An indoor preparation device for an environmentally friendly CO2 microbubble fluid and its application in improving the capillary CO2 capture efficiency of sandstone saline aquifers.

Abstract

The application belongs to the technical field of CO2 geological storage, and discloses a kind of indoor preparation device of environment-friendly CO2 micro-foam fluid and its application in improving capillary trapping CO2 efficiency of sandstone saltwater layer. The device comprises: a gas injection path composed of a CO2 gas cylinder, a gas booster pump and a gas flow control meter; a liquid injection path composed of a water source, an advection pump and a piston container; the parallel gas injection path and the liquid injection path converge in a high-pressure and high-speed stirring container; the high-pressure and high-speed stirring container is connected with a multi-stage shearing device, a core holder, a two-dimensional high-pressure visual observation cabin, a back pressure valve and a liquid receiving cylinder in sequence; the liquid receiving cylinder is placed on the tray of a precision electronic balance; the mixed fluid stirred uniformly by the high-pressure and high-speed stirring container flows to the multi-stage shearing device, the core holder, the two-dimensional high-pressure visual observation cabin, the back pressure valve and the liquid receiving cylinder in sequence. The application can improve the capillary storage efficiency of CO2 in saltwater layer and improve the safety of CO2 storage in saltwater layer.

Description

Technical Field

[0001] This invention belongs to the field of CO2 geological storage technology, specifically relating to an indoor preparation device for an environmentally friendly CO2 microbubble fluid and its application in improving the efficiency of CO2 capture by capillary action in sandstone saline aquifers. Background Technology

[0002] Deep saline aquifers are the most widely distributed geological formations in China with the greatest potential for CO2 sequestration. For CO2 sequestration projects in saline aquifers, the sequestration mechanisms can be categorized into tectonic capture, capillary capture, dissolution capture, and mineralization capture. Among these, capillary capture is safer than tectonic capture, and it occurs in a shorter time than dissolution and tectonic capture. Furthermore, increased capillary capture efficiency in seepage channels enhances the flow resistance of CO2 in dominant seepage channels, promoting CO2 flow to low-permeability areas with high flow resistance. This also expands the reach of CO2 within the saline aquifer.

[0003] Given the similarities in engineering processes between CO2 sequestration in saline aquifers and enhanced oil and gas recovery (EOR) using CO2, there have been reports of using foam flooding technology to improve CO2 sequestration efficiency in saline aquifers. However, due to the public welfare nature of saline aquifer CO2 sequestration projects, the application of high-concentration foaming and foam-stabilizing colloidal materials inevitably increases the cost. Furthermore, ordinary foam fluids without special injection processes contain large-diameter bubble clusters, which need to overcome significant capillary resistance to enter small pores. Considering that most suitable saline aquifers for CO2 sequestration in China are located in terrestrial sedimentary basins, these aquifers generally have low porosity and low permeability, ordinary foam flooding technology is unlikely to achieve industrial widespread adoption in improving the capillary capture efficiency of CO2 in saline aquifers. In addition, since ordinary foam flooding technology is derived from enhanced oil recovery technology, the environmental toxicity of foaming agents and foam stabilizers has not been considered during the selection process. In the process of CO2 sequestration in saline aquifers, it is necessary to consider the impact of the toxicity of the agents used on the saline aquifer and the water bodies in the vicinity, which is a point that has been overlooked in previous studies.

[0004] In recent years, with the promotion of nano- and micro-bubble technology in municipal engineering projects such as industrial wastewater treatment, aquaculture, and river management, practical applications of this technology in drilling fluids and enhanced oil recovery have also emerged. The small particle size of nano- and micro-bubbles allows them to enter some small-sized pores without overcoming high capillary entry pressure thresholds, thus improving the injection capacity of CO2-containing fluids and expanding the reach of CO2 in these high capillary resistance regions. Although nano- and micro-bubbles possess a certain degree of stability due to the like charge on their surfaces resulting in strong Coulomb repulsion, their stability still faces significant challenges in certain high-temperature and high-mineralization saline aquifers: at high temperatures, the increased Brownian motion easily leads to coalescence between adjacent bubbles; in highly saline environments, the surface charge of the bubble film is easily neutralized by counterions, causing a decrease or even disappearance of the Coulomb repulsion between bubbles, similarly leading to bubble coalescence. Summary of the Invention

[0005] The purpose of this invention is to provide an environmentally friendly indoor preparation device for CO2 microbubble fluid and its application in improving the capillary CO2 capture efficiency of sandstone saline aquifers. Based on the inherent self-stability of microbubbles, adding a low dose of green foaming material to the aqueous phase effectively enhances the stability of the microbubbles. This reduces CO2 sequestration costs while expanding and improving the CO2 sweep range and capillary capture efficiency in saline aquifers, thus strengthening the safety of CO2 sequestration in saline aquifers.

[0006] To achieve the above objectives, the present invention employs the following technical measures:

[0007] An indoor preparation device for an environmentally friendly CO2 microbubble fluid, comprising:

[0008] The gas injection passage consists of a CO2 cylinder, a gas booster pump, and a gas flow controller; the liquid injection passage consists of a water source, a horizontal flow pump, and a piston container; the parallel gas injection passage and liquid injection passage merge into a high-pressure, high-speed stirring container.

[0009] The rear of the high-pressure high-speed mixing container is sequentially connected to a multi-stage shearing device, a core holder, a two-dimensional high-pressure visual observation chamber, a back pressure valve, and a liquid receiving cylinder, which is placed on the tray of a precision electronic balance. The mixed fluid, after being uniformly stirred at high speed by the high-pressure high-speed mixing container, flows sequentially to the multi-stage shearing device, the core holder, the two-dimensional high-pressure visual observation chamber, the back pressure valve, and the liquid receiving cylinder.

[0010] The back pressure control interface of the back pressure valve is connected to a high-pressure nitrogen cylinder to control the back pressure of the back pressure valve.

