Device for pressurizing CO2 and reinjecting CO2 into underground

Abstract

The utility model discloses a device for pressurizing and reinjecting CO2 underground. The device comprises a first heat exchanger, a second heat exchanger, a refrigeration unit, a buffer tank, a booster pump and a third heat exchanger, wherein the input end of the first heat exchanger is connected with the CO2 storage tank through a pressure regulating valve; the output end of the first heat exchanger is connected with the input end of the buffer tank through the second heat exchanger; a cold source of the second heat exchanger is provided by the refrigeration unit; the output end of the buffer tank is connected with the ground layer through the booster pump, the first heat exchanger and the third heat exchanger in sequence; according to the utility model, CO2 high-pressure reinjection can be realized, the phase state in the pressurizing process is stable, the damage of two-phase flow to equipment is avoided, the service life of the equipment is prolonged, meanwhile, the energy consumption is low, and the CO2 utilization rate is high.

Description

Technical Field

[0001] This invention belongs to the technical field of CO2 liquid or supercritical state reinjection and utilization, and particularly relates to a device for pressurizing and reinjecting CO2 underground. Background Technology

[0002] Supercritical CO2 exhibits high diffusivity and fluidity, facilitating its transport within the wellbore. 1. Supercritical State: In the initial stages of injection, CO2 remains in a supercritical state because the pressure within the wellbore is much higher than its critical pressure. 2. Liquid State: As injection progresses, the temperature of CO2 gradually decreases, potentially causing it to transition from a supercritical to a liquid state. This transition occurs in the cooler regions of the wellbore, particularly near the reservoir. 3. Return to Supercritical State: When liquid CO2 is further injected and comes into contact with higher temperature regions, it returns to a supercritical state. This phase transition process completes at the end of injection, leaving the wellbore filled with supercritical CO2.

[0003] CO2 reinjection is a technology that captures and injects carbon dioxide (CO2) underground, primarily used to reduce greenhouse gas emissions, enhance oil and gas recovery (EOR), and for geological storage. Specifically: Greenhouse gas emission reduction: CO2 is one of the major greenhouse gases, and its large-scale emissions contribute to global warming. By capturing CO2 emitted from industry and injecting it underground, its entry into the atmosphere can be reduced. Enhanced oil and gas recovery: In oil and gas extraction, CO2 reinjection can improve recovery rates, especially in the later stages of oilfield development, as CO2 can mix with crude oil, reducing viscosity and facilitating extraction. Geological storage: Injecting CO2 into deep geological structures (such as depleted oil and gas fields, saline aquifers, etc.) allows for long-term storage, reducing the concentration of CO2 in the atmosphere. How to effectively reinject CO2 into formations is a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0004] To address the technical problems existing in current technologies, this invention provides a device for pressurizing and reinjecting CO2 underground. This device can effectively release CO2 into the formation, preventing CO2 pollution from atmospheric emissions and protecting the ecological environment. Simultaneously, this invention utilizes a series of processes including pre-cooling, liquefaction, pressurization, and reheating of gaseous CO2. Specifically, a circulating refrigeration system provides the cold source during the liquefaction process, a cryogenic booster pump achieves the pressurization process, and the reheating can be performed using an ambient temperature reheater or a water bath reheater. This invention enables high-pressure CO2 reinjection, reduces CO2 emissions, improves oil and gas recovery, and achieves CO2 geological sequestration.

[0005] To solve the problems of the existing technology, the present invention adopts the following technical solution:

[0006] A device for pressurizing and reinjecting CO2 underground, the device comprising: a first heat exchanger, a second heat exchanger, a refrigeration unit, a buffer tank, a booster pump, and a third heat exchanger; wherein: the input end of the first heat exchanger is connected to a CO2 storage tank via a pressure regulating valve; the output end of the first heat exchanger is connected to the input end of the buffer tank via the second heat exchanger; the cold source for the second heat exchanger is provided by the refrigeration unit; the output end of the buffer tank is connected to the formation sequentially via the booster pump, the first heat exchanger, and the third heat exchanger; wherein:

[0007] Gaseous or supercritical CO2 stored in a storage tank at a high pressure of 3-15 MPa is depressurized to 0.5-3 MPaG via a pressure regulating valve and then fed into the first heat exchanger, the second heat exchanger, and the refrigeration unit for heat exchange and cooling into cryogenic liquid CO2 at -5℃ to -60℃ before being sent to a buffer tank for buffering. At this time, the booster pump pressurizes the cryogenic liquid CO2 to high-pressure liquid CO2 at 10-40 MPa, and then the high-pressure liquid CO2 is heated to liquid or supercritical CO2 at 0-50℃ via the third heat exchanger and injected into the formation.

