CO2-water-rock reaction process in-situ measurement system and method

Abstract

The invention discloses a CO2-water-rock reaction process in-situ measurement system and a CO2-water-rock reaction process in-situ measurement method, and relates to the technical field of geochemical water-rock reaction. The system comprises a reaction kettle unit, a CO2 injection unit, a pure water / salt water injection unit and a data acquisition unit, the reaction kettle unit comprises a reaction kettle, a vacuum pump and a temperature control device, the reaction kettle is provided with a containing cavity, the vacuum pump is communicated with the containing cavity of the reaction kettle, the temperature control device is located outside the reaction kettle, the CO2 injection unit is communicated with the reaction kettle, the pure water / saline water injection unit is communicated with the reaction kettle, and the temperature control device is located outside the reaction kettle. The data acquisition unit comprises a light source, an optical fiber, a spectrum analyzer and a data acquisition and analysis device; the CO2-water-rock reaction monitoring system has the beneficial effects that real-time monitoring of the whole CO2-water-rock reaction process is realized, and the problem that the reaction process cannot be monitored in real time in the previous CO2-water-rock reaction is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of geochemical water-rock reaction, and more specifically, the present invention relates to a system and method for in-situ measurement of the CO2-water-rock reaction process. Background Art

[0002] Carbon capture and storage technology is one of the key strategies to achieve the global carbon neutrality goal. It refers to the process of capturing carbon dioxide from emission sources such as fossil fuel plants and industrial processes, purifying, compressing, transporting it to a suitable site, and finally injecting it into deep underground reservoirs such as depleted oil and gas fields, unmineable coal seams, deep saline aquifers, or basic and ultrabasic rock masses for long-term storage.

[0003] The geochemical reactions between the injected CO2 and formation water and rocks will directly cause the dissolution of primary minerals and the precipitation of secondary minerals, affect the composition of formation water and the physical and mechanical properties of rocks, and ultimately affect the CO2 injection efficiency, storage capacity, and long-term safety and stability of storage. Therefore, it is particularly important to master the kinetic interaction mechanism of CO2-water-rock under formation temperature and pressure conditions.

[0004] High-temperature and high-pressure static reaction experiments are an effective method for studying CO2-water-rock reactions. They can be used to simulate the reaction process under different reservoir environmental conditions (such as pH value, temperature, pressure, etc.), different mineral contact surface areas, and different reaction fluid conditions, and explore the influence degree of different factors on water-rock reactions. For example, the prior art (Chinese Patent No. CN201320545160.5) discloses a supercritical CO2-water-rock reaction experimental device for studying the characteristics of water-rock reactions during carbon dioxide geological storage. Similar to this device, most current CO2-water-rock reaction studies analyze the degree of CO2-water-rock reactions by comparing the changes in rock mineral composition, microscopic structure, and aqueous solution ion concentration before and after the reaction, and then indirectly discuss the influence of various factors on CO2-water-rock reactions. However, due to the lack of in-situ observation means for CO2-water-rock reactions, it is impossible to evaluate the process of CO2-water-rock reactions in real time, and only two final states before and after the reaction can be compared.

[0005] The prior art (Chinese Patent No. CN201911280509.5) discloses an experimental device and method for simulating the CO2-water-rock reaction under formation conditions. By adding a pH probe in the reaction kettle to monitor the pH change of the solution in the reaction kettle, and finally combining the core data and numerical simulation to study the entire water-rock reaction process. However, carbonic acid formed by dissolving CO2 in water is a weak acid, which will cause the pH of the solution to decrease, but the decrease range is not large. In addition, different types of carbonate minerals, silicate minerals and metal hydroxides and other precipitates will be generated during the CO2-water-rock reaction process according to different rock mineral compositions and reaction conditions, which may cause the pH value to increase, but the increase range is also not large. Therefore, during the actual CO2-water-rock reaction process, the pH value changes within a range from weakly acidic to weakly alkaline, with low sensitivity to the CO2-water-rock reaction process and complex influencing factors, and it is impossible to directly judge the water-rock reaction process in real time through the pH value. In addition, during actual use, the pH probe needs to be frequently calibrated, and its temperature and pressure resistance capabilities are limited, making it impossible to achieve measurements in extreme environments. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the present invention provides an in-situ measurement system and method for the CO2-water-rock reaction process, which realizes real-time monitoring of the entire CO2-water-rock reaction process by monitoring the change law of the reflected light intensity of the optical fiber over time, filling the gap in the problem that the reaction process cannot be monitored in real time in the previous CO2-water-rock reaction.