[0011] As described above, this invention uses CO2 and the green foaming agent APG to generate CO2 foam fluid in a high-pressure, high-speed stirring vessel. The CO2 foam fluid is then further sheared into micron-sized bubbles with diameters ranging from 10 to 50 μm by a multi-stage shearing device. By injecting the CO2 microfoam fluid into a sandstone core saturated with simulated target saline aquifer, the low capillary ingress pressure threshold of the microbubbles allows a large number of microbubbles to displace the saline water inside the pores of the sandstone core, improving the capillary sequestration efficiency of CO2 in the saline aquifer and enhancing the safety of CO2 sequestration in the saline aquifer.

[0012] Optionally, a first pressure sensor is installed between the multi-stage shearing device and the core holder, and a second pressure sensor is installed between the core holder and the two-dimensional high-pressure visual observation chamber. The first and second pressure sensors communicate with the monitoring computer through a pressure and mass data acquisition box, and are used to monitor the displacement pressure of CO2 foam fluid at the inlet and outlet of the core holder, respectively, so as to obtain the dynamic pressure difference change of CO2 foam in the displacement process in real time.

[0013] The precision electronic balance communicates with the monitoring computer through a pressure and mass data acquisition box, and is used to obtain the dynamic changes in the liquid phase mass in the produced fluid in real time by monitoring the changes in the mass data of the precision electronic balance.

[0014] Optionally, an electric mixer is installed on the top of the high-pressure and high-speed mixing container, and the maximum speed of the electric mixer is 3000 rpm; the high-pressure and high-speed mixing container is connected to the mixing blade speed control box via an electric wire, and the mixing blade speed of the electric mixer is adjusted by adjusting the mixing blade speed control box.

[0015] The inlet of the high-pressure resistant high-speed mixing container is located at the top, and the gas injection passage and liquid injection passage are merged at the top inlet of the high-pressure resistant high-speed mixing container; the outlet of the high-pressure resistant high-speed mixing container is located at the bottom, and the uniformly stirred foam fluid flows into the multi-stage shearing device through the bottom of the high-pressure resistant high-speed mixing container.

[0016] Optionally, the multi-stage shearing device includes a stainless steel pressure-resistant cylinder, a metal screen, and porous ceramics. The metal screen and porous ceramics are arranged from left to right inside the stainless steel pressure-resistant cylinder. The metal screen is woven from 304 stainless steel with a mesh size ranging from 1600 to 2000 mesh, a diameter of 25 mm, and a length of 30 mm. The porous ceramics have an average pore size of 5 μm, a diameter of 25 mm, and a length of 50 mm. The CO2 foam fluid flowing out from the outlet of the high-pressure, high-speed stirring container flows sequentially through the metal screen and porous ceramics, undergoing staged shearing to reduce the particle size of the bubble cluster.

[0017] Optionally, the two-dimensional high-pressure visual observation chamber is placed under an optical microscope, and the CO2 micro foam fluid flowing out from the core holder enters the two-dimensional high-pressure visual observation chamber to observe the particle size distribution of the CO2 micro foam fluid.

[0018] The visualization part of the two-dimensional high-pressure visual observation chamber is made of sapphire glass with high pressure resistance, with a diameter and thickness of 100 mm and 10 mm, respectively; the internal thickness of the two-dimensional high-pressure visual observation chamber is 1 mm; the maximum operating temperature and pressure of the two-dimensional high-pressure visual observation chamber are 130℃ and 25 MPa, respectively.

[0019] Optionally, the gas flow controller has an operating pressure range of 0.1-20 MPa and a gas flow rate control range of 0.10-9.99 mL / min; the horizontal flow pump has an operating pressure range of 0.1-42 MPa and a liquid flow rate control range of 0.001-9.999 mL / min.

[0020] Optionally, the middle interface of the core holder is connected to the confining pressure control pump to achieve real-time control of the internal confining pressure of the core holder; the foaming liquid uses nonionic surfactant alkyl polysaccharide APG, and according to the different lengths of the hydrophobic chain segments of the APG molecules, APG includes APG-0810, APG-10, APG-0812 and APG-0814, which are composed of 0.1-1.0 parts of APG and 100 parts of distilled water.

[0021] Accordingly, the present invention also claims the application of the aforementioned indoor preparation device for environmentally friendly CO2 microbubble fluid in improving the capillary CO2 capture efficiency of sandstone saline aquifers, comprising the following steps:

[0022] 1) A multi-stage shearing device is formed by placing a metal screen and porous ceramic inside a stainless steel pressure-resistant cylinder.

[0023] 2) Prepare the injection fluid, including simulated saline water, foaming liquid phase, and CO2 gas;

[0024] 3) Place the sandstone core into a small acrylic sealed box, turn on the vacuum pump to remove the air from inside the acrylic sealed box, and then pump simulated saline water into the acrylic sealed box until the simulated saline water level is higher than the top of the core, thereby fully saturating the core with simulated saline water. Measure the porosity of the sandstone core. The core was then placed in a core holder and a confining pressure control pump was used to track the confining pressure of the holder. Simulated saline water was injected into the sandstone core at a certain flow rate, and the permeability K of the sandstone core was measured.

[0025] 4) Use a high-pressure nitrogen cylinder as a back pressure valve to apply back pressure to the target pressure;

[0026] 5) Open the CO2 cylinder valve, adjust the pressure of the gas booster pump, and adjust the gas flow controller and the horizontal flow pump to control the volumetric flow rate of CO2 and foaming liquid respectively. Inject CO2 and foaming liquid into the high-pressure, high-speed stirring container at the same time; and turn on the electric stirrer to the maximum speed of 3000 rpm at the same time.

[0027] 6) When the internal pressure of the high-pressure and high-speed mixing container reaches the system back pressure, open the bottom valve of the high-pressure and high-speed mixing container and introduce the uniformly mixed CO2 foam fluid inside the high-pressure and high-speed mixing container into the multi-stage shearing device and core holder.

