Efficient carbon dioxide reinjection system and method based on double-phase-state mixed injection

Abstract

The invention belongs to the technical field of CO2 reinjection, and particularly relates to an efficient carbon dioxide reinjection system and method based on double-phase-state mixed injection. According to the technical scheme, the efficient carbon dioxide reinjection system and method based on double-phase-state mixed injection are further provided with a medium efficient mixing system, a liquid-phase flow adjusting system, a liquid-phase bypass temperature adjusting system and the like on the basis of a liquid-phase CO2 and supercritical CO2 wellhead reinjection basic process, efficient and safe liquid-phase CO2 and supercritical CO2 mixed wellhead reinjection is achieved, and the system and method have the advantages of being simple in structure, convenient to operate and high in practicability. The problems of temperature fluctuation after low-temperature liquid-phase CO2 and supercritical CO2 are mixed, return pressure fluctuation after injection flow changes, flow and temperature compensation after the supercritical CO2 flow is lower than the basic reinjection amount and the like are effectively relieved.

Description

Technical Field

[0001] The present invention belongs to CO 2 The technical field of reinjection, in particular, relates to a system and method for efficiently reinjecting carbon dioxide based on dual-phase mixed injection. Background Art

[0002] Against the backdrop of the growing demand for energy conservation, emission reduction and environmental protection in the energy and chemical industry, the large-scale capture and utilization of carbon dioxide is the preferred way to effectively reduce carbon emissions. Among them, carbon dioxide storage is an effective means to achieve carbon emission reduction. Its basic concept is to capture and pressurize carbon dioxide, inject it into the reinjection well through the reinjection pipeline, and then enter the depleted oil and gas reservoir or saline layer for storage. The critical temperature of a relatively pure carbon dioxide medium is about 31.1°C and the critical pressure is about 7.38MPa; carbon dioxide used for reinjection and storage generally also includes impurities such as nitrogen and hydrogen sulfide, which have an impact on the critical pressure and critical temperature.

[0003] Carbon dioxide reinjection can be used for oilfield recovery (EOR) or geological storage, and is achieved through long-distance pipeline transportation followed by wellhead reinjection and wellhead storage followed by liquid phase reinjection. Compared with oilfield recovery, geological storage has relatively low requirements for injection temperature, injection rate, etc., while oilfield recovery requires maintaining a supercritical injection phase to improve the recovery effect. To this end, for the scenario of reinjection and storage, the energy saving and economic efficiency of reinjection should be considered. Furthermore, the reinjection methods include wellhead low-temperature liquid phase reinjection, pressurized pipeline transportation reinjection, etc. The main difference is the different reinjection phases. In order to match the progress of carbon sources, construction and dual carbon goals, a mixed injection mode of pipeline reinjection and wellhead liquid phase reinjection can be used to achieve CO 2 Reinjection: Enhance the carbon source adaptability of the reinjection system.

[0004] However, the mixed injection mode has the significant characteristics of the same reinjection pressure and significantly different reinjection temperatures. Since pipeline reinjection is affected by the pressurization process, mainly supercritical transportation, the reinjection medium temperature is generally higher than 20°C; while the CO 2 The temperature is affected by the operating temperature of the storage tank, which is generally -20°C. It can be seen that the temperature of the medium during mixed injection is greatly affected by the mixing amount, which directly affects the density of the injected medium. Furthermore, for the sealing scenario, when the reinjection temperature is relatively low, the wellhead reinjection pressure will also be low, which is mainly caused by the high pressure of the static liquid column in the wellbore. At the same time, since the horizontal distance between the reinjection point and the wellhead is short, the contribution of the reinjection temperature change to the wellhead reinjection pressure is more significant than the change in the reinjection flow rate. For this reason, it is necessary to fully consider the control of temperature changes during mixed reinjection.

[0005] At present, although liquid CO 2 Reinjection, supercritical CO 2There are relatively many cases of single-phase reinjection such as reinjection, but there are few cases of liquid phase and supercritical CO 2 There are only a few case reports on mixed injection, but the technical points of mixed injection have not been deeply explored and revealed. Therefore, it is necessary to fully carry out systematic research, integrate the surface reinjection process, combine the static liquid column problem in the wellbore, and carry out dual-phase mixed injection of CO from the perspective of efficient and energy-saving reinjection. 2 Research on efficient reinjection systems and methods to form feasible, reasonable and efficient reinjection strategies. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the object of the present invention is to provide a system and method for efficient reinjection of carbon dioxide based on dual-phase mixed injection.

[0007] The technical solution adopted by the present invention is:

[0008] A high-efficiency carbon dioxide reinjection system based on dual-phase mixed injection includes a static mixer, the inlet ends of the static mixer are respectively connected to supercritical CO 2 Reinjection pipeline and liquid CO 2 Mixing line, liquid CO 2 The other end of the mixing pipeline is connected to the liquid CO 2 Reinjection pipeline, liquid CO 2 The other end of the reinjection pipeline is connected to liquid CO 2 The outlet end of the storage tank and the static mixer is connected to a wellhead reinjection pipeline, and the other end of the wellhead reinjection pipeline is connected to the reinjection wellhead;

[0009] The supercritical CO 2 The reinjection pipeline is connected in sequence with supercritical CO 2 Inlet temperature transmitter, supercritical CO 2 Inlet flow transmitter and supercritical CO 2 Pipeline end pressure transmitter; the liquid phase CO 2 The return pipe is connected in sequence with the tank outlet temperature transmitter, the first-stage booster pump, the first-stage booster pressure transmitter, the second-stage booster pump, the second-stage booster pressure transmitter, the liquid CO 2 Inlet temperature transmitter and liquid CO 2 Inlet flow transmitter; the wellhead reinjection pipeline is connected in sequence with a post-mixing temperature transmitter, a post-mixing pressure transmitter and a post-mixing flow transmitter;

[0010] The liquid CO 2 The reinjection pipeline is connected in parallel with liquid CO 2 Bypass, liquid CO 2 One end of the bypass is connected between the first-stage booster pump and the pressure transmitter after the first-stage booster. 2The other end of the bypass is connected between the secondary booster pump and the secondary booster pressure transmitter; the liquid CO 2 The bypass is connected in sequence with a bypass primary booster pump, a bypass air bath heat exchanger and a bypass secondary booster pump.