[0007] The technical solution adopted by the present invention to solve its technical problems is: an in-situ measurement system for the CO2-water-rock reaction process, which is improved in that it includes a reaction kettle unit, a CO2 injection unit, a pure water / saline water injection unit and a data acquisition unit; The reaction kettle unit includes a reaction kettle, a vacuum pump and a temperature control device. The reaction kettle has a cavity for accommodating the rock sample to be measured. The vacuum pump is connected to the cavity of the reaction kettle for evacuating the inside of the reaction kettle. The temperature control device is located outside the reaction kettle for controlling the temperature inside the reaction kettle; The CO2 injection unit is connected to the reaction kettle for injecting CO2 into the inside of the reaction kettle; The pure water / saline water injection unit is connected to the reaction kettle for injecting pure water / saline water into the inside of the reaction kettle, and the rock sample to be measured is located below the water level of the pure water / saline water; The data acquisition unit includes a light source, an optical fiber, a spectral analyzer, and a data acquisition and analysis device. One end of the optical fiber is connected to the light source, and the other end is connected to the spectral analyzer. The optical fiber has a portion where the outer cladding is removed to expose the fiber core, and the optical fiber extends into the reaction kettle so that the exposed fiber core is below the water level of pure water / saline water. The data acquisition and analysis device includes a data collector installed on the reaction kettle to collect data during the CO2-water-rock reaction process. The data during the reaction process includes the temperature, pressure, pH value, and the variation relationship of the optical signal parameters in the spectral analyzer over time.

[0008] In the above structure, the reaction kettle includes an autoclave, an autoclave lid, and a high-pressure clamp. The autoclave is a container with an open top. The autoclave lid covers the top opening of the autoclave, and the autoclave and the autoclave lid are clamped tightly by the high-pressure clamp.

[0009] In the above structure, the CO2 injection unit includes a CO2 gas cylinder and a constant-speed and constant-pressure pump. A pressure gauge and a first CO2 injection control valve are installed at the outlet of the CO2 gas cylinder. The CO2 gas cylinder and the constant-speed and constant-pressure pump, and the constant-speed and constant-pressure pump and the autoclave are connected through a main pipeline. A second CO2 injection control valve and a constant-speed and constant-pressure pump liquid injection valve are sequentially arranged on the main pipeline between the CO2 gas cylinder and the constant-speed and constant-pressure pump, and a constant-speed and constant-pressure pump liquid discharge valve is arranged on the main pipeline between the constant-speed and constant-pressure pump and the autoclave.

[0010] In the above structure, the data collector includes a temperature sensor, a pressure sensor, and a pH meter. The data acquisition and analysis device further includes a computer. The temperature sensor, the pressure sensor, and the pH meter all pass through the autoclave lid and extend into the autoclave. The bottoms of the temperature sensor, the pressure sensor, and the pH meter are all below the water level of pure water / saline water, and their tops are connected to the computer through data transmission lines.

[0011] In the above structure, the reaction kettle further includes a sealing gasket. A through hole is provided on the autoclave lid, and both ends of the optical fiber are located in the through hole. The sealing gasket covers the opening of the through hole, and the wires on the light source and the spectral analyzer respectively pass through the sealing gasket and are connected to both ends of the optical fiber.

[0012] In the above structure, a magnetic stirrer is arranged inside the autoclave to stir the pure water / saline water in the autoclave.

[0013] In the above structure, the temperature control device includes a heating plate and a thermal insulation cover; The thermal insulation cover is fixed on the heating plate. The thermal insulation cover has a cavity for accommodating the autoclave, and the bottom of the autoclave is in contact with the heating plate.

[0014] In the above structure, the light source is a white halogen lamp.

[0015] In the above structure, the pure water / saline water injection unit includes a pure water / saline water container and a pure water / saline water injection pump. The water inlet of the pure water / saline water injection pump is connected to the pure water / saline water container through a pipeline, and the water outlet of the pure water / saline water injection pump is connected to the inside of the reaction kettle.

[0016] In the above structure, the in-situ measurement system for the CO2-water-rock reaction process further includes a waste liquid discharging unit. The waste liquid discharging unit includes a liquid discharging pipeline connected to the inside of the reaction kettle, and a filter and a liquid discharging valve are installed on the liquid discharging pipeline.