[0028] 7) Activate the computer monitoring software to monitor the pressure, gas flow rate, and liquid phase mass changes at various points within the device; calculate the CO2 saturation S of the sandstone core inside the core holder using the mass conservation method. CO2 ;

[0029] 8) At least the following should be changed: foaming agent type, foaming agent concentration, brine salinity, CO2-liquid phase volume ratio, CO2-liquid phase injection flow rate, mixer speed, and back pressure valve pressure to adjust the bubble size distribution of microfoam and observe the effect of microfoam size on CO2 saturation and CO2 and water distribution in sandstone cores.

[0030] Furthermore, in step 3), the porosity of the sandstone core is measured. The method for calculating the penetration rate K is as follows:

[0031] The sandstone core was placed in a constant temperature chamber at 105℃ and dried for 48 hours. After drying, the dry weight of the core was measured as m0. Then, the sandstone core was placed in a beaker containing simulated brine, with the brine level higher than the core. The beaker was placed in a vacuum chamber, and the vacuum pump was turned on to allow the core to fully absorb the brine from the beaker. After 48 hours, the core was removed from the vacuum chamber, the surface moisture was wiped dry, and the wet weight of the core was measured as m1. The porosity of the sandstone core was calculated using formula (1). :

[0032]

[0033] In equation (1), ρ is the density of the simulated brine, and D and L are the core diameter and length, respectively.

[0034] The sandstone core, after being saturated with saline water, was placed in a core holder, and the confining pressure of the core holder was adjusted to always be 3 MPa higher than the injection pressure. Then, saline water was injected into the sandstone core at a constant volumetric flow rate, and the pressures at the front and rear ends of the core holder were monitored. After the pressure difference stabilized, the permeability K of the sandstone core was calculated according to formula (2):

[0035]

[0036] In equation (2), Q is the volumetric flow rate of the simulated brine, ranging from 0.1 to 1.0 mL / min; μ is the viscosity of the simulated brine; ΔP is the pressure difference between the front and rear ends of the core holder; and A is the cross-sectional area of ​​the sandstone core.

[0037] Further, in step 7), the CO2 saturation S in the sandstone core is calculated according to formula (3). CO2 :

[0038]

[0039] In equation (3), PV is the pore volume of the sandstone core; V in With V out Q1 represents the volume of liquid entering the sandstone core and the volume of liquid flowing out of the sandstone core within the experimental time t, respectively; Q1 is the liquid flow rate in the injected core fluid; t is the liquid pumping time; m is the mass increase at the precision electronic balance; ρ is the liquid density.

[0040] As described above, micron-sized bubble clusters, when entering regions with low porosity and low permeability, do not need to overcome high capillary entry pressure thresholds, resulting in better injectability of microfoam technology compared to conventional foam flooding technology. Simultaneously, utilizing the small particle size advantage of microfoam technology, CO2-containing fluids can occupy dominant seepage channels while also entering small-pore regions with high seepage resistance, expanding the reach of CO2-containing fluids in the saline aquifer and enhancing the capillary capture efficiency of CO2-containing fluids in the saline aquifer, further strengthening the safety of CO2 sequestration projects in saline aquifers. This invention incorporates a green, non-toxic surfactant, alkyl polysaccharide glycoside (APG), with excellent foaming properties, during the preparation of nano- and microbubbles. APG molecules stably adsorb onto the bubble liquid film to bind water in the CO2 bubble liquid film. Simultaneously, the hydrophilic groups of APG molecules contact a large number of metal ions in the brine to strengthen the Coulomb repulsion between liquid films, inhibiting the aggregation of CO2 microbubbles in high-temperature and high-mineralization brine environments, thus improving the stability of CO2 microbubbles in this harsh environment.

[0041] The beneficial effects of this invention are as follows:

[0042] 1. A uniform distribution of CO2 in the liquid phase is achieved through a high-pressure, high-speed stirring container, and the size of the bubble cluster is further reduced by a multi-stage shearing device composed of a metal screen and porous ceramics, thereby increasing the sweep range of CO2-containing fluid in the sandstone core.

[0043] 2. With the help of a horizontal flow pump and a precise electronic balance, the liquid phase and CO2 saturation inside the sandstone core can be obtained in real time during the displacement process, and the microbubble size can be adjusted in a timely manner according to the changes in CO2 saturation inside the sandstone core.

[0044] 3. The size of the microbubbles can be adjusted in real time by adjusting parameters such as the ratio of CO2 to liquid phase flow rate, overall flow rate, back pressure valve pressure, and agitator speed, based on the size of the microbubbles inside the two-dimensional visual observation chamber. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of the device described in this invention;

[0046] Figure 2 The particle size distribution of CO2 bubbles in the fluids produced by different displacement methods in Example 1 is shown.

[0047] Figure 3 The CO2 saturation S inside the sandstone core after displacement by different displacement methods in Example 1 is shown. CO2 ;

[0048] Figure 4 The water saturation of sandstone cores after displacement by different displacement methods in Example 1.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1. CO2 cylinder; 2. Gas booster pump; 3. Gas flow meter; 4. Water source; 5. Flow pump; 6. Piston container; 7. High-pressure high-speed mixing container; 8. Agitator speed control box; 9. Multi-stage shearing device; 10. Metal screen; 11. Porous ceramic; 12. Core holder; 13. Confining pressure control pump; 14. Two-dimensional high-pressure visual observation chamber; 15. Back pressure valve; 16. Precision electronic balance; 17. Liquid receiving cylinder; 18. Pressure and mass data acquisition box; 19. High-pressure nitrogen cylinder; 20. Optical microscope; 21. First pressure sensor; 22. Monitoring computer; 23. Second pressure sensor. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] An environmentally friendly indoor preparation device for CO2 microbubble fluid, such as Figure 1As shown, the system includes: CO2 cylinder 1, gas booster pump 2, gas flow controller 3, water source 4, horizontal flow pump 5, piston container 6, high-pressure high-speed stirring container 7, stirring paddle speed control box 8, multi-stage shearing device 9, metal screen 10, porous ceramic 11, core holder 12, confining pressure control pump 13, two-dimensional high-pressure visual observation chamber 14, back pressure valve 15, precision electronic balance 16, liquid receiving cylinder 17, pressure and mass data acquisition box 18, high-pressure nitrogen cylinder 19, optical microscope 20, first pressure sensor 21, monitoring computer 22, and second pressure sensor 23, wherein:

[0053] The gas injection passage consists of a CO2 cylinder 1, a gas booster pump 2, and a gas flow controller 3.

