A supercritical CO 2 Extraction treatment system and method

Abstract

The purpose of the present invention is to provide a supercritical CO2 extraction treatment system and method for drilling oily sludge, which belongs to the technical field of environmental protection treatment of drilling oily sludge in unconventional oil and gas production in oil and gas fields. It includes a processing system such as a CO2 circulation tank, a pressure pump, a reaction heater, a reactor, a separation heater and a separation reactor connected in sequence. The oil-soluble substances separated by the separation reactor enter the oil collecting tank, and the separated extraction-end gas CO2 flows into the CO2 circulation tank through a condenser for recycling; after the reaction of the reactor is completed, the CO2 in the reactor is recycled to the CO2 circulation tank through a primary recovery pipeline, a secondary recovery pipeline and a tertiary recovery pipeline. Under the premise of ensuring that the recovered oil-soluble substances have a high quality, the present invention recovers the CO2 in the reactor through the CO2 tertiary recovery pipeline, so that a large amount of CO2 is recycled and recycled, which solves the technical problem that the CO2 in the reactor is directly discharged before the existing reactor extraction is completed and unloaded, resulting in a large amount of CO2 waste.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection treatment of oily sludge from drilling of unconventional oil and gas production in oil and gas fields, and specifically relates to a supercritical CO 2 Extraction processing system and method. Background Art

[0002] Oil-based mud is a kind of slurry specially formulated for horizontal well drilling operations in the exploitation of oil and gas resources such as unconventional shale (oil) gas and tight oil, in order to clean the bottom of the well, carry rock cuttings, cool and lubricate the drill bit, reduce drill tool wear, increase the service life of the drill tool, balance the rock side pressure of the well wall, prevent the well wall from collapsing, and improve drilling efficiency. It is mainly composed of base oil (diesel or white oil) and organic emulsifiers, fluid loss reducers, viscosity enhancers, weighting agents and other chemical treatment agents in a certain proportion. During the drilling process, the oil-based mud carries the rock cuttings cut by the drill bit out of the ground, and a layer of oil-based mud adheres to the surface of the rock cuttings. The rock cuttings with oil-based mud adhered to the surface are called oil-based cuttings. The industry collectively refers to the oil-based cuttings and waste oil-based mud generated by the above drilling process as drilling oily sludge. The chemicals contained in drilling oily sludge are stable in nature and poorly degradable. If not handled properly, they will cause great harm to the surrounding ecological environment. Drilling oily sludge has been included in the "National List of Hazardous Wastes" (codenamed HW08).

[0003] Supercritical CO 2 Extraction technology is a new green separation technology that uses CO 2 As an extraction carrier, it is dissolved and mixed with the oil-soluble substances in the material in the supercritical fluid state, and then the mixed fluid is successively reduced in pressure and heated to make the oil-soluble substances and gaseous CO 2 Separation, so as to achieve the purpose of extracting the oil-soluble substances in the material. Supercritical CO 2 The extraction process has the advantages of no environmental pollution, good selectivity and low extraction temperature, so it is widely praised.

[0004] Currently, CO 2 The recovery is mostly gaseous CO after separation in the separation kettle. 2 Return to CO via pipeline 2 The circulation tank is recycled, and the CO in the reactor after the extraction is completed 2 It has not been effectively recycled. 2 The extraction of the material by the fluid is a high-pressure extraction. After the material extraction is completed, the CO in the reactor needs to be 2 After emptying, the reactor can be opened to remove the remaining solid phase. 2 The direct discharge not only pollutes the environment, but also causes CO 2 A lot of waste increases production costs. Summary of the invention

[0005] The purpose of the present invention is to provide a supercritical CO 2 Extraction treatment system and method, under the premise of ensuring that the recovered oil-soluble substances have high quality, it uses CO 2 The three-stage recovery pipeline recovers CO in the reactor 2 To recover the high pressure CO in the reactor 2 The pressure in the kettle is reduced to 0.1 MPa, so that a large amount of CO 2 It can be recycled and reused, solving the problem of removing CO from the reactor before unloading after extraction. 2 Direct discharge, resulting in CO 2 A lot of wasted technical problems.

[0006] To achieve the above purpose, the present invention adopts the following technical scheme: a supercritical CO 2 The extraction treatment system includes a CO 2 Circulation tank, pressure pump, reaction heater, reactor, separation heater and separation reactor. The oil-soluble substances separated by the separation reactor enter the oil collecting tank, and the separated gas CO 2 CO flows into the condenser 2 Recycling tanks for recycling;

[0007] After the reaction in the reactor is finished, close the reactor inlet control valve Ⅰ and outlet control valve Ⅲ. 2 The CO2 is recovered through the primary recovery pipeline, the secondary recovery pipeline and the tertiary recovery pipeline in sequence. 2 Recycling tanks for recycling;

[0008] The primary recovery pipeline includes a condenser;

[0009] The secondary recovery pipeline includes a gas recovery tank, a primary recovery compressor and a condenser connected in sequence;

[0010] The three-stage recovery pipeline includes a secondary recovery compressor, a gas recovery tank, a primary recovery compressor and a condenser which are connected in sequence.

[0011] As an improvement of the present invention, it also includes a control valve II for controlling the inlet and outlet of the reactor to be connected or disconnected.

[0012] As an improvement of the present invention, CO 2 Storage tanks and transfer pumps, CO 2 CO in storage tank 2 Delivered to CO via a delivery pump 2 Circulation tank or condenser.

