METHOD OF GEOTHERMAL DRIVEN CO2 CATALYTIC REDUCTION FOR ENHANCING CO2 SEQUESTRATION AND OIL RECOVERY

Abstract

The present invention provides a mixed injection fluid and a corresponding method for enhancing CO.sub.2 sequestration and oil recovery, which is a method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery. In the present invention, a technical solution of the liquid nitrogen fracturing, an injection fluid injection, and the catalysis transportation and storage were adopted, which makes full use of the thermal energy of deep geothermal reservoir in combination with nano-Cu-based catalysts to activate the hydrothermal cracking reaction of crude oil and CO.sub.2 thermal reduction reaction, so to simultaneously enhance crude oil recovery and CO.sub.2 sequestration, fundamentally solving the existing problems of CO.sub.2-EOR technologies. Moreover, CO.sub.2 thermal catalytic reduction products can also work as a surfactant to accelerate the desorption crude oil from the rock surface and decrease the interfacial tension, and finally EOR.

Claims

1. A mixed injection fluid, in parts by weight, comprising: crude oil 100 parts by weight; water 8.0 to 12.0 parts by weight; proppant 5.0 to 20.0 parts by weight; nano-Cu-based catalyst 0.01 to 0.05 parts by weight.

2. The injection fluid according to claim 1, wherein the crude oil is high-viscosity crude oil rich in asphaltene and resin; the viscosity of the crude oil is 50 to 150 mP.Math.s; the content of the asphaltene is 8% to 25%; the content of the resin is greater than 15%

3. The injection fluid according to claim 1, wherein the proppant comprises one or more of quartz sand, bauxite and ceramsite; the nano-Cu-based catalyst comprises a copper catalyst and/or a copper alloy catalyst; the injection fluid enters the fractured fracture in the state of water-in-oil as the basic liquid carrying proppant and nano-Cu-based catalyst; the injection fluid is in the deep geothermal reservoir, and the nano-Cu-based catalyst adheres to the porous petroleum coke carrier formed by the hydrothermal cracking of the crude oil.

4. A method for enhancing CO.sub.2 sequestration and oil recovery comprising the following steps: 1) arranging an injection well and a transfer well around a production well; wherein, the injection well is an injection well that is drilled through the crude oil reservoir to reach the deep geothermal reservoir, and the transfer well is a transfer well that is drilled through the crude oil reservoir to reach the deep geothermal reservoir; wherein the perforation of the injection well in the deep geothermal reservoir is in an open state; wherein the perforation of the transfer well in the deep geothermal reservoir is in an open state; 2) using the high-pressure liquid nitrogen to fracture the deep geothermal reservoir between the injection well and the transfer well; 3) injecting an injection fluid into the injection well until the production in the transfer well is equal to that of injection, then stopping the injection, and placing packers in the injection well and the transfer well respectively, and then performing well soaking; 4) removing the packers, injecting CO.sub.2 into the deep geothermal reservoir through the injection well to displace light crude oil components that produced by the hydrothermal cracking of crude oil, producing the light crude oil components through the transfer well until the light crude oil components are no longer produced, and stopping the CO.sub.2 injection; 5) opening the perforation of the transfer well at the crude oil reservoir, then placing a cylinder containing nano-Cu-based catalyst and porous nano-catalyst carrier into the wellbore of transfer well between the crude oil reservoir and deep geothermal reservoir, and placing a wellbore packer in the wellbore of the transfer well above crude oil reservoir; 6) injecting the mixture of H.sub.2O and CO.sub.2 into the deep geothermal reservoir through the injection well and thermally reducing CO.sub.2; the water steam, CO.sub.2 and CO.sub.2 thermal reduction products flowing through the cylinder containing the catalysts in the transfer wellbore, and the unreacted CO.sub.2 being continuously reduced; and then the water steam, CO.sub.2, CO.sub.2 thermal reduction products and nano-Cu-based catalyst entering the crude oil reservoir and activating the hydrothermal cracking reaction of crude oil and CO.sub.2 thermal reduction reaction.

5. The method according to claim 4, wherein the production well is a production well that is drilled through and perforates the crude oil reservoir; the number of the production well is one or more; the number of the injection well is one.

6. The method according to claim 4, wherein the number of the transfer well is one or more; the deep geothermal reservoir is a deep geothermal reservoir comprising hot dry rock; the duration of the well soaking is 20 to 30 days.