[0054] The injection passage consists of water source 4, horizontal flow pump 5, and piston container 6;

[0055] The parallel gas injection passage and liquid injection passage merge in the high-pressure, high-speed stirring vessel 7;

[0056] The rear of the high-pressure high-speed mixing container 7 is connected in sequence to the multi-stage shearing device 9, the core holder 12, the two-dimensional high-pressure visual observation chamber 14, the back pressure valve 15, and the liquid receiving cylinder 17 via stainless steel pipelines. The mixed fluid, after being uniformly stirred at high speed by the high-pressure high-speed mixing container 7, flows sequentially to the multi-stage shearing device 9, the core holder 12, the two-dimensional high-pressure visual observation chamber 14, the back pressure valve 15, and the liquid receiving cylinder 17.

[0057] The liquid receiving cylinder 17 is placed on the tray of the precision electronic balance 16;

[0058] The back pressure control interface of the back pressure valve 15 is connected to the high-pressure nitrogen cylinder 19 via a stainless steel pipeline to control the back pressure of the back pressure valve 15.

[0059] Furthermore, the precision electronic balance 16 communicates with the monitoring computer 22 through the pressure and mass data acquisition box 18, and can obtain the dynamic changes in the liquid phase mass in the produced fluid in real time by monitoring the changes in the mass data of the precision electronic balance 16.

[0060] Furthermore, a first pressure sensor 21 is installed between the multi-stage shearing device 9 and the core holder 12, and a second pressure sensor 23 is installed between the core holder 12 and the two-dimensional high-pressure visual observation chamber 14. The first pressure sensor 21 and the second pressure sensor 23 communicate with the monitoring computer 22 through the pressure and mass data acquisition box 18, and are used to monitor the displacement pressure of CO2 foam fluid at the inlet and outlet of the core holder 12, so as to obtain the dynamic pressure difference change of CO2 foam in the displacement process in real time.

[0061] According to a preferred embodiment of the present invention, the working pressure range of the gas flow controller 3 is 0.1-20 MPa, and the gas flow rate control range is 0.10-9.99 mL / min; the working pressure range of the horizontal flow pump 5 is 0.1-42 MPa, and the liquid flow rate control range is 0.001-9.999 mL / min.

[0062] According to a preferred embodiment of the present invention, the maximum withstand pressure of the high-pressure high-speed mixing container 7 is 32 MPa. The gas injection passage and the liquid injection passage are joined at the top inlet of the high-pressure high-speed mixing container 7. An electric mixer is installed at the top of the high-pressure high-speed mixing container 7. The electric mixer includes a propeller-type mixing blade and has a maximum speed of 3000 rpm. The outlet of the high-pressure high-speed mixing container 7 is also located at the bottom of the container. The uniformly stirred foam fluid flows through the bottom of the high-pressure high-speed mixing container and into the multi-stage shearing device 9 through a stainless steel pipeline.

[0063] According to a preferred embodiment of the present invention, the impeller speed control box 8 is connected to the high-pressure high-speed mixing container 7 by wire, and the impeller speed control box 8 is adjusted to adjust the impeller speed of the electric mixer inside the high-pressure high-speed mixing container 7; through the high-speed stirring and shearing of the impeller inside the high-pressure high-speed mixing container 7, the CO2 and the foaming liquid are fully mixed to form a CO2 foam fluid with a large number of bubbles.

[0064] According to a preferred embodiment of the present invention, the multi-stage shearing device 9 comprises a stainless steel pressure-resistant cylinder, a metal screen 10, and a porous ceramic 11. The metal screen 10 and the porous ceramic 11 are arranged from left to right inside the stainless steel pressure-resistant cylinder. The metal screen 10 is woven from 304 stainless steel with a mesh size ranging from 1600 to 2000 mesh (approximately 6.5 to 10 μm), a diameter of 25 mm, and a length of 30 mm. The porous ceramic 11 has an average pore size of 5 μm, a diameter of 25 mm, and a length of 50 mm. The CO2 foam fluid flowing from the outlet of the high-pressure, high-speed stirring vessel 7 flows sequentially through the metal screen 10 and the porous ceramic 11, undergoing staged shearing to reduce the particle size of the bubble cluster.

[0065] According to a preferred embodiment of the present invention, a stainless steel pipeline is used to connect the confining pressure control pump 13 to the middle interface of the core holder 12, so as to achieve real-time control of the internal confining pressure of the core holder 12. In actual use, the confining pressure of the core holder 12 is always controlled to be 2-3 MPa higher than the injection pressure at the injection end of the core holder 12, so as to prevent CO2 foam fluid from flowing along the side of the core.

[0066] According to a preferred embodiment of the present invention, the two-dimensional high-pressure visual observation chamber 14 is a chamber for observing the microscopic morphology of high-pressure fluids. It consists of two flat-welded flanges (outer diameter and thickness 150mm and 15mm, respectively). High-temperature resistant, CO2 corrosion resistant, and high-sealing nitrile rubber rings are installed in grooves at the bottom of the upper and lower flanges. High-pressure resistant sapphire glass (diameter and thickness 100mm and 10mm, respectively) is embedded into the nitrile rubber rings to form the visible part of the observation chamber. High-strength stainless steel bolts are used to secure the two flanges. The flanges of the sapphire glass are connected to form a two-dimensional high-pressure visual observation chamber 14. The internal height of the high-pressure chamber (i.e., the distance between the two pieces of sapphire glass) is 1 mm. The maximum operating temperature and pressure of the two-dimensional high-pressure visual observation chamber 14 are 130℃ and 25MPa, respectively. The CO2 microbubble fluid flowing out from the core holder 12 enters the two-dimensional high-pressure visual observation chamber 14 through a stainless steel pipeline. By placing the two-dimensional high-pressure visual observation chamber 14 under an optical microscope 20, the particle size distribution of the CO2 microbubble fluid flowing out from the core holder 12 is observed.