[0008] Furthermore, a compressor is also connected between the CO2 storage tank and the first heat exchanger.

[0009] Furthermore, both the first heat exchanger and the second heat exchanger adopt a plate or shell-and-tube structure.

[0010] Furthermore, the refrigeration unit includes a refrigerant, a refrigerant compressor, a condenser, an evaporator, and an online control module. The refrigerant used is R22, R23, R404A, R14, ethanol, propane, ethylene, ethane, etc., and the refrigerant is recycled.

[0011] Furthermore, the third heat exchanger is an air-temperature reheater or a water-bath reheater.

[0012] Furthermore, the booster pump is a reciprocating pump or a multi-stage centrifugal pump.

[0013] Furthermore, the device adopts a fully skid-mounted structure.

[0014] Beneficial effects

[0015] 1. This utility model overcomes the technical problem that traditional methods of directly compressing gaseous CO2 to high pressure (such as 40MPa) require a lot of energy and have low efficiency, and improves the energy consumption efficiency of direct compression of high-pressure gaseous CO2.

[0016] 2. This invention overcomes the technical problem of phase change fluctuations (such as liquefaction or supercritical state) during the compression of gaseous CO2 in traditional methods, which affect the stable operation of the equipment. This invention ensures phase stability and avoids damage to the booster pump by cooling the CO2 to a liquid state (-5 to -60℃) before pressurization. At the same time, the low-temperature liquid CO2 (-5 to -60℃) is pressurized and then heated to 0 to 50℃ before injection, avoiding the problem of ground temperature sensitivity (such as permafrost or rock fracturing).

[0017] 3. This utility model adopts a skid-mounted design to integrate all components, which facilitates transportation and rapid on-site installation, adapts to different geological conditions, and is easy to deploy in different scenarios such as oil fields and factories; this utility model overcomes the technical problem of traditional CO2 reinjection devices being large and difficult to move.

[0018] 4. In order to improve the CO2 utilization rate of the storage tank, this utility model device is equipped with a CO2 compressor, which makes better use of the low-pressure CO2 in the storage tank, reduces transportation costs, and improves utilization efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a device for pressurizing and reinjecting CO2 underground, according to this utility model.

[0020] Figure 2 This is a schematic diagram of an example of a device for pressurizing and reinjecting CO2 underground, according to this utility model.

[0021] in:

[0022]

[0023] Detailed Implementation

[0024] The following is in conjunction with the appendix Figure 1 ~Attached Figure 2 The present invention is described as follows:

[0025] like Figure 1 As shown, this utility model provides a device for pressurizing and reinjecting CO2 underground, comprising: a first heat exchanger E-101, a second heat exchanger E-102, a refrigeration unit X-101, a buffer tank V-102, a booster pump P-101, and a third heat exchanger E-103; the refrigeration unit X-101 includes a refrigerant, a refrigerant compressor, a condenser, an evaporator, and an online control module, wherein the refrigerant is R22, R23, R404A, R14, ethanol, propane, ethylene, ethane, etc., and the refrigerant is recycled.