[0011] As a preferred embodiment of the present invention, the supercritical CO 2 The supercritical CO2 injection pipeline is connected to a supercritical CO2 injection pipeline cut-off valve. 2 The inlet temperature transmitter is far from the supercritical CO 2 One side of the inlet flow transmitter.

[0012] As a preferred embodiment of the present invention, the liquid phase CO 2 The re-injection pipeline is connected to a liquid phase tank outlet shut-off valve, which is located at the liquid phase CO 2 Between the tank and the tank outlet temperature transmitter.

[0013] As a preferred solution of the present invention, a wellhead reinjection shutoff valve is connected to the wellhead reinjection pipeline, and the wellhead reinjection shutoff valve is located on the side of the mixed flow transmitter close to the reinjection wellhead.

[0014] As a preferred embodiment of the present invention, the supercritical CO 2 The section of the reinjection pipeline near the static mixer is connected to a spare supercritical CO 2 Mixing valve, liquid CO 2 A section of the mixing pipeline close to the static mixer is connected to a spare liquid CO 2 Mixing valve: A section of the wellhead reinjection pipeline close to the static mixer is connected with a spare post-mixing shut-off valve.

[0015] As a preferred embodiment of the present invention, the liquid phase CO 2 The bypass is also connected to a first liquid phase bypass shut-off valve and a second liquid phase bypass shut-off valve. The first liquid phase bypass shut-off valve is located on the side of the bypass first-stage booster pump away from the bypass air bath heat exchanger, and the second liquid phase bypass shut-off valve is located on the side of the bypass second-stage booster pump away from the bypass air bath heat exchanger.

[0016] A method for efficiently reinjecting carbon dioxide based on dual-phase mixed injection comprises the following steps:

[0017] S1: During normal operation, supercritical CO 2 The reinjection pipeline is connected to the supercritical CO2 from the upstream reinjection booster station. 2 ; Reinjection well site to low temperature liquid CO 2 Supercritical CO 2 With pressurized liquid CO 2 Mixing is carried out in a static mixer according to the designed injection ratio;2 Inlet flow transmitter, liquid CO 2 The inlet flow transmitter detects the injection volume in real time; the temperature transmitter detects the temperature change of the injected mixed medium in real time after mixing; the standard value of temperature control is set to stabilize the temperature of the injected medium after mixing;

[0018] S2: During normal reinjection, the liquid phase CO 2 Adjust and control the reinjection volume;

[0019] S3: Supercritical CO 2 Inlet flow transmitter and mixed temperature transmitter, based on supercritical CO 2 The liquid CO2 with reinjection flow as the basic variable 2 Flow regulation function;

[0020] S4: In supercritical CO 2 When the inlet flow transmitter is lower than the minimum reinjection volume specified in the project, turn on the bypass first-stage booster pump, bypass air bath heat exchanger, and bypass second-stage booster pump.

[0021] As a preferred embodiment of the present invention, step S2 is specifically as follows: when the actual temperature detected by the temperature transmitter after mixing is 2°C higher than the re-injection temperature setting value, the liquid phase CO is increased by increasing the displacement of the primary booster pump and the secondary booster pump. 2 The amount of reinjection is reduced to lower the temperature of the mixed medium; when the actual temperature detected by the temperature transmitter after mixing is 2°C lower than the reinjection temperature setting value, the liquid phase CO is reduced by reducing the displacement of the first-stage booster pump and the second-stage booster pump. 2 Reinjection volume to increase the temperature of the mixed medium;

[0022] As a preferred embodiment of the present invention, step S3 specifically comprises: in supercritical CO 2 When the inlet flow transmitter exceeds the set value, and the actual temperature detected by the temperature transmitter after mixing is 2°C higher than the re-injection temperature set value, increase the displacement of the first-stage booster pump and the second-stage booster pump to increase the liquid phase CO 2 The amount of reinjection is used to reduce the temperature of the mixed medium; in supercritical CO 2 When the inlet flow transmitter is lower than the set value, and the actual temperature detected by the temperature transmitter after mixing is 2°C lower than the re-injection temperature set value, the liquid phase CO is reduced by reducing the displacement of the first-stage booster pump and the second-stage booster pump. 2 Reinjection volume to increase the temperature of the mixed medium.

[0023] As a preferred embodiment of the present invention, in step S4, supercritical CO 2 When the reinjection volume remains at a low level, gradually reduce the liquid CO2 passing through the bypass primary booster pump, bypass air bath heat exchanger, and bypass secondary booster pump within 24 hours.2 flow rate, gradually increasing the liquid CO passing through the first-stage booster pump and the second-stage booster pump 2 flow rate, maintaining liquid CO 2 The total flow rate is stable, and the overall mixing and reinjection of CO is gradually reduced. 2 temperature and reduce the reinjection pressure.

[0024] The beneficial effects of the present invention are:

[0025] The present invention is based on CO 2 The basic physical properties of liquid phase wellhead injection, the basic process of supercritical phase wellhead injection, the factors affecting wellhead injection pressure, the medium mixing law, etc. 2 In order to meet the engineering requirements of wellhead mixed reinjection, a medium efficient mixing system, a liquid phase flow control system and a liquid phase bypass temperature control system were set up respectively. From the perspective of efficient and stable reinjection, the liquid phase CO 2 Reinjection, supercritical CO 2 On the basis of the basic reinjection process, the problems of the influence of the temperature difference of the mixed medium on the mechanical properties of the mixed reinjection pipeline, the increase of wellhead back pressure and its fluctuation are effectively overcome. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the present invention.