[0017] The present invention also provides a method for in-situ measurement of the CO2-water-rock reaction. The improvement lies in that the method includes the following steps: Calibrate the optical fiber used to establish the standard correspondence between the light intensity and the refractive index; Conduct SEM-EDS petrographic composition test analysis before the reaction to obtain the rock mineral composition of the rock sample to be measured before the reaction; Place the rock sample to be measured into the reaction kettle, and at the same time place the optical fiber in the reaction kettle. There is a part on the optical fiber where the outer cladding is removed to expose the fiber core. Both ends of the optical fiber are respectively connected to a light source and a spectral analyzer; After sealing the reaction kettle, perform a vacuum treatment, inject pure water / saline water into the reaction kettle, so that the rock sample to be measured and the part of the fiber core of the optical fiber are below the horizontal plane, heat the reaction kettle and keep it constant; inject CO2 into the reaction kettle to increase the pressure in the reaction kettle to the target value and keep it constant; Conduct a CO2-water-rock reaction experiment, and continuously monitor the variation relationships of the temperature, pressure, pH value and the optical signal parameters in the spectral analyzer with time during the reaction process; Conduct SEM-EDS petrographic composition test analysis after the reaction to obtain the rock mineral composition of the rock sample to be measured after the reaction, and determine the ionic components and contents in the reaction solution after the reaction; Calculate the variation rules of the ionic components and their contents in the reaction solution at different times based on the pH values, light intensities, ionic components of the reaction solution at different times, and rock mineral components before and after the reaction under different temperature and pressure conditions obtained by monitoring, so as to determine the reaction rate and reaction process of the CO2-water-rock reaction at different times.

[0018] Further, the calibration of the optical fiber used and the establishment of the standard correspondence between the light intensity and the refractive index further include: Put the optical fiber into a standard sample with a known refractive index and monitor the light intensity, thereby establishing the standard correspondence between the light intensity and the refractive index.

[0019] Further, the continuous monitoring of the variation relationships of the temperature, pressure, pH value, and the optical signal parameters in the spectral analyzer with time during the reaction process further includes: During the reaction process, take out a small amount of the reaction solution at regular intervals for water quality analysis to determine the ionic components and their contents in the reaction solution.

[0020] Further, the calculation of the variation rules of the ionic components and their contents in the reaction solution at different times based on the pH values, light intensities, ionic components of the reaction solution at different times, and rock mineral components before and after the reaction under different temperature and pressure conditions obtained by monitoring, so as to determine the reaction rate and reaction process of the CO2-water-rock reaction at different times, includes: Determine the refractive index in the reaction solution according to the variation of the light intensity with time, and calculate the concentration of the solute in the reaction solution according to the variation of the solution refractive index by using the Lorentz-Lorenz equation; According to the ionic components and their contents in the reaction solution at different times, use multiple linear regression analysis or the least squares method to determine the corresponding relationships between multiple groups of ionic contents in the reaction solution and the solute concentration; Combined with the changes in the rock mineral components before and after the reaction, realize the analysis of the entire kinetic process of the CO2-water-rock reaction.

[0021] The beneficial effects of the present invention are as follows: Compared with the traditional method that only analyzes the components in two states before and after the reaction or measures the pH in the solution by using a pH meter, the use of an optical fiber sensor for monitoring has the characteristics of high reaction sensitivity, high precision, strong durability and corrosion resistance. It can calculate the concentration of the solute in the reaction solution at different times by monitoring the variation of the refractive index of the reaction solution with time, and is especially suitable for the monitoring of the CO2-water-rock reaction under high temperature and high pressure conditions; the present invention realizes the real-time monitoring of the entire process of the CO2-water-rock reaction, filling the gap in the problem that the reaction process cannot be monitored in real time in the previous CO2-water-rock reaction. Description of the Drawings

[0022] Figure 1Schematic diagram of the principle of an in-situ measurement system for the CO2-water-rock reaction process of the present invention.

[0023] Figure 2 Schematic top view of the reaction kettle in an in-situ measurement system for the CO2-water-rock reaction process of the present invention.

[0024] Figure 3 Schematic cross-sectional view of the optical fiber in an in-situ measurement system for the CO2-water-rock reaction process of the present invention.