[0013] As an improvement of the present invention, it also includes a heat exchange system, which includes a hot water tank, a cold water tank, a heat pump and a cooling tower for cooling the heat pump;

[0014] The water outlet of the hot water tank is divided into two paths, one path is used to heat the reaction kettle, separation kettle, reaction heater and separation heater; the other path is used to heat the reaction kettle, separation kettle, reaction heater and separation heater after heat exchange by the heat pump;

[0015] The water outlet of the cold water tank is divided into two ways, one for CO 2 The circulation tank, booster pump, primary recovery compressor and secondary recovery compressor are cooled, and the other route is refrigerated by the heat pump to cool the condenser.

[0016] As an improvement of the present invention, the separation heater includes a separation heater I and a separation heater II, and the separation kettle includes a separation kettle I and a separation kettle II;

[0017] The outlet control valve III is connected to the separation heater I and the separation kettle I in sequence. The oil-soluble substances separated by the separation kettle I enter the oil collecting tank, and the separated gas CO containing trace amounts of oil-soluble substances is 2 The oil-soluble substances separated by the separation kettle II enter the oil collecting tank, and the separated gas CO 2 CO flows into the condenser 2 Recycling tanks for recycling;

[0018] The primary recovery pipeline includes a separation heater II, a separation kettle II and a condenser which are connected in sequence.

[0019] As an improvement of the present invention, the number of the booster pumps is two, one is used for normal pressurization, and the other is used as a backup pressure pump.

[0020] A method of utilizing the above-mentioned drilling oily sludge supercritical CO 2 Extraction treatment system for supercritical CO 2 The extraction treatment method specifically comprises the following steps:

[0021] Supercritical CO 2 Extraction: CO 2 Liquid CO in the circulation tank 2 After being pressurized by a pressure pump and heated by a reaction heater, it reaches a supercritical fluid state, and then enters the reactor to extract the oil-soluble substances in the drilling oil sludge to form a supercritical mixed fluid; the supercritical mixed fluid passes through the reactor outlet pressure regulating valve to throttle and reduce the pressure, and is heated by a separation heater to convert the CO in the supercritical fluid state into a supercritical fluid. 2 Converted to gaseous CO 2 , originally dissolved in supercritical CO 2The oil-soluble substances in the fluid are transformed into a free state and then enter the separation kettle for separation. The separated oil-soluble substances enter the oil collecting tank. The separated gaseous CO 2 After cooling in the condenser, it turns into liquid CO 2 Enter CO 2 The circulation tank is recycled.

[0022] CO 2 First-level recovery: After the reactor extraction is completed, close the reactor inlet control valve Ⅰ and outlet control valve Ⅲ, open the exhaust control valve Ⅳ and the first-level recovery pipeline control valve Ⅴ, and use the reactor and CO 2 The pressure difference between the circulation tanks makes the CO in the reactor 2 After passing through the pipeline and cooling in the condenser, it turns into liquid CO 2 Enter CO 2 The circulation tank is recycled until the reactor and CO 2 When the pressure of the circulation tank is the same, the first-stage recovery is completed and the CO 2 Secondary recycling;

[0023] CO 2 Secondary recovery: Close the primary recovery pipeline control valve V, open the exhaust control valve IV and the secondary pipeline control valve VII, and the CO in the reactor 2 The gas enters the gas recovery tank through the pipeline, and the first-stage recovery compressor recovers the CO in the gas recovery tank. 2 The pressure is increased and the temperature is reduced by the condenser to convert it into liquid CO 2 Transport to CO 2 The circulating tank is recycled, and the secondary recovery can recover the CO in the reactor. 2 The pressure in the kettle is recovered until it drops to 0.6MPa. After the secondary recovery is completed, the CO 2 Tertiary recycling;

[0024] CO 2 Three-stage recovery: close the first-stage recovery pipeline control valve V and the second-stage pipeline control valve VII, open the third-stage recovery pipeline control valve VI, and the CO in the reactor 2 The gas is pressurized by the secondary recovery compressor and transported to the gas recovery tank. Then the CO in the gas recovery tank is compressed by the primary recovery compressor. 2 Boost pressure and send to CO through condenser 2 The circulating tank is recycled, and the three-stage recovery can recover the CO in the reactor. 2 Recover until the pressure in the kettle drops to 0.1MPa.

[0025] As an improvement of the present invention, it also includes a control valve II for controlling the inlet and outlet of the reactor to be connected or disconnected;

[0026] During the pressure increase of the reactor, open control valve II to allow CO to flow into both the inlet and outlet of the reactor at the same time. 2 Boost the pressure to avoid pressure boost at only one end, which may cause damage to the barrel in the reactor. During the reaction, control valve II is used to balance the pressure at the inlet and outlet of the reactor to ensure stable reaction.

