A system and method for real-time monitoring of rock pore structure changes by CO2 immersion

Abstract

The present invention discloses a CO 2 The system and method for real-time monitoring of rock pore structure changes by immersion are applied in the field of rock microstructure analysis technology. 2 The immersion technology lacks effective real-time monitoring means during implementation; the present invention combines the sample to be tested with dry ice (solid CO 2 ) is placed inside the reactor, and the pressure and temperature inside the reactor are changed to change the CO 2 Phase; Different phases of CO 2 Soak the rock, react with the rock, and use real-time CT to view the changes in the rock's internal structure; according to the soaking effect, adjust the temperature and pressure inside the reactor in real time to obtain different phases of CO 2 Soaking effect.

Description

Technical Field

[0001] The invention belongs to the technical field of rock microstructure analysis, and particularly relates to a device and method for real-time monitoring of rock pore structure by CO2 immersion based on CT scanning. Background Art

[0002] Under the current global greenhouse effect crisis, CO2 utilization and long-term geological storage have become key solutions to reduce greenhouse gas concentrations and meet the urgent need to mitigate climate change. In the process of mineral resource development, CO2 fracturing is an important reservoir transformation method and an important manifestation of CO2 utilization. Traditional hydraulic fracturing has problems such as low efficiency, high cost and environmental pollution. In recent years, CO2 fracturing technology has gradually attracted attention due to its environmental protection and high efficiency. CO2 fracturing technology is an emerging reservoir transformation method. It uses CO2 as a working medium and injects it into underground rocks under high pressure to cause cracks in the rocks to achieve the purpose of reservoir transformation. Therefore, it is necessary to study the reaction between rocks and CO2 in different phases during CO2 fracturing, and the changes in the porosity and permeability of the rocks themselves. At the same time, the sealing of the caprock is also crucial when carrying out CO2 geological storage. As an impermeable layer or low permeability layer covering the underground reservoir, the sealing performance of the caprock directly affects the effectiveness and safety of CO2 geological storage. The cap rock should have sufficient permeability barrier capacity, mechanical strength and chemical stability to prevent CO2 from leaking to the surface or groundwater through tiny pores or cracks, thereby avoiding environmental pollution and geological disasters. Therefore, in the process of CO2 geological storage, it is crucial to study and evaluate the sealing performance of CO2 on the cap rock and take effective monitoring and management measures to ensure the long-term stable storage of underground CO2.

[0003] However, the existing CO2 immersion technology has an obvious flaw in its implementation, which is the lack of effective real-time monitoring methods. This means that during the immersion process, it is impossible to accurately evaluate the immersion effect and optimize the operating parameters. First, the lack of real-time monitoring methods makes it difficult to evaluate the immersion effect. Moreover, in actual construction, with the changes in temperature and pressure, the phase state of CO2 is also changing dramatically. This phase change has an important impact on the properties of rocks, such as the permeability, pore structure and mechanical properties of rocks, but this aspect has rarely been involved in past studies. Strengthening the study of the effects of CO2 phase changes on rock properties will help to deepen our understanding of its role in underground engineering and geological storage, thereby improving the safety and sustainability of projects. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a system and method for real-time monitoring of rock pore structure changes by CO2 immersion.

[0005] One of the technical solutions adopted by the present invention is: a system for real-time monitoring of rock pore structure changes by CO2 immersion, comprising: a reactor, a pressurizing device, a heating power supply, a micro-focus X-ray source, a flat-panel detector, an image collector, and also a rock sample to be tested and dry ice placed in the reactor;

[0006] The two sides directly in front and directly behind the reactor are made of high-pressure resistant organic glass;

[0007] The CT scanning device consists of a micro-focus X-ray source and a flat-panel detector. The micro-focus X-ray source is placed in front of the reactor. The micro-focus X-ray source generates a high-energy X-ray beam, which passes through the rock sample to be scanned. The flat-panel detector is used to receive the X-rays after passing through the rock sample to be scanned.

[0008] The image collector is connected to the flat panel detector to obtain CT image data, thereby realizing monitoring of the pore structure changes of the rock to be tested;

[0009] The pressurizing device is connected to the pressure boosting valve on the reactor;

[0010] The heating power supply is connected to the thermocouple on the reaction kettle;

[0011] The reactor also includes a pressure gauge.

