A temperature-sensitive self-fusion blocking agent, a preparation method and application thereof

Abstract

The application belongs to the technical field of water drive reservoir development, and particularly relates to a temperature-sensitive self-fusion plugging agent and a preparation method and application thereof. The temperature-sensitive self-fusion plugging agent comprises temperature-sensitive organic particles and inorganic particles; the volume ratio of the temperature-sensitive organic particles and the inorganic particles is 5-30:70-95; and the inorganic particles are silicon-containing mineral particles. The temperature-sensitive self-fusion plugging agent has excellent temperature resistance, salt resistance and shear resistance, and high plugging strength, so that the plugging rate is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water drive reservoir development, and particularly relates to a temperature-sensitive self-fusion plugging agent and a preparation method and application thereof. BACKGROUND

[0002] Water drive reservoir development has entered a "double high" development stage. Long-term water injection scouring causes reservoir rock structure damage and formation of dominant channels, ultimately leading to inefficient and ineffective circulation of injected water. Therefore, it is necessary to use a plugging agent to plug the damaged structure of the reservoir rock and the formed dominant channels. Existing plugging agents include polymer solutions, gel-type plugging agents and particle-type plugging agents. Among them, the existing polymer solutions and gel-type plugging agents not only have low plugging strength, but also have poor temperature resistance, salt resistance and shear resistance, which cannot meet the technical requirements of plugging dominant channels in high-temperature and high-salt reservoirs.

[0003] The most widely used is the particle-type plugging agent, but it is easy to migrate or even be produced after entering the dominant channel, and the plugging effect is poor. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a temperature-sensitive self-fusion plugging agent and a preparation method and application thereof, which has excellent temperature resistance, salt resistance and shear resistance, and high plugging strength, thereby improving the plugging rate.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] The present application provides a temperature-sensitive self-fusion plugging agent, which comprises temperature-sensitive organic particles and inorganic particles; the volume ratio of the temperature-sensitive organic particles and the inorganic particles is 5-30:70-95; and the inorganic particles are silicon-containing mineral particles.

[0007] Preferably, the temperature-sensitive organic particles comprise polyvinyl chloride particles and / or asphalt particles.

[0008] Preferably, the particle size of the temperature-sensitive organic particles is 20-300 mesh; and the particle size of the inorganic particles is 20-200 mesh.

[0009] Preferably, the silicon-containing mineral particles comprise one or more of quartz sand, fly ash and modified fly ash.

[0010] Preferably, the temperature-sensitive self-fusion plugging agent comprises a deep well section plugging agent, an intermediate section plugging agent or a near well section plugging agent; the volume ratio of the temperature-sensitive organic particles and the inorganic particles in the deep well section plugging agent is 5-10:90-95; the volume ratio of the temperature-sensitive organic particles and the inorganic particles in the intermediate section plugging agent is 15-20:80-85; and the volume ratio of the temperature-sensitive organic particles and the inorganic particles in the near well section plugging agent is 20-30:70-80.

[0011] The application provides a preparation method of the temperature-sensitive self-fusion plugging agent.

[0012] The temperature-sensitive organic particles and the inorganic particles are mixed to obtain the temperature-sensitive self-fusion plugging agent.

[0013] The application provides an application of the temperature-sensitive self-fusion plugging agent or the temperature-sensitive self-fusion plugging agent prepared by the preparation method in reservoir plugging.

[0014] The application provides a plugging mixed solution, which comprises a plugging agent and a carrying liquid.

[0015] Preferably, the carrying liquid comprises a thickening agent and water; the thickening agent is polyacrylamide; the hydrolysis degree of the thickening agent in the carrying liquid is 20-30%; the mass concentration of the thickening agent in the carrying liquid is 0.05-0.2%; and the mass ratio of the plugging agent to the carrying liquid is 20-40:60-80.

[0016] The application provides a reservoir plugging method, which comprises the following steps.

[0017] The plugging mixed solution is injected into a reservoir to be plugged for plugging.

[0018] The plugging mixed solution is the plugging mixed solution in the above technical solution.

