Modified graphite coated soft particles, their preparation methods, profile control and water-blocking agents, and their applications

Abstract

This invention relates to the field of oilfield chemical profile control and water shut-off technology, and discloses a modified graphite-coated soft particle, its preparation method, and a profile control and water shut-off agent and its application. The modified graphite-coated soft particle comprises soft particles and a first modified graphite coating the surface of the soft particles. The soft particles include one or more of a rubber-based agent, an antioxidant, an auxiliary antioxidant, a density regulator, and a second modified graphite. The first and second modified graphites may be the same or different, each being modified graphite with a surface rich in hydroxyl and carboxyl groups. This profile control and water shut-off agent, after penetrating deep into the formation and aging for a period of time, can agglomerate with each other, effectively sealing water channeling.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical profile control and water shut-off technology, specifically to a modified graphite-coated soft particle and its preparation method, as well as a profile control and water shut-off agent and its application. Background Technology

[0002] With the development of unconventional oil and gas resources in my country, deep oil reservoir extraction technology has become increasingly sophisticated, making it a research hotspot and strategic focus in the international energy field. These reservoirs are widely distributed around the world, including but not limited to deep-sea sedimentary basins and deep structures in desert regions, collectively constituting a vast, underdeveloped energy reserve on Earth. However, the extreme environments of high temperature, high pressure, and high salinity pose unprecedented challenges to existing exploration and development technologies. Deep oil reservoirs have an average burial depth exceeding 4,500 meters and are characterized by ultra-high pressure (>120 MPa), ultra-high temperature (≥130℃), and ultra-high salinity (≥20 Wmg / L). Deep oil reservoirs are typically located in geologically complex areas and may contain traces of multiple tectonic movements, such as faults and folds. These complex geological structures affect the connectivity and fluid flow of the reservoir. Deep oil reservoirs are mainly developed using water drive, and the uneven distribution of formation porosity and permeability can lead to complex oil-water distribution, increasing the uncertainty and difficulty of extraction and making water channeling highly likely. Injecting plugging agents into water-channeling formations to create blockages has become an effective way to further develop deep oil reservoirs, with the core being the research and development of plugging agents. Rubber particles have advantages such as not being diluted by formation water and being widely available, but they are prone to oxidation and failure under high temperature and high salinity conditions, poor plugging effect due to particle stacking, insufficient viscoelasticity, and low density making them difficult to inject, which are problems that urgently need to be overcome.

[0003] CN114426712A discloses a rubber composition and vulcanized rubber based on nitrile rubber and styrene-butadiene rubber. The rubber composition includes a rubber matrix, polyvinyl chloride, carbon black, silica, acrylic metal salts, calcium sulfate whiskers, a silane coupling agent, a vulcanizing agent, a vulcanization accelerator, a vulcanization activator, an antioxidant, and a plasticizer. The vulcanized rubber prepared from this composition exhibits good processing properties, low shrinkage, good tensile strength, tear strength, and anti-slip properties, and excellent acid and alkali resistance and oil resistance. This invention does not involve research in the field of water control and oil enhancement in high-temperature, high-salinity oil reservoirs.

[0004] CN106554513A discloses a nanocomposite rubber composition and vulcanized rubber. The nanocomposite material contains nano-calcium carbonate modified with a modifier, wherein the modifier is a substance containing groups A, B, and C, wherein group A is -S-, group B is -COOH, and group C is -NH2. The nanocomposite material exhibits good dispersibility in a rubber matrix, can reinforce rubber independently, and is beneficial to the vulcanization performance, mechanical properties, and processing of the prepared rubber products, while also being energy-saving and environmentally friendly. However, performance studies of this nanocomposite rubber material under high temperature and high salt conditions have not been conducted.

[0005] CN108300436B discloses a selectively expanding rubber plugging agent for fractured-vuggy reservoirs, comprising the following raw materials in parts by weight: 100 parts nitrile rubber, 50-110 parts water-absorbing resin, 5-15 parts oil-swellable resin, 15-30 parts reinforcing agent, 0.5-2 parts softener, 2-5 parts accelerator, 3-6 parts zinc oxide, and 0.5-3.5 parts vulcanizing agent. The water-absorbing resin is sodium polystyrene sulfonate, sodium polyethylene sulfonate, or sodium polyallyl sulfonate. The invention relates to a single or mixture thereof, wherein the oil-swellable resin is one or a mixture of hydrogenated petroleum resin, phenolic resin, styrene-butadiene rubber, or polyethylene resin; the vulcanized rubber is benzoyl peroxide, dicumyl peroxide, or a mixture thereof; the reinforcing agent is carbon black 550, silica, or a mixture thereof; the softening agent is stearic acid; and the accelerator is zinc oxide. This plugging agent possesses high mechanical strength, strong resistance to mineralization, high toughness, and high volume expansion ratio. The plugging mechanism is particle expansion plugging. The patent is applicable to burial depths of 5400-6600m, temperatures of 120-140℃, and mineralization ≤20×10⁻⁶. 4 Oil reservoir with a concentration of mg / L.

[0006] Therefore, there is an urgent need to develop modified graphite-coated soft particles that are resistant to thermal oxidation, can be suspended in formation water, slowly aggregate at high temperatures, and have high sealing strength to meet the requirements of water control and oil production in high-temperature and high-salinity reservoirs. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies for rubber particle regulators in high-temperature and high-salinity (≥140℃, salinity ≥200,000 mg / L) oil reservoirs, which are prone to oxidation and failure in high-temperature and high-salinity formations, have poor deep injection capabilities due to low-density floating and rapid agglomeration, and lack of agglomeration ability. This invention provides a modified graphite-coated soft particle, its preparation method, a profile control and water shut-off agent, and its application. This profile control and water shut-off agent can agglomerate after entering deep formations and aging for a period of time, effectively sealing water channeling and expanding the impact.

[0008] To achieve the above objectives, the first aspect of the present invention provides a modified graphite-coated soft particle, wherein the modified graphite-coated soft particle includes a soft particle and a first modified graphite coated on the surface of the soft particle, wherein the soft particle includes one or more of a rubber main agent, an antioxidant, an auxiliary antioxidant, a density regulator, and a second modified graphite, wherein the first modified graphite and the second modified graphite are the same or different, and each is a modified graphite with a surface rich in hydroxyl and carboxyl groups.

[0009] A second aspect of the present invention provides a method for preparing the aforementioned modified graphite-coated soft particles, wherein the preparation method includes:

[0010] (1) Rubber main agent, antioxidant, auxiliary antioxidant, second modified graphite and density regulator are contacted and melt-blended to obtain integral rubber;

[0011] (2) The whole rubber is crushed, sheared and extruded into granules to obtain soft granules;

[0012] (3) The first modified graphite and water are mixed to obtain the first modified graphite dispersion. The first modified graphite dispersion is brought into contact with the soft particles, and the first modified graphite is adhered to the surface of the soft particles under heating and rotation conditions to obtain modified graphite coated soft particles.