7. The method according to claim 4, wherein the cylinder is a cylinder without a top cover and with a porous bottom; the outer wall of the cylinder is wrapped with a high temperature resistant sealing ring; a porous fixing device is arranged inside the cylinder; the porous nano-catalyst carrier compounded with the nano-Cu-based catalyst is dispersed and fixed on the porous fixing device.

8. The method according to claim 4, wherein the mass ratio of the nano-Cu-based catalyst to the porous nano-catalyst carrier is 1:(10 to 20); above the crude oil reservoir is specifically a position above the crude oil reservoir close to the crude oil reservoir; in the mixture of H.sub.2O and CO.sub.2, the volume ratio of H.sub.2O to CO.sub.2 is 1:(2.5 to 4), and the volume ratio is the volume ratio under formation pressure and temperature.

9. The method according to claim 4, wherein the injection of the mixture of H.sub.2O and CO.sub.2 is specifically continuous injection during the oil recovery enhancement process; the products of CO.sub.2 thermal reduction reaction comprise small organic molecules; the small organic molecules comprise one or more of methane, methanol and formic acid.

10. The method according to claim 4, wherein the method further comprises the following steps: 7) when the crude oil production gradually decreases, plugging the perforation of the transfer well in the crude oil reservoir, perforating the injection well at the crude oil reservoir, and continuing reverse displacement by using the mixture of H.sub.2O and CO.sub.2.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0049] FIG. 1 is the schematic diagram 1 of the reservoir stimulation (including liquid nitrogen fracturing; the mixed fluid injection; the hydrothermal cracking of crude oil into light crude oil and petroleum coke; and the light crude oil displacement) in the geothermal reservoir of the method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention;

[0050] FIG. 2 is the schematic diagram 2 of the characteristics of catalyst cylinder in the wellbore of transfer well of the method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention;

[0051] FIG. 3 is the schematic diagram 3 of the all the reaction mechanisms of the method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention;

[0052] FIG. 4 is a comparative statistical diagram of the crude oil production and the CO.sub.2 injection and production before and after the implementation of the method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention.

DETAILED DESCRIPTION

[0053] In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the claims of the present invention patent.

[0054] All the raw materials of the present invention are not particularly limited in their source, which can be purchased in the market or prepared according to conventional methods well known to those skilled in the art.

[0055] The raw materials used in the present invention are not particularly limited in their purity. In the present invention, they are preferably of industrial purity or conventional purity in the field of oil recovery.

[0056] The abbreviations of all the processes of the present invention belong to the conventional abbreviations in the art, and each abbreviation is clear and definite in its relevant use field. Those skilled in the art can understand the conventional process steps according to the abbreviations.

[0057] All the noun expressions and abbreviations of the present invention belong to the conventional noun expressions and abbreviations in the art, and each noun expression and abbreviation is clear and definite in its relevant application field. Those skilled in the art can understand clearly, accurately and uniquely according to the noun expressions and abbreviations.

[0058] The present invention provides a mixed injection fluid, which, in parts by weight, comprises:

TABLE-US-00002 crude oil 100 parts by weight; water 8.0 to 12.0 parts by weight; proppant 5.0 to 20.0 parts by weight; nano-Cu-based catalyst 0.01 to 0.05 parts by weight.

[0059] In the present invention, the water is added in an amount of 8.0 to 12.0 parts by weight, may be 8.5 to 11.5 parts by weight, preferably 9 to 11 parts by weight, and more preferably 9.5 to 10.5 parts by weight.

[0060] In the present invention, the proppant is added in an amount of 5.0 to 20.0 parts by weight, may be 8.0 to 17 parts by weight, preferably 11 to 14 parts by weight.

[0061] In the present invention, the nano-Cu-based catalyst is added in an amount of 0.01 to 0.05 parts by weight, may be 0.015 to 0.045 parts by weight, preferably 0.02 to 0.04 parts by weight, preferably 0.025 to 0.035 parts by weight.

[0062] In the present invention, the crude oil is preferably high-viscosity crude oil rich in asphaltene and resin.

[0063] In the present invention, the viscosity of the crude oil is preferably 50 to 150 mP.Math.s, more preferably 70 to 130 mP.Math.s, and more preferably 90 to 110 mP.Math.s.

[0064] In the present invention, the content of the asphaltene is preferably 8% to 25%, more preferably 11% to 22%, and more preferably 14% to 19%.