[0027] As an improvement of the present invention, it also includes a heat exchange system, which includes a hot water tank, a cold water tank, a heat pump and a cooling tower for cooling the heat pump;

[0028] The water outlet of the hot water tank is divided into two paths, one of which is that after the water temperature in the hot water tank is raised to the set temperature by the electric heater, the control valve IX is opened, and the hot water is transported to the reactor, the separation kettle, the reaction heater and the separation heater by the hot water pump for heating, and the water discharged from the reactor, the separation kettle, the reaction heater and the separation heater is returned to the hot water tank for circulation; the other path is that when the water in the hot water tank is not electrically heated, the control valve IX is closed, the control valve VIII is opened, and the unheated water in the hot water tank is transported to the reactor, the separation kettle, the reaction heater and the separation heater by the hot water pump after heat exchange by the heat pump for heating, and the water discharged from the reactor, the separation kettle, the reaction heater and the separation heater is returned to the hot water tank for circulation;

[0029] The water outlet of the cold water tank is divided into two ways. One way is for the water in the cold water tank to be transported to the CO 2 The circulation tank, booster pump, primary recovery compressor and secondary recovery compressor are cooled, CO 2 The water discharged from the cooling of the circulation tank, booster pump, primary recovery compressor and secondary recovery compressor returns to the cold water tank for circulation; the other route is that the water in the cold water tank is transported to the heat pump through the cold water pump for refrigeration and then refrigerates the condenser, and the water discharged from the condenser returns to the cold water tank for circulation.

[0030] As an improvement of the present invention, the separation heater includes a separation heater I and a separation heater II, and the separation kettle includes a separation kettle I and a separation kettle II;

[0031] The outlet control valve III is connected to the separation heater I and the separation kettle I in sequence. The oil-soluble substances separated by the separation kettle I enter the oil collecting tank, and the separated gas CO containing trace amounts of oil-soluble substances is 2 The oil-soluble substances separated by the separation kettle II enter the oil collecting tank, and the separated gas CO 2 CO flows into the condenser 2 Recycling tanks for recycling;

[0032] The primary recovery pipeline includes a separation heater II, a separation kettle II and a condenser which are connected in sequence.

[0033] The beneficial effects of the present invention are as follows: the present invention provides a supercritical CO 2 Extraction treatment system, which uses CO 2 The three-stage recovery pipeline recovers CO in the reactor 2 Recycle the CO in the reactor 2 The pressure is recovered until the pressure in the kettle drops to 0.1MPa. In the first stage recovery pipeline, the reactor and CO 2 The pressure difference between the circulation tanks and the CO 2 After passing through the pipeline and cooling in the condenser, it turns into liquid CO 2 Enter CO 2 The circulation tank is used for recycling; in the second-stage recovery pipeline, a gas recovery tank is set in front of the first-stage recovery compressor to make the high-pressure CO in the reactor 2 First enter the gas recovery tank for buffering to prevent the high-pressure CO in the reactor 2 The primary recovery compressor is damaged, the service life of the primary recovery compressor is extended, and the CO in the reactor can be recovered through the secondary recovery. 2 The pressure in the reactor is recovered to 0.6 MPa. In the third-stage recovery pipeline, the CO in the reactor 2 CO is recovered through the secondary recovery compressor, gas recovery tank, primary recovery compressor and condenser in sequence. 2 The circulation tank is used for recycling, so that the CO in the reactor 2 The pressure in the reactor is reduced to 0.1 MPa, so that a large amount of CO 2 It can be recycled and reused. After the oily drilling sludge is extracted and treated by this system, the oil-soluble substances are of high quality and can be reused to prepare oil-based drilling fluid; the total petroleum hydrocarbon content (TPH) in the treated solid waste residue is much lower than the limit value (<3000mg / kg) of the national standard (GB4284-2018) "Control Standards for Pollutants in Agricultural Sludge". The treated solid waste residue can meet the national standard (GB41518-2022) "Shale Gas Exploration and Development Oil-Based Drilling Cuttings Treatment Methods and Control Indicators", and can also meet the Sichuan Provincial Environmental Protection Standard (DB51 / 2850-2021) "Natural Gas Extraction Oil-Containing Sludge Comprehensive Utilization Residual Solid Phase Utilization and Disposal Standards" Class A standards, which can be used to pave the well site and its roads to achieve safe reuse and disposal.

[0034] CO in the reactor 2 In terms of recycling, if two-stage recycling is adopted, CO 2 The recovery effect is not ideal; if the fourth-level recovery is adopted, it will cost more to recover trace amounts of CO 2 The present invention uses a three-stage recovery pipeline to ensure that the CO in the reactor is recycled at a relatively low cost. 2The recovery efficiency reaches the optimal state, the structure is simple and the operation is convenient. The present invention is particularly suitable for 2 Places where supply is inconvenient and transportation costs are too high, such as offshore drilling platforms and onshore cluster well drilling platforms.

[0035] Furthermore, it also includes a control valve II for controlling the inlet and outlet of the reactor to be connected or disconnected. During the pressure increase of the reactor, the control valve II is opened to allow CO to flow into both the inlet and outlet of the reactor at the same time. 2 Boost the pressure to avoid pressure boost at only one end, which may cause damage to the barrel in the reactor. During the reaction, if the material in the barrel in the reactor is too densely packed, causing a large pressure difference between the reactor inlet and outlet, use control valve II to balance the pressure between the reactor inlet and outlet to ensure stable reaction.

[0036] Furthermore, CO 2 Storage tanks and transfer pumps, CO 2 CO in storage tank 2 Delivered to CO via a delivery pump 2 Circulation tank or condenser. If the transfer pump is connected to the CO 2 When the circulation tank is close, CO 2 Liquid CO in storage tank 2 Directly delivered to CO via a transfer pump 2 Circulation tank; if the delivery pump is connected to the CO 2 When the circulation tank is far away, especially in summer, to prevent CO 2 Vaporization requires the CO in the transmission pipeline to 2 It is cooled by the condenser to keep it in liquid state so that it can be transported to the CO 2 Circulation tank. Users can choose different modes according to the actual situation on site, expanding the application of the system.