[0067] In this invention, the foaming liquid uses the environmentally friendly nonionic surfactant alkyl polysaccharide APG, which can be divided into APG-0810, APG-10, APG-0812 and APG-0814 according to its hydrophobic segment length. Its composition is 0.1-1.0 parts of APG and 100 parts of distilled water. Before the experiment, the prepared foaming liquid of a certain concentration needs to be poured into the piston container 6. After setting the flow rate of the horizontal flow pump 5, the horizontal flow pump 5 draws water from the water source 4 at a set rate to push the foaming liquid in the piston container 6 into the high-pressure high-speed stirring container 7. The CO2 foam fluid flowing out of the high-pressure high-speed stirring container 7 enters the multi-stage shearing device 9 through the stainless steel pipeline. The purpose is to perform secondary shearing and refinement of the CO2 foam fluid, and further reduce the average particle size of the CO2 bubble group.

[0068] As described above, this invention injects CO2 and foaming liquid into a high-pressure homogenized container at a predetermined flow rate ratio through a high-pressure gas injection channel and a high-pressure liquid injection channel to control the volume fraction of CO2 in the microfoam. Subsequently, a high-pressure high-speed stirring container is used to rapidly stir the CO2 and liquid phase, ensuring thorough mixing. The thoroughly mixed CO2 and liquid phase mixture is then injected into a multi-stage shearing device to further reduce the CO2 foam particle size, achieving a particle size range of 10-50 μm.

[0069] An application of the aforementioned device in improving the capillary CO2 capture efficiency of sandstone saline aquifers includes the following steps:

[0070] 1) The metal screen 10 and the porous ceramic 11 are placed inside the stainless steel pressure-resistant cylinder to form a multi-stage shearing device 9;

[0071] 2) Prepare the injection fluid, including simulated saline water, foaming liquid phase, and CO2 gas;

[0072] 3) Place the sandstone core into a small acrylic sealed box. After connecting the vacuum pump to the acrylic sealed box with a stainless steel pipeline, turn on the vacuum pump to remove the air inside the acrylic sealed box, and then pump simulated saline water into the acrylic sealed box until the simulated saline water level is higher than the top of the core, thus fully saturating the core with simulated saline water. Measure the porosity of the sandstone core. The core was then placed in the core holder 12, and a stainless steel pipeline was used to connect the core holder 12 and the confining pressure control pump 13. The confining pressure control pump 13 tracked the confining pressure of the holder and injected simulated saline water into the sandstone core at a certain flow rate to measure the permeability K of the sandstone core.

[0073] 4) Connect the high-pressure nitrogen cylinder 19 to the back pressure valve 15 with a stainless steel pipeline, and use the high-pressure nitrogen cylinder 19 to apply back pressure to the back pressure valve 15 to the target pressure.

[0074] 5) Connect CO2 cylinder 1 to gas booster pump 2 with stainless steel pipeline, open the valve of CO2 cylinder 1, adjust the pressure of gas booster pump 2, and adjust gas flow controller 3 and horizontal flow pump 5 to control the volume flow rate of CO2 and foaming liquid respectively. Inject CO2 and foaming liquid into high pressure resistant high speed stirring container 7 at the same time; and turn on electric stirrer to the maximum speed of 3000 rpm at the same time.

[0075] 6) When the internal pressure of the high-pressure and high-speed mixing container 7 reaches the system back pressure, open the bottom valve of the high-pressure and high-speed mixing container 7. The CO2 foam fluid that is uniformly mixed inside the high-pressure and high-speed mixing container 7 is introduced into the multi-stage shearing device 9 and the core holder 12 through the stainless steel pipeline.

[0076] 7) Activate the computer monitoring software to monitor the pressure, gas flow rate, and liquid phase mass changes at various points within the device; calculate the CO2 saturation S of the sandstone core inside the core holder 12 using the mass conservation method. CO2 The distribution of CO2 and water inside the sandstone core after CO2 microfoam displacement was detected by low-field nuclear magnetic resonance spectrometer.

[0077] 8) At least the following should be changed: foaming agent type, foaming agent concentration, brine salinity, CO2-liquid phase volume ratio, CO2-liquid phase injection flow rate, mixer speed, and back pressure valve pressure to adjust the bubble size distribution of microfoam and observe the effect of microfoam size on CO2 saturation and CO2 and water distribution in sandstone cores.

[0078] According to a preferred embodiment of the present invention, in step 3), the porosity of the sandstone core is measured. The method for calculating the penetration rate K is as follows:

[0079] The sandstone core was placed in a constant temperature chamber at 105℃ and dried for 48 hours. After drying, the dry weight of the core was measured as m0. The sandstone core was then placed in a beaker containing simulated brine (the brine level was higher than the core), placed in a vacuum chamber, and the vacuum pump was turned on to allow the core to fully absorb the brine from the beaker. After 48 hours, the core was removed from the vacuum chamber, the surface moisture was wiped dry, and the wet weight of the core was measured as m1. The porosity of the sandstone core was calculated using formula (1). :

[0080]

[0081] In equation (1), ρ is the simulated brine density, and D and L are the core diameter and length, respectively.

[0082] The sandstone core, after being saturated with saline water, was placed in a core holder, and the confining pressure of the core holder was adjusted to always be 3 MPa higher than the injection pressure. Saline water was then injected into the sandstone core at a constant volumetric flow rate, and the pressures at the front and rear ends of the core holder were monitored. After the pressure difference stabilized, the permeability K of the sandstone core was calculated according to formula (2):

[0083]

[0084] In Equation (2), Q is the volumetric flow rate of the simulated brine (flow rate range 0.1-1.0 mL / min), μ is the viscosity of the simulated brine, ΔP is the pressure difference between the front and rear ends of the core holder, and A is the cross-sectional area of ​​the sandstone core.