[0027] In the figure: 1-supercritical reinjection pipeline cut-off valve; 2-wellhead reinjection cut-off valve; 3-reinjection wellhead; 4-reinjection wellbore; 5-liquid CO 2 Storage tank; 6-Liquid phase storage tank outlet cut-off valve; 7-First stage booster pump; 8-Liquid phase CO 2 Reinjection pipeline; 9-secondary booster pump; 10-tank outlet temperature transmitter; 11-primary booster pressure transmitter; 12-secondary booster pressure transmitter; 13-supercritical CO 2 Pipeline end pressure transmitter; 14-wellhead reinjection pipeline; 21-liquid CO 2 Mixing pipeline; 22-static mixer; 23-spare supercritical CO 2 Mixing valve; 24-spare liquid CO 2 Mixing valve; 25-spare mixing post-blocking valve; 31-supercritical CO 2 Inlet temperature transmitter; 32-supercritical CO 2 Inlet flow transmitter; 33-liquid CO 2 Inlet temperature transmitter; 34-Liquid CO 2Inlet flow transmitter; 35-temperature transmitter after mixing; 36-pressure transmitter after mixing; 37-flow transmitter after mixing; 41-liquid phase bypass first shut-off valve; 42-bypass first-stage booster pump; 43-bypass air bath heat exchanger; 44-bypass second-stage booster pump; 45-liquid phase bypass second shut-off valve. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0030] The present invention is based on CO 2 The basic physical properties of liquid phase wellhead injection, the basic process of supercritical phase wellhead injection, the factors affecting wellhead injection pressure, the medium mixing law, etc. 2 The engineering requirements for wellhead mixed reinjection are based on efficient and stable reinjection. 2 Reinjection, supercritical CO 2 On the basis of the basic reinjection process, the influence of mixed medium temperature difference on the mechanical properties of mixed reinjection pipeline, wellhead back pressure and its fluctuation is fully considered, and a medium efficient blending system, liquid phase flow regulation system, liquid phase bypass temperature regulation system, etc. are set up respectively. Among them, the medium efficient blending system promotes the liquid phase CO 2 With supercritical CO 2 Quick and uniform mixing to ensure the CO 2 The temperature is uniform, and the stress and strain of the high-efficiency mixer are monitored to provide basic deformation parameters for subsequent projects; the liquid phase flow regulation system is set up based on supercritical CO 2 Flow rate of liquid CO 2 The flow control function takes the stable mixed temperature as the control target, and 2 When the reinjection volume is higher than the basic (minimum) reinjection volume, adjust the liquid CO 2Reinjection flow to form a stable mixed temperature and avoid supercritical CO 2 When the injection volume is increased alone, the wellhead back pressure increases rapidly; the liquid bypass temperature regulation system is set by supercritical CO 2 Low flow alarm and liquid CO 2 Bypass heat exchange function, by actively increasing the liquid phase CO 2 temperature, avoiding supercritical CO 2 When the reinjection rate is lower than the basic reinjection rate, liquid CO 2 The reinjection volume is reduced to ensure the minimum injection capacity and keep the temperature and pressure of the reinjected mixed medium stable. This achieves efficient and safe liquid phase CO 2 , supercritical CO 2 Mixed reinjection.

[0031] The medium efficient blending system, liquid phase flow control system, liquid phase bypass temperature control system, etc., realize efficient and safe liquid phase CO 2 , supercritical CO 2 Mixed wellhead reinjection effectively alleviates low-temperature liquid phase CO 2 With supercritical CO 2 Temperature fluctuation after mixing, back pressure fluctuation after injection flow rate change, and supercritical CO 2 The flow rate is lower than the basic re-injection flow rate and temperature compensation. 2 , supercritical CO 2 The basic process of wellhead reinjection only serves as the basis of the present invention and is not the content of invention or innovation.

[0032] The wellhead reinjection basic system includes a supercritical reinjection pipeline cutoff valve 1 arranged near the reinjection wellhead 3, a wellhead reinjection cutoff valve 2, a reinjection wellhead 3, a reinjection wellbore 4, a liquid CO 2 Storage tank 5, liquid phase storage tank outlet cut-off valve 6, primary booster pump 7, liquid phase CO 2 Reinjection pipeline 8, secondary booster pump 9, tank outlet temperature transmitter 10, primary booster pressure transmitter 11, secondary booster pressure transmitter 12, supercritical CO 2 The pressure transmitter 13 at the end of the pipeline and the wellhead reinjection pipeline are used to provide liquid CO 2 and supercritical CO 2 The wellhead reinjection channel. The wellhead reinjection basic system and the process are only used as the basis of the present invention and are not used as the content of invention and innovation.

[0033] The medium efficient mixing system includes liquid phase CO 2 Mixing pipeline 21, static mixer 22, spare supercritical CO 2 Mixing valve 23, spare liquid phase CO 2The blending valve 24, the standby blending post-blocking valve 25, etc. are used to control the liquid CO 2 and supercritical CO 2 Provide efficient and uniform mixing to achieve liquid phase CO 2 and supercritical CO 2 The temperature of the medium is mixed quickly; at the same time, the static mixer 22 is provided with a stress-strain monitoring sheet to characterize the temperature field distribution and stress-strain distribution after mixing; the spare valve provides the spare static mixer 22 with an online access function to avoid the impact of the replacement of the static mixer 22 on production.

[0034] The liquid phase flow regulation system includes supercritical CO 2 Inlet temperature transmitter 31, supercritical CO 2 Inlet flow transmitter 32, liquid CO 2 Inlet temperature transmitter 33, liquid CO 2 The inlet flow transmitter 34, the post-mixing temperature transmitter 35, the post-mixing pressure transmitter 36, the post-mixing flow transmitter 37, etc. are used to establish the liquid phase CO 2 With supercritical CO 2 The flow rate after mixing is coordinated and controlled to prevent the temperature fluctuation after mixing from deviating from the set value by 2°C.