[0037] Furthermore, it also includes a heat exchange system, which includes a hot water tank, a cold water tank, a heat pump and a cooling tower for cooling the heat pump; the water outlet of the hot water tank is divided into two paths, one of which is an electric heating mode, that is, the water in the hot water tank is heated to a set temperature by an electric heater, and then the hot water is transported to the reactor, the separation kettle, the reaction heater and the separation heater for heating by a hot water pump; the other is a heat pump heat exchange mode, that is, the unheated water in the hot water tank is transported to the reactor, the separation kettle, the reaction heater and the separation heater for heating by a hot water pump. By adopting the above two heat exchange modes, when the ambient temperature is relatively high, such as in summer, the heat pump heat exchange mode can be directly adopted; when the ambient temperature is relatively low, such as in winter, when the system is just turned on, the electric heating mode is adopted, and after the system runs stably, it is switched to the heat pump heat exchange mode, thereby avoiding the high power consumption in the electric heating mode and effectively reducing the power consumption of the whole system.

[0038] The water outlet of the cold water tank is divided into two ways, one for CO 2 The circulation tank, booster pump, primary recovery compressor and secondary recovery compressor are cooled, and the other route is refrigerated by the heat pump to cool the condenser. The structure is simple and the cost is low.

[0039] Furthermore, the separation heater includes a separation heater I and a separation heater II, and the separation kettle includes a separation kettle I and a separation kettle II. Through the above two-stage separation, whether the CO discharged from the reactor outlet during the extraction process 2 , or CO recovered through the primary recovery pipeline after the extraction is completed 2 , the recovered CO 2 The purity has been further improved.

[0040] Furthermore, there are two booster pumps, one for normal boosting and the other for backup, which effectively improves the production efficiency of the system. Moreover, once one booster pump fails, the other booster pump can be used to take into account both normal boosting and backup functions, reducing the impact on system operation and ensuring that the system does not shut down.

[0041] The present invention also provides a method for utilizing the above-mentioned drilling oily sludge supercritical CO 2 Extraction treatment system for supercritical CO 2 The extraction treatment method adopts the above-mentioned supercritical CO 2 The extraction treatment system therefore has corresponding beneficial effects. For details, please refer to the previous description and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The supercritical CO of oily sludge from drilling according to the first embodiment of the present invention 2 Schematic diagram of the overall structure of the extraction treatment system;

[0043] Figure 2 This is a schematic diagram of the structure of the cold and heat exchange system of the first embodiment of the present invention.

[0044] Figure 3 The drilling oily sludge supercritical CO 2 Schematic diagram of the overall structure of the extraction processing system.

[0045] In the figure: 1. CO 2 Storage tank; 2. Delivery pump; 3. CO 2 Circulation tank; 4. Pressure pump; 5. Reaction heater; 6. Control valve I; 7. Reactor; 8. Control valve II; 9. Control valve III; 10. Separation heater; 101. Separation heater I; 102. Separation heater II; 11. Separation kettle; 111. Separation kettle I; 112. Separation kettle II; 12. Oil collecting tank; 13. Control valve IV; 14. Control valve V; 15. Control valve VI; 16. Secondary recovery compressor; 17. Control valve VII; 18. Gas recovery tank; 19. Primary recovery compressor; 20. Condenser; 21. Cold water tank; 22. Hot water tank; 23. Control valve VIII; 24. Control valve IX; 25. Heat pump; 26. Cooling tower; 27. Control valve X. DETAILED DESCRIPTION

[0046] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0047] It should be noted that the terms "front", "rear" and the like in the embodiments of the present invention are merely relative concepts or are based on the normal use state of the product and should not be considered as restrictive.

[0048] Embodiment 1:

[0049] like Figure 1 As shown, a supercritical CO 2 The extraction treatment system includes a CO 2 Circulation tank 3, booster pump 4, reaction heater 5, reactor 7, separation heater 10 and separation reactor 10. The oil-soluble substances separated by the separation reactor 10 enter the oil collecting tank 12, and the separated extraction end gas CO 2 After cooling in the condenser 20, it is converted into liquid CO 2 Inflow CO 2 After the reaction in the reactor 7 is finished, close the reactor inlet control valve Ⅰ6 and outlet control valve Ⅲ9, and the CO in the reactor2 The CO2 is recovered through the primary recovery pipeline, the secondary recovery pipeline and the tertiary recovery pipeline in sequence. 2 The circulation tank 3 is recycled. The primary recovery pipeline includes the condenser 20, the CO in the reactor 7 2 After passing through the pipeline and cooling in the condenser 20, it is converted into liquid CO 2 Enter CO 2 The circulation tank 3 is recycled; the secondary recovery pipeline includes a gas recovery tank 18, a primary recovery compressor 19 and a condenser 20 connected in sequence; the tertiary recovery pipeline includes a secondary recovery compressor 16, a gas recovery tank 18, a primary recovery compressor 19 and a condenser 20 connected in sequence. Control valves II8 for controlling the inlet and outlet of the reactor 7 to be connected or disconnected are also provided at both ends of the reactor 7. During the pressure increase process of the reactor 7, the control valve II8 is opened to allow CO to flow into both the inlet and outlet of the reactor 7 at the same time. 2 The pressure is increased to avoid the pressure being increased at only one end, which would cause damage to the barrel in the reactor 7; in addition, during the reaction, the pressure balance between the inlet and outlet of the reactor 7 is adjusted by the control valve II8 to ensure the stable reaction.