[0019] The application provides a temperature-sensitive self-fusion plugging agent, which comprises temperature-sensitive organic particles and inorganic particles; the volume ratio of the temperature-sensitive organic particles to the inorganic particles is 5-30:70-95; and the inorganic particles are silicon-containing mineral particles. The temperature-sensitive self-fusion plugging agent provided by the application is a mixture of temperature-sensitive organic particles and inorganic particles, which can be deformed or even form adhesion between the temperature-sensitive organic particles and the inorganic particles when the temperature exceeds the softening point of the temperature-sensitive organic particles after entering the reservoir dominant channel, so that the inorganic particles are difficult to migrate, and the adhesion and bridging between the particles can greatly improve the plugging effect. The inorganic particles have high strength and can improve the plugging strength. Moreover, the temperature-resistant and salt-resistant and shear-resistant properties of the temperature-sensitive organic particles and the inorganic particles are excellent. Since the temperature-sensitive organic particles and the inorganic particles are insoluble in water and have poor fluidity, the interaction between the temperature-sensitive organic particles and the inorganic particles and the ions in the aqueous solution and the porous medium is small, the deformation ability is weak, and the temperature-sensitive organic particles and the inorganic particles are not easily affected by the solvent water salinity and the shear effect. Moreover, since the temperature-sensitive organic particles have high bond energy, the temperature-sensitive organic particles can be degraded only at 150-200 DEG C. Therefore, the temperature-sensitive self-fusion plugging agent provided by the application is especially suitable for high-temperature (more than 90 DEG C) and high-salt oil and gas reservoirs, in which polymer solution and gel plugging agents cannot work.

[0020] In addition, both quartz sand and fly ash are inexpensive inorganic particles, so that the temperature-sensitive self-fusion plugging agent is low in cost and good in technical and economic effect. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Figure for the mixture of quartz sand and polyvinyl chloride (PVC) particles in the examples;

[0022] Figure 2 Figure for the sand-filled pipe;

[0023] Figure 3 Figure for the schematic diagram of the experimental equipment for permeability test;

[0024] Figure 4 Figure for the relationship between the liquid production rate and time of the sand-filled pipe with quartz sand of different particle sizes before heating;

[0025] Figure 5 Figure for the relationship between the liquid production rate and time of the sand-filled pipe with quartz sand of different particle sizes after heating;

[0026] Figure 6 Figure for the relationship between the liquid production rate and time of the sand-filled pipe with PVC particles of different contents before heating;

[0027] Figure 7 Figure for the relationship between the liquid production rate and time of the sand-filled pipe with PVC particles of different contents after heating;

[0028] Figure 8 Figure for the relationship between the liquid production rate and time of the sand-filled pipe before heating at different temperatures;

[0029] Figure 9 Figure for the relationship between the liquid production rate and time of the sand-filled pipe after heating at different temperatures;

[0030] Figure 10 Figure for the relationship between the liquid production rate and time of the sand-filled pipe at different heating times. DETAILED DESCRIPTION

[0031] The temperature-sensitive self-fusion plugging agent provided by the present application comprises temperature-sensitive organic particles and inorganic particles.

[0032] Unless otherwise specified, the present application does not have special requirements for the source of the raw materials used, and commercially available goods known to those skilled in the art can be used.

[0033] The temperature-sensitive self-fusion plugging agent provided by the present application comprises temperature-sensitive organic particles.

[0034] As an embodiment, the temperature-sensitive organic particles comprise polyvinyl chloride particles and / or asphalt particles, and in particular embodiments, polyvinyl chloride particles or asphalt particles; the polyvinyl chloride particles have a weight average molecular weight of 800-1000, and in particular embodiments, 800-900.

[0035] As an embodiment, the polyvinyl chloride particles have a softening point of 75℃ and a strength of 10-20 MPa, and in particular embodiments, 15-20 MPa; the asphalt particles have a softening point of 80℃ and a strength of 10-20 MPa, and in particular embodiments, 15-20 MPa.

[0036] As an embodiment, the temperature-sensitive organic particles have a particle size of 20-300 mesh, and in particular embodiments, 100-200 mesh; the temperature-sensitive organic particles have a bulk density of 0.5-0.8 g / cm 3 , and in particular embodiments, 0.6-0.8 g / cm 3 .

[0037] The temperature-sensitive self-fusion plugging agent provided by the present application comprises inorganic particles.

[0038] As an embodiment, the inorganic particles are silicon-containing mineral particles; the silicon-containing mineral particles comprise one or more of quartz sand, fly ash and modified fly ash, and in particular embodiments, quartz sand or fly ash; the inorganic particles have a strength of 15-25 MPa, and in particular embodiments, 16-20 MPa.