[0085] According to a preferred embodiment of the present invention, in step 7), the CO2 saturation S in the sandstone core can be calculated according to formula (3). CO2 :

[0086]

[0087] In equation (3), PV is the pore volume of the sandstone core, and V in With V out Q1 represents the volume of liquid entering the sandstone core and the volume of liquid flowing out of the sandstone core within the experimental time t, respectively. Q1 is the liquid flow rate in the fluid injected into the core, t is the liquid pumping time, m is the mass added at the precision electronic balance (which can be regarded as the liquid phase mass in the produced fluid), and ρ is the liquid phase density.

[0088] The invention will now be described in detail with reference to examples and accompanying drawings.

[0089] Example 1

[0090] An indoor preparation device for the aforementioned environmentally friendly CO2 microbubble fluid is used to improve the capillary CO2 capture efficiency of sandstone saline aquifers, comprising the following steps:

[0091] 1) The metal screen 10 and the porous ceramic 10 are placed inside the stainless steel pressure-resistant cylinder to form a multi-stage shearing device 9.

[0092] 2) Prepare the injection fluid, including the simulated saline water (the composition of the saline water used in the examples is shown in Table 1), the foaming liquid phase (0.10 wt% alkyl polysaccharide APG-10 solution) and CO2 gas;

[0093] 3) Place three artificial sandstone cores in a constant temperature chamber at 105℃. When the mass change does not exceed 0.0010g for two consecutive days, the internal moisture of the cores can be considered evaporated. Weigh the cores using a precision electronic balance to determine their dry weight (m0). Place the artificial sandstone cores in a beaker. Then place the beaker in an acrylic sealed box, connecting the vacuum pump to the box using a stainless steel pipeline. Turn on the vacuum pump to extract air from inside the acrylic sealed box at a pumping speed of 2-5m / s. 3 / h, the ultimate vacuum is 2-4Pa, and then simulated saline water is pumped into the acrylic sealed box under this environment until the saline water level is higher than the core surface. The vacuum pump continuously pumps vacuum for 24h. After removing the beaker from the acrylic sealed box, wipe the surface of the sandstone core dry and weigh it with a precision electronic balance to determine its mass m1. The porosity of the sandstone core is calculated using formula (1). The length, diameter, and porosity of the three core samples in this embodiment are shown in Table 2.

[0094] 4) Place the artificial sandstone core saturated with simulated saline water into the core holder 12. Connect the confining pressure control pump 13 and the core holder 12 with a stainless steel pipeline. Use the confining pressure control pump 13 to apply confining pressure to the core holder 12 (set the confining pressure to always be 3 MPa higher than the injection pressure). Inject simulated saline water into the sandstone core at a flow rate of 0.50 mL / min. Stop injecting simulated saline water when the pressure at both ends of the core holder 12 is stable. Calculate the permeability K of the sandstone core using formula (2). The permeability information of the three sandstone cores in this embodiment is shown in Table 2.

[0095] 5) Connect the high-pressure nitrogen cylinder 19 to the back pressure valve 15 with a stainless steel pipeline, and adjust the output pressure of the high-pressure nitrogen cylinder 19 to the back pressure valve 15 to apply back pressure to the target pressure; in this embodiment, the back pressure is 12MPa.

[0096] 6) A stainless steel pipeline is used to connect the vacuum oil pump and the high-pressure and high-speed mixing container 7. The vacuum oil pump is used to extract the air inside the high-pressure and high-speed mixing container 7, so that the inside of the high-pressure and high-speed mixing container 7 is in a vacuum state.

[0097] 7) For core #1 (CO2 drive group): connect CO2 cylinder 1 and gas booster pump 2 with stainless steel pipeline, open the valve of CO2 cylinder 1, adjust the pressure of gas booster pump 2 to 10MPa, and adjust the gas flow controller 3 to control the CO2 volume flow rate to 2mL / min.

[0098] For core #2 (ordinary CO2 foam group): connect CO2 cylinder 1 and gas booster pump 2 with stainless steel pipeline, open the valve of CO2 cylinder 1, adjust the pressure of gas booster pump 2 to 10MPa, and adjust gas flow controller 3 and horizontal flow pump 5 to control the volume flow rate of CO2 and foaming liquid to 1mL / min respectively. CO2 and foaming liquid do not pass through high pressure and high speed stirring container and multi-stage shearing device. The two fluids directly enter the sandstone core in the core holder.

[0099] For core #3 (CO2 microfoam group): connect CO2 cylinder 1 and gas booster pump 2 using stainless steel pipelines. Open the valve of CO2 cylinder 1, adjust the pressure of gas booster pump 2 to 10MPa, and adjust the gas flow controller 3 and the horizontal flow pump 5 to control the volumetric flow rate of CO2 and foaming liquid to 1mL / min respectively. Simultaneously inject CO2 and foaming liquid into the high-pressure resistant high-speed stirring container 7, and connect the high-pressure resistant high-speed stirring container 7 to the multi-stage shearing device 9 and core holder 12 with stainless steel pipelines. At the same time, turn on the electric mixer to the maximum speed of 3000rpm. When the internal pressure of the high-pressure resistant high-speed stirring container 7 reaches the system back pressure, open the bottom valve of the high-pressure resistant high-speed stirring container. The uniformly stirred CO2 foam fluid inside the high-pressure resistant high-speed stirring container is sequentially introduced into the multi-stage shearing device 9 and core holder 12 through the stainless steel pipelines.

[0100] In the above three groups of displacement experiments, the outlet end of the core holder 12 was connected to the two-dimensional high-pressure visual observation chamber 14 with a stainless steel pipeline, and the two-dimensional high-pressure visual observation chamber 14 was placed under the optical microscope 20 to observe the micromorphology of the displaced fluid.