[0050] The system also includes CO 2 Storage tank 1 and delivery pump 2, CO 2 CO in storage tank 1 2 Delivered to CO via delivery pump 2 2 Circulation tank 3 or condenser 20, CO 2 Storage tank 1 is mainly used to supplement CO for the entire system. 2 If the delivery pump 2 is connected to CO 2 When the circulation tank 3 is close, CO 2 Liquid CO in storage tank 3 2 Directly delivered to CO via delivery pump 2 2 Circulation tank 3; if the delivery pump 2 and CO 2 When the circulation tank 3 is far away, especially in summer, to prevent CO 2 Vaporization requires the CO in the transmission pipeline to 2 The condenser 20 cools the gas to keep it in liquid state so that it can be transported to the CO 2 Circulation tank 3. Users can choose different modes according to the actual situation on site, expanding the application of the system.

[0051] like Figure 2As shown, the system also includes a cold and heat exchange system, which includes a hot water tank 22, a cold water tank 21, a heat pump 25 and a cooling tower 26 for cooling the heat pump 25. The water outlet of the hot water tank is divided into two paths, one of which is an electric heating mode, that is, after the water temperature in the hot water tank 22 is raised to the set temperature by the electric heater, the hot water is transported to the reactor 7, the separation kettle 11, the reaction heater 4 and the separation heater 10 for heating by the hot water pump; the other is a heat pump heat exchange mode, that is, the unheated water in the hot water tank 22 is transported to the reactor 7, the separation kettle 11, the reaction heater 4 and the separation heater 10 for heating by the hot water pump 25. By adopting the above two heat exchange modes, when the ambient temperature is relatively high, such as in summer, the heat pump heat exchange mode can be directly adopted; when the ambient temperature is relatively low, such as in winter, when the system is just turned on, the electric heating mode is adopted, and after the system runs stably, it is switched to the heat pump heat exchange mode, thereby avoiding the high power consumption in the electric heating mode and effectively reducing the power consumption of the whole system. The water outlet of the cold water tank 21 is divided into two ways, one for CO 2 The circulation tank 3, the booster pump 4, the primary recovery compressor 19 and the secondary recovery compressor 16 are cooled, and the other path is refrigerated by the heat pump 25 and then refrigerated to the condenser 20. The structure is simple and the cost is low.

[0052] Preferably, the number of the booster pumps 4 is two, one for normal pressurization and the other for backup pressure, which effectively improves the production efficiency of the system. In addition, once one booster pump fails, the other booster pump can be used to take into account the functions of normal pressurization and backup pressure, reducing the impact on the system operation and ensuring that the system does not stop.

[0053] The present invention also discloses a method for utilizing the drilling oily sludge supercritical CO 2 Extraction treatment system for supercritical CO 2 The extraction method specifically comprises the following steps:

[0054] Supercritical CO 2 Extraction: CO 2 Liquid CO in circulation tank 3 2 After being pressurized by the pressure pump 4 and heated by the reaction heater 5, it reaches a supercritical fluid state, and then enters the reactor 7 to extract the oil-soluble substances in the drilling oil sludge to form a supercritical mixed fluid; the supercritical mixed fluid is successively throttled and depressurized by the outlet pressure regulating valve of the reactor 7 and heated by the separation heater 10 to convert the CO in the supercritical fluid state into 2 Converted to gaseous CO 2 , originally dissolved in supercritical CO 2 The oil-soluble substances in the fluid are transformed into a free state and then enter the separation kettle 7 for separation. The separated oil-soluble substances enter the oil collecting tank 12. The separated gaseous CO 2After cooling in the condenser 20, it is converted into liquid CO 2 Enter CO 2 The circulation tank 3 is used for recycling.

[0055] CO 2 First-level recovery: After the extraction of reactor 7 is completed, close the inlet control valve Ⅰ6, outlet control valve Ⅲ9 and control valve Ⅱ8 of reactor 7, open the exhaust control valve Ⅳ13 and the first-level recovery pipeline control valve Ⅴ14, and use the reactor 7 and CO 2 The pressure difference between the circulation tank 3 makes the CO in the reactor 7 2 After passing through the pipeline and cooling in the condenser 20, it is converted into liquid CO 2 Enter CO 2 The circulation tank 3 is recycled until the reactor 7 and CO 2 When the pressure of the circulation tank 20 is the same, the first-stage recovery is completed and the CO 2 Secondary recycling.

[0056] CO 2 Secondary recovery: close control valve I6, control valve III9, control valve II8 and primary recovery pipeline control valve V14, open control valve IV13 and secondary pipeline control valve VII17. 2 The gas enters the gas recovery tank 18 through the pipeline, and the first-stage recovery compressor 19 converts the CO in the gas recovery tank 18 into 2 The pressure is increased and the temperature is reduced by the condenser 20 to convert it into liquid CO 2 Transport to CO 2 The circulating tank 20 is recycled, and the secondary recovery can recover the CO in the reactor 7. 2 The pressure in the kettle is recovered until it drops to 0.6MPa. After the secondary recovery is completed, the CO 2 Three-level recycling.