[0039] As an embodiment, the preparation method of the modified fly ash comprises the following steps:

[0040] The fly ash and the alkaline solution are mixed to perform a crystallization reaction, and the obtained product is subjected to solid-liquid separation, and then the obtained solid is sequentially subjected to drying and crushing to obtain the modified fly ash.

[0041] As an embodiment, the alkaline solution is a sodium hydroxide solution; the concentration of the sodium hydroxide solution is 1.0-2.0 mol / L, and in a specific embodiment, 1.2-1.6 mol / L; the mass ratio of the fly ash and the alkaline solution is 2-3:1-2, and in a specific embodiment, 3:1; the temperature of the crystallization reaction is 80-150°C, and in a specific embodiment, 90°C; the time of the crystallization reaction is 30-270 min, and in a specific embodiment, 60-120 min; the equipment used for the crystallization reaction is a high-pressure reaction kettle; the pressure in the high-pressure reaction kettle is 2-40 MPa, and in a specific embodiment, 2-10 MPa; the solid-liquid separation is negative pressure filtration separation; the temperature of the drying is 60-100°C, and in a specific embodiment, 70-80°C; the time of the drying is 5-32 h, and in a specific embodiment, 12-24 h; the pulverization is grinding; the pulverization is to a particle size of 10-500 μm, and in a specific embodiment, 20-127 μm.

[0042] As an embodiment, the particle size of the inorganic particles is 20-200 mesh, and in a specific embodiment, 20-70 mesh; the bulk density of the inorganic particles is 0.5-2.7 g / cm 3 , and in a specific embodiment, 1-2.5 g / cm 3 .

[0043] As an embodiment, the volume ratio of the temperature-sensitive organic particles and the inorganic particles is 5-30:70-95, and in a specific embodiment, 10-25:75-90.

[0044] As an embodiment, the temperature-sensitive self-fusion plugging agent includes a plugging agent for a deep well section, a plugging agent for an intermediate section, or a plugging agent for a near well section; the volume ratio of the temperature-sensitive organic particles and the inorganic particles in the plugging agent for the deep well section is 5-10:90-95; the volume ratio of the temperature-sensitive organic particles and the inorganic particles in the plugging agent for the intermediate section is 15-20:80-85; the volume ratio of the temperature-sensitive organic particles and the inorganic particles in the plugging agent for the near well section is 20-30:70-80.

[0045] The present application uses a mixture of temperature-sensitive organic particles and inorganic particles as a plugging agent. Once the temperature exceeds the softening point of the temperature-sensitive organic particles after the mixture enters a dominant channel of a reservoir, the temperature-sensitive organic particles soften and deform, and even form adhesion between the inorganic particles, which makes the inorganic particles difficult to migrate, and the adhesion and bridging between the particles greatly enhances the plugging effect. The high strength of the inorganic particles can improve the plugging strength. Moreover, the temperature-resistant, salt-resistant, and shear-resistant properties of the temperature-sensitive organic particles and the inorganic particles in the present application are excellent, and thus the present application is particularly suitable for use in high-temperature (more than 90°C) and high-salt oil and gas reservoirs where polymer solutions and gel plugging agents cannot function.

[0046] In addition, the quartz sand or fly ash is a cheap inorganic particle, so that the temperature-sensitive self-fusion plugging agent is low in cost and good in technical and economic effect.

[0047] The application further provides a preparation method of the temperature-sensitive self-fusion plugging agent.

[0048] The temperature-sensitive organic particle and the inorganic particle are mixed to obtain the temperature-sensitive self-fusion plugging agent.

[0049] The mixing process is not specially limited in the application, and the materials can be uniformly mixed.

[0050] The application further provides an application of the temperature-sensitive self-fusion plugging agent in reservoir plugging.

[0051] The application further provides a plugging mixed solution, which comprises a plugging agent and a carrying liquid.

[0052] As an embodiment, the carrying liquid comprises a thickening agent and water; the thickening agent is polyacrylamide with a salt-resistant or temperature-resistant functional group; and the salt-resistant or temperature-resistant functional group is a sulfonic acid group or a benzene ring. The sulfonic acid group or the benzene ring group can increase the steric hindrance of the molecule and has good temperature-resistant and salt-resistant properties.