[0035] The liquid phase bypass temperature adjustment system includes a liquid phase bypass first shutoff valve 41, a bypass first-stage booster pump 42, a bypass air bath heat exchanger 43, a bypass second-stage booster pump 44, a liquid phase bypass second shutoff valve 45, etc., which are used in supercritical CO 2 When the injection volume is lower than the basic injection volume, the liquid phase CO 2 The injection volume is supplemented and the liquid phase CO is actively adjusted (increased) 2 Reinjection temperature: keep the temperature after mixing as stable as possible to avoid excessive changes in the temperature of the reinjection system and the resulting excessive changes in the reinjection pressure.

[0036] Embodiment 1:

[0037] like Figure 1 As shown, the carbon dioxide efficient reinjection system based on dual-phase mixed injection of this embodiment includes a static mixer 22, and the inlet ends of the static mixer 22 are respectively connected to supercritical CO 2 Reinjection pipeline and liquid CO 2 Mixing pipeline 21, liquid CO 2 The other end of the mixing pipeline 21 is connected to the liquid CO 2 Reinjection pipeline 8, liquid CO 2 The other end of the reinjection pipeline 8 is connected to the liquid CO 2 The outlet end of the storage tank 5 and the static mixer 22 is connected to the wellhead reinjection pipeline 14, and the other end of the wellhead reinjection pipeline 14 is connected to the reinjection wellhead 3;

[0038] The supercritical CO 2 The reinjection pipeline is connected in sequence with supercritical CO 2 Inlet temperature transmitter 31, supercritical CO 2 Inlet flow transmitter 32 and supercritical CO 2 Pipeline end pressure transmitter 13; the liquid phase CO 2 The re-injection pipeline 8 is connected in sequence with the tank outlet temperature transmitter 10, the primary booster pump 7, the primary booster pressure transmitter 11, the secondary booster pump 9, the secondary booster pressure transmitter 12, the liquid CO 2 Inlet temperature transmitter 33 and liquid CO 2 Inlet flow transmitter 34; the wellhead reinjection pipeline 14 is connected in sequence with a post-mixing temperature transmitter 35, a post-mixing pressure transmitter 36 and a post-mixing flow transmitter 37;

[0039] The liquid CO 2 The reinjection pipeline 8 is connected in parallel with liquid CO 2 Bypass, liquid CO 2 One end of the bypass is connected between the primary booster pump 7 and the primary booster pressure transmitter 11. 2 The other end of the bypass is connected between the secondary booster pump 9 and the secondary booster pressure transmitter 12; the liquid CO 2 The bypass is connected in sequence with a bypass primary booster pump 42, a bypass air bath heat exchanger 43 and a bypass secondary booster pump 44.

[0040] The supercritical CO 2 The reinjection pipeline is connected to a supercritical reinjection pipeline cut-off valve 1, which is located at the supercritical CO 2 The inlet temperature transmitter 31 is far from the supercritical CO 2 One side of the inlet flow transmitter 32.

[0041] The liquid CO 2 The re-injection pipeline 8 is connected to a liquid phase storage tank outlet cut-off valve 6, which is located at the liquid phase CO 2 Between the storage tank 5 and the storage tank outlet temperature transmitter 10.

[0042] The wellhead reinjection pipeline 14 is connected to a wellhead reinjection shutoff valve 2 , which is located on the side of the post-mixing flow transmitter 37 close to the reinjection wellhead 3 .

[0043] The supercritical CO 2 A section of the reinjection pipeline near the static mixer 22 is connected to a spare supercritical CO 2 Mixing valve 23, liquid CO 2A section of the mixing pipeline 21 near the static mixer 22 is connected to a standby liquid CO 2 A mixing valve 24 , a section of the wellhead reinjection pipeline 14 close to the static mixer 22 is connected with a spare post-mixing shut-off valve 25 .

[0044] The liquid CO 2 The bypass is also connected to a first liquid phase bypass shut-off valve 41 and a second liquid phase bypass shut-off valve 45. The first liquid phase bypass shut-off valve 41 is located on the side of the bypass first-stage booster pump 42 away from the bypass air bath heat exchanger 43, and the second liquid phase bypass shut-off valve 45 is located on the side of the bypass second-stage booster pump 44 away from the bypass air bath heat exchanger 43.

[0045] Among them, supercritical reinjection pipeline cut-off valve 1, wellhead reinjection cut-off valve 2, reinjection wellhead 3, reinjection wellbore 4, liquid CO 2 Storage tank 5, liquid phase storage tank outlet cut-off valve 6, primary booster pump 7, liquid phase CO 2 Reinjection pipeline 8, secondary booster pump 9, tank outlet temperature transmitter 10, primary booster pressure transmitter 11, secondary booster pressure transmitter 12, supercritical CO 2 The pipeline end pressure transmitter 13, the wellhead reinjection pipeline 14 and other components constitute the wellhead reinjection basic system, which is used to provide liquid CO 2 and supercritical CO 2 The wellhead reinjection channel. The wellhead reinjection basic system and the process are only used as the basis of the present invention and are not used as the content of invention and innovation.

[0046] Among them, liquid CO 2 Mixing pipeline 21, static mixer 22, spare supercritical CO 2 Mixing valve 23, spare liquid phase CO 2 The mixing valve 24, the spare post-mixing shut-off valve 25 and the like constitute a medium efficient mixing system for the liquid phase CO 2 and supercritical CO 2 Provide efficient and uniform mixing to achieve liquid phase CO 2 and supercritical CO 2 The temperature of the medium is mixed quickly. At the same time, the static mixer 22 is equipped with a stress-strain monitoring sheet to characterize the temperature field distribution and stress-strain distribution after mixing. The spare valve provides the spare static mixer 22 with online access function to avoid the impact of the replacement of the static mixer 22 on production.