[0057] CO 2 The third-level recovery: close the control valve I6, control valve III9, control valve II8, control valve V14 and control valve VII17, open the control valve IV13 and the third-level recovery pipeline control valve VI15. 2 Through the secondary recovery compressor 16 2 The gas is then compressed and transported to the gas recovery tank 18, and then the CO in the gas recovery tank 18 is compressed by the primary recovery compressor 19. 2 The pressure is increased and the temperature is reduced by the condenser 20 to convert it into liquid CO 2 Transport to CO 2 The circulating tank 3 is used for recycling, and the three-stage recovery can recover the CO in the reactor 7. 2 Recover until the pressure in the kettle drops to 0.1MPa.

[0058] During the pressure increase of the reactor 7, open the control valve II8 to allow CO to flow into both the inlet and outlet of the reactor 7. 2 The pressure is increased to avoid the impact on the barrel in the reactor 7 due to the pressure increase at only one end. In the reaction process, when the pressure difference between the inlet and outlet of the reactor 7 is too large due to the dense accumulation of materials in the barrel in the reactor 7, the control valve II 8 is used to balance the pressure between the inlet and outlet of the reactor 7 to ensure the stable reaction. The structure is simple, safe and reliable, and the performance is stable.

[0059] Preferably, the present invention further comprises a heat exchange system, which comprises a hot water tank 22 , a cold water tank 21 , a heat pump 25 , and a cooling tower 26 for cooling the heat pump 25 .

[0060] The water outlet of the hot water tank 22 is divided into two routes, one of which is the electric heating mode, that is, after the water in the hot water tank 22 is heated to the set temperature by the electric heater, the control valve IX 24 on the pipeline leading to the heating equipment such as the reactor 7, the separation reactor 11, the reaction heater 4 and the separation heater 10 is opened, and the control valve VIII 23 on the pipeline leading to the heat pump 25 is closed; the hot water in the hot water tank 22 is transported to the reactor 7, the separation reactor 11, the reaction heater 4 and the separation heater 10 for heating by the hot water pump. The other route is the heat exchange mode of the heat pump, the control valve VIII 23 is opened, and the control valve IX 24 is closed, that is, the unheated water in the hot water tank 22 is transported to the reactor 7, the separation reactor 11, the reaction heater 4 and the separation heater 10 for heating by the hot water pump after heat exchange by the heat pump 25, and the water discharged from the above reactor 7, the separation reactor 11, the reaction heater 4 and the separation heater 10 after heating is returned to the hot water tank 22, and the cycle works. By adopting the above two heat exchange modes, when the ambient temperature is relatively high such as in summer, the heat pump heat exchange mode can be directly adopted; when the ambient temperature is relatively low such as in winter, the electric heating mode is adopted when the system is just started, and after the system runs stably, it is switched to the heat pump heat exchange mode, thereby avoiding the high power consumption in the electric heating mode and effectively reducing the overall system operating power consumption.

[0061] The water outlet of the cold water tank is divided into two ways. One way is for the water in the cold water tank 21 to be transported to the CO 2 The circulation tank 3, the booster pump 4, the primary recovery compressor 19 and the secondary recovery compressor 16 are cooled, and CO 2 The water discharged from the cooling of the circulation tank 3, the booster pump 4, the primary recovery compressor 19 and the secondary recovery compressor 16 returns to the cold water tank 21 for circulation; the other way is that the water in the cold water tank 21 is transported to the heat pump 25 through the cold water pump for refrigeration and then refrigerates the condenser 20, and the water discharged from the condenser 20 returns to the cold water tank 21 for circulation.

[0062] Oily sludge (also called oil-based drill cuttings) produced by drilling with diesel-based mud and white oil-based mud was collected from a shale gas production capacity demonstration area in Sichuan and Chongqing. Among them, the oil-soluble substances recovered from the oily sludge containing diesel-based mud after extraction by the present invention were tested, and the indicators were as follows: density (20℃) was 0.8654g / cm 3 , flash point (closed cup) is 60°C, sulfur content is 0.138%, solidification point is -16°C, kinematic viscosity (20°C) is 6.854mm 2 / s, ash content is 0.009%, and there is no water and mechanical impurities. The total petroleum hydrocarbon (TPH) content in the solid waste after treatment is 515mg / kg. The oil-soluble substances recovered after the extraction of the drilling oily sludge containing white oil-based mud by the present invention are tested and the indicators are as follows: density (20℃) is 0.808g / cm 3 , flash point (closed cup) is 109.5℃, pour point is -15℃, kinematic viscosity (40℃) is 3.021mm 2 / s, copper sheet corrosion (50°C, 3h) is 1, and there is no water and mechanical impurities. The content of total petroleum hydrocarbons (TPH for short) in the solid waste residue after treatment is 459mg / kg. In summary, the oil-soluble substances recovered from drilling oily sludge by the present invention have high quality, and the treated solid waste residue is far lower than the limit value (<3000mg / kg) of the national standard (GB4284-2018) "Control Standards for Pollutants in Agricultural Sludge". The treated solid waste residue can meet the national standard (GB41518-2022) "Shale Gas Exploration and Development Oil-Based Drilling Cuttings Treatment Method and Control Indicators", and can also reach the Sichuan Provincial Environmental Protection Standard (DB51 / 2850-2021) "Natural Gas Extraction Oily Sludge Comprehensive Utilization Residual Solid Phase Utilization and Disposal Standard" Class A standard, which can be used to pave the well site and its roads to achieve safe reuse and disposal.