[0012] It also includes a transverse positioning axis and a longitudinal positioning axis that carry the reaction kettle, and is used to adjust the transverse and longitudinal positions of the reaction kettle.

[0013] The second technical solution adopted by the present invention is: a method for real-time monitoring of rock pore structure changes by CO2 immersion, comprising:

[0014] S1. Put the rock sample to be tested and dry ice into the reactor together, and change the temperature and pressure inside the reactor to make the dry ice turn into liquid CO2;

[0015] S2. The rock sample to be tested is immersed in liquid CO2. The liquid CO2 interacts with the rock sample to be tested, and the changes in the internal pore structure of the rock sample to be tested are checked by CT scanning equipment;

[0016] S3, by changing the temperature and pressure inside the reactor, the liquid CO2 becomes a supercritical state;

[0017] S4, the rock sample to be tested is immersed in supercritical CO2, and the changes in the internal pore structure of the rock sample to be tested are checked by CT scanning equipment;

[0018] S5, processing the real-time CT image data obtained in steps S2 and S4 by a threshold segmentation method, extracting the crack and pore information of the target area, and obtaining structural data of changes in the fluid flow channel inside the rock sample to be tested caused by different phases of CO2; the structural data includes the crack and pore information of the rock sample to be tested;

[0019] S6. Based on the crack and pore information of the rock sample to be tested, the internal structural changes of the rock sample to be tested after immersion in liquid CO2 and supercritical CO2 are calculated. The internal structural changes of the rock sample to be tested include the porosity and permeability of the sample to be tested before and after immersion.

[0020] The present invention adjusts the pressure of the booster pump and the temperature of the heating couple in real time, thereby changing the phase of CO2, so as to study the soaking effect of CO2 in different phases at different pressures and temperatures.

[0021] Beneficial effects of the invention: The invention utilizes the uniqueness of the device to achieve the interaction between different phases of CO2 (liquid and supercritical) and rock by adjusting the pressure and temperature in the reactor chamber, and records the changes in the internal cracks and pore structure of the rock through real-time CT observation, providing theoretical guidance for CO2 fracturing technology and CO2 storage technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0023] Figure 2 It is a schematic diagram of the overall device of the present invention;

[0024] Figure 3 It is an overall schematic diagram of the reaction kettle of the present invention;

[0025] Figure 4 It is a cross-sectional schematic diagram of a reaction kettle of the present invention;

[0026] Figure 5 CT scans of mudstone samples of the present invention at different immersion times;

[0027] in, Figure 5 (a) is the CT scan image after immersion for 0 hours. Figure 5 (b) is the CT scan after immersion for 5 hours. Figure 5 (c) is the CT scan after immersion for 10 hours. Figure 5 (d) is the CT scan after immersion for 15 hours. Figure 5 (e) is the CT scan after immersion for 20 hours. Figure 5 (f) is the CT scan after immersion for 25 hours. DETAILED DESCRIPTION

[0028] 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; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0029] Embodiment 1:

[0030] like Figure 2 As shown, a real-time monitoring system for CO2 soaked rocks based on CT scanning of the present invention comprises: a reactor 1, a pressurizing device 2, a heating power supply 3, a micro-focus X-ray source 4, a flat panel detector 5, an image collector 6, a transverse positioning axis 7, and a longitudinal positioning axis 8;

[0031] The micro-focus X-ray source 4 is placed in front of the reactor and is used to scan the inside of the rock sample to be tested in the reactor 1; the image collector 6 is connected to the flat panel detector 5 and is used to obtain CT image data.

[0032] The front and rear sides of the reactor 1 are made of high-pressure resistant organic glass; Figure 3 As shown, the reactor 1 also includes: a booster valve 1-1, a thermocouple 1-2, a pressure gauge 1-3, high-pressure resistant organic glass 1-4, and a metal shell 1-5 of the reactor; the thermocouple 1-2 is connected to a heating power source 3; the pressure gauge 1-3 is used to measure the internal pressure of the reactor; Figure 4 As shown, one end of the booster valve 1 - 1 is connected to the inner cavity of the reactor 1 , and the other end of the booster valve 1 - 1 is connected to the pressurizing device 2 .