[0026] Both the first heat exchanger E-101 and the second heat exchanger E-102 adopt a plate or shell-and-tube structure. Specifically: the input end of the first heat exchanger E-101 is connected to the CO2 storage tank V-101 via a pressure regulating valve; the output end of the first heat exchanger E-101 is connected to the input end of the buffer tank V-101 via the second heat exchanger E-102; the cold source for the second heat exchanger is provided by a refrigeration unit; the output end of the buffer tank V-101 is connected to the ground via a booster pump P-101, the first heat exchanger E-101, and the third heat exchanger E-103 in sequence; the booster pump P-101 is a reciprocating pump or a multi-stage centrifugal pump. A compressor C-101 is also connected between the CO2 storage tank V-101 and the first heat exchanger E-101. This invention involves purifying and cooling CO2 in a CO2 storage tank to become liquid CO2, then pressurizing it to 15 MPaG using a booster pump, and finally reheating it to become a room-temperature, high-pressure liquid or supercritical state for reinjection. This invention is fully skid-mounted, requiring minimal floor space and facilitating on-site installation. Specifically:

[0027] Gaseous CO2 stored in a storage tank at a high pressure of 3-15 MPa is depressurized to 0.5-3 MPaG by a pressure regulating valve and then fed into the first heat exchanger E-101, the second heat exchanger E-102, and the refrigeration unit X-101 for heat exchange and cooling into cryogenic liquid CO2 at -5℃ to -60℃. After cooling, the liquid CO2 is sent to the buffer tank V-102 for buffering. At this time, the booster pump P-101 pressurizes the cryogenic liquid CO2 to a high pressure liquid CO2 of 10-40 MPa, and then the high pressure liquid CO2 is heated to 0-50℃ by the third heat exchanger E-103 and injected into the formation.

[0028] Example

[0029] The CO2 storage tank stores CO2 at 8 MPa. After passing through a pressure regulating valve, the pressure is reduced to 1.2 MPaG. Then, it is cooled to -32.8°C through heat exchangers E-101 and E-102 and refrigeration unit X-101, becoming cryogenic liquid CO2. It is then pressurized to 15 MPaG by booster pump P-101. The low temperature after pressurization provides a cold source for E-101. The CO2 is then reheated to 33°C by E-103. The CO2 is in a supercritical state, realizing reinjection.

[0030] To reduce the residual CO2 in the CO2 storage tank, a compressor is required. When the pressure in storage tank V-101 is less than 1.2 MPaG, compressor C-101 is started to depressurize storage tank V-101 to 0.3 MPaG. The outlet pressure of compressor C-101 is 1.2 MPaG, which flows into the first heat exchanger and subsequent equipment. Figure 2 As shown.

[0031] Although the present invention has been described above, it is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from its spirit, and these modifications are all within the scope of protection of the present invention.

Claims

1. A device for pressurizing and reinjecting CO2 underground, characterized in that, The device includes: a first heat exchanger, a second heat exchanger, a refrigeration unit, a buffer tank, a booster pump, and a third heat exchanger; wherein: the input end of the first heat exchanger is connected to a CO2 storage tank via a pressure regulating valve; the output end of the first heat exchanger is connected to the input end of the buffer tank via the second heat exchanger; the cold source for the second heat exchanger is provided by the refrigeration unit; and the output end of the buffer tank is connected to the formation in sequence via the booster pump, the first heat exchanger, and the third heat exchanger.

2. The device for pressurizing and reinjecting CO2 underground according to claim 1, characterized in that, A compressor is also connected between the CO2 storage tank and the first heat exchanger.

3. The device for pressurizing and reinjecting CO2 underground according to claim 1, characterized in that, Both the first heat exchanger and the second heat exchanger adopt a plate or shell-and-tube structure.

4. The device for pressurizing and reinjecting CO2 underground according to claim 1, characterized in that, The refrigeration unit includes a refrigerant, a refrigerant compressor, a condenser, an evaporator, and an online control module. The refrigerant used is R22, R23, R404A, R14, ethanol, propane, ethylene, or ethane, and the refrigerant is recycled.

5. The device for pressurizing and reinjecting CO2 underground according to claim 1, characterized in that, The third heat exchanger is either an air-temperature reheater or a water-bath reheater.

6. The device for pressurizing and reinjecting CO2 underground according to claim 1, characterized in that, The booster pump is a reciprocating pump or a multi-stage centrifugal pump.

7. A device for pressurizing and reinjecting CO2 underground according to any one of claims 1-6, characterized in that, The device adopts a fully skid-mounted structure.

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