[0101] 8) Activate the computer monitoring software to monitor the pressure, gas flow rate, and liquid phase mass changes at various points within the device; calculate the CO2 saturation S of the sandstone core inside the core holder using the mass conservation method. CO2 The distribution of CO2 and water inside the sandstone core after CO2 microfoam displacement was detected by low-field nuclear magnetic resonance spectrometer.

[0102] See Figure 2 The median particle size d of CO2 flooding, conventional CO2 foam flooding, and CO2 microfoam flooding 50The particle sizes were 170.75, 60.38, and 33.65 μm, respectively. After incorporating a high-speed mixer and a multi-stage shearing device, the bubble swarm size of the CO2 foam significantly decreased. Smaller bubble swarm size facilitates the entry of more CO2 bubbles into the small pores of the sandstone core, thus expanding the sweep range of the CO2-containing fluid within the sandstone core. See also... Figure 3 After CO2 flooding, conventional CO2 foam flooding, and CO2 microfoam flooding, the CO2 saturation S in the sandstone core was... CO2 The percentages were 35.71%, 62.43%, and 81.68%, respectively. This means that CO2 microbubbles can effectively improve the CO2 sequestration efficiency in sandstone, with most of the aqueous phase in the sandstone being displaced by the CO2 microbubbles. See also Figure 4 After the displacement was completed, the water saturation of the entire sandstone core of the CO2 microfoam group dropped to about 20% and was evenly distributed. The CO2 microfoam exhibited a uniform piston-like displacement morphology in the sandstone core, which helped to significantly improve the CO2 sequestration efficiency in the sandstone saline aquifer.

[0103] Table 1. Composition of simulated saline water in this embodiment.

[0104] Types of inorganic salts NaCl <![CDATA[CaCl2]]> <![CDATA[MgCl2·6H2O]]> <![CDATA[NaHCO3]]> <![CDATA[Na2SO4]]> total Concentration (g / L) 75.26 19.99 9.61 0.68 1.17 101.60

[0105] Table 2 shows the geometric dimensions, porosity, and permeability information of the three core samples in this embodiment.

[0106] Core number Diameter / cm Length / cm Porosity / % Permeability / mD 1# 2.47 10.25 19.17 118.90 2# 2.51 10.17 19.99 107.10 3# 2.45 10.07 19.66 136.99

[0107] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any transformations or substitutions that can be understood by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of the present invention.

Claims

1. An indoor preparation device for an environmentally friendly CO2 microbubble fluid, characterized in that, include: A gas injection passage is composed of a CO2 cylinder (1), a gas booster pump (2), and a gas flow controller (3); a liquid injection passage is composed of a water source (4), a horizontal flow pump (5), and a piston container (6); the parallel gas injection passage and liquid injection passage converge in a high-pressure high-speed stirring container (7); an electric stirrer is installed on the top of the high-pressure high-speed stirring container (7), the maximum speed of the electric stirrer is 3000 rpm, the inlet of the high-pressure high-speed stirring container (7) is located at the top, and the outlet of the high-pressure high-speed stirring container (7) is located at the bottom; The high-pressure high-speed mixing container (7) is connected in sequence to a multi-stage shearing device (9), a core holder (12), a two-dimensional high-pressure visual observation chamber (14), a back pressure valve (15), and a liquid receiving cylinder (17). The liquid receiving cylinder (17) is placed on the tray of a precision electronic balance (16). The mixed fluid, after being uniformly stirred by the high-pressure high-speed mixing container (7), flows sequentially to the multi-stage shearing device (9), the core holder (12), the two-dimensional high-pressure visual observation chamber (14), the back pressure valve (15), and the liquid receiving cylinder (17). The back pressure control interface of the back pressure valve (15) is connected to the high-pressure nitrogen cylinder (19) to control the back pressure of the back pressure valve (15); The multi-stage shearing device (9) includes a stainless steel pressure-resistant cylinder, a metal screen (10), and a porous ceramic (11). The metal screen (10) and the porous ceramic (11) are arranged from left to right inside the stainless steel pressure-resistant cylinder. The metal screen (10) is woven from 304 stainless steel with a mesh size ranging from 1600 to 2000 mesh. The metal screen (10) has a diameter of 25 mm and a length of 30 mm. The porous ceramic (11) has an average pore size of 5 μm, a diameter of 25 mm, and a length of 50 mm. The foaming liquid uses the environmentally friendly nonionic surfactant alkyl polysaccharide APG. CO2 foam fluid is generated by using CO2 and the green foaming agent APG in a high-pressure, high-speed stirring container. The CO2 foam fluid flowing out of the outlet of the high-pressure high-speed stirring container (7) flows sequentially through the metal screen (10) and the porous ceramic (11), and is sheared step by step to reduce the particle size of the bubble cluster.

2. The indoor preparation apparatus for the environmentally friendly CO2 microbubble fluid according to claim 1, characterized in that, A first pressure sensor (21) is arranged between the multi-stage shearing device (9) and the core holder (12), and a second pressure sensor (23) is arranged between the core holder (12) and the two-dimensional high-pressure visual observation chamber (14). The first pressure sensor (21) and the second pressure sensor (23) communicate with the monitoring computer (22) through the pressure and mass data acquisition box (18) and are used to monitor the displacement pressure of CO2 foam fluid at the inlet and outlet of the core holder (12) respectively, so as to know the dynamic pressure difference change of CO2 foam in the displacement process in real time. The precision electronic balance (16) communicates with the monitoring computer (22) through the pressure and mass data acquisition box (18) to obtain the dynamic changes in the liquid phase mass in the produced fluid in real time by monitoring the changes in the mass data of the precision electronic balance (16).

3. The indoor preparation apparatus for the environmentally friendly CO2 microbubble fluid according to claim 1, characterized in that, The high-pressure resistant high-speed mixing container (7) is connected to the mixing blade speed control box (8) by wires. The mixing blade speed of the electric mixer can be adjusted by adjusting the mixing blade speed control box (8). The gas injection passage and the liquid injection passage are joined at the top inlet of the high-pressure resistant high-speed stirring container (7); the foam fluid that has been stirred evenly flows into the multi-stage shearing device (9) through the bottom of the high-pressure resistant high-speed stirring container (7).