[0033] It also includes a transverse positioning shaft 7 and a longitudinal positioning shaft 8 that support the reactor 1 and are used to adjust the transverse and longitudinal positions of the reactor 1 .

[0034] Example 2

[0035] like Figure 1 As shown, the present invention also provides a CO2 immersion real-time monitoring method based on CT scanning, comprising the following steps:

[0036] S1. Put the sample to be tested and dry ice (solid CO2) into the reactor together. When dry ice is present, the surface temperature is -78.5°C. Heat the dry ice to -18°C through a thermocouple. At the same time, pressurize the reactor to 2Mpa, and the dry ice turns into liquid CO2.

[0037] S2, start soaking the rock and react with the rock, at this time, real-time CT can be used to obtain the internal cracks and pores data of the rock;

[0038] S3, further pressurizing to 7.3MPa and heating to 37.8℃ can turn it into a supercritical state. During this process, real-time CT can be used to obtain data on cracks and pores inside the rock.

[0039] S4, processing the acquired CT image data to extract rock crack and pore information in the target area. This step can be achieved by existing image processing software;

[0040] S5. Based on the rock fracture and pore information, calculate the changes in the rock internal structure after immersion in liquid and supercritical CO2, as well as the changes in porosity and permeability path. This step can be achieved using existing numerical simulation software.

[0041] S6. Adjust the pressure of the booster pump and the temperature of the heating couple in real time to change the phase of CO2, so as to study the immersion effect of CO2 in different phases at different pressures and temperatures.

[0042] How to use: By adjusting the pressure and temperature, we can achieve the interaction between different phases of CO2 (liquid and supercritical) and rocks. At the beginning of the experiment, we put the sample to be tested and solid CO2 (dry ice) into the reactor together. As the pressurization process progresses, the solid dry ice gradually turns into liquid CO2 and begins to soak the rock and react chemically with the rock. At this point, we can use computed tomography (CT) technology to observe the changes in the cracks and pore structure inside the rock. When the pressure and temperature are further increased, the liquid CO2 will further transform into a supercritical state. During this process, real-time computed tomography observations continue to be used to understand the changes in the internal structure of the rock. This ability to observe in real time enables us to better understand the interaction mechanism between CO2 and rock.

[0043] The principle of dry ice turning into liquid CO2 in step S1 is as follows: Initially, in the reactor, the sample to be tested is in close contact with the dry ice, forming a closed environment. As the pressurization progresses, the pressure in the reactor gradually increases, and the CO2 begins to undergo a phase change and turns into a liquid state. Solid CO2 is a very stable substance at room temperature and pressure, but its structure changes under high pressure. When the pressure reaches a certain level, the CO2 molecules in the dry ice begin to rearrange, thereby forming liquid CO2.

[0044] By placing the sample and dry ice in a reactor and applying appropriate pressure, the interaction between the sample and dry ice can be achieved. This interaction may involve chemical reaction, physical adsorption or other types of interaction. The specific interaction mechanism depends on the nature of the sample and the purpose of the experiment.

[0045] The principle of soaking the rock with liquid CO2 in step S2 is as follows: the liquid CO2 begins to soak the rock and reacts with the rock. At this time, CT can be used to view the changes in the internal cracks and pore structure of the rock. As the soaking time increases, tiny cracks and depressions gradually appear on the surface of the rock. This is caused by chemical reactions. These cracks and depressions form new channels and pores inside the rock, causing the internal structure of the rock to change. Through CT scanning technology, we can clearly observe these structural changes. CT scanning uses the absorption and scattering characteristics of X-rays to obtain images of the internal structure of the rock by scanning in both directions. During the soaking process, we can perform CT scans regularly to monitor changes in the internal structure of the rock. The soaking time is set to 5h, 10h, 15h, 20h and 25h, a total of 5 time levels, such as Figure 5 As shown, Figure 5 (a) is the CT scan image after immersion for 0 hours. Figure 5 (b) is the CT scan after immersion for 5 hours. Figure 5 (c) is the CT scan after immersion for 10 hours. Figure 5 (d) is the CT scan after immersion for 15 hours. Figure 5 (e) is the CT scan after immersion for 20 hours. Figure 5 (f) is a CT scan after immersion for 25 hours. As the immersion time of the sample to be tested in this embodiment goes on, the cracks and pores inside the rock will gradually expand and increase. These cracks and pores are formed due to chemical reactions that cause the minerals in the rock to dissolve or recrystallize after dissolution. This process of dissolution and recrystallization will cause the volume of the rock to expand or shrink, thereby causing structural changes. Through CT scanning, we can quantitatively measure the changes in the internal structure of the rock. For example, we can measure the length, width and depth of the cracks, as well as the size and distribution of the pores. These data are very important for studying the mechanical properties and geological processes of the rock. In addition, by comparing the CT scan images at different immersion times, we can also observe the rate and trend of changes in the internal structure of the rock. This helps us understand the extent of the impact of chemical reactions on the rock and infer possible further changes in the rock;