[0047] Specifically, in the system shown, liquid CO 2 The mixing pipeline 21 connects the secondary booster pump 9 and the static mixer 22, and is used to provide the static mixer 22 with pressurized liquid CO. 2The static mixer 22 is made of carbon steel, preferably a horizontal structure, and the mixing unit structure is optimized through CFD simulation to provide supercritical CO 2 With liquid CO 2 Fast and efficient mixing improves the temperature stability of the outlet fluid. Stress strain gauges are set on the external surface of the static mixer 22, which are respectively set upstream of the mixing unit, in the mixing unit area and downstream of the mixing unit to detect the stress and strain data on the surface of the static mixer 22 under long-term operation. 2 Mixing valve 23, spare liquid phase CO 2 The blending valve 24 and the standby post-blending shut-off valve 25 are both made of carbon steel and are respectively arranged at the end of the supercritical reinjection pipeline and the liquid CO 2 The end of the blending pipeline 21 and the beginning of the wellhead reinjection pipeline 14 are used to provide online access to the spare static mixer 22 to improve the reliability of the reinjection system.

[0048] Among them, supercritical CO 2 Inlet temperature transmitter 31, supercritical CO 2 Inlet flow transmitter 32, liquid CO 2 Inlet temperature transmitter 33, liquid CO 2 The inlet flow transmitter 34, the post-mixing temperature transmitter 35, the post-mixing pressure transmitter 36, the post-mixing flow transmitter 37 and the like constitute a liquid phase flow control system for establishing a liquid phase CO 2 With supercritical CO 2 The flow rate after mixing is coordinated and controlled to prevent the temperature fluctuation after mixing from deviating from the set value by 2°C.

[0049] Specifically, supercritical CO 2 The inlet temperature transmitter 31 is arranged at the end of the supercritical reinjection pipeline to detect the supercritical CO 2 The real-time temperature of the medium entering the static mixer 22. Supercritical CO 2 The inlet flow transmitter 32 is arranged at the end of the supercritical reinjection pipeline to detect the supercritical CO 2 The real-time flow rate of the medium entering the static mixer 2222 will alarm when it deviates from the set flow rate by 1%. 2 The inlet temperature transmitter 33 is set at the liquid phase CO 2 Mixing line 21, used to detect liquid CO 2 The real-time temperature of the medium entering the static mixer 2222. Liquid CO 2 The inlet flow transmitter 34 is set at the liquid phase CO 2 Mixing line 21, used to detect liquid CO 2The real-time flow rate of the medium entering the static mixer 22. The mixed temperature transmitter 35 is set at the beginning of the wellhead reinjection pipeline 14 to detect the temperature of the mixed medium. When the detected temperature deviates from the reinjection temperature setting value by 2°C, the liquid phase CO 2 The reinjection pump sends a flow rate adjustment signal. The mixed pressure transmitter 36 is set at the beginning of the wellhead reinjection pipeline 14 to detect the wellhead back pressure value. The mixed flow transmitter 37 is set at the beginning of the wellhead reinjection pipeline 14 to detect the real-time flow rate of the mixed medium.

[0050] The liquid phase bypass first shutoff valve 41, the bypass first-stage booster pump 42, the bypass air bath heat exchanger 43, the bypass second-stage booster pump 44, the liquid phase bypass second shutoff valve 45 and the like constitute a liquid phase bypass temperature adjustment system for supercritical CO 2 When the injection volume is lower than the basic injection volume, the liquid phase CO 2 The injection volume is supplemented and the liquid phase CO is actively adjusted (increased) 2 Reinjection temperature: keep the temperature after mixing as stable as possible to avoid excessive changes in the temperature of the reinjection system and the resulting excessive changes in the reinjection pressure.

[0051] Specifically, the first liquid phase bypass shutoff valve 41 is set at the liquid phase CO 2 Bypass, normally closed, ball valve, for controlling liquid CO 2 The bypass booster and temperature control channel is opened and closed. The bypass primary booster pump 42 is arranged downstream of the liquid phase bypass first shut-off valve 41 to provide liquid phase CO 2 The bypass first-stage boosting function is preferably between 5 and 6 MPa to ensure that the liquid phase CO after heat exchange in the bypass air bath heat exchanger 43 2 The bypass air bath heat exchanger 43 is preferably an air bath heat exchanger made of carbon steel and is used to bypass the liquid CO at the outlet of the first-stage booster pump 42. 2 Heat exchange is performed to increase the temperature of the medium appropriately, which is used to increase the liquid phase CO 2 Flow rate and supercritical CO 2 The bypass secondary booster pump 44 is arranged downstream of the bypass air bath heat exchanger 43 to compensate for the temperature drop of the mixed medium. 2 The second shutoff valve 45 of the liquid phase bypass is set at the liquid phase CO 2 Bypass, normally closed, ball valve, for controlling liquid CO 2 The bypass booster and temperature control channels are opened and closed. The bypass primary booster pump 42 and the bypass secondary booster pump 44 have a flow linear regulation function to achieve bypass liquid phase CO 2 Compensation and adjustment flexibility.

[0052] The working principle of the present invention is:

[0053] First, the present invention is based on CO 2 The basic physical properties of supercritical CO 2 With liquid CO 2 Based on the engineering requirements of mixed injection, the authors extracted problems such as uneven temperature distribution of mixed media and excessive temperature variation of mixed media, and identified potential impacts and hazards. 2 The injection temperature is high, and the liquid CO 2 The reinjection temperature is about -20°C, so there is a large temperature difference between the two. When using the conventional mixing mode, there are problems of uneven temperature distribution at the mixing point and its downstream pipelines and in the wellbore, which is mainly reflected in the uneven temperature field distribution and the periodic changes in the temperature field distribution. It will cause high-cycle and large-scale stress changes in some pipelines and equipment; for this reason, the proposed medium efficient mixing system adopts a static mixer 22 as the core, and takes the mixing temperature as the control index to shorten the uniform mixing time as much as possible to achieve the effect of "cold and hot" rapid mixing; further, in order to monitor the stress changes of the static mixer 22, a stress and strain monitoring plate is set in the static mixer 2222 to characterize the temperature field distribution and stress and strain distribution after mixing; in addition, in order to ensure the continuity of production, a spare valve is set to provide an online access function for the spare static mixer 22 to avoid the impact of the replacement of the static mixer 22 on production.