[0013] A third aspect of the present invention provides a profile-adjusting and water-blocking agent, wherein the profile-adjusting and water-blocking agent is the aforementioned modified graphite-coated soft particles.

[0014] The fourth aspect of the present invention provides an application of the aforementioned profile control and water shut-off agent in an oil reservoir.

[0015] Through the above technical solution, the present invention has the following beneficial effects:

[0016] (1) The profile control and water plugging agent of the present invention can withstand heat oxidation without failure in high temperature and high salinity formation environment, with a validity period of ≥90 days, which can ensure the long-term effectiveness of profile control and water plugging operations.

[0017] (2) The profile control and water plugging agent of the present invention has higher viscoelasticity than ordinary rubber particles and has cohesive ability, thus possessing higher sealing strength.

[0018] (3) The profile control and water shut-off agent of the present invention has a density similar to that of formation water. The density can be adjusted according to the actual density of formation water. It has the ability to slow down aggregation at high temperature. It only starts to aggregate after aging for 2 days at high temperature. The particle size is adjustable from 200μm to 3.5mm. It has good injection performance and prevents reservoir damage.

[0019] (4) The profile control and water shut-off agent of the present invention has good compatibility with water and is simple to prepare. It can be injected with fresh water or with reinjection water from high-mineralization oilfields, which alleviates the problem of freshwater shortage during complex and harsh construction processes in deserts, Gobi, and oceans. Attached Figure Description

[0020] Figure 1 This is a microscope image of the high-temperature agglomeration of temperature-resistant and salt-resistant modified graphite-coated soft particles prepared with EPDM rubber as the main agent in Example 1 of this invention.

[0021] Figure 2 This is a microscope image of the high-temperature agglomeration of heat-resistant and salt-resistant modified graphite-coated soft particles prepared with styrene-butadiene rubber as the main agent in Example 2 of the present invention.

[0022] Figure 3 This is a microscope image of the high-temperature agglomeration of temperature-resistant and salt-resistant modified graphite-coated soft particles prepared with natural rubber as the main agent in Example 3 of the present invention.

[0023] Figure 4 This is a macroscopic schematic diagram of the temperature-resistant and salt-resistant modified graphite-coated soft particles prepared in Example 3 of the present invention before and after high-temperature agglomeration;

[0024] Figure 5 This is a comparison of the thermal stability of the temperature-resistant and salt-resistant modified graphite-coated soft particles prepared with EPDM rubber as the main agent in Example 1 and the EPDM rubber particles in Comparative Example 1.

[0025] Figure 6 The results of viscoelastic modulus test at 25-150℃ are for the heat-resistant and salt-resistant modified graphite-coated soft particles prepared by EPDM rubber as the main agent in Example 1.

[0026] Figure 7 These are actual images of the heat-resistant and salt-resistant modified graphite-coated soft particles prepared with EPDM rubber as the main agent in Examples 1, 2, and 3, which were then bonded together in rock cores with crack sizes of 5mm, 8mm, and 10mm to form a seal. Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] As previously stated, the first aspect of the present invention provides a modified graphite-coated soft particle, wherein the modified graphite-coated soft particle includes a soft particle and a first modified graphite coated on the surface of the soft particle, wherein the soft particle includes one or more of a rubber main agent, an antioxidant, an auxiliary antioxidant, a density regulator, and a second modified graphite, wherein the first modified graphite and the second modified graphite are the same or different, and each is a modified graphite with a surface rich in hydroxyl and carboxyl groups.

[0029] The inventors of this invention have discovered that: (1) using modified graphite (first modified graphite and / or second modified graphite) as a reinforcing agent can enhance the stability of rubber particles under high temperature and high salt conditions, which is beneficial to the continuous plugging of rubber particles; (2) at high temperature, the soft particles with surface coating can delay the aggregation between rubber particles and prevent the rubber particles from agglomerating too quickly under high temperature and high salt conditions, which would cause reservoir damage; (3) strengthening the viscoelasticity of the particles helps to increase the plugging effect; (4) the carboxyl and hydroxyl groups in the modified graphite can increase the hydrophilicity of the rubber particles and the electrostatic repulsion between the particles, assist in the density adjustment of the rubber particles, and help the rubber particles to be uniformly dispersed and efficiently injected into the formation water.

[0030] According to the present invention, the thickness of the first modified graphite coating on the surface of the soft particles is 30nm-50μm, preferably 80nm-20μm.

[0031] According to the present invention, based on the total weight of the soft particles, the content of the rubber main agent is 65-85% by weight, the content of the antioxidant is 0.1-0.5% by weight, the content of the auxiliary antioxidant is 0.05-0.3% by weight, the content of the second modified graphite is 5-10% by weight, and the content of the density regulator is 4-30% by weight; preferably, based on the total weight of the soft particles, the content of the rubber main agent is 70-80% by weight, the content of the antioxidant is 0.15-0.3% by weight, and the content of the auxiliary antioxidant is... The content of the first modified graphite is 7.5-9% by weight, and the content of the density modifier is 10-25% by weight, more preferably 12.8-18.6% by weight, based on the total weight of the soft particles. More preferably, the content of the rubber main agent is 74-77% by weight, the content of the antioxidant is 0.15-0.3% by weight, the content of the auxiliary antioxidant is 0.1-0.2% by weight, the content of the second modified graphite is 7.5-8.7% by weight, and the content of the density modifier is 14-17% by weight.

[0032] In this invention, if the content of the second modified graphite (reinforcing agent) is too high, it will lead to the defect that the soft particles cannot agglomerate, which will seriously affect the sealing effect. If the content of the second modified graphite (reinforcing agent) is too low, it will lead to the defect that the soft particles agglomerate too quickly, causing damage to the near-wellbore reservoir.

[0033] In this invention, it should be noted that the total content of rubber main agent, antioxidant, auxiliary antioxidant, density regulator and second modified graphite in the soft particles is 100%.

[0034] According to the present invention, the first modified graphite and the second modified graphite may be the same or different, each being a modified graphite with a surface rich in hydroxyl and carboxyl groups. The modified graphite contains oxygen-containing groups, including hydroxyl, carboxyl, and epoxy groups. Based on the total number of oxygen-containing groups in the modified graphite, hydroxyl groups account for 30-60% of the oxygen-containing groups, carboxyl groups account for 10-30%, and epoxy groups account for 30-40%. Preferably, based on the total number of oxygen-containing groups in the modified graphite, hydroxyl groups account for 45-55%, carboxyl groups account for 20-30%, and epoxy groups account for 20-30%. In the present invention, the total percentage of hydroxyl, carboxyl, and epoxy groups is 100%.

[0035] In this invention, the structure of modified graphite can be as shown in the schematic diagram of formula (1). However, it should be noted that the number of hydroxyl and carboxyl groups represented in formula (1) is not limited to the number shown in formula (1).

[0036]

[0037] According to the present invention, the modified graphite has a particle size of 200-1000 nm, preferably 300-800 nm, more preferably 300-500 nm, and / or 500-800 nm.