[0053] As an embodiment, the hydrolysis degree of the thickening agent in the carrying liquid is 20-30%, and specifically 22-25%; the mass concentration of the thickening agent in the carrying liquid is 0.05-0.2%, and specifically 0.1-0.15%; the relative molecular mass of the thickening agent is 12-25 million, and specifically 12-20 million; the water is oilfield injection water, and the total mineralization degree of the oilfield injection water is 700 mg / L-28*10 4 mg / L, and specifically 1000-10176.6 mg / L, wherein the total content of Ca 2+ and Mg 2+ is 40 mg / L-5000*10 4 mg / L, and specifically 500-887.4 mg / L.

[0054] As an embodiment, the mass ratio of the plugging agent to the carrying liquid is 20-40:60-80, and specifically 25-30:70-75.

[0055] The present application can make the temperature-sensitive organic particles and inorganic particles in the temperature-sensitive self-fusion plugging agent suspended in the carrying liquid by adjusting the viscosity of the carrying liquid through the thickening agent, and facilitate injection into the reservoir to be plugged.

[0056] The present application also provides a reservoir plugging method, comprising the following steps:

[0057] injecting the plugging mixture into the reservoir to be plugged;

[0058] The plugging mixture is the plugging mixture described in the above technical solution.

[0059] As an embodiment, the temperature of the reservoir to be plugged is 65-120 DEG C, and in a specific embodiment, 80-95 DEG C.

[0060] When the temperature of the reservoir to be plugged is lower than the softening point of the temperature-sensitive organic particles in the temperature-sensitive self-fusion plugging agent, the method further comprises heating the plugging mixture injected into the reservoir to be plugged by an electric heating device.

[0061] The general reservoir temperature is between 65-120 DEG C, if the reservoir temperature is lower, the softening temperature cannot be reached, and the electric heating device can be turned off after injection to promote crosslinking between the particles.

[0062] According to the permeability and the size of the distribution area of the reservoir to be plugged, the plugging agent is composed of multiple plugging agents with different compositions.

[0063] As an embodiment, the volume of the plugging agent for the deep well section accounts for 60-70% of the total pore volume in the reservoir to be plugged; the volume of the plugging agent for the middle section accounts for 15-25% of the total pore volume in the reservoir to be plugged; and the volume of the plugging agent for the near well section accounts for 10-15% of the total pore volume in the reservoir to be plugged.

[0064] The reservoir average porosity x the reservoir volume requiring profile control = the plugging agent injection amount, and the total injection amount can be divided into multiple slugs and injected in multiple rounds. The plugging agent for the deep well section is mainly used for plugging into the deep part of the reservoir, the plugging agent for the middle section is mainly used for plugging the middle part of the reservoir, and the plugging agent for the near well section is mainly used for plugging the large channels in the near well zone. This part of the area is mainly radial flow and has strong permeability, so it is necessary to adjust the ratio of the temperature-sensitive organic particles and the inorganic particles to improve the plugging strength of the plugging slug. When the content of the temperature-sensitive organic particles is large, the crosslinking degree is high, and the plugging strength is large. Conversely, the plugging strength is small.

[0065] Part of oilfield injection water salinity is as high as 30000 mg / L, and the reservoir temperature is higher than 120 DEG C, under normal circumstances, the temperature resistance effect of polymer water shutoff agent is poor, and it is easy to degrade at 90 DEG C, therefore, it is not suitable for the water shutoff operation of high temperature and high salt reservoir, and the temperature resistance and salt resistance and shear resistance of the temperature sensitive organic particle and inorganic particle in the application are excellent, because the C-Cl bond exists in the PVC particle, the bond energy is high, therefore, it will degrade at 150-200 DEG C, therefore, the temperature sensitive self-fusion plugging agent provided in the application is especially suitable for the water shutoff of high temperature (more than 90 DEG C) and high salt oil and gas reservoirs where polymer solution and gel cannot work.

[0066] The technical solutions in the application will be described clearly and completely in combination with the embodiments in the application, but they cannot be understood as the limitation on the protection scope of the application.

[0067] Example 1

[0068] 20 mesh quartz sand (the bulk density is 2.5 g / cm 3 , and the strength is 20 MPa) and 200 mesh polyvinyl chloride (PVC) particles (the weight average molecular weight is 800, the bulk density is 0.8 g / cm 3 , the softening point is 75 DEG C, and the strength is 20 MPa) are mixed in a volume ratio of 7:3 to obtain the temperature sensitive self-fusion plugging agent.