[0054] Second, due to CO 2 The reinjection pressure is relatively high, and the density of the reinjection medium is much greater than that of conventional natural gas storage. Therefore, the main influencing factors of the reinjection pressure include the medium temperature, which will directly affect the static liquid column pressure of the wellbore. Efficiently controlling the reinjection temperature and avoiding excessive reinjection temperature will directly optimize the wellhead reinjection pressure. To this end, a liquid phase flow control system is set up to control the liquid phase CO 2 The injection rate varies with supercritical CO 2 The mode of adjusting the proportion of reinjection volume can effectively control the temperature of reinjection medium and is used to deal with supercritical CO 2 The problem of increased reinjection temperature caused by increased flow rate is solved, so that the reinjection flow rate is increased and the reinjection pressure does not change significantly. In addition, during normal operation, the reinjection pressure calculation cycle is set finely, taking into account the effects of season, morning and evening on supercritical CO 2 The influence of medium temperature is effectively controlled by setting the reinjection temperature setting value and establishing a reinjection temperature detection mechanism. 2 The injection volume is controlled to achieve relative stability of the reinjection temperature and to achieve the goal of economical and stable reinjection pressure.

[0055] Third, in order to cope with supercritical CO 2 In order to solve the problem of too low flow rate, the present invention sets up a liquid phase bypass temperature adjustment system, by setting up a bypass CO with a bypass air bath heat exchanger 43 2The booster-heat exchange system increases the liquid CO 2 While injecting the amount of liquid CO, moderately increase the 2 The temperature of the mixed gas can be kept stable to avoid a large change in the injection temperature in a short period of time, which may affect the stability of the injection booster system. 2 The problem of low reinjection flow rate can be solved by reducing the flow rate of the liquid phase bypass temperature control system and increasing the original liquid phase CO 2 The flow rate is adjusted to gradually reduce the comprehensive mixing temperature to increase the density of the comprehensive mixed medium and reduce the reinjection pressure. 2 To address the problem of low traffic, a strategy of short-term maintenance and long-term adjustment was established, taking into account both system stability and economy.

[0056] Thus, a CO2-based liquid injection method was formed. 2 The working principle of the efficient storage and reinjection system.

[0057] Embodiment 2:

[0058] The present invention also discloses a high-efficiency carbon dioxide reinjection method based on dual-phase mixed injection, which includes the following main contents:

[0059] S1: During normal operation, supercritical CO 2 Pipeline access to the upstream supercritical CO2 injection booster station 2 ; Reinjection well site to low temperature liquid CO 2 The supercritical CO 2 With pressurized liquid CO 2 Mixing is performed in a static mixer 22 according to the designed injection amount ratio; 2 Inlet flow transmitter 32, liquid CO 2 The inlet flow transmitter 34 detects the injection volume in real time; the temperature change of the injected mixed medium is detected in real time through the mixed temperature transmitter 35. The standard value of temperature control is set by designing the supercritical CO 2 Injection volume, supercritical CO 2 Temperature before injection (preferably monthly average temperature), designed liquid CO 2 Injection volume, liquid CO 2 The injection temperature is used to obtain a standard value for temperature control, which is used to stabilize the temperature of the mixed injected medium. The standard value for temperature control is preferably adjusted monthly. Since the pressure at the reinjection wellhead 3 is mainly affected by the static liquid column pressure in the wellbore, the medium density has a great influence on the static liquid column pressure. Therefore, by controlling the stability of the reinjection temperature, a large change in the static liquid column pressure can be effectively avoided.

[0060] S2: During normal reinjection, the liquid phase CO 2 When the actual temperature detected by the temperature transmitter 35 after mixing is 2°C higher than the set value of the reinjection temperature, the liquid phase CO 2 When the actual temperature detected by the temperature transmitter 35 after mixing is 2°C lower than the set value of the reinjection temperature, the liquid phase CO is reduced by reducing the displacement of the primary booster pump 7 and the secondary booster pump 9. 2 Reinjection volume to increase the temperature of the mixed medium.

[0061] S3: Due to supercritical CO 2 The upstream treatment plant captures the gas and continuously pressurizes it, so the reinjection flow rate may fluctuate. Therefore, the liquid phase flow regulation system is configured to meet the requirements of supercritical CO 2 The liquid CO2 with reinjection flow as the basic variable 2 Flow regulation function. In supercritical CO 2 When the inlet flow transmitter 32 exceeds the set value and the actual temperature detected by the temperature transmitter 35 after mixing is 2°C higher than the set value of the reinjection temperature, increase the displacement of the first-stage booster pump 7 and the second-stage booster pump 9 to increase the liquid phase CO 2 The amount of reinjection is used to reduce the temperature of the mixed medium; in supercritical CO 2 When the inlet flow transmitter 32 is lower than the set value, and the actual temperature detected by the temperature transmitter 35 after mixing is 2°C lower than the re-injection temperature set value, the liquid phase CO is reduced by reducing the displacement of the first-stage booster pump 7 and the second-stage booster pump 9. 2 Reinjection volume to increase the temperature of the mixed medium.