[0038] In this invention, according to a particularly preferred embodiment, the modified graphite is prepared in the laboratory from natural graphite using the Hummers oxidation method, specifically:

[0039] (1) Low-temperature reaction stage:

[0040] Assemble a 250mL three-necked flask in an ice-water bath, add an appropriate amount of concentrated sulfuric acid, and add a solid mixture of 1-5g (preferably 2g) of natural nano-graphite powder and 1-3g (preferably 1g) of sodium nitrate while stirring. Then add 5-10g (preferably 6g) of potassium permanganate in portions, control the reaction temperature below -5-5℃ (preferably 3℃), and stir the reaction for 30-60min (preferably 45min).

[0041] (2) Intermediate temperature reaction stage:

[0042] Raise the temperature to about 25-50℃ (preferably 35℃) and continue stirring for 30-60 minutes (preferably 45 minutes);

[0043] (3) High-temperature reaction stage:

[0044] Then, a certain amount of deionized water is added dropwise, and the mixture is stirred for 15-30 minutes (preferably 20 minutes). Then, hydrogen peroxide is added as a reducing agent to reduce the residual oxidant in the solution, making the solution bright yellow. The dispersion is then centrifuged and filtered. The washed solution is dried in an oven at 30-50℃ (preferably 35℃), ground and dispersed to obtain modified graphite particles.

[0045] In the embodiments of the present invention, the modified graphite particles used are modified graphite particles prepared under the above-described preferred conditions.

[0046] According to the present invention, the first modified graphite (reinforcing agent) can form a coating on the surface of rubber particles, thereby delaying the aggregation of rubber particles and enhancing the viscoelasticity of the particles. In addition, it can also assist in density adjustment. Its surface hydrophilic groups increase the hydrophilicity of the particles and the electrorepulsion between the particles. After reaching the deep part of the formation, it can effectively aggregate and block the flow channels.

[0047] According to the present invention, the rubber main agent is selected from one or more of natural rubber, styrene-butadiene rubber and ethylene propylene diene monomer rubber, and the rubber main agent has excellent viscoelasticity and is the core of sealing water channeling.

[0048] According to the present invention, the antioxidant is selected from pentaerythritol bis(2,6-di-tert-butyl-p-cresol) and / or pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], wherein the antioxidant can donate a hydrogen atom to a free radical and transform itself into a relatively stable free radical. This process can break the free radical chain reaction and prevent the rubber molecules from being further oxidized and damaged. Since the hindered phenolic free radical is relatively stable, it is not easy to initiate a new oxidation reaction, thereby effectively preventing the oxidation process.

[0049] According to the present invention, the auxiliary antioxidant is tris(2,4-di-tert-butylphenyl) phosphite, and the auxiliary antioxidant is used synergistically with the antioxidant to improve the long-term thermal stability of the rubber material.

[0050] According to the present invention, the antioxidant and the auxiliary antioxidant can effectively prevent the particles from oxidizing and failing under the action of high temperature and oxygen.

[0051] According to the present invention, the density regulator is ceramic sand and / or steel shot; the ceramic sand is spherical and has a density of 3-4 g / cm³. 3 The preferred value is 3.85 g / cm³. 3 Preferably, the ceramic sand has a particle size of 45-90 μm; the steel shot is spherical with a density of 7-7.5 g / cm³. 3 The preferred value is 7.2 g / cm³. 3 Preferably, the steel shot has a particle size of 45-75 μm. The density regulator can adjust the density of the rubber particles according to the formation water salinity, making it similar to the density of the formation water to achieve suspension in the formation water, which is beneficial for continuous deep injection under different formation water salinity conditions. That is, the density regulator can adjust the density of the rubber particles to ensure that the soft particles are suspended in the water, facilitating water transport into the formation interior.

[0052] According to the present invention, the particle size of the modified graphite coated soft particles is 200 μm to 3.5 mm; preferably, the particle size of the modified graphite coated soft particles is 500 μm to 2 mm.

[0053] A second aspect of the present invention provides a method for preparing the aforementioned modified graphite-coated soft particles, wherein the preparation method includes:

[0054] (1) Rubber main agent, antioxidant, auxiliary antioxidant, second modified graphite and density regulator are contacted and melt-blended to obtain integral rubber;

[0055] (2) The whole rubber is crushed, sheared and extruded into granules to obtain soft granules;

[0056] (3) The first modified graphite and water are mixed to obtain the first modified graphite dispersion. The first modified graphite dispersion is brought into contact with the soft particles, and the first modified graphite is adhered to the surface of the soft particles under heating and rotation conditions to obtain modified graphite coated soft particles.

[0057] According to the present invention, in step (1), the twin-screw extruder melt-mixes the rubber main agent, antioxidant, auxiliary antioxidant, reinforcing agent and density regulator in contact at 250°C; specifically, the melt-mixing conditions include a temperature of 180-350°C, preferably 200-250°C.

[0058] According to the present invention, in a preferred case, step (1) can be repeated 2-3 times to ensure that the antioxidant, auxiliary antioxidant, reinforcing agent and density regulator can be uniformly dispersed in the rubber main agent.

[0059] According to the present invention, in step (2), the temperature-resistant and salt-resistant modified graphite coated soft material is placed into a low-temperature pulverizing and granulating machine to obtain temperature-resistant and salt-resistant modified graphite coated soft material particles, and the soft material particles are adjustable from 200μm to 3.5mm.

[0060] According to the present invention, a twin-screw extruder known to those skilled in the art can be used, wherein the extrusion granulation conditions include a temperature of 180-350°C, preferably 200-220°C.

[0061] According to the present invention, in step (3), the concentration of the first modified graphite dispersion is 0.1-1%.

[0062] According to the present invention, in step (3), the weight ratio of the first modified graphite dispersion to the soft particles is 100:(2-20), preferably 100:(10-15).

[0063] According to the present invention, in step (3), the conditions for heating and rotating include: a temperature of 180-200°C and a rotation speed of 50-150 rpm.

[0064] A third aspect of the present invention provides a profile-adjusting and water-blocking agent, wherein the profile-adjusting and water-blocking agent is the aforementioned modified graphite-coated soft particles.

[0065] According to the present invention, the profile control and water shut-off agent has a density similar to that of the simulated formation water; preferably, the density of the profile control and water shut-off agent is 1.0-1.2 g / cm³. 3 .

[0066] According to the present invention, the profile control and water shut-off agent has good dispersion in formation water, can be injected into deep layers under high temperature and then aggregate, has good viscoelasticity, and has strong long-term stability under high temperature and high salinity conditions.

[0067] According to the present invention, the profile control and water-blocking agent has a first modified graphite structure with soft particles as the core and the core covered by the first modified graphite; preferably, the soft particles contain one or more of a rubber main agent, an antioxidant, an auxiliary antioxidant, a density regulator, and a second modified graphite.

[0068] According to the present invention, the profile-adjusting and water-blocking agent is a modified graphite-coated soft particle.

[0069] According to the present invention, the particle size of the profile control and water-blocking agent is 200 μm to 3.5 mm; preferably, the particle size of the profile control and water-blocking agent is 500 μm to 2 mm.