[0046] The specific principle of liquid CO2 becoming a supercritical state in step S3 is: on the basis of step S1, further pressurizing to 7.3MPa and heating to 37.8℃ can turn it into a supercritical state. In this process, real-time CT can be used to observe changes in the internal structure of the rock. By pressurizing and heating, we can change the internal structure of the rock. When the rock is subjected to sufficient pressure, its physical properties will change. At the same time, heating will also allow the atoms and molecules inside the rock to gain more energy, making their movement more violent. In this process, we can use CT (computed tomography) technology to observe changes in the internal structure of the rock in real time. CT technology is a non-invasive imaging method that can obtain three-dimensional images of the interior of an object through multiple X-ray scans. By combining CT scanning with pressurization and heating processes, we can monitor the evolution of the internal structure of the rock in real time;

[0047] The rock cracks and pore information of the target area are extracted as described in step S4. The specific implementation process is as follows: the acquired CT image data is processed to extract the rock cracks and pore structure information of the target area, the acquired CT image data is processed to extract the rock cracks and pore information of the target area, and the extracted edge information is converted into a binary image or grayscale value using the Canny algorithm. It is necessary to use a CT scanner to scan the target area to obtain high-resolution CT image data. These image data contain rock cracks and pore information at different positions in the target area. Before subsequent processing, the CT image needs to be preprocessed. This includes operations such as noise reduction, smoothing images, and adjusting contrast to improve image quality and accuracy. According to actual needs, the target area in the CT image needs to be segmented from the background area. This can be achieved by methods such as threshold segmentation, edge detection, and regional growth. After segmenting the target area, the grayscale value of each pixel can be analyzed to extract rock cracks and pore information. This can be achieved by calculating the average grayscale value, maximum grayscale value or minimum grayscale value of the area around the pixel point. In order to more intuitively display the rock crack and pore information, the extracted crack and pore information can be visualized. This can be achieved by drawing contour maps, crack and pore distribution maps, etc. According to the extracted rock crack and pore information, further data analysis and mining can be carried out. For example, the distribution law of rock cracks and pores in different regions can be analyzed, or correlation analysis can be carried out with other geological parameters to reveal the relationship between rock cracks and pores and different phases of CO2 immersion;

[0048] The specific implementation process of step S5 is: according to the rock fracture and pore information, the porosity and permeation path of CO2 in the target area are calculated. According to the differences in rock fractures and pores, we can divide the target area into different permeation units. Each permeation unit has specific fracture and pore values ​​and is connected to the surrounding rock units. By establishing a mathematical model, we can simulate the flow process of CO2 in these permeation units. During the simulation process, we need to consider the physical properties and chemical reactions of CO2. Through calculation and simulation, we can obtain the porosity and permeation path of CO2 in the target area. These results are of great significance for evaluating the development potential of CO2 in underground reservoirs and optimizing injection strategies. At the same time, these results can also provide a reference for geological exploration and engineering design to ensure the efficient utilization and environmental safety of supercritical CO2;

[0049] Step S6 specifically includes: adjusting the pressure of the booster pump and the temperature of the heating couple in real time, thereby changing the phase of CO2 to study the immersion effect of CO2 in different phases at different pressures and temperatures.

