel; in the subsequent water drive stage, the micron-sized double-layer coated particle profile control system effectively blocks the cracks, forcing the subsequent injected water to enter the low-permeability matrix, significantly expanding the water drive sweep efficiency. The present invention overcomes the limitation that conventional rigid particle-type profile control agents cannot take into account both injectability and plugging properties at the same time.

[0112] Application Example 2

[0113] This application example uses the double-layer coated particle profile control agent prepared in Example 2 to carry out a core displacement experiment, and the inlet pressure and outlet liquid production are 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 diameter was 2.5 cm, placed in a core holder, evacuated, saturated with oil, and the core pore volume (PV) was calculated;

[0115] A water drive was performed at a constant rate of 0.5 mL / min. When no oil came out of the outlet, the water drive 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, 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 was stable and no oil was produced at the outlet. The pressure and recovery factor 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 are adaptively bonded to form particle clusters according to the fracture size, blocking the fracture channel; in the subsequent water drive stage, the micron-sized double-layer coated particle profile control system effectively blocks the fracture, forcing the subsequent injected water to enter the low-permeability matrix, the crude oil in the matrix is ​​activated, and the recovery rate increases. When 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 plugging effect in low-permeability / ultra-low-permeability oil reservoirs, and the effect of improving the recovery rate is significant.

[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 morphologies 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 are 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 the hawthorn seed particles have a clear hierarchical structure before coating, which is composed of layers of plant fibers. After coating, the surface of the hawthorn seed particles is smooth, indicating that the coating is successful and uniform without 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 test tubes, and observe them. Fig. 9 .Depend on Fig. 9 It can be seen that at the initial moment, the particles are evenly dispersed in the dispersant, and the dispersibility is good; 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, while the suspension performance with a guar gum concentration of 0.5% is excellent, and there is no obvious precipitation. Therefore, the guar gum concentration in the suspension dispersant is preferably 0.5%.

Claims

1. A method for preparing coated particles, characterized in that: include: Mixing a coating material and an organic solvent to obtain a coating solution; in the coating solution, the mass concentration of the coating material is 30 to 50%; The coating solution and the core particles are mixed at a mass ratio of 1 to 3:1 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.

2. The preparation method according to claim 1, characterized in that: The particle size of the core particles is 0.5 to 50 microns; and / or, The core particles include inorganic core particles and / or biomass core particles; Preferably, the inorganic core particles include metal oxide core particles; the biomass core particles are obtained by ball milling of fruit shell materials; and / or, The coating material includes one or a combination of two or more of a thermoplastic resin and a thermosetting resin; and / or, The organic solvent includes ethanol and / or acetone.

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

4. The preparation method according to claim 1, characterized in that: The spray drying process is performed more than twice to sequentially form two or more layers of coating on the surface of the core particles.

5. A 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.

6. 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 and 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 to 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 10 to 20%; 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 layer of coating to obtain double-layer coated particles, wherein the thickness of the second layer of coating 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%.

7. The preparation method according to claim 6, characterized in that: The core particles include inorganic core particles and / or biomass core particles; Preferably, the material of the inorganic core particles is selected from silicon dioxide or floating beads; preferably, the particle size of the silicon dioxide includes: 0.5-1 micron, 1-10 microns, 10-30 microns or a combination of two or more; preferably, the particle size of the floating beads is 30-50 microns; and / or, The biomass core particles are obtained by ball milling of fruit shell materials; preferably, the particle size of the biomass core particles includes 5 to 10 microns and / or 10 to 30 microns.

8. The preparation method according to claim 6, 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.

9. A double-layer coated particle profile control agent, characterized in that: Prepared according to the preparation method described in any one of claims 6 to 8.

10. Use of the double-layer coated particle profile control agent according to claim 9 in profile control of low permeability / ultra-low permeability oil reservoirs.

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