[0070] According to the present invention, the profile control and water shut-off agent is used at 140°C and has a salinity of 20 × 10⁻⁶. 4 The elastic modulus under the mg / L condition is 700-800 kPa, and the viscous modulus is 350-450 kPa.

[0071] The fourth aspect of the present invention provides an application of the aforementioned profile control and water shut-off agent in an oil reservoir.

[0072] According to the present invention, the application includes: in the reservoir, the profile control and water shut-off agent particles agglomerate with each other to seal the reservoir.

[0073] According to the present invention, the reservoir conditions include: a depth of ≥4500m, a temperature of ≥140℃, and a salinity of ≥20×10⁻⁶. 4 mg / L; preferably, the reservoir conditions include: a depth of 4500-6500m, a temperature of 140-200℃, and a salinity of 20×10⁻⁶ mg / L. 4 mg / L to 30×10 4 mg / L.

[0074] The present invention will be described in detail below through embodiments.

[0075] In the following examples and comparative examples:

[0076] The microscopic cohesion pattern of soft particles was obtained using a microscope;

[0077] Thermal stability was determined by differential scanning calorimetry.

[0078] The viscoelastic modulus parameter was obtained by high-temperature viscoelastic testing using a rheometer.

[0079] The core plugging rate parameter was obtained by the high-temperature, high-salt fracture core displacement test method;

[0080] The rheometer was purchased from Haake, model number Haake Rheostree RS75.

[0081] The microscope was purchased from Leica Microsystems Ltd., model Leica DMi8 C;

[0082] Ceramic sand and steel shot are commercially available products from Lianzhiyan Surface Treatment Materials Co., Ltd.

[0083] Ethylene propylene diene monomer (EPDM) rubber, styrene-butadiene rubber (SBR), and natural rubber are commercially available products of Hengshui Mingguan Rubber & Plastic Products Co., Ltd.

[0084] Antioxidants and co-antioxidants are commercially available products from Shanghai Yuanye Biotechnology Co., Ltd.

[0085] Example 1

[0086] The present invention describes the preparation of the temperature-resistant and salt-resistant modified graphite coated soft particles (i.e., profile control and water-blocking agent).

[0087] The soft particles consist of: a rubber main agent, EPDM rubber, 75% by mass; an antioxidant, pentaerythritol bis(2,6-di-tert-butyl-p-cresol), 0.3% by mass; a secondary antioxidant, tris(2,4-di-tert-butylphenyl) phosphite, 0.2% by mass; a reinforcing agent, modified graphite (second-modified graphite), 300-500nm, 7.5% by mass; and a density modifier, ceramic sand, 45μm, 17% by mass. The sum of the mass fractions of all components is 100%.

[0088] Modified graphite (first modified graphite), 300-500nm, wherein the weight ratio of the dispersion of the first modified graphite to the soft particles is 100:10.

[0089] In addition, the structure of the modified graphite can be shown in the schematic diagram of formula (1) in the specification. Specifically, based on the total number of oxygen-containing groups in the modified graphite, the number of hydroxyl groups in the modified graphite is 48%, the number of carboxyl groups is 28%, and the number of epoxy groups is 24%.

[0090] (1) Under the condition of 250℃ in a twin-screw extruder, 75g of rubber granules, 0.3g of antioxidant, 0.2g of auxiliary antioxidant, 7.5g of reinforcing agent (second modified graphite) and 17g of density regulator are put into the twin-screw extruder for melt mixing and repeated 3 times to ensure uniform mixing, and 100g of whole rubber is obtained.

[0091] (2) Then the whole rubber is put into a low temperature crushing and granulation machine for fixed-scale low temperature shearing to obtain temperature-resistant and salt-resistant soft particles of a certain particle size.

[0092] (3) 100g of modified graphite (first modified graphite) dispersion with a concentration of 0.1% and 10g of soft particles are loaded into a drum. Under the conditions of heating and rotation (180℃, 100rpm), the modified graphite is adhered to the surface of the soft particles to obtain modified graphite coated soft particles. The particle size of the modified graphite coated soft particles is 0.3-0.5mm, and the modified graphite coated soft particles include soft particles and first modified graphite coated on the surface of the soft particles. The thickness of the first modified graphite coating on the surface of the soft particles is 120nm.

[0093] Modified graphite-coated soft particles were used as profile control and water shut-off agents and aged in a 130℃ oven. It was found that the particles did not settle or suspend in simulated formation water at 200,000 mg / L, and began to aggregate significantly after 48 hours. At 140℃ and a salinity of 20 × 10⁻⁶, the particle temperature remained stable. 4 The elastic modulus was 790.30 kPa and the viscous modulus was 434.04 kPa under the condition of mg / L. The aggregate did not show any damage after 90 days of aging.

[0094] Figure 6 The results of viscoelastic modulus tests in Example 1, using EPDM rubber as the main agent, on the temperature-resistant and salt-resistant modified graphite-coated soft particles and pure EPDM rubber matrix at 25-150℃. The left graph represents the elastic modulus, and the right graph represents the viscosity modulus. After mixing, the rubber particles are still mainly elastic, with an elasticity 2.6 times higher than that of the pure rubber matrix and a viscosity 2.5 times higher. This demonstrates the good viscoelasticity of the temperature-resistant and salt-resistant modified graphite-coated soft particles at high temperatures, which helps to improve the sealing effect.

[0095] Example 2

[0096] The present invention describes the preparation of the temperature-resistant and salt-resistant modified graphite coated soft particles (i.e., profile control and water-blocking agent).

[0097] The soft particles consist of: a rubber main agent, styrene-butadiene rubber, 74% by mass; an antioxidant, pentaerythritol bis(2,6-di-tert-butyl-p-cresol), 0.2% by mass; a secondary antioxidant, tris(2,4-di-tert-butylphenyl) phosphite, 0.1% by mass; a reinforcing agent, modified graphite (second-modified graphite), 500-800 nm, 8.7% by mass; and a density modifier, ceramic sand, 60 μm, 17% by mass. The sum of the mass fractions of all components is 100%.

[0098] Modified graphite (first modified graphite), 500-800nm, wherein the weight ratio of the dispersion of the first modified graphite to the soft particles is 100:10.

[0099] In addition, the structure of the modified graphite can be as shown in the schematic diagram of formula (1) in the specification. Specifically, based on the total number of oxygen-containing groups in the modified graphite, the number of hydroxyl groups in the modified graphite is 51%, the number of carboxyl groups is 25%, and the number of epoxy groups is 24%.

[0100] (1) Under the condition of 250℃ in a twin-screw extruder, 74g of rubber granules, 0.2g of antioxidant, 0.1g of auxiliary antioxidant, 8.7g of reinforcing agent (second modified graphite) and 17g of density regulator were put into the twin-screw extruder for melt mixing and repeated 3 times to ensure uniform mixing, so as to obtain 100g of integral rubber with the same density as simulated formation water with a mineralization of 200,000mg / L (of which sodium ions 73282mg / L, calcium ions 6000mg / L, and magnesium ions 1000mg / L);

[0101] (2) Then the whole rubber is put into a low temperature crushing and granulation machine for fixed-scale low temperature shearing to obtain temperature-resistant and salt-resistant soft particles of a certain particle size.