[0050] Example 3

[0051] The other steps remain unchanged. Step S1 is specifically as follows: the sample to be tested and dry ice (solid CO2) are placed into the reactor together. When dry ice is present, the surface temperature is -78.5°C. The dry ice is heated to -19°C by a thermocouple. At the same time, the inside of the reactor is pressurized to 2MPa, and the dry ice becomes liquid CO2.

[0052] Example 4

[0053] The other steps remain unchanged. Step S1 is specifically as follows: the sample to be tested and dry ice (solid CO2) are placed into the reactor together. When dry ice is present, the surface temperature is -78.5°C. The dry ice is heated to -20°C by a thermocouple. At the same time, the inside of the reactor is pressurized to 2MPa, and the dry ice becomes liquid CO2.

[0054] The method of the present invention mainly involves the following technologies:

[0055] 1. CO2 immersion technology

[0056] The device first heats and pressurizes the solid to liquid CO2, which begins to react with the rock, and then pushes the CO2 gas to its supercritical state through the heating and pressurizing device. In the supercritical state, CO2 has the properties of both gas and liquid, and the cracks and pores are greatly increased, which allows it to penetrate deeper into the rock and achieve more efficient immersion and interaction. The supercritical state is that CO2 is between liquid and gas under the temperature and pressure conditions of 50°C and 8MPa, and will fill the entire space like a gas, but its cracks and pores are similar to liquids. Since the cracks and pores of CO2 in the supercritical state are greatly increased, it can penetrate deeper into the rock and achieve more efficient immersion and interaction. Secondly, since CO2 has the properties of both gas and liquid in the supercritical state, it can better contact the rock surface;

[0057] When CO2 is in a gaseous state, it can enter the interior of the rock through the pores and cracks in the rock, allowing CO2 to quickly diffuse to all parts of the rock. Once CO2 enters the interior of the rock, it will chemically react with the minerals in the rock. This process is called carbonation. During carbonation, CO2 reacts with water to form carbonic acid, which further reacts with minerals in the rock to form soluble carbonates. This soluble carbonate can dissolve in water, thereby releasing CO2. As CO2 is released, it will gradually diffuse from the interior of the rock to the surface. This process is affected by many factors, including the porosity, temperature, pressure and groundwater flow of the rock. In some cases, CO2 may be trapped deep underground, forming what is called "sequestration" or "storage." In this case, CO2 does not enter the atmosphere, but is permanently fixed underground;

[0058] Under high pressure conditions, CO2 can dissolve in minerals in rocks to form carbonate minerals. This dissolution can change the chemical properties of rocks and may cause the dissolution and destruction of rocks. When CO2 dissolves in minerals in rocks, it reacts chemically with cations in the minerals to form corresponding carbonate minerals. These carbonate minerals usually have high solubility, so they can be more easily dissolved in water under high pressure conditions. This dissolution will cause changes in the mineral composition of the rock, thereby changing the chemical properties of the rock. Secondly, due to the dissolution of CO2, the minerals in the rock will gradually be dissolved, resulting in a decrease in the volume of the rock. This dissolution may cause the rock to break and be destroyed. Especially under high pressure conditions, the rock is subjected to greater pressure, so its ability to resist dissolution will be weakened accordingly. This means that under high pressure environments, rocks are more susceptible to damage caused by the dissolution of CO2;

[0059] When CO2 is in liquid form, it can undergo physical adsorption and chemical reactions with rocks. Liquid CO2 has a high surface tension and can penetrate into tiny pores in rocks. Under low temperature conditions, liquid CO2 can react chemically with minerals in rocks to form new compounds, which affects their stability and strength. Liquid CO2 has a high surface tension, which allows it to penetrate into tiny pores in rocks. These tiny pores are usually voids or cracks inside rocks, through which liquid CO2 can enter the interior of rocks. Under low temperature conditions, liquid CO2 can react chemically with minerals in rocks. This chemical reaction may form new compounds, which may affect the stability and strength of rocks. For example, liquid CO2 can react with certain minerals to form carbonates, which can cause the dissolution and erosion of rocks. In addition, liquid CO2 can also react with other chemicals in rocks to change their chemical composition and properties. Through physical adsorption and chemical reactions, liquid CO2 can form a certain amount of pressure in rocks. This pressure may cause the rocks to break or deform, which affects their stability and strength. In addition, liquid CO2 can also lower the melting point of rocks, making them easier to melt or flow;