[0065] In the present invention, the content of the resin is preferably greater than 15%, more preferably greater than or equal to 18%, and more preferably greater than or equal to 20%.

[0066] In the present invention, the proppant preferably comprises one or more of quartz sand, bauxite and ceramsite, more preferably is quartz sand, bauxite or ceramsite.

[0067] In the present invention, the nano-Cu-based catalyst preferably comprises a copper catalyst and/or a copper alloy catalyst, more preferably is a copper catalyst or a copper alloy catalyst. Specifically, the copper alloy catalyst preferably comprises one or more of CuSn, CuIn and CuPb.

[0068] In the present invention, the injection fluid enters the fractured fracture in the state of water-in-oil preferably as the basic liquid carrying proppant and nano-Cu-based catalyst.

[0069] In the present invention, the injection fluid is in the deep geothermal reservoir, and the nano-Cu-based catalyst preferably adheres to the porous petroleum coke carrier that formed by the hydrothermal cracking of crude oil.

[0070] The present invention provides a method for enhancing CO.sub.2 sequestration and oil recovery, comprising the following steps: [0071] 1) arranging an injection well and a transfer well around a production well; wherein, the injection well is an injection well that is drilled through the crude oil reservoir to reach the deep geothermal reservoir, and the transfer well is a transfer well that is drilled through the crude oil reservoir to reach the deep geothermal reservoir; [0072] wherein the perforation of the injection well in the deep geothermal reservoir is in an open state; [0073] wherein the perforation of the transfer well in the deep geothermal reservoir is in an open state; [0074] 2) using high pressure liquid nitrogen to fracture the deep geothermal reservoir between the injection well and the transfer well; [0075] 3) injecting a mixed injection fluid into the injection well until the production of the crude oil mixture in the transfer well is equal to the injection, then stopping the injection, and placing packers in the injection well and the transfer well respectively to perform well soaking; [0076] 4) removing the packers, injecting CO.sub.2 into the deep geothermal reservoir through the injection well to displace light crude oil components that produced by hydrothermal cracking of crude oil; producing the light crude oil components from the transfer well; and stopping the CO.sub.2 injection until the light crude oil components are no longer produced from the transfer well; [0077] 5) opening the perforation of the transfer well at the crude oil reservoir, then placing a cylinder containing nano-Cu-based catalyst and porous nano-catalyst carrier into the wellbore of the transfer well between the crude oil reservoir and the deep geothermal reservoir, and then placing a wellbore packer in the wellbore of the transfer well above the crude oil reservoir; [0078] 6) injecting the mixture of H.sub.2O and CO.sub.2 into the deep geothermal reservoir through the injection well to activate CO.sub.2 thermal reduction reaction; the water steam, CO.sub.2 and the CO.sub.2 thermal reduction products flowing through the cylinder containing the catalysts in the transfer wellbore, and the unreacted CO.sub.2 being continuously reduced; and then the water steam, CO.sub.2, the CO.sub.2 thermal reduction products and nano-Cu-based catalyst entering the crude oil reservoir to activate the hydrothermal cracking reaction of crude oil and thermal reduction reaction of CO.sub.2.

[0079] The above-mentioned hydrothermal cracking reaction of crude oil of the present invention can significantly reduce the viscosity of crude oil, increase the fluidity of crude oil, and enhance the oil recovery. Meanwhile, the thermal reduction reaction of CO.sub.2 occurs to generate molecules such as methanol and formic acid, so as to achieve the permanent and stable CO.sub.2 sequestration.

[0080] In the present invention, an injection well and a transfer well are firstly arranged around a production well; wherein, the injection well is an injection well that is drilled through the crude oil reservoir to reach the deep geothermal reservoir, and the transfer well is a transfer well that is drilled through the crude oil reservoir to reach the deep geothermal reservoir;

[0081] In the present invention, the perforation of the injection well in the deep geothermal reservoir is preferably in an open state.

[0082] In the present invention, the perforation of the transfer well in the deep geothermal reservoir is preferably in an open state.

[0083] In the present invention, the production well is preferably a production well that is drilled through and perforated the crude oil reservoir.

[0084] In the present invention, the number of the production well is preferably one or more.

[0085] In the present invention, the number of the injection well is preferably one.

[0086] In the present invention, the number of the transfer well is preferably one or more.