[0102] (3) 100g of modified graphite (first modified graphite) dispersion with a concentration of 0.1% and 10g of soft particles are loaded into a drum. The modified graphite is adhered to the surface of the soft particles under heating and rotation (200℃, 150rpm) to obtain modified graphite coated soft particles. The particle size of the modified graphite coated soft particles is 0.5-1.0mm. The modified graphite coated soft particles include soft particles and first modified graphite coated on the surface of the soft particles. The thickness of the first modified graphite coating on the surface of the soft particles is 1μm.

[0103] Modified graphite-coated soft particles were used as profile control and water shut-off agents and aged in a 130℃ oven. It was found that the particles did not settle or suspend in simulated formation water at 200,000 mg / L, and began to aggregate significantly after 48 hours. At 140℃ and a salinity of 20 × 10⁻⁶, the particles showed good performance. 4 The elastic modulus was 730.81 kPa and the viscous modulus was 401.34 kPa under the condition of mg / L. The aggregate did not show any damage after 90 days of aging.

[0104] Example 3

[0105] The present invention describes the preparation of the temperature-resistant and salt-resistant modified graphite coated soft particles (i.e., profile control and water-blocking agent).

[0106] The soft granules consist of: a rubber base, natural rubber, 77% by mass; an antioxidant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.15% by mass; a secondary antioxidant, tris(2,4-di-tert-butylphenyl) phosphite, 0.15% by mass; a reinforcing agent, modified graphite (second-modified graphite), 500-800 nm, 8.7% by mass; and a density modifier, steel shot, 90 μm, 14% by mass. The sum of the mass fractions of all components is 100%.

[0107] Modified graphite (first modified graphite), 500-800nm, wherein the weight ratio of the first modified graphite to the soft particles is 100:10.

[0108] In addition, the structure of the modified graphite can be shown in the schematic diagram of formula (1) in the specification. Specifically, based on the total number of oxygen-containing groups in the modified graphite, the number of hydroxyl groups in the modified graphite is 52%, the number of carboxyl groups is 24%, and the number of epoxy groups is 24%.

[0109] (1) Under the condition of 250℃ in a twin-screw extruder, 77g of rubber granules, 0.15g of antioxidant, 0.15g of auxiliary antioxidant, 8.7g of reinforcing agent (second modified graphite) and 14g of density regulator are put into the twin-screw extruder for melt mixing and repeated 3 times to ensure uniform mixing, so as to obtain 100g of integral rubber with the same density as simulated formation water with a mineralization of 200,000mg / L (of which sodium ions are 73282mg / L, calcium ions are 6000mg / L, and magnesium ions are 1000mg / L);

[0110] (2) Then the whole rubber is put into a low temperature crushing and granulation machine for fixed-scale low temperature shearing to obtain temperature-resistant and salt-resistant soft particles of a certain particle size.

[0111] (3) 100g of modified graphite (first modified graphite) dispersion with a concentration of 0.1% and 100g of soft particles are loaded into a drum. Under the conditions of heating and rotation (200℃, 150rpm), the modified graphite is adhered to the surface of the soft particles to obtain modified graphite coated soft particles. The particle size of the modified graphite coated soft particles is 1.0-1.6mm, and the modified graphite coated soft particles include soft particles and first modified graphite coated on the surface of the soft particles. The thickness of the first modified graphite coating on the surface of the soft particles is 500nm.

[0112] Modified graphite-coated soft particles were used as profile control and water shut-off agents and aged in a 130℃ oven. It was found that the particles did not settle or suspend in simulated formation water at 200,000 mg / L, and began to aggregate significantly after 48 hours. At 140℃ and a salinity of 20 × 10⁻⁶, the particles showed good performance. 4 The elastic modulus was 692.38 kPa and the viscous modulus was 387.22 kPa under the condition of mg / L. The aggregate did not show any damage after aging for 90 days.

[0113] Figure 1 These are microscopic images of the heat-resistant and salt-resistant modified graphite-coated soft particles prepared with EPDM rubber as the main agent, before and after high-temperature agglomeration, prepared in Example 1 of this invention. Figure 2 This is a microscope image of the high-temperature agglomeration of heat-resistant and salt-resistant modified graphite-coated soft particles prepared with styrene-butadiene rubber as the main agent, as prepared in Example 2 of this invention. Figure 3 These are microscopic images of the high-temperature agglomeration of temperature-resistant and salt-resistant modified graphite-coated soft particles prepared with natural rubber as the main agent, as described in Example 1 of this invention. It should be noted that... Figure 1-3 In the images on the left, the interfaces of the coated soft particles are clear before agglomeration, while the images on the right show significant mutual adhesion between the interfaces after agglomeration. Figure 1 , 2 3 shows that after the rubber particles aged at high temperature for 2 days, the interface between the particles began to agglomerate, changing from a single small particle to a large aggregate of multiple particles, which can seal larger-scale cracks.

[0114] Figure 4 This is a macroscopic schematic diagram of the temperature-resistant and salt-resistant modified graphite-coated soft particles prepared in Example 3 of the present invention before and after high-temperature agglomeration. The left diagram shows the coated soft particles dispersed in water, and the right diagram shows the particles agglomerating at high temperature to form an effective blockage of the water body. It can be seen from both diagrams that the agglomerated rubber particles can indeed effectively block the water body.

[0115] Figure 7 These are images showing the physical specimens of the temperature- and salt-resistant modified graphite-coated soft particles prepared in Examples 1, 2, and 3, which agglomerated in rock cores with crack sizes of 5mm, 8mm, and 10mm, respectively, to form seals. Figure 7 It can be seen that the temperature-resistant and salt-resistant modified graphite-coated soft particles effectively seal cracks of different scales.

[0116] Example 4

[0117] The present invention describes the preparation of the temperature-resistant and salt-resistant modified graphite coated soft particles (i.e., profile control and water-blocking agent).

[0118] The heat-resistant and salt-resistant modified graphite-coated soft particles were prepared using the same method as in Example 1, except that:

[0119] The soft particles consist of: a rubber main agent, EPDM rubber, 62.2% by weight; an antioxidant, pentaerythritol bis(2,6-di-tert-butyl-p-cresol), 0.5% by weight; an auxiliary antioxidant, tris(2,4-di-tert-butylphenyl) phosphite, 0.3% by weight; a reinforcing agent (second modified graphite), modified graphite, 500-1000 nm, 10% by weight; and a density modifier, ceramic sand, 45 μm, 27% by weight. The sum of the mass fractions of all components is 100%.

[0120] Modified graphite (first modified graphite), 500-1000nm, wherein the weight ratio of the dispersion of the first modified graphite to the soft particles is 100:10.

[0121] In addition, the structure of the modified graphite can be shown in the schematic diagram of formula (1) in the specification. Specifically, based on the total number of oxygen-containing groups in the modified graphite, the modified graphite has 57% hydroxyl groups, 11% carboxyl groups, and 32% epoxy groups.