[0063] Embodiment 2:

[0064] like Figure 3 As shown, the present embodiment is different from the first embodiment in that the separation heater 10 includes a separation heater Ⅰ101 and a separation heater Ⅱ102, and the separation kettle 11 includes a separation kettle Ⅰ111 and a separation kettle Ⅱ112. The outlet control valve Ⅲ9 of the reactor 7 is connected to the separation heater Ⅰ101 and the separation kettle Ⅰ111 in sequence, and the oil-soluble substances separated by the separation kettle Ⅰ111 enter the oil collecting tank 12, and the separated gas CO carrying trace oil-soluble substances is 2 The oil-soluble substances separated by the separation kettle Ⅱ 112 enter the oil collecting tank 12, and the separated extraction end gas CO 2 CO flows into the condenser 20 2The circulation tank 3 is recycled. In this embodiment, the primary recovery pipeline includes a separation heater II 102, a separation kettle II 112 and a condenser 20 connected in sequence. The separation heater I 101 and the separation heater II 102 are mainly used to keep CO 2 The vaporization state of the whole extraction performance is stable and the effect is excellent. Through the two-stage separation of this embodiment, whether it is the CO discharged from the outlet of the reactor 7 during the extraction process, 2 , or CO recovered through the primary recovery pipeline after the extraction is completed 2 , the recovered CO 2 The purity of the gas CO separated by the separation kettle I is further improved. 2 The trace oil-soluble substances in the sample were recovered, thereby improving the recovery rate of the oil-soluble substances.

[0065] It should be noted that the number of the reaction kettles 7 and separation kettles 11 can be configured according to the system processing capacity, and the present invention does not limit the specific number.

[0066] The above is a supercritical CO2 treatment method for oily sludge from drilling provided by the present invention. 2 The extraction treatment system and method are introduced in detail. Specific examples are used in this article to illustrate the technical principles and implementation methods of the present invention. The above embodiments are only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A supercritical CO2 extraction treatment system for oily drilling sludge, characterized in that: It includes a CO2 circulation tank, a pressure pump, a reaction heater, a reaction kettle, a separation heater and a separation kettle connected in sequence. The oil-soluble substances separated by the separation kettle enter the oil collecting tank, and the separated gas CO2 flows into the CO2 circulation tank through the condenser for recycling; After the reaction in the reactor is finished, the reactor inlet control valve Ⅰ and outlet control valve Ⅲ are closed, and the CO2 in the reactor is recycled to the CO2 circulation tank through the primary recovery pipeline, the secondary recovery pipeline and the tertiary recovery pipeline in turn; The primary recovery pipeline includes a condenser, which utilizes the pressure difference between the reactor and the CO2 circulation tank to convert the CO2 in the reactor through the pipeline, cool it down in the condenser, and then convert it into liquid CO2 to enter the CO2 circulation tank for recycling; The secondary recovery pipeline includes a gas recovery tank, a primary recovery compressor and a condenser connected in sequence, and the secondary recovery can recover the CO2 in the reactor until the pressure in the reactor drops to 0.6MPa; The three-stage recovery pipeline includes a secondary recovery compressor, a gas recovery tank, a primary recovery compressor and a condenser connected in sequence. The three-stage recovery can recover the CO2 in the reactor until the pressure in the reactor drops to 0.1 MPa; It also includes a control valve II for controlling the inlet and outlet of the reactor to be connected or disconnected. During the pressure increase of the reactor, the control valve II is opened to allow CO2 to be introduced into both the inlet and outlet of the reactor to increase the pressure at the same time, so as to avoid the impact of only one end increasing the pressure and causing damage to the barrel in the reactor. During the reaction, the control valve II is used to balance the pressure of the inlet and outlet of the reactor to ensure the stable reaction. It also includes a CO2 storage tank and a delivery pump. The CO2 in the CO2 storage tank is delivered to the CO2 circulation tank or the condenser through the delivery pump. If the delivery pump is close to the CO2 circulation tank, the liquid CO2 in the CO2 storage tank can be directly delivered to the CO2 circulation tank through the delivery pump; if the delivery pump is far from the CO2 circulation tank, in order to prevent the CO2 from vaporizing, the CO2 in the delivery pipeline needs to be cooled through the condenser to keep it in a liquid state so as to be delivered to the CO2 circulation tank; It also includes a heat exchange system, which includes a hot water tank, a cold water tank, a heat pump and a cooling tower for cooling the heat pump; The water outlet of the hot water tank is divided into two paths, one of which is an electric heating mode, that is, the water in the hot water tank is heated to a set temperature by an electric heater, and then the hot water is transported to the reactor, the separation kettle, the reaction heater and the separation heater for heating by a hot water pump; the other is a heat pump heat exchange mode, that is, the unheated water in the hot water tank is transported to the reactor, the separation kettle, the reaction heater and the separation heater for heating by a hot water pump after heat exchange by the heat pump; The water outlet of the cold water tank is divided into two paths, one path is used to cool the CO2 circulation tank, the booster pump, the primary recovery compressor and the secondary recovery compressor, and the other path is used to cool the condenser after being refrigerated by the heat pump; The separation heater includes a separation heater I and a separation heater II, and the separation kettle includes a separation kettle I and a separation kettle II; The outlet control valve III is connected to the separation heater I and the separation kettle I in sequence. The oil-soluble substances separated by the separation kettle I enter the oil collecting tank. The separated gas CO2 carrying trace oil-soluble substances passes through the separation heater II to the separation kettle II. The oil-soluble substances separated by the separation kettle II enter the oil collecting tank. The separated gas CO2 flows into the CO2 circulation tank through the condenser for recycling. The primary recovery pipeline includes a separation heater II, a separation kettle II and a condenser which are connected in sequence.