[0062] S4: Further, when supercritical CO 2 When the reinjection volume is lower than the minimum reinjection volume specified in the project, the liquid phase bypass temperature adjustment system is activated. 2 When the inlet flow transmitter 32 is lower than the minimum reinjection amount specified in the project, if step S3 is continued, the mixed medium reinjection amount will not meet the reinjection amount requirement specified in the project. Therefore, the first liquid phase bypass shutoff valve 41, the bypass primary booster pump 42, the bypass air bath heat exchanger 43, the bypass secondary booster pump 44, the liquid phase bypass second shutoff valve 45, etc. are opened to increase the liquid phase CO 2 The injection temperature is adjusted to match the mixing temperature downstream of the static mixer 22 to meet the reinjection temperature requirements, while increasing the reinjection volume of the mixed medium to avoid the reinjection pressure being increased due to the large amount of liquid phase low temperature CO 2 Furthermore, in supercritical CO 2When the reinjection volume continues to remain at a low level, preferably within 24 hours, the flow rate of the liquid phase bypass temperature regulation system (i.e., the liquid phase CO2 passing through the bypass primary booster pump 42, the bypass air bath heat exchanger 43, and the bypass secondary booster pump 44) is gradually reduced. 2 flow), gradually increase the first-stage booster pump 7, liquid CO 2 Liquid CO2 from the reinjection pipeline 8 and the secondary booster pump 9 2 flow rate, maintaining liquid CO 2 The total flow rate is stable, and the overall mixing and reinjection of CO is gradually reduced. 2 temperature and reduce the reinjection pressure.

[0063] Therefore, through the control of multiple key issues, the dual-phase CO 2 Efficient and safe mixed injection.

[0064] Compared with the prior art, the present invention has the following positive effects:

[0065] First, set up science

[0066] The present invention is directed to supercritical CO 2 With liquid CO 2 The engineering requirements for mixed injection were analyzed, the potential impact of temperature mixing on pipeline material properties, wellhead back pressure, operating efficiency, etc., and a medium efficient mixing system was set up to achieve low-temperature liquid phase CO 2 With high temperature supercritical CO 2 Rapid and uniform mixing can avoid excessive uneven temperature sections, which can protect the downstream pipelines and equipment. A liquid phase flow regulation system is set up. From the perspective that the main influencing factor of wellhead injection pressure is medium density, liquid phase CO 2 Dynamic blending of supercritical CO 2 The process effectively ensures the temperature stability of the mixed medium during a specific injection period, thereby achieving stable density and wellhead back pressure; a liquid phase bypass temperature adjustment system is set up to ensure the supercritical CO 2 When the flow rate is too low, the liquid phase CO 2 temperature to achieve overall reinjection temperature stability.

[0067] Second, good economic performance

[0068] The present invention has obvious economic benefits. In terms of mixing temperature uniformity, by setting up a high-efficiency mixer, rapid mixing of low-temperature medium and medium-high temperature medium is achieved, and stress fluctuations and uneven deformation of the pipeline and accessories downstream of the mixing point caused by uneven medium temperature are avoided, thereby ensuring the structural safety of the pipeline system and having great potential economic advantages. By setting a relatively stable reinjection temperature, the reinjection pressure within the reinjection cycle is effectively controlled, and the supercritical CO is avoided. 2When the reinjection volume is too large, the reinjection pressure increases sharply due to the increase in mixing temperature, which has a significant energy-saving effect. At the same time, a liquid phase bypass temperature adjustment system is set up to avoid supercritical CO 2 When the flow rate is too low, it causes a sharp change in the wellhead back pressure. At the same time, it also has the function of reducing the wellhead back pressure in the later stage, thus achieving the same energy-saving effect.

[0069] Third, promote technological development

[0070] At present, my country has not yet carried out supercritical CO 2 With liquid CO 2 In the practice of mixed injection, reinjection and sealing, the scheme proposed by this system plays an important role in engineering guidance and reference. The proposed key process system configurations such as the medium efficient blending system, liquid phase flow regulation system, liquid phase bypass temperature regulation system, etc. can effectively promote the development of technical concepts and technological progress in this field and ensure efficient and safe production.

[0071] The present invention is not limited to the above-mentioned optional implementation modes. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that fall within the scope defined by the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A high-efficiency carbon dioxide reinjection system based on dual-phase mixed injection, characterized by: It comprises a static mixer (22), the inlet end of the static mixer (22) is respectively connected to a supercritical CO2 reinjection pipeline and a liquid CO2 blending pipeline (21), the other end of the liquid CO2 blending pipeline (21) is connected to a liquid CO2 reinjection pipeline (8), the other end of the liquid CO2 reinjection pipeline (8) is connected to a liquid CO2 storage tank (5), the outlet end of the static mixer (22) is connected to a wellhead reinjection pipeline (14), the other end of the wellhead reinjection pipeline (14) is connected to a reinjection wellhead (3); The supercritical CO2 reinjection pipeline is sequentially connected with a supercritical CO2 inlet temperature transmitter (31), a supercritical CO2 inlet flow transmitter (32) and a supercritical CO2 pipeline terminal pressure transmitter (13); the liquid phase CO2 reinjection pipeline (8) is sequentially connected with a storage tank outlet temperature transmitter (10), a primary booster pump (7), a primary booster pressure transmitter (11), a secondary booster pump (9), a secondary booster pressure transmitter (12), a liquid phase CO2 inlet temperature transmitter (33) and a liquid CO2 inlet flow transmitter (34); the wellhead reinjection pipeline (14) is sequentially connected with a post-mixing temperature transmitter (35), a post-mixing pressure transmitter (36) and a post-mixing flow transmitter (37); A liquid phase CO2 bypass is connected in parallel to the liquid phase CO2 reinjection pipeline (8), one end of the liquid phase CO2 bypass is connected between the primary boosting pump (7) and the primary boosting pressure transmitter (11), and the other end of the liquid phase CO2 bypass is connected between the secondary boosting pump (9) and the secondary boosting pressure transmitter (12); the liquid phase CO2 bypass is sequentially connected to a bypass primary boosting pump (42), a bypass air bath heat exchanger (43) and a bypass secondary boosting pump (44).