[0087] In the present invention, the high-pressure liquid nitrogen is used to fracture the deep geothermal reservoir between the injection well and the transfer well.

[0088] In the present invention, the deep geothermal reservoir is preferably a deep geothermal reservoir comprising hot dry rock.

[0089] In the present invention, the mixed injection fluid is injected into the injection well until the output in the transfer well is equal to that of the injection, then the injection is stopped, and packers are placed in the injection well and the transfer well respectively to perform well soaking.

[0090] In the present invention, the duration of the well soaking is preferably 20 to 30 days, more preferably 22 to 28 days, and more preferably 24 to 26 days.

[0091] In the present invention, the packers are then removed, CO.sub.2 is injected into the deep geothermal reservoir through the injection well to displace light crude oil components that produced in the hydrothermal cracking of crude oil, then the light crude oil components are produced through the transfer well until the light crude oil components are no longer produced through the transfer well, and the CO.sub.2 injection is stopped.

[0092] In the present invention, the perforation of the transfer well at the crude oil reservoir is opened, then a cylinder containing the nano-Cu-based catalyst and porous nano-catalyst carrier is placed in the wellbore of transfer well between crude oil reservoir and deep geothermal reservoir, and then a wellbore packer is placed in the wellbore above crude oil reservoir.

[0093] In the present invention, the cylinder is preferably a cylinder without a top cover and with a porous bottom.

[0094] In the present invention, the outer wall of the cylinder is preferably wrapped with a high temperature resistant sealing ring.

[0095] In the present invention, a porous fixing device is preferably arranged inside the cylinder.

[0096] In the present invention, the porous nano-catalyst carrier compounded with the nano-Cu-based catalyst is preferably dispersed and fixed on the porous fixing device.

[0097] In the present invention, the mass ratio of the nano-Cu-based catalyst to the porous nano-catalyst carrier is preferably 1:(10 to 20), more preferably 1:(12 to 18), more preferably 1:(14 to 16).

[0098] In the present invention, above the crude oil reservoir specifically preferably refers to a position above the crude oil reservoir close to the crude oil reservoir.

[0099] In the present invention, finally, the mixture of H.sub.2O and CO.sub.2 is injected into the deep geothermal reservoir through the injection well to activate CO.sub.2 thermal reduction reaction, the water steam, CO.sub.2 and CO.sub.2 thermal reduction products pass through the cylinder containing the catalysts in the transfer wellbore, and the unreacted CO.sub.2 is continuously reduced, and then the water steam, CO.sub.2, CO.sub.2 thermal reduction products and nano-Cu-based catalyst enter the crude oil reservoir to activate the hydrothermal cracking reaction of crude oil and thermal reduction reaction of CO.sub.2.

[0100] In the present invention, by adjusting the operation, the proppant and/or nano-Cu-based catalyst in the mixed injection fluid in the deep geothermal reservoir preferably not enter the transfer well, or substantially not enter the transfer well.

[0101] In the present invention, the nano-Cu-based catalyst entering the crude oil reservoir is the catalyst in the catalyst cylinder, and the mixed fluid that generated from the geothermal layer can carry the catalyst in the cylinder into the crude oil reservoir. In the present invention, the catalyst cylinder can be replaced periodically.

[0102] In the present invention, in the mixture of H.sub.2O and CO.sub.2, the volume ratio of H.sub.2O to CO.sub.2 is preferably 1:(2.5 to 4), more preferably 1:(2.8 to 3.7), and more preferably 1:(3.1 to 3.4). Specifically, the above-mentioned volume ratio in the present invention refers to the volume ratio under formation pressure.

[0103] In the present invention, the injection of the mixture of H.sub.2O and CO.sub.2 is specifically preferably continuous injection during the oil recovery enhancement process.

[0104] In the present invention, the products of CO.sub.2 thermal reduction reaction preferably comprise small organic molecules. Specifically, the small organic molecules preferably comprise one or more of methane, methanol and formic acid, more preferably are methane, methanol or formic acid. The products of CO.sub.2 thermal reduction reaction obtained by the present invention can achieve the permanent and stable CO.sub.2 sequestration. Further, the products of CO.sub.2 thermal reduction, such as methanol, formic acid and other small organic molecules, can act as surfactants to improve the oil displacement efficiency and ultimate oil recovery.