2. A supercritical CO2 extraction treatment system for oily drilling sludge according to claim 1, characterized in that: There are two pressure pumps, one for normal pressure boosting and the other for backup pressure boosting.

3. A supercritical CO2 extraction method using the supercritical CO2 extraction system for oily sludge from drilling according to claim 1 or 2, characterized in that: The specific steps include: Supercritical CO2 extraction: The liquid CO2 in the CO2 circulation tank is pressurized by a pressure pump and heated by a reaction heater to reach a supercritical fluid state, and then enters the reactor to extract the oil-soluble substances in the drilling oil-containing sludge to form a supercritical mixed fluid; the supercritical mixed fluid is throttled and depressurized by the reactor outlet pressure regulating valve and heated by the separation heater in turn, so that the CO2 in the supercritical fluid state is converted into gaseous CO2, and the oil-soluble substances originally dissolved in the supercritical CO2 fluid are converted into a free state, and then enter the separation kettle for separation. The separated oil-soluble substances enter the oil collecting tank, and the separated gaseous CO2 is cooled by the condenser and converted into liquid CO2 and enters the CO2 circulation tank for recycling; Primary recovery of CO2: After the reactor extraction is completed, close the reactor inlet control valve I and outlet control valve III, open the exhaust control valve IV and the primary recovery pipeline control valve V, and use the pressure difference between the reactor and the CO2 circulation tank to make the CO2 in the reactor pass through the pipeline and be cooled by the condenser to be converted into liquid CO2 and enter the CO2 circulation tank for recycling. When the pressure of the reactor and the CO2 circulation tank is the same, the primary recovery is completed and the CO2 secondary recovery is started; Secondary recovery of CO2: close the primary recovery pipeline control valve V, open the secondary pipeline control valve VII, the CO2 in the reactor enters the gas recovery tank through the pipeline, the primary recovery compressor pressurizes the CO2 in the gas recovery tank, and transports it to the CO2 circulation tank through the condenser for recycling. The secondary recovery can recover the CO2 in the reactor until the pressure in the reactor drops to 0.6MPa. After the secondary recovery is completed, it enters the tertiary recovery of CO2; Tertiary recovery of CO2: Close the primary recovery pipeline control valve V and the secondary pipeline control valve VII, open the tertiary recovery pipeline control valve VI, and the CO2 in the reactor is pressurized by the secondary recovery compressor and transported to the gas recovery tank. The CO2 in the gas recovery tank is then pressurized by the primary recovery compressor and transported to the CO2 circulation tank through the condenser for recycling. The tertiary recovery can recover the CO2 in the reactor until the pressure in the reactor drops to 0.1MPa.

4. The supercritical CO2 extraction method according to claim 3, characterized in that , and also includes a control valve II for controlling the inlet and outlet of the reactor to be connected or disconnected; During the pressure-raising process of the reactor, open control valve II to allow CO2 to be introduced into both the inlet and outlet of the reactor to increase the pressure at the same time, so as to avoid pressure-raising at only one end, which would cause damage to the barrel in the reactor. During the reaction, control valve II is used to balance the pressure at the inlet and outlet of the reactor to ensure stable reaction.

5. The supercritical CO2 extraction method according to claim 3, characterized in that , also includes a heat exchange system, the heat exchange system includes a hot water tank, a cold water tank, a heat pump and a cooling tower for cooling the heat pump; The water outlet of the hot water tank is divided into two paths, one of which is that after the water temperature in the hot water tank is raised to the set temperature by the electric heater, the control valve IX is opened, and the hot water is transported to the reactor, the separation kettle, the reaction heater and the separation heater by the hot water pump for heating, and the water discharged from the reactor, the separation kettle, the reaction heater and the separation heater is returned to the hot water tank for circulation; the other path is that when the water in the hot water tank is not electrically heated, the control valve IX is closed, the control valve VIII is opened, and the unheated water in the hot water tank is transported to the reactor, the separation kettle, the reaction heater and the separation heater by the hot water pump after heat exchange by the heat pump for heating, and the water discharged from the reactor, the separation kettle, the reaction heater and the separation heater is returned to the hot water tank for circulation; The water outlet of the cold water tank is divided into two paths. One path is for the water in the cold water tank to be transported to the CO2 circulation tank, the booster pump, the first-level recovery compressor and the second-level recovery compressor for cooling through a cold water pump. The water discharged from the cooling of the CO2 circulation tank, the booster pump, the first-level recovery compressor and the second-level recovery compressor returns to the cold water tank for circulation. The other path is for the water in the cold water tank to be transported to the heat pump for refrigeration through a cold water pump to refrigerate the condenser. The water discharged from the condenser for refrigeration returns to the cold water tank for circulation.

6. The supercritical CO2 extraction method according to claim 3, characterized in that , the separation heater includes a separation heater I and a separation heater II, and the separation kettle includes a separation kettle I and a separation kettle II; The outlet control valve III is connected to the separation heater I and the separation kettle I in sequence. The oil-soluble substances separated by the separation kettle I enter the oil collecting tank. The separated gas CO2 carrying trace oil-soluble substances passes through the separation heater II to the separation kettle II. The oil-soluble substances separated by the separation kettle II enter the oil collecting tank. The separated gas CO2 flows into the CO2 circulation tank through the condenser for recycling. The primary recovery pipeline includes a separation heater II, a separation kettle II and a condenser which are connected in sequence.

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