[0025] In the figure: CO2 gas cylinder 1, pressure gauge 2, first CO2 injection control valve 3, second CO2 injection control valve 4, constant speed and constant pressure pump 5, liquid injection valve of the constant speed and constant pressure pump 6, liquid discharge valve of the constant speed and constant pressure pump 7, main pipeline 8, pure water container 9, pure water injection pump 10, control valve of the pure water injection pump 11, vacuum pump 12, light source 13, spectral analyzer 14, computer 15, electric heating plate 16, thermal insulation cover 17, high-pressure clamp 18, autoclave 19, autoclave cover 20, air extraction pipe 21, sealing gasket 22, rock sample 23, pure water 24, magnetic stirrer 25, optical fiber core 26, optical fiber 27, temperature sensor 28, pressure sensor 29, pH meter 30, filter 31, liquid discharge valve 32. Detailed implementation mode

[0026] The present invention will be further described below in conjunction with the drawings and embodiments.

[0027] The concept, specific structure and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments and the drawings to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. In addition, all the connection / connection relationships involved in the patent do not refer only to the direct connection of components, but refer to the more optimal connection structure that can be formed by adding or reducing connection accessories according to the specific implementation situation. The various technical features in the present invention can be combined with each other without conflict.

[0028] Embodiment 1 Refer to Figure 1 、 Figure 2 As shown, the present invention provides an in-situ measurement system for the CO2-water-rock reaction process. Specifically, the system includes a reaction kettle unit, a CO2 injection unit, a pure water injection unit and a data acquisition unit; among them, the reaction kettle unit includes a reaction kettle, a vacuum pump 12 and a temperature control device, and the reaction kettle has a cavity for accommodating the rock sample 23 to be measured. Figure 1The figure in the middle is a schematic cross-sectional view of the reactor. Generally, the reactor is cylindrical; the vacuum pump 12 is connected to the cavity of the reactor through the suction pipe 21 and is used to control the pressure inside the reactor. In this embodiment, the inside of the reactor is evacuated by the vacuum pump 12; the temperature control device is located outside the reactor and is used to control the temperature inside the reactor; the specific composition of the temperature control device will be further described below. Further, the CO2 injection unit is connected to the reactor and is used to inject CO2 into the reactor; the pure water injection unit is connected to the reactor and is used to inject pure water 24 into the reactor, and the rock sample to be tested 23 is located below the water level of the pure water; it should be noted that in another embodiment, the pure water injection unit can be a salt water injection unit to inject salt water into the reactor.

[0029] Continue to refer to Figure 1 As shown, the data acquisition unit includes a light source 13, an optical fiber 27, a spectral analyzer 14, and a data acquisition and analysis device. One end of the optical fiber 27 is electrically connected to the light source 13, and the other end of the optical fiber 27 is electrically connected to the spectral analyzer 14. The spectral analyzer 14 is used to display the spectral characteristics of the optical fiber 27; in combination with Figure 1 , Figure 3 As shown, a part of the optical fiber 27 has its outer cladding removed to expose the fiber core 26, and the optical fiber 27 extends into the reactor so that the exposed fiber core 26 is located below the water level of the pure water; the data acquisition and analysis device includes a data collector installed on the reactor to realize the acquisition of data during the CO2-water-rock reaction process. The data during the reaction process includes the temperature, pressure, pH value, and the change relationship of the optical signal parameters in the spectral analyzer 14 over time.

[0030] Combined with the above structure, we will explain the working principle of an in-situ measurement system for the CO2-water-rock reaction process of the present invention. CO2 is injected into the reaction kettle through the CO2 injection unit to provide supercritical CO2 required for the reaction; pure water 24 required for the reaction is injected into the reaction kettle through the pure water injection unit, so that the rock sample 23 to be measured and the optical fiber core 26 are located below the water surface of the pure water; the temperature inside the reaction kettle is controlled by the temperature control device to make the temperature inside the reaction kettle reach the set temperature. When the CO2-water-rock reaction is carried out, through the data acquisition and analysis device, the collection of the variation relationships of temperature, pressure, pH value and the optical signal parameters in the spectral analyzer 14 with time during the reaction process is realized, and the real-time monitoring in the CO2-water-rock reaction is achieved. Since when light is conducted in the optical fiber 27 through total internal reflection, an evanescent wave that propagates along the surface of the core will be formed. This wave has a small penetration depth and its energy decays exponentially with distance, but as long as it is not disturbed, it will not cause the loss of the reflected light. Generally, a transparent polymer cladding is coated outside the optical fiber 27 to ensure