2. The high-efficiency carbon dioxide reinjection system based on dual-phase mixed injection according to claim 1 is characterized in that: The supercritical CO2 reinjection pipeline is connected to a supercritical reinjection pipeline shutoff valve (1), and the supercritical reinjection pipeline shutoff valve (1) is located on a side of the supercritical CO2 inlet temperature transmitter (31) away from the supercritical CO2 inlet flow transmitter (32).

3. The high-efficiency carbon dioxide reinjection system based on dual-phase mixed injection according to claim 1 is characterized in that: The liquid phase CO2 reinjection pipeline (8) is connected to a liquid phase storage tank outlet shutoff valve (6), and the liquid phase storage tank outlet shutoff valve (6) is located between the liquid phase CO2 storage tank (5) and the storage tank outlet temperature transmitter (10).

4. The high-efficiency carbon dioxide reinjection system based on dual-phase mixed injection according to claim 1, characterized in that: The wellhead reinjection pipeline (14) is connected to a wellhead reinjection shutoff valve (2), and the wellhead reinjection shutoff valve (2) is located on the side of the post-mixing flow transmitter (37) close to the reinjection wellhead (3).

5. The high-efficiency carbon dioxide reinjection system based on dual-phase mixed injection according to claim 1 is characterized in that: A section of the supercritical CO2 reinjection pipeline close to the static mixer (22) is connected to a spare supercritical CO2 blending valve (23), a section of the liquid phase CO2 blending pipeline (21) close to the static mixer (22) is connected to a spare liquid phase CO2 blending valve (24), and a section of the wellhead reinjection pipeline (14) close to the static mixer (22) is connected to a spare post-blending shut-off valve (25).

6. The high-efficiency carbon dioxide reinjection system based on dual-phase mixed injection according to claim 1, characterized in that: The liquid phase CO2 bypass is also connected to a first liquid phase bypass shut-off valve (41) and a second liquid phase bypass shut-off valve (45). The first liquid phase bypass shut-off valve (41) is located on a side of the bypass first-stage booster pump (42) away from the bypass air-bath type heat exchanger (43), and the second liquid phase bypass shut-off valve (45) is located on a side of the bypass second-stage booster pump (44) away from the bypass air-bath type heat exchanger (43).

7. A method for efficient reinjection of carbon dioxide based on dual-phase mixed injection, characterized in that: The high-efficiency carbon dioxide reinjection system based on dual-phase mixed injection according to any one of claims 1 to 6 comprises the following steps: S1: During normal operation, the supercritical CO2 reinjection pipeline is connected to the supercritical CO2 of the upstream reinjection booster station; the low-temperature liquid CO2 is pressurized at the reinjection well site; the connected supercritical CO2 and the pressurized liquid CO2 are mixed in a static mixer (22) according to the designed injection volume ratio; the injection volume is detected in real time through the supercritical CO2 inlet flow transmitter (32) and the liquid CO2 inlet flow transmitter (34); the temperature change of the injected mixed medium is detected in real time through the post-mixing temperature transmitter (35); and the standard value of temperature control is set to stabilize the temperature of the injected medium after mixing; S2: During normal reinjection, the amount of liquid CO2 reinjection is adjusted and controlled according to the set reinjection temperature control value; S3: The configured supercritical CO2 inlet flow transmitter (32) and post-mixing temperature transmitter (35) satisfy the liquid phase CO2 flow regulation function based on the supercritical CO2 reinjection flow as the basic variable; S4: When the supercritical CO2 inlet flow transmitter (32) is lower than the minimum reinjection amount specified in the project, the bypass primary booster pump (42), the bypass air bath heat exchanger (43), and the bypass secondary booster pump (44) are turned on.

8. The method for efficient reinjection of carbon dioxide based on dual-phase mixed injection according to claim 7, characterized in that: Step S2 is specifically as follows: when the actual temperature detected by the temperature transmitter (35) after mixing is higher than the reinjection temperature setting value by 2°C, the liquid CO2 reinjection amount is increased by increasing the displacement of the first-stage booster pump (7) and the second-stage booster pump (9), thereby reducing the temperature of the mixed medium; when the actual temperature detected by the temperature transmitter (35) after mixing is lower than the reinjection temperature setting value by 2°C, the liquid CO2 reinjection amount is reduced by reducing the displacement of the first-stage booster pump (7) and the second-stage booster pump (9), thereby increasing the temperature of the mixed medium.

9. The method for efficient reinjection of carbon dioxide based on dual-phase mixed injection according to claim 7, characterized in that: Step S3 is specifically as follows: when the supercritical CO2 inlet flow transmitter (32) exceeds the set value, and the actual temperature detected by the temperature transmitter (35) after mixing is higher than the reinjection temperature set value by 2°C, the displacement of the first-stage booster pump (7) and the second-stage booster pump (9) is increased to increase the liquid CO2 reinjection amount and reduce the temperature of the mixed medium; when the supercritical CO2 inlet flow transmitter (32) is lower than the set value, and the actual temperature detected by the temperature transmitter (35) after mixing is lower than the reinjection temperature set value by 2°C, the displacement of the first-stage booster pump (7) and the second-stage booster pump (9) is reduced to reduce the liquid CO2 reinjection amount and increase the temperature of the mixed medium.

10. The method for efficient reinjection of carbon dioxide based on dual-phase mixed injection according to claim 7, characterized in that: In step S4, when the supercritical CO2 reinjection amount continues to maintain a low level, within 24 hours, the liquid CO2 flow rate passing through the bypass first-level booster pump (42), the bypass air bath heat exchanger (43), and the bypass second-level booster pump (44) is gradually reduced, and the liquid CO2 flow rate passing through the first-level booster pump (7) and the second-level booster pump (9) is gradually increased to maintain the total liquid CO2 flow rate stable, gradually reduce the temperature of the overall mixed reinjected CO2, and reduce the reinjection pressure.

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