[0105] In the present invention, the method further preferably comprises the following steps: [0106] 7) when the crude oil production gradually decreases, plugging the perforation of the transfer well in crude oil reservoir, and perforating the crude oil reservoir layer in the injection well, and continuing reverse displacement by using the mixture of H.sub.2O and CO.sub.2.

[0107] In the present invention, in order to better complete and refine the overall technical solution, further improve the stability of the permanent sequestration of CO.sub.2, better improve the oil displacement efficiency, and increase the oil production, the above-mentioned method for geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery can specifically comprise the following steps: [0108] (1) Drilling an injection well through the crude oil reservoir to reach the deep geothermal reservoir (comprising hot dry rock), and opening the perforation thereof in the deep geothermal reservoir (comprising hot dry rock); correspondingly, drilling one or several transfer wells through both the crude oil reservoir and deep geothermal reservoir simultaneously, and opening the perforation thereof in the deep geothermal reservoir; drilling a production well only through the crude oil reservoir and perforating; [0109] (2) Using high pressure liquid nitrogen to fracture the deep geothermal reservoir (comprising hot dry rock) between the injection well and the transfer well; [0110] (3) Ultrasonically mixing crude oil, water, proppant and nano-Cu-based catalyst in a certain ratio (preferably a mass ratio of 100:10:8.0:0.01), then quickly injecting the mixture into the deep geothermal reservoir (comprising hot dry rock) that fractured by liquid nitrogen, until the production in the transfer well is equal to that of injection, and then stopping the injection, in which the crude oil should comprise more heavy components (including asphaltene and resin), and the viscosity thereof should be within 50 to 150 mP.Math.s.

[0111] Referring to FIG. 1, FIG. 1 is the schematic diagram 1 of the reservoir stimulation (including liquid nitrogen fracturing; the mixed fluid injection; the hydrothermal cracking of crude oil into light crude oil and petroleum coke; and the light crude oil displacement) in the geothermal reservoir of the method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention [0112] (4) Placing packers in the injection well and the transfer well respectively, i.e., performing the well soak for 20 days; [0113] (5) Removing the packers, injecting CO.sub.2 into the deep geothermal reservoir (comprising hot dry rock) through the injection well to displace the light crude oil components that produced by hydrothermal cracking of crude oil, producing the light crude oil components through the transfer well, until the light crude oil components are no longer produced through the transfer well, stopping the CO.sub.2 injection; [0114] (6) Opening the perforation of the transfer well at the position of crude oil reservoir; [0115] (7) Mixing the nano-Cu-based catalyst and the porous nano-catalyst carrier (mass ratio 1:20) evenly, placing the mixture in a cylinder with a diameter of 12 cm and a length of 5 m, wherein the cylinder has no top cover and has a porous bottom surface, and the outer wall thereof is wrapped with a high temperature resistant sealing ring with a thickness of about 3 cm, and the cylinder is integrally clamped in the wellbore of the transfer well between the crude oil reservoir and the geothermal reservoir (comprising hot dry rock); [0116] Referring to FIG. 2, FIG. 2 is the schematic diagram 2 of the characteristics of catalyst cylinder in the wellbore of transfer well of the method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention; [0117] (8) Placing a wellbore packer in the wellbore of the transfer well above but close to the crude oil reservoir; [0118] (9) Mixing H.sub.2O and CO.sub.2 in a certain ratio (1:(2.5 to 4) under formation pressure and temperature), injecting the mixture into deep geothermal reservoir (comprising hot dry rocks) through the injection well; thermally reducing CO.sub.2 in deep geothermal reservoir (comprising hot dry rocks) and generating the small organic molecules such as methanol and formic acid, so as to achieve permanent and stable CO.sub.2 sequestration; the mixture of H.sub.2O vapor and CO.sub.2 carrying CO.sub.2 reduction products flowing through the nano-Cu-based catalyst cylinder in the transfer wellbore, in which CO.sub.2 was also thermally reduced into the small organic molecules such as methanol and formic acid; subsequently, the mixture of H.sub.2O vapor and CO.sub.2 carrying CO.sub.2 reduction products and nano-Cu-based catalyst entering into the crude oil reservoir to activate the hydrothermal cracking reaction of crude oil, which significantly reduces the viscosity of crude oil, increases the fluidity of crude oil, and enhances oil recovery; moreover, also activating the thermal catalytic reduction reaction of CO.sub.2 and generating methanol, formic acid and other molecules, achieving permanent and stable CO.sub.2 sequestration, wherein, specifically, the products of CO.sub.2 thermal reduction-organic small molecules such as methanol and formic acid act as surfactants can improve the oil displacement efficiency and enhances oil recovery;

[0119] Referring to FIG. 3, FIG. 3 is the schematic diagram 3 of the all the reaction mechanisms of the method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention. [0120] (10) When the crude oil production gradually decreases, plugging the perforation of transfer well in crude oil reservoir, perforating the crude oil reservoir in injection well and continuing reverse displacement to further enhance oil recovery and CO.sub.2 sequestration.