[0122] As a result, modified graphite-coated soft particles were prepared. The particle size of the modified graphite-coated soft particles was 0.3-0.5 mm. The modified graphite-coated soft particles included soft particles and a first modified graphite coating on the surface of the soft particles. The thickness of the first modified graphite coating on the surface of the soft particles was 50 nm.

[0123] Example 5

[0124] The present invention describes the preparation of the temperature-resistant and salt-resistant modified graphite coated soft particles (i.e., profile control and water-blocking agent).

[0125] The heat-resistant and salt-resistant modified graphite-coated soft particles were prepared using the same method as in Example 1, except that:

[0126] The soft particles consist of: a rubber main agent, EPDM rubber, 82% by mass; an antioxidant, pentaerythritol bis(2,6-di-tert-butyl-p-cresol), 0.3% by mass; a secondary antioxidant, tris(2,4-di-tert-butylphenyl) phosphite, 0.1% by mass; a reinforcing agent, modified graphite (second-modified graphite), 300-500nm, 5% by mass; and a density modifier, ceramic sand, 45μm, 12.6% by mass. The sum of the mass fractions of all components is 100%.

[0127] Modified graphite (first modified graphite), 300-500nm, wherein the weight ratio of the dispersion of the first modified graphite to the soft particles is 100:10.

[0128] In addition, the structure of the modified graphite can be shown in the schematic diagram of formula (1) in the specification. Specifically, based on the total number of oxygen-containing groups in the modified graphite, the modified graphite has 55% hydroxyl groups, 12% carboxyl groups, and 33% epoxy groups.

[0129] As a result, modified graphite-coated soft particles were prepared. The particle size of the modified graphite-coated soft particles was 0.3-0.5 mm. The modified graphite-coated soft particles included soft particles and a first modified graphite coating on the surface of the soft particles. The thickness of the first modified graphite coating on the surface of the soft particles was 30 μm.

[0130] Application Example 1

[0131] This invention also provides a method for using temperature- and salt-resistant modified graphite-coated soft particles as profile control and water-blocking agents. Temperature- and salt-resistant modified graphite-coated soft particles of 0.3-0.5 mm prepared in Example 1 were used for fracture plugging experiments. The simulated formation water salinity was 200,000 mg / L (containing 73,282 mg / L sodium ions, 6,000 mg / L calcium ions, and 1,000 mg / L magnesium ions), the core fracture size was 5 mm, the injection volume was 1 FV, the injection aging temperature was 150℃, the aging time was 48 h, and the permeability before plugging was 2.69 × 10⁻⁶. 6 mD, with a permeability of 31.58 mD after injection.

[0132] Application Example 2

[0133] This invention also provides a method for applying temperature- and salt-resistant modified graphite-coated soft particles as profile control and water-blocking agents. Temperature- and salt-resistant modified graphite-coated soft particles of 0.5-1.0 mm prepared in Example 2 were used for fracture plugging experiments. The simulated formation water salinity was 200,000 mg / L (containing 73,282 mg / L sodium ions, 6,000 mg / L calcium ions, and 1,000 mg / L magnesium ions), the core fracture size was 8 mm, the injection volume was 1 FV, the injection aging temperature was 150℃, the aging time was 48 h, and the permeability before plugging was 17.33 × 10⁻⁶. 6 mD, with a permeability of 109.20 mD after injection.

[0134] Application Example 3

[0135] This invention also provides a method for using temperature- and salt-resistant modified graphite-coated soft particles as profile control and water-blocking agents. Temperature- and salt-resistant modified graphite-coated soft particles of 1.0-1.6 mm prepared in Example 3 were used for fracture plugging experiments. The simulated formation water salinity was 200,000 mg / L (containing 73,282 mg / L sodium ions, 6,000 mg / L calcium ions, and 1,000 mg / L magnesium ions), the core fracture size was 10 mm, the injection volume was 1 FV, the injection aging temperature was 150℃, the aging time was 48 h, and the permeability before plugging was 42.35 × 10⁻⁶. 6 mD, with a permeability of 279.47 mD after injection.

[0136] Application Example 4

[0137] This invention also provides a method for using temperature- and salt-resistant modified graphite-coated soft particles as profile control and water-blocking agents. Temperature- and salt-resistant modified graphite-coated soft particles of 1.0-1.6 mm prepared in Example 3 were used for fracture plugging experiments. The simulated formation water salinity was 200,000 mg / L (containing 73,282 mg / L sodium ions, 6,000 mg / L calcium ions, and 1,000 mg / L magnesium ions), the core fracture size was 15 mm, the injection volume was 1 FV, the injection aging temperature was 150℃, the aging time was 48 h, and the permeability before plugging was 214.61 × 10⁻⁶. 6 mD, with a permeability of 319.55 mD after injection.

[0138] Application Example 5

[0139] This invention also provides a method for applying temperature- and salt-resistant modified graphite-coated soft particles as profile control and water-blocking agents. A fracture plugging experiment was conducted using 0.3-0.5 mm temperature- and salt-resistant modified graphite-coated soft particles prepared in Example 4. The simulated formation water salinity was 200,000 mg / L (containing 73,282 mg / L sodium ions, 6,000 mg / L calcium ions, and 1,000 mg / L magnesium ions), the core fracture size was 5 mm, the injection volume was 1 FV, the injection aging temperature was 150℃, the aging time was 48 h, and the permeability before plugging was 2.71 × 10⁻⁶. 6 mD, with a permeability of 48.77 mD after injection.

[0140] Application Example 6

[0141] This invention also provides a method for applying temperature- and salt-resistant modified graphite-coated soft particles as profile control and water-blocking agents. A fracture plugging experiment was conducted using 0.3-0.5 mm temperature- and salt-resistant modified graphite-coated soft particles prepared in Example 5. The simulated formation water salinity was 200,000 mg / L (containing 73,282 mg / L sodium ions, 6,000 mg / L calcium ions, and 1,000 mg / L magnesium ions), the core fracture size was 5 mm, the injection volume was 1 FV, the injection aging temperature was 150℃, the aging time was 48 h, and the permeability before plugging was 2.70 × 10⁻⁶. 6 mD, with a permeability of 62.51 mD after injection.

[0142] Comparative Example 1

[0143] The EPDM rubber matrix from Example 1 was selected, meaning it only includes EPDM rubber and excludes antioxidants, auxiliary antioxidants, first modified graphite, second modified graphite, and density modifiers. Aging was performed at the same temperature and salinity. Rapid agglomeration occurred within 0.5 hours, and after 20 days of aging, the rubber particle agglomerates showed significant oxidation and discoloration, and their volume began to collapse.

[0144] Figure 5This is a comparison of the thermal stability of the temperature-resistant and salt-resistant modified graphite-coated soft particles prepared with EPDM rubber as the main agent in Example 1 (right figure) and the EPDM rubber particles in Comparative Example 1 (left figure). The temperature-resistant and salt-resistant modified graphite-coated soft particles that are slow-polymerized at high temperature with the same density as formation water do not show any other impurity peaks. Comparative Example 1 (left figure) represents the thermal stability of the rubber matrix, and Example 1 (right figure) represents the thermal stability of the coated soft particles. This shows that the mixing effect is good, and the density regulator and graphite do not affect the excellent temperature resistance of the rubber particles themselves, and may even improve it to some extent.