[0069] Example 2

[0070] The difference from example 1 is that the 20 mesh quartz sand is replaced by 70 mesh quartz sand.

[0071] Example 3

[0072] The difference from example 1 is that the 20 mesh quartz sand is replaced by mixed sand, and the mixed sand comprises 50% of 20 mesh quartz sand and 50% of 70 mesh quartz sand in volume percentage.

[0073] Example 4

[0074] The difference from example 1 is that the volume ratio of the quartz sand and the PVC particles is 8:2.

[0075] Example 5

[0076] The difference from example 1 is that the volume ratio of the quartz sand and the PVC particles is 9:1.

[0077] Comparative example 1

[0078] The difference from example 1 is that the 20 mesh quartz sand is replaced by 10 mesh quartz sand.

[0079] Comparative example 2

[0080] The difference from Example 1 is that the volume ratio of quartz sand and PVC particles is 97:3.

[0081] Application Example 1

[0082] The temperature-sensitive self-fusion plugging agent of Example 1 is carried into a reservoir to be plugged at a temperature of 95°C by a carrying fluid, the mass ratio of the plugging agent to the carrying fluid is 3:7, the polymer in the carrying fluid is polyacrylamide, the degree of hydrolysis of the polymer in the carrying fluid is 25%, the mass concentration of the polymer in the carrying fluid is 0.1%, the relative molecular mass of the polymer is 12 million, the water is oilfield injection water, the total mineralization of the oilfield injection water is 10176.6 mg / L, wherein the total content of Ca 2+ and Mg 2+ is 887.4 mg / L.

[0083] Application Examples 2-5 and Comparative Application Examples 1-2

[0084] The difference from Example 1 is that the temperature-sensitive self-fusion plugging agent of Example 1 is respectively replaced by the temperature-sensitive self-fusion plugging agents of Examples 2-5 and the plugging agents of Comparative Examples 1-2.

[0085] Performance Test

[0086] 1 Experimental Conditions

[0087] 1.1 Experimental Materials

[0088] 1) Water

[0089] The experimental water is oilfield simulated injection water, and the simulated water mineral composition ingredients are shown in Table 1.

[0090] Table 1 Simulated water mineral composition ingredients (mg / L)

[0091]

[0092] 2) Filling Material

[0093] The experimental filling material is quartz sand particles (20-70 mesh) and polyvinyl chloride (PVC) particles (100-200 mesh), and the photograph of the mixture of the two particles is shown in Figure 1 .

[0094] 3) Sand Filling Pipe

[0095] The stainless steel sand filling pipe has the following dimensions: Diameter x L length = 2.5 cm x 30 cm.

[0096] 1.2 Experimental Equipment and Process

[0097] The experimental device includes 1. gas cylinder, 2. valve, 3. pressure reducing valve, 4. valve, 5. intermediate container, 6. valve, 7. precision pressure gauge, 8. valve, 9. pressure gauge, 10. visual sand filling pipe, 11. incubator, 12. produced liquid collector, the sand filling pipe is seen in Figure 2 , the permeability test experimental equipment is seen Figure 3 .

[0098] (1) Sand filling pipe production

[0099] 1) Select the inner diameter of the ordinary stainless steel pipe, process it into a short connection with a length L = 30 cm, process the threads on both ends of the stainless steel pipe, and process the threaded end cap at the same time to form a sand filling pipe.

[0100] 2) Because oil stains will affect the adhesion of epoxy resin on the surface of the steel pipe, the sand filling pipe is soaked in dilute hydrochloric acid to clean the dirt on the inner wall of the pipe, and then washed with clean water and dried. In order to prevent the quartz sand in the sand filling pipe from sliding as a whole, the inner wall of the sand filling pipe is coated with epoxy resin, the quartz sand (40-300 mesh) fills the sand filling pipe, and it is placed in an 80°C incubator for 24 hours to promote the quartz sand to solidify and adhere to the epoxy resin on the inner wall of the pipe. The inner wall of the sand filling pipe has a high roughness, and the excess quartz sand in the sand filling pipe is removed and ready for use.

[0101] (2) Preparation of temperature-sensitive self-fusion plugging agent

[0102] 1) Fill the sand filling pipe with quartz sand, and estimate the required mixture volume.

[0103] 2) According to the design ratio of "temperature-sensitive organic particles: inorganic particles", measure the temperature-sensitive organic particles and inorganic particles respectively, and mix and stir them uniformly for use.