[0121] The above content of the present invention provides a method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery and a mixed injection fluid used. The injection fluid with a specific composition and content and the corresponding method for enhancing CO.sub.2 sequestration and oil recovery designed by the present invention provide a technical solution of liquid nitrogen fracturing in combination with injecting the injection fluid. Since the temperature of deep geothermal reservoir, especially hot dry rock, is generally higher than 200 C., such a high temperature has severe damage to the drill unit, and conventional fracturing fluid and sand-carrying fluid are so easy to vaporize hence they cannot work normally. The temperature of liquid nitrogen is as low as 196 C. to 210 C., and the use of liquid nitrogen fracturing can effectively reduce the damage of deep geothermal reservoir to the drill unit. The most important thing is that liquid nitrogen can quickly cool the formation within a period of time, providing conditions for subsequent fluid injection, and avoiding immediate vaporization of fluid after injection. An injection fluid with a specific formulation of a mixture of crude oil and water, nano-Cu-based catalyst carried with proppant is injected into the deep geothermal reservoir (comprising hot dry rock). This is because the boiling point of crude oil is much higher than that of aqueous solution, and with the assistant of the cooling effect of liquid nitrogen, water-in-oil as the basic liquid can effectively carry proppant and nano-Cu-based catalyst into the fractured fracture. As the cooling effect of liquid nitrogen gradually decreases, the high temperature of deep geothermal reservoir (comprising hot dry rock) vaporizes H.sub.2O and accelerates the dissociation of H.sub.2O. The crude oil is combined with H.sup.+ generated by the dissociation of H.sub.2O, catalyzed by the nano-Cu-based catalyst, and activate the hydrothermal cracking reaction to generate light crude oil and petroleum coke. During this process, H.sub.2O and light components vaporize from the crude oil, promoting the formation of porous petroleum coke. The porous petroleum coke, as a good and stable carrier for nano-Cu-based catalysts, provides good conditions for the functioning of nano-Cu-based catalysts. In addition, CO.sub.2 is combined with H.sup.+ generated by the dissociation of H.sub.2O, catalyzed by the nano-Cu-based catalyst, and activate the thermal reduction reaction to generate small organic molecules such as methane, methanol or formic acid.

[0122] The method provided by the present invention is a technical solution of continuous injection of CO.sub.2 and H.sub.2O to displace oil and sequestrate CO.sub.2. CO.sub.2 and H.sub.2O are injected into the deep geothermal reservoir (comprising hot dry rock), where CO.sub.2 is thermally reduced into the small organic molecules such as methane, methanol and formic acid, with the assistant of H.sup.+ generated from H.sub.2O vaporization in combination with uniformly distributed nano-Cu-based catalyst supported in porous petroleum coke. Then high-temperature CO.sub.2, H.sub.2O vapor and the generated small organic molecules flow through the catalyst cylinder that installed in the transfer well, during which the CO.sub.2 thermal reduction reaction occurs continuously. Finally, the high-temperature CO.sub.2, H.sub.2O vapor and CO.sub.2 reduction products together carry the nano-Cu-based catalyst into the crude oil reservoir to activate the hydrothermal cracking reaction of crude oil and the thermal catalytic reduction of CO.sub.2 simultaneously. Among them, the products of CO.sub.2 thermal catalytic reduction (formic acid, methanol, etc.) can play the role of surfactants to accelerate the desorption of crude oil from the rock surface and further improve the oil displacement efficiency. Moreover, the present invention makes full use of the thermal energy of deep geothermal reservoir in combination with nano-Cu-based catalysts to achieve hydrothermal cracking reaction of crude oil and CO.sub.2 thermal reduction reaction, so as to simultaneously achieve the enhancement of the crude oil recovery and CO.sub.2 sequestration, fundamentally solving the existing problems of CO.sub.2-EOR technologies.