4. The indoor preparation apparatus for the environmentally friendly CO2 microbubble fluid according to claim 1, characterized in that, The two-dimensional high-pressure visual observation chamber (14) is placed under the optical microscope (20). The CO2 micro foam fluid flowing out from the core holder (12) enters the two-dimensional high-pressure visual observation chamber (14) to observe the particle size distribution of the CO2 micro foam fluid. The visualization part of the two-dimensional high-pressure visual observation chamber (14) is sapphire glass with high pressure resistance, with a diameter and thickness of 100 mm and 10 mm, respectively; the internal thickness of the two-dimensional high-pressure visual observation chamber (14) is 1 mm; the maximum operating temperature and pressure of the two-dimensional high-pressure visual observation chamber (14) are 130 ℃ and 25 MPa, respectively.

5. The indoor preparation apparatus for the environmentally friendly CO2 microbubble fluid according to claim 1, characterized in that, The gas flow controller (3) has a working pressure range of 0.1-20 MPa and a gas flow rate control range of 0.10-9.99 mL / min; the horizontal flow pump (5) has a working pressure range of 0.1-42 MPa and a liquid flow rate control range of 0.001-9.999 mL / min.

6. The indoor preparation apparatus for the environmentally friendly CO2 microbubble fluid according to claim 1, characterized in that, The middle interface of the core holder (12) is connected to the confining pressure control pump (13) to achieve real-time control of the internal confining pressure of the core holder (12).

7. The application of an indoor preparation device for an environmentally friendly CO2 microbubble fluid according to any one of claims 1-6 in improving the capillary CO2 capture efficiency of sandstone saline aquifers, characterized in that, Includes the following steps: 1) A multi-stage shearing device (9) is formed by placing a metal screen (10) and a porous ceramic (11) inside a stainless steel pressure-resistant cylinder; 2) Prepare the injection fluid, including the simulated saline water layer, the foaming liquid phase, and CO2 gas; the foaming liquid phase uses the nonionic surfactant alkyl polysaccharide APG, which is composed of 0.1-1.0 parts of APG and 100 parts of distilled water. 3) Place the sandstone core into a small acrylic sealed box, turn on the vacuum pump to extract the air inside the acrylic sealed box, and then pump simulated saline water into the acrylic sealed box until the simulated saline water level is higher than the top of the core, so that the core is fully saturated with simulated saline water and the porosity φ of the sandstone core is measured; then place the core in the core holder (12) and use the confining pressure control pump (13) to track the confining pressure of the holder, inject simulated saline water into the sandstone core at a certain flow rate, and measure the permeability K of the sandstone core; 4) Use a high-pressure nitrogen cylinder (19) as a back pressure valve (15) to apply back pressure to the target pressure; 5) Open the valve of CO2 cylinder (1), adjust the pressure of gas booster pump (2), adjust the gas flow controller (3) and the horizontal flow pump (5) to control the volume flow rate of CO2 and foaming liquid respectively, and inject CO2 and foaming liquid into the high pressure resistant high speed stirring container (7) at the same time; and turn on the electric stirrer to the maximum speed of 3000 rpm at the same time. 6) When the internal pressure of the high-pressure high-speed mixing container (7) reaches the system back pressure, open the bottom valve of the high-pressure high-speed mixing container (7) and introduce the uniformly stirred CO2 foam fluid inside the high-pressure high-speed mixing container (7) into the multi-stage shearing device (9) and the core holder (12). 7) Turn on the computer monitoring software to monitor the pressure, gas flow rate and liquid phase mass changes in various parts of the device; calculate the CO2 saturation S of the sandstone core inside the core holder (12) according to the mass conservation method. CO2 ; 8) At least the following should be changed: foaming agent type, foaming agent concentration, brine salinity, CO2-liquid phase volume ratio, CO2-liquid phase injection flow rate, mixer speed, and back pressure valve pressure to adjust the bubble size distribution of microfoam and observe the effect of microfoam size on CO2 saturation and CO2 and water distribution in sandstone cores.

8. The application according to claim 7, characterized in that, In step 3), the method for measuring the porosity φ and permeability K of the sandstone core is as follows: The sandstone core was placed in a 105 ℃ constant temperature oven and dried for 48 h. After drying, the dry weight of the core was measured as m0. Then, the sandstone core was placed in a beaker containing simulated brine, with the brine level higher than the core. The beaker was placed in a vacuum chamber, and the vacuum pump was turned on to allow the core to fully absorb the brine from the beaker. After 48 h, the core was removed from the vacuum chamber, the surface moisture was wiped dry, and the wet weight of the core was measured as m1. The porosity φ of the sandstone core was calculated using formula (1): (1) In equation (1), ρ is the density of the simulated brine, and D and L are the core diameter and length, respectively. The sandstone core, after being saturated with saline water, was placed in a core holder, and the confining pressure of the core holder was adjusted to always be 3 MPa higher than the injection pressure. Then, saline water was injected into the sandstone core at a constant volumetric flow rate, and the pressures at the front and rear ends of the core holder were monitored. After the pressure difference stabilized, the permeability K of the sandstone core was calculated according to formula (2): (2) In equation (2), Q is the volumetric flow rate of the simulated brine, ranging from 0.1 to 1.0 mL / min; μ is the viscosity of the simulated brine; ΔP is the pressure difference between the front and rear ends of the core holder; and A is the cross-sectional area of ​​the sandstone core.

9. The application according to claim 7, characterized in that, In step 7), the CO2 saturation S in the sandstone core is calculated according to formula (3). CO2 : (3) In equation (3), PV is the pore volume of the sandstone core; Q1 is the fluid velocity injected into the core. t is the liquid pumping time; m is the mass added at the precision electronic balance; ρ is the density of the liquid phase.

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