[0060] When CO2 is in a supercritical state, it has properties between gas and liquid. Supercritical CO2 has high diffusion and solubility, and can quickly penetrate into rocks. Under high temperature and high pressure conditions, supercritical CO2 can react chemically with minerals in rocks to form new compounds. The diffusion capacity of supercritical CO2 is very strong, and it can quickly penetrate the tiny pores and cracks of soaked rocks and enter the interior of the rocks. This makes supercritical CO2 an ideal solvent that can effectively extract useful substances from rocks. For example, in the process of oil exploration and extraction, supercritical CO2 can be injected into oil reservoirs to extract hydrocarbons from rocks by dissolving and carrying them.

[0061] 2. Transparent glass design

[0062] Transparent glass is used at both ends of the pressurizing device. The transparency facilitates the real-time CT scanning and provides intuitive monitoring of the immersion process. The transparency of the transparent glass enables us to observe the changes in the immersion process in real time. Using transparent glass materials at both ends of the pressurizing device allows CT scanning to obtain internal information of the rock. When performing CT scanning, we need to scan the object to be measured multiple times to obtain more data information. The use of transparent glass allows us to more conveniently observe the state of the object to be measured between each scan, ensuring the accuracy and continuity of the scan. At the same time, the transparency of the transparent glass also enables us to better capture the details of the object to be measured, thereby improving the efficiency of CT scanning. In addition, the design of transparent glass is also aesthetically pleasing and practical. At the same time, the material of transparent glass also has good corrosion resistance and wear resistance, and can maintain its transparency and stability for a long time, ensuring the normal operation and use of the device.

[0063] 3. Real-time CT scanning technology

[0064] The device is equipped with advanced real-time CT scanning equipment, which can scan the inside of the rock with high resolution and high precision. The scanning is not done all the time, but at intervals, such as every half an hour. This interval is defined by the user. The working principle of this real-time CT scanning technology is to generate a three-dimensional image of the inside of the rock by emitting X-rays and receiving the reflected signals, and then processing these signals through a computer. Due to the use of advanced real-time CT scanning equipment, this technology has the characteristics of high resolution and high precision, and can clearly display the fine structure inside the rock. Compared with traditional CT scanning, this real-time CT scanning technology has some obvious advantages. First, it does not require the rock to be moved into the scanner, but can be scanned on the surface of the rock, reducing the complexity and risk of the operation. Secondly, since the scan is performed at intervals instead of continuously, this technology can save time and resources. In addition, users can customize the scanning interval according to their needs and actual conditions, making the scanning process more flexible and controllable;

[0065] 4. Rock structure analysis technology

[0066] A detailed analysis of the changes in rock structure during supercritical CO2 immersion can be conducted. Through real-time CT scanning, we can further obtain changes in key parameters such as rock porosity and permeability. Rock structure analysis can help us understand the porosity of rocks. Porosity refers to the ratio of the pore volume to the total volume in a rock, which reflects the degree of porosity inside the rock. During supercritical CO2 immersion, the pores in the rock may expand or contract, thereby affecting the porosity of the rock. Through real-time CT scanning, we can accurately measure and record these changes, and then infer the trend of porosity changes in the rock during the immersion process. Secondly, rock structure analysis can also help us study the permeability of rocks. Permeability refers to the ability of rocks to penetrate fluids (such as water or gas). During supercritical CO2 immersion, the pores in the rock may change due to changes in pressure and temperature, thereby affecting the permeability of the rock. Through real-time CT scanning, we can observe the changes in these pores and then infer the trend of permeability changes in the rock during the immersion process;

[0067] Rock porosity is calculated by calculating the ratio of the pore space inside the rock to the total volume of the sample. In the calculation of rock porosity based on CT data, CT scanning can provide a three-dimensional image of the rock sample, and then the porosity can be estimated through image processing and analysis. The following is the calculation method of rock porosity based on CT data:

[0068] Obtaining CT scan data: First, the rock sample immersed in the reactor needs to be scanned using a CT scanner to obtain its 3D image data. This data will provide information about the internal structure of the rock, including pores and solid parts.