[0104] (3) Preparation of carrying liquid and "carrying liquid + temperature-sensitive self-fusion plugging agent" system

[0105] 1) Use the target reservoir injection water to prepare a polymer solution,

[0106] 2) Mix according to the mass ratio of carrying liquid to temperature-sensitive self-fusion plugging agent 70:30, stir uniformly to obtain a mixed solution, and wait for use.

[0107] 3) The sand filling pipe is placed vertically, the upper end cap is removed, the bottom end cap (a 300 mesh metal filter screen is pre-installed in the end cap to prevent particle migration in the sand filling pipe) is connected and the gate on the end cap is opened; the mixed solution is slowly poured from the upper part of the sand filling pipe, the carrying liquid is discharged through the lower gate, the solid particles are retained in the pipe, and the sand filling pipe is ready for use.

[0108] (4) Evaluation of plugging effect of plugging agent

[0109] 1) Put the sandpack into the incubator and connect to the displacement experiment system, inject water into the sandpack at room temperature and "constant pressure δP(0.1 MPa)", until the liquid production rate is stable, record the liquid production rate Q o .

[0110] 2) Incubate the sandpack to 70-95℃, inject water into the sandpack at "constant pressure δP(0.1 MPa)" after a predetermined time (12-72h), until the liquid production rate is stable, record the liquid production rate Q i .

[0111] 3) Calculation of plugging rate

[0112] Initial water permeability K o and K i after plugging

[0113] K o = (Q o μ o L) / (AδP) (1)

[0114] K i = (Q i μ i L) / (AδP) (2)

[0115] Wherein, Q o — initial liquid production rate, cm 3 / s;

[0116] Q i — liquid production rate after solid-liquid-solid fusion, cm 3 / s;

[0117] μ o — water viscosity at room temperature, mPa·s;

[0118] μ i — water viscosity at experimental temperature, mPa·s;

[0119] L— length of sandpack, cm.

[0120] By testing the water phase permeability before and after plugging the sandpack, the plugging rate ε is calculated:

[0121]

[0122] Wherein, K0— permeability before plugging the sandpack, ×10 -3 μm 2 ;

[0123] K i — permeability after plugging the sandpack, ×10 -3 μm 2 ;

[0124] ε—sealing efficiency, dimensionless.

[0125] 2.2 Scheme design

[0126] 2.1 Effect of quartz sand particle size on sealing effect

[0127] Quartz sand mesh number: 20 mesh, 70 mesh and mixed sand (50% by volume of 20 mesh quartz sand + 50% by volume of 70 mesh quartz sand);

[0128] Quartz sand and PVC particle mixing volume ratio: 7:3;

[0129] Ambient temperature: 95℃;

[0130] Heating time: 24h;

[0131] Evaluation index: permeability.

[0132] 2.2 Effect of PVC particle content on sealing effect

[0133] Quartz sand mesh number: 20 mesh;

[0134] Quartz sand and PVC particle mixing volume ratio: 7:3, 8:2 and 9:1;

[0135] Ambient temperature: 95℃;

[0136] Heating time: 24h;

[0137] Evaluation index: permeability.

[0138] 2.3 Effect of ambient temperature on sealing effect

[0139] Quartz sand mesh number: 20 mesh;

[0140] Quartz sand and PVC particle mixing volume ratio: 7:3;

[0141] Ambient temperature: 95℃, 85℃ and 75℃;

[0142] Heating time: 24h;

[0143] Evaluation index: permeability.

[0144] 2.4 Effect of heating time on sealing effect

[0145] Quartz sand mesh number: 20 mesh;

[0146] Quartz sand and PVC particle mixing volume ratio: 7:3;

[0147] Ambient temperature: 95℃;

[0148] Heating time: 24h, 48h and 72h;

[0149] Evaluation index: permeability.

[0150] 3 Result analysis

[0151] 3.1 Influence of quartz sand particle size on plugging effect

[0152] The 20 mesh, 70 mesh quartz sand and mixed sand (50% of 20 mesh quartz sand by volume + 50% of 70 mesh quartz sand by volume) were mixed with 200 mesh PVC particles (volume ratio = 7:3), and the mixture was filled into the sandpack, and the water side permeability was measured. Then, the sandpack was placed in a 95°C incubator for 24h, and the liquid production rate was tested periodically during the period, and the plugging rate was calculated. The relationship between the sandpack plugging rate and the mesh size of the quartz sand is shown in Table 2, and the relationship between the liquid production rate and the time is shown in Figure 4 and Figure 5 .