[0145] Comparative Example 2

[0146] The styrene-butadiene rubber matrix from Example 2 was selected, i.e., it only includes styrene-butadiene rubber and excludes antioxidants, auxiliary antioxidants, first modified graphite, second modified graphite, and density modifiers. Aging was carried out at the same temperature and salinity. Rapid agglomeration occurred in 0.5 hours, and after 35 days of aging, the rubber particle agglomerates showed obvious oxidation and discoloration, and their volume began to collapse.

[0147] Comparative Example 3

[0148] The natural rubber matrix used in Example 3 was selected, i.e., it only includes natural rubber and excludes antioxidants, auxiliary antioxidants, first modified graphite, second modified graphite, and density modifiers. Aging was carried out at the same temperature and salinity. Rapid agglomeration occurred within 0.5 hours, and after aging for 60 days, the rubber particle agglomerates showed significant oxidation and discoloration, and their volume began to collapse.

[0149] Comparative Example 4

[0150] Rubber particles were prepared using the same method as in Example 1, except that the composition was different. The EPDM rubber matrix from Example 1 was selected, specifically including EPDM rubber, antioxidant, auxiliary antioxidant, second modified graphite, and density regulator, but excluding the first modified graphite. Aging was performed at the same temperature and salinity. Rapid agglomeration occurred in 0.5 hours, but after aging for 60 days, the rubber particle agglomerates did not show significant oxidation.

[0151] Comparative Example 5

[0152] Rubber granules were prepared using the same method as in Example 2, except that the component contents were different. The styrene-butadiene rubber matrix from Example 2 was selected, comprising styrene-butadiene rubber, an antioxidant, an auxiliary antioxidant, a first modified graphite, a second modified graphite, and a density regulator. The difference was that the content of the first modified graphite was doubled. Aging was performed at the same temperature and salinity. The cohesive effect was significantly weakened, and after 60 days of aging, the rubber granule aggregates did not undergo significant oxidation.

[0153] Comparative Example 6

[0154] Rubber granules were prepared using the same method as in Example 3, except that the component content was different. The natural rubber matrix from Example 3 was selected, specifically including only natural rubber, antioxidant, auxiliary antioxidant, first modified graphite, second modified graphite, and density regulator. The difference was that the content of the first modified graphite was reduced to half of its original amount. Aging was performed at the same temperature and salinity. The granules agglomerated rapidly after 10 hours, with a significant decrease in viscoelasticity. However, after aging for 60 days, the rubber granule agglomerates did not show significant oxidation.

[0155] Comparative Example 7

[0156] Rubber particles were prepared using the same method as in Example 1, except that the EPDM rubber matrix from Example 1 was selected, comprising EPDM rubber, antioxidants, auxiliary antioxidants, density modifiers, and reinforcing agents. However, the reinforcing agents (first modified graphite and second modified graphite) from Example 1 were replaced with natural nano-graphite without hydrophilic groups on its surface. Due to insufficient hydrophilicity and surface negative charge, the resulting soft particles exhibited poor dispersibility in water, affecting the injection effect and shortening the aggregation rate to 40 hours at high temperatures.

[0157] Application Comparative Example 1

[0158] The plugging experiment was conducted using the same method as in Application Example 1, except that carbon black-reinforced rubber particles were used, i.e., the rubber particles prepared in Comparative Example 1, with a permeability of 2.69 × 10⁻⁶ before plugging. 6 mD, permeability after injection 2831.58mD.

[0159] Application Comparative Example 2

[0160] The plugging experiment was conducted using the same method as in Application Example 2, except that carbon black-reinforced rubber particles were used, i.e., the rubber particles prepared in Comparative Example 2, with a permeability of 17.33 × 10⁻⁶ before plugging. 6 mD, with a permeability of 36609.62 mD after injection.

[0161] Application Comparative Example 3

[0162] The plugging experiment was conducted using the same method as in Application Example 3, except that the plugging was done with pure rubber particles, i.e., the rubber particles prepared in Comparative Example 3, without any other additives. They floated on the surface of the formation water and were not easy to inject. After being pre-embedded and aged in the core for 2 hours, they formed a completely plugging effect, causing damage to the reservoir.

[0163] Application Comparative Example 4

[0164] The sealing experiment was conducted using the same method as in Application Example 4. The difference was that the material was pure rubber granules without any other additives. It floated on the surface of the formation water and was not easy to inject. After being pre-embedded and aged in the rock core for 2 hours, it formed a completely sealed effect, making subsequent injection impossible.

[0165] Application Comparative Example 5

[0166] The soft particles prepared in Comparative Example 4 were used to conduct a plugging experiment in the same way as in Application Example 2. Due to the lack of a reinforcing agent and the excessively rapid aggregation between particles, which made them difficult to inject, the insufficient viscoelasticity resulted in poor resistance to formation water erosion, leading to a poor plugging effect.

[0167] Application Comparative Example 6

[0168] The soft particles prepared using Comparative Example 5 were subjected to a plugging experiment using the same method as in Application Example 2. Due to excessive reinforcing agent, the particles lost most of their cohesive ability, resulting in a permeability of 17.33 × 10⁻⁶ before plugging. 6 mD, with a permeability of 32658.22 mD after injection.

[0169] Application Comparative Example 7

[0170] The soft particles prepared using Comparative Example 6 were subjected to a plugging experiment using the same method as in Application Example 2. The particles aggregated rapidly, and after 12 hours of aging, insufficient reinforcing agent led to inadequate viscoelasticity, resulting in poor plugging performance. The permeability before plugging was 17.33 × 10⁻⁶. 6 mD, permeability after injection: 21390.42mD.

[0171] Application Comparative Example 8

[0172] The soft particles prepared using Comparative Example 7 were used in the same plugging experiment as in Application Example 2. Since the reinforcing agent no longer imparted hydrophilicity and negative charge to the soft particles, the particles had poor dispersibility in formation water, which was not conducive to injection. The aggregation rate was accelerated, which was not conducive to deep migration.

[0173] In summary, the temperature- and salt-resistant modified graphite-coated soft particles prepared using this invention utilize an antioxidant that donates a hydrogen atom to a free radical, transforming itself into a relatively stable free radical. This process breaks the free radical chain reaction, preventing further oxidation and damage to rubber molecules. Because the hindered phenolic free radicals are relatively stable, they are less likely to trigger new oxidation reactions, thus effectively inhibiting the oxidation process. The auxiliary antioxidant works synergistically with the antioxidant to improve the long-term thermal stability of the rubber material. The coating effect of the first modified graphite can delay the aggregation between soft particles, preventing near-wellbore reservoir damage. The second modified graphite enhances the viscoelasticity of the particles, strengthening the sealing effect, and also has auxiliary functions of density adjustment and dispersion. The density regulator can adjust the density of the rubber particles according to the formation water salinity, making it similar to the formation water density to achieve suspension in the formation water, which is beneficial for continuous deep injection under different formation water salinity conditions. These soft particles can aggregate under high temperature and high salinity conditions for 2 days, forming large-size, high-strength aggregates, controlling water outflow from fractures and holes, with a stability of ≥90 days.