[0123] The experimental results show that during the conventional technology of injection of mixed CO.sub.2 and H.sub.2O was used, the crude oil production gradually decreased from 560 m.sup.3/d to 350 m.sup.3/d, and then CO.sub.2 channeling emerged, so that the crude oil production dropped sharply to 170 m.sup.3/d. During this process, CO.sub.2 production increased from 200 m.sup.3/d to 320 m.sup.3/d, and CO.sub.2 channeling occurred in May 2019, resulting in a large amount of CO.sub.2 leakage. When the method provided by the present invention was adopted, the crude oil production rose to 620 m.sup.3/d and remained stable, and the CO.sub.2 production decreased to 100 m.sup.3/d and remained stable.

[0124] In order to further illustrate the present invention, the injection fluid and the method for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention are described in detail below with reference to the examples, but it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given only to further illustrate the features and advantages of the present invention, not to limit the claims of the present invention, and the protection scope of the present invention is not limited to the following examples.

Example 1

[0125] From December 2017 to June 2019, CO.sub.2 and H.sub.2O were mixed at a ratio of 500 m.sup.3:150 m.sup.3 (under formation pressure and temperature), and the mixture was injected into the crude oil reservoir through the injection well. The crude oil production gradually decreased from 560 m.sup.3/d to 350 m.sup.3/d, and then CO.sub.2 channeling emerged, and the crude oil production sharply reduced to 170 m.sup.3/d. During this process, the CO.sub.2 production increased from 200 m.sup.3/d to 320 m.sup.3/d and CO.sub.2 channeling occurred in May 2019, resulting in a large amount of CO.sub.2 leakage. In particular, the temperature of the injection water was stable at 250 C., which was consistent with the temperature of the target geothermal reservoir.

[0126] From June 2019 to October 2019, the technical solution in the present invention was implemented. The technical solution comprised: (1) an injection well was drilled through the geothermal reservoir and perforated; a transfer well was drilled through the crude oil reservoir into the deep geothermal reservoir around the production well and perforated both crude oil reservoir and the geothermal reservoir; (2) the high-pressure liquid nitrogen was used to fracture the deep geothermal reservoir between the injection well and transfer well; (3) the prepared injection fluid (100 parts by weight of crude oil; 10 parts by weight of water; 10 parts by weight of ceramic particle proppant; 0.025 parts by weight of nano-Cu-based catalyst) was injected into the injection well, until the production in the transfer well was equal to that of injection, the injection was stopped, the packers were placed in the injection well and the transfer well respectively, and then the well soaked for 30 days; (4) the packers were removed, then CO.sub.2 was injected into the deep geothermal reservoir through the injection well to displace the light crude oil components that produced by hydrothermal cracking of crude oil, the light crude oil components were produced through the transfer well, until no light crude oil components were produced through the transfer well, the injection of CO.sub.2 was stopped; (5) the perforation of the transfer well at the crude oil reservoir was opened, then the cylinder containing the nano-Cu-based catalyst and the porous nano-catalyst carrier was placed in the wellbore of transfer well between the crude oil reservoir and deep geothermal reservoir, and a wellbore packer was then placed in the wellbore of transfer well above the crude oil reservoir; (6) the mixture of CO.sub.2 and H.sub.2O with a ratio of 500 m 3:150 m.sup.3 (under formation pressure and temperature) was injected into the deep geothermal reservoir through the injection well, then the transfer well and the production well were connected to extract crude oil. The crude oil production rose to 620 m.sup.3/d and remained stable and the CO.sub.2 output decreased to 100 m.sup.3/d and remained stable.

[0127] Referring to FIG. 4, FIG. 4 is a comparative statistical diagram of the crude oil production and the CO.sub.2 injection and production before and after the implementation of the method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention.

[0128] The method of the geothermal driven CO.sub.2 catalytic reduction for enhancing CO.sub.2 sequestration and oil recovery provided by the present invention has been described above in detail. Specific examples are used herein to illustrate the principles and implementations of the present invention. The descriptions of the above examples are only used to help understand the method and the core idea of the present invention, including the best manner, and to enable any person skilled in the art to practice the present invention, including making and using any devices or systems, and implementing any combined methods. It should be noted that for those skilled in the art, several improvements and modifications can also be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present patent for invention is defined by the claims, and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.