[0153] Table 2 Relationship between sandpack plugging rate and mesh size of quartz sand

[0154]

[0155] As can be seen from Table 2, the smaller the mesh size of the quartz sand particles (the larger the particle size), the greater the water permeability of the sandpack. After heating, the permeability of the sandpack decreases, and the plugging rate increases. The lower the permeability, the higher the plugging rate. It is believed that under high temperature conditions, the PVC particles are deformed by heat, resulting in a decrease in the pore size of the mixture of the quartz sand particles, an increase in the plugging effect, and an increase in the plugging rate.

[0156] As can be seen from Figure 4 , in the initial state, the liquid production rate gradually decreases and tends to be stable with the increase of the water injection time. Under constant pressure water injection conditions, the liquid production rate gradually decreases and the permeability decreases with the increase of the mesh size of the quartz sand.

[0157] As can be seen from Figure 5 , after heating, the degree of adhesion between the PVC particles and the quartz sand particles increases. Under constant pressure conditions, the liquid production rate gradually decreases and tends to be stable with the increase of the water injection time. Compared with the initial state, after heating, the pore space decreases, the liquid production rate decreases, and the permeability decreases.

[0158] 3.2 Influence of PVC particle content on plugging effect

[0159] The 20 mesh quartz sand was mixed with 200 mesh PVC particles (volume ratio = 7:3, 8:2 and 9:1), and the mixture was filled into the sandpack, and the water side permeability was measured. Then, the sandpack was placed in a 95°C incubator for 24h, and the liquid production rate was tested periodically during the period, and the plugging rate was calculated. The relationship between the sandpack plugging rate and the PVC particle content is shown in Table 3, and the relationship between the liquid production rate and the time is shown in Figure 6 andFigure 7 .

[0160] Table 3 Relationship between sandpack plugging rate and PVC particle content

[0161]

[0162]

[0163] As can be seen from Table 3, with the increase of PVC particle content, the permeability of the sandpack decreases. After heating, the permeability of the sandpack decreases and the plugging rate increases. The more the PVC particle content, the higher the plugging rate. It is believed that with the increase of PVC particle content, the decrease of pore size of the mixture of quartz sand particles is increased, the plugging effect is enhanced, and the plugging rate is increased.

[0164] As can be seen from Table 3, with the increase of PVC particle content, the permeability of the sandpack decreases. After heating, the permeability of the sandpack decreases and the plugging rate increases. The more the PVC particle content, the higher the plugging rate. It is believed that with the increase of PVC particle content, the decrease of pore size of the mixture of quartz sand particles is increased, the plugging effect is enhanced, and the plugging rate is increased. Figure 6 As can be seen from Table 3, with the increase of PVC particle content, the permeability of the sandpack decreases. After heating, the permeability of the sandpack decreases and the plugging rate increases. The more the PVC particle content, the higher the plugging rate. It is believed that with the increase of PVC particle content, the decrease of pore size of the mixture of quartz sand particles is increased, the plugging effect is enhanced, and the plugging rate is increased.

[0165] As can be seen from Table 3, with the increase of PVC particle content, the permeability of the sandpack decreases. After heating, the permeability of the sandpack decreases and the plugging rate increases. The more the PVC particle content, the higher the plugging rate. It is believed that with the increase of PVC particle content, the decrease of pore size of the mixture of quartz sand particles is increased, the plugging effect is enhanced, and the plugging rate is increased. Figure 7 As can be seen from Table 3, with the increase of PVC particle content, the permeability of the sandpack decreases. After heating, the permeability of the sandpack decreases and the plugging rate increases. The more the PVC particle content, the higher the plugging rate. It is believed that with the increase of PVC particle content, the decrease of pore size of the mixture of quartz sand particles is increased, the plugging effect is enhanced, and the plugging rate is increased.

[0166] 3.3 Effect of environmental temperature on plugging effect

[0167] The mixture of 20 mesh quartz sand and 200 mesh PVC particles (volume ratio = 7:3) was filled into the sandpack, and the water-side permeability was measured. The sandpack was placed in a 75℃, 85℃ and 95℃ incubator for 24 hours, and the liquid production rate was measured periodically during the period. The relationship between the sandpack plugging rate and the environmental temperature is shown in Table 4, and the relationship between the liquid production rate and the time is shown in Figure 8 and Figure 9 .