[0174] Compared to the examples, the comparative examples 1, 2, and 3 showed insufficient stability of the polymers under high temperature and high salt conditions after aging. This is because the rubber particles, lacking antioxidants and auxiliary antioxidants, are easily oxidized and destroyed under high temperature and high salt conditions. The absence of reinforcing agents and density modifiers results in poor viscoelasticity and dispersibility, which is not conducive to injection and sealing.

[0175] Compared to the examples, the comparative examples 4-7 above showed poor viscoelasticity / dispersibility of the particles due to changes in the properties or dosage of the reinforcing agent.

[0176] The permeability of comparative examples 1 and 2 after plugging was higher than that of the example. The main reason for the poor plugging effect is that the carbon black reinforced rubber particles do not have the ability to coagulate and rely only on their own blocking effect. Therefore, the plugging effect of small-sized particles is not good.

[0177] The aforementioned comparative examples 3 and 4, lacking density modifiers, had excessively low densities, causing them to agglomerate and float on the surface of formation water, hindering injection. Furthermore, the lack of modified graphite on the surface of rubber particles delayed particle aggregation, leading to immediate particle aggregation upon temperature changes, resulting in near-wellbore blockage, reservoir damage, and the inability to perform deep-source water control.

[0178] The above-mentioned comparative examples 5-8 have different reinforcing agents from the scope and characteristics proposed in this invention, resulting in the soft particles having deficiencies in cohesiveness / injectability / blocking properties, leading to poor actual injection and blocking effects.

[0179] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A modified graphite-coated soft particle, characterized in that, The modified graphite-coated soft particles include soft particles and a first modified graphite coated on the surface of the soft particles. The soft particles include one or more of a rubber main agent, an antioxidant, an auxiliary antioxidant, a density regulator, and a second modified graphite. The first modified graphite and the second modified graphite may be the same or different, and each is a modified graphite with a surface rich in hydroxyl and carboxyl groups. The thickness of the first modified graphite coating on the surface of the soft particles is 30nm-50μm; The modified graphite contains oxygen-containing groups, including hydroxyl, carboxyl, and epoxy groups. Based on the total number of oxygen-containing groups in the modified graphite, the proportion of hydroxyl groups is 30-60%, the proportion of carboxyl groups is 10-30%, and the proportion of epoxy groups is 30-40%. The modified graphite has a particle size of 200-1000 nm; Based on the total weight of the soft particles, the content of the rubber main agent is 65-85% by weight, the content of the antioxidant is 0.1-0.5% by weight, the content of the auxiliary antioxidant is 0.05-0.3% by weight, the content of the second modified graphite is 5-10% by weight, and the content of the density regulator is 4-30% by weight.

2. The modified graphite-coated soft particles according to claim 1, wherein, The thickness of the first modified graphite coating on the surface of the soft particles is 80nm-20μm.

3. The modified graphite-coated soft particles according to claim 1, wherein, The modified graphite has a particle size of 300-800 nm.

4. The modified graphite-coated soft particles according to claim 3, wherein, The modified graphite has a particle size of 300-500 nm, and / or the modified graphite has a particle size of 500-800 nm.

5. The modified graphite-coated soft particles according to claim 1, wherein, Based on the total weight of the soft particles, the content of the rubber main agent is 70-80% by weight, the content of the antioxidant is 0.15-0.3% by weight, the content of the auxiliary antioxidant is 0.1-0.2% by weight, the content of the second modified graphite is 7.5-9% by weight, and the content of the density regulator is 10-25% by weight.

6. The modified graphite-coated soft particles according to claim 1 or 5, wherein, The rubber main agent is selected from one or more of natural rubber, styrene-butadiene rubber and ethylene propylene diene monomer rubber; And / or, the antioxidant is selected from pentaerythritol bis(2,6-di-tert-butyl-p-cresol) and / or pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]; And / or, the auxiliary antioxidant is tris(2,4-di-tert-butylphenyl) phosphite; And / or, the density adjuster is ceramic sand and / or steel shot.

7. The modified graphite-coated soft particles according to claim 6, wherein, The ceramic sand has a particle size of 45-90 μm.

8. The modified graphite-coated soft particles according to claim 6, wherein, The steel shot has a particle size of 45-75 μm.

9. The modified graphite-coated soft particles according to claim 1, wherein, The particle size of the modified graphite-coated soft particles is 200 μm to 3.5 mm.

10. The modified graphite-coated soft particles according to claim 9, wherein, The particle size of the modified graphite-coated soft particles is 500μm-2mm.

11. A method for preparing modified graphite-coated soft particles according to any one of claims 1-10, characterized in that, The preparation method includes: (1) The rubber main agent, antioxidant, auxiliary antioxidant, second modified graphite and density regulator are melt-blended together to obtain integral rubber; (2) The whole rubber is crushed, sheared and extruded into granules to obtain soft granules; (3) The first modified graphite and water are mixed to obtain the first modified graphite dispersion. The first modified graphite dispersion is brought into contact with the soft particles, and the first modified graphite is adhered to the surface of the soft particles under heating and rotation conditions to obtain modified graphite coated soft particles.

12. The preparation method according to claim 11, wherein, In step (1), the conditions for melt mixing include: a temperature of 180-350℃; And / or, in step (2), the conditions for the extrusion granulation include: a temperature of 180-350°C; And / or, in step (3), the conditions for heating and rotating include: a temperature of 180-200°C and a rotation speed of 50-150 rpm; And / or, in step (3), the concentration of the first modified graphite dispersion is 0.1-1%; And / or, in step (3), the weight ratio of the first modified graphite dispersion to the soft particles is 100:(5-20).

13. A profile control and water-blocking agent, characterized in that, The profile-adjusting and water-blocking agent is the modified graphite-coated soft particle as described in any one of claims 1-10.

14. The profile control and water-blocking agent according to claim 13, wherein, The profile control and water shut-off agent is at 140℃ and has a salinity of 20×10. 4 The elastic modulus under the mg / L condition is 700-800 kPa, and the viscous modulus is 350-450 kPa; And / or, the density of the profile control and water-blocking agent is 1-1.2 g / cm³. 3 .

15. The application of the profile control and water shut-off agent according to claim 13 or 14 in an oil reservoir.

16. The application according to claim 15, wherein, The application includes: in the oil reservoir, the profile control and water shut-off agent particles agglomerate and thus seal; And / or, the reservoir conditions include: a depth of ≥4500m, a temperature of ≥140℃, and a salinity of ≥20×10⁻⁶. 4 mg / L.

17. The application according to claim 16, wherein, The reservoir conditions include: a depth of 4500-6500m, a temperature of 140-200℃, and a salinity of 20×10⁻⁶. 4 mg / L to 30×10 4 mg / L.

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