[0069] Image processing and segmentation: Using image processing software, the CT scan images are segmented to separate the porous and solid parts of the rock. This usually requires threshold segmentation or other image processing techniques to identify and separate the pores and solids.

[0070] Calculating Porosity: Once the pore and solid components have been separated, the porosity can be calculated. Porosity is usually defined as the ratio of the pore volume to the total volume and can be calculated using the following formula:

[0071] Porosity (%) = pore volume / total volume × 100%

[0072] The pore volume can be obtained by calculating the volume of the pores in the segmented image, while the total volume is the entire volume of the rock sample.

[0073] The above is only a preferred specific implementation of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and its improved conception within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0074] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for real-time monitoring of rock pore structure changes by CO2 immersion, characterized in that: The monitoring system includes: a reactor, a pressurizing device, a heating power supply, a micro-focus X-ray source, a flat-panel detector, an image acquisition device, and also includes a rock sample to be tested and dry ice placed in the reactor; The two sides directly in front and directly behind the reactor are made of high-pressure resistant organic glass; The CT scanning device consists of a micro-focus X-ray source and a flat-panel detector. The micro-focus X-ray source is placed in front of the reactor. The micro-focus X-ray source generates a high-energy X-ray beam, which passes through the rock sample to be scanned. The flat-panel detector is used to receive the X-rays after passing through the rock sample to be scanned. The image collector is connected to the flat panel detector to obtain CT image data, thereby realizing monitoring of the pore structure changes of the rock to be tested; The pressurizing device is connected to the pressure boosting valve on the reactor; The heating power supply is connected to the thermocouple on the reaction kettle; The reactor also includes a pressure gauge; The monitoring method comprises: S1. Put the rock sample to be tested and dry ice into the reactor together, and change the temperature and pressure inside the reactor to make the dry ice turn into liquid CO2; S2. The rock sample to be tested is immersed in liquid CO2. The liquid CO2 interacts with the rock sample to be tested, and the changes in the internal pore structure of the rock sample to be tested are checked by CT scanning equipment; S3, by changing the temperature and pressure inside the reactor, the liquid CO2 becomes a supercritical state; S4, the rock sample to be tested is immersed in supercritical CO2, and the changes in the internal pore structure of the rock sample to be tested are checked by CT scanning equipment; S5, processing the real-time CT image data obtained in steps S2 and S4 by a threshold segmentation method, extracting the crack and pore information of the target area, and obtaining structural data of changes in the fluid flow channel inside the rock sample to be tested caused by different phases of CO2; the structural data includes the crack and pore information of the rock sample to be tested; S6. Based on the crack and pore information of the rock sample to be tested, the internal structural changes of the rock sample to be tested after immersion in liquid CO2 and supercritical CO2 are calculated. The internal structural changes of the rock sample to be tested include the porosity and permeability of the sample to be tested before and after immersion.

2. The method for real-time monitoring of rock pore structure changes by CO2 immersion according to claim 1, characterized in that: It also includes a transverse positioning axis and a longitudinal positioning axis that carry the reaction kettle, and is used to adjust the transverse and longitudinal positions of the reaction kettle.

3. The method for real-time monitoring of rock pore structure changes by CO2 immersion according to claim 1 is characterized in that: In step S1, when dry ice is present, the surface temperature is -78.5°C. The dry ice is heated to -18°C-20°C by a thermocouple, and the interior of the reactor is pressurized to 2MPa, so that the dry ice becomes liquid CO2.

4. The method for real-time monitoring of rock pore structure changes by CO2 immersion according to claim 1, characterized in that: In step S3, the interior of the reactor is pressurized to 7.3 MPa and heated to 37.8°C, and the liquid CO2 becomes a supercritical state.

5. The method for real-time monitoring of rock pore structure changes by CO2 immersion according to claim 1, characterized in that: Porosity is the ratio of the pore volume to the total volume of the rock sample to be tested.

6. The method for real-time monitoring of rock pore structure changes by CO2 immersion according to claim 1, characterized in that: In step S2, the liquid CO2 interacts with the rock sample to be tested, including physical adsorption and chemical reaction between the liquid CO2 and the rock sample to be tested.

Images