[0168] Table 4 Relationship between sandpack plugging rate and environmental temperature

[0169]

[0170] As can be seen from Table 4, with the increase of environmental temperature, the deformation amplitude of PVC particles increases, the flow cross section between particles in the sandpack decreases, the flow resistance increases, and the plugging effect is enhanced.

[0171] As can be seen from Table 3, with the increase of PVC particle content, the permeability of the sandpack decreases. After heating, the permeability of the sandpack decreases and the plugging rate increases. The more the PVC particle content, the higher the plugging rate. It is believed that with the increase of PVC particle content, the decrease of pore size of the mixture of quartz sand particles is increased, the plugging effect is enhanced, and the plugging rate is increased. Figure 8 and Figure 9 As can be seen from Table 3, with the increase of PVC particle content, the permeability of the sandpack decreases. After heating, the permeability of the sandpack decreases and the plugging rate increases. The more the PVC particle content, the higher the plugging rate. It is believed that with the increase of PVC particle content, the decrease of pore size of the mixture of quartz sand particles is increased, the plugging effect is enhanced, and the plugging rate is increased.

[0172] 3.4 Effect of heating time on plugging effect

[0173] A mixture of 20-mesh quartz sand and 200-mesh PVC particles (volume ratio = 7:3) was used to fill sand-filled pipes. Water permeability was measured. Three sand-filled pipes were placed in a 95℃ incubator for 24h, 48h, and 72h, respectively. During this period, the liquid collection rate was periodically tested, and the plugging rate was calculated. The relationship between the plugging rate of the sand-filled pipes and heating time is shown in Table 5, and the relationship between the liquid collection rate and time is shown in Table 6. Figure 10 .

[0174] Table 5 Relationship between Sand-filled Pipe Blockage Rate and Heating Time

[0175]

[0176]

[0177] As can be seen from Table 5, the sealing effect of the sand-filled pipe weakens and the sealing rate decreases with increasing heating time.

[0178] Depend on Figure 10 It can be seen that with increasing heating time, water permeability first decreases and then increases after heating, while the sealing effect first increases and then decreases. Analysis suggests that the adhesion between PVC particles and quartz sand reaches a stable level after 24 hours of heating, and further increases in heating time have little impact.

[0179] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A sealing mixture, characterized in that, It includes a plugging agent and a carrier fluid; the plugging agent is a temperature-sensitive self-fusion plugging agent; The temperature-sensitive self-fusion plugging agent is composed of temperature-sensitive organic particles and inorganic particles; the volume ratio of the temperature-sensitive organic particles to the inorganic particles is 5~30:70~95; the inorganic particles are silicon-containing mineral particles; The temperature-sensitive organic particles are polyvinyl chloride particles; The temperature-sensitive organic particles have a particle size of 20-300 mesh; the inorganic particles have a particle size of 20-200 mesh. The silicon-containing mineral particles include one or more of quartz sand, fly ash, and modified fly ash; The temperature-sensitive self-fusion plugging agent includes a plugging agent for deep well sections, a plugging agent for intermediate sections, or a plugging agent for near-wellbore sections; the volume ratio of temperature-sensitive organic particles to inorganic particles in the plugging agent for deep well sections is 5~10:90~95; the volume ratio of temperature-sensitive organic particles to inorganic particles in the plugging agent for intermediate sections is 15~20:80~85; and the volume ratio of temperature-sensitive organic particles to inorganic particles in the plugging agent for near-wellbore sections is 20~30:70~80. The carrier fluid includes a thickener and water; the thickener is polyacrylamide; the degree of hydrolysis of the thickener in the carrier fluid is 20-30%; the mass concentration of the thickener in the carrier fluid is 0.05-0.2%; and the mass ratio of the plugging agent to the carrier fluid is 20-40:60-80.

2. The sealing mixture according to claim 1, characterized in that, The preparation method of the temperature-sensitive self-fusion plugging agent includes the following steps: Thermosensitive organic particles and inorganic particles are mixed to obtain the thermosensitive self-fusion plugging agent.

3. A method for reservoir plugging, characterized in that, Includes the following steps: The sealing mixture is injected into the reservoir to be sealed for sealing purposes; The sealing mixture is the sealing mixture according to any one of claims 1 to 2.

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