Modified graphite-coated soft particle and method for preparing same, and profile control and water shutoff agent and application thereof

1 . A modified graphite-coated soft particle, comprising a soft particle and first modified graphite coating on a surface of the soft particle, wherein the soft particle comprises a rubber main agent, an antioxidant, an auxiliary antioxidant, a density regulator, and second modified graphite, and the first modified graphite and the second modified graphite are the same or different and each are modified graphite with a surface rich in hydroxyl groups and carboxyl groups;

wherein a particle size of the modified graphite is 200 nm-1000 nm, a thickness of the first modified graphite coating on the surface of the soft particle is 30 nm-50 μm, and a particle size of the modified graphite-coated soft particle is 200 μm-3.5 mm;

wherein the modified graphite contains oxygen-containing groups, the oxygen-containing groups comprise hydroxyl groups, carboxyl groups, and epoxy groups, and based on a total number of the oxygen-containing groups of the modified graphite, the number of the hydroxyl groups accounts for 30%-60%, the number of the carboxyl groups accounts for 10%-30%, and the number of the epoxy groups accounts for 30%-40%;

wherein based on a total weight of the soft particle, a content of the rubber main agent is 65 wt %-85 wt %, a content of the antioxidant is 0.1 wt %-0.5 wt %, a content of the auxiliary antioxidant is 0.05 wt %-0.3 wt %, a content of the second modified graphite is 5 wt %-10 wt %, and a content of the density regulator is 4 wt %-30 wt %; and

wherein the modified graphite-coated soft particle is formed by a method comprising mixing the first modified graphite and water to obtain a first modified graphite dispersion, the first modified graphite dispersion having a concentration of 0.1%-1%; bringing the first modified graphite dispersion and the soft particle into contact, wherein a weight ratio of the amount of the first modified graphite dispersion to the amount of the soft particle is 100:(2-20); and causing the first modified graphite to adhere to the surface of the soft particle under conditions of heating and rotation.

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

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

4 . The modified graphite-coated soft particle according to claim 1 , wherein the particle size of the modified graphite is 300 nm-500 nm, or, the particle size of the modified graphite is 500 nm-800 nm.

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

6 . The modified graphite-coated soft particle according to claim 1 , wherein the rubber main agent is selected from one or more of natural rubber, styrene butadiene rubber, or ethylene propylene diene monomer;

or, the antioxidant is selected from pentaerythritol bis(2,6-di-tert-butyl-p-cresol) ester or pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate];

or, the auxiliary antioxidant is tris(2,4-di-tert-butylphenyl)phosphite;

or, the density regulator is ceramic sand or steel shots.

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

8 . The modified graphite-coated soft particle according to claim 6 , wherein a particle size of the steel shots is 45 μm-75 μm.

9 . The modified graphite-coated soft particle according to claim 1 , wherein the particle size of the modified graphite-coated soft particle is 500 μm-2 mm.

10 . A method for preparing the modified graphite-coated soft particle according to claim 1 , comprising:

(1) bringing the rubber main agent, the antioxidant, the auxiliary antioxidant, the second modified graphite, and the density regulator into contact for melt mixing to obtain integral rubber;

(2) performing crushing, shearing, and extrusion granulation on the integral rubber to obtain the soft particle; and

(3) mixing the first modified graphite and water to obtain the first modified graphite dispersion, bringing the first modified graphite dispersion and the soft particles into contact, and causing the first modified graphite to adhere to the surface of the soft particle under conditions of heating and rotation to obtain the modified graphite-coated soft particle.

11 . The method for preparing according to claim 10 , wherein in step (1), a condition for the melt mixing comprises: a temperature of 180° C.-350° C.; or,

in step (2), a condition for the extrusion granulation comprises: a temperature of 180° C.-350° C.; or, in step (3), the conditions of the heating and rotation comprise: a temperature of 180° C.-200° C. and a rotation rate of 50 rpm-150 rpm; or,

in step (3), the weight ratio of the amount of the first modified graphite dispersion to the amount of the soft particles is 100:(5-20).

12 . A profile control and water shutoff agent, being the modified graphite-coated soft particle according to claim 1 .

13 . The profile control and water shutoff agent according to claim 12 , wherein the profile control and water shutoff agent has an elastic modulus of 700 kPa-800 kPa and a viscous modulus of 350 kPa-450 kPa at 140° C. and under a condition of a salinity of 20×10 4 mg/L; or, a density of the profile control and water shutoff agent is 1 g/cm 3 -1.2 g/cm 3 .

14 . The profile control and water shutoff agent according to claim 12 , wherein the profile control and water shutoff agent is useful in an oil reservoir.

15 . The profile control and water shutoff agent according to claim 14 , wherein agglomeration of particles of the profile control and water shutoff agent forms a seal in the oil reservoir;

or, conditions of the oil reservoir: a depth of ≥4500 m, a temperature of ≥140° C., and a salinity of ≥20×10 4 mg/L.

16 . The profile control and water shutoff agent according to claim 15 , wherein the conditions of the oil reservoir: a depth of 4500 m-6500 m, a temperature of 140° C.-200° C., and a salinity of 20×10 4 mg/L to 30×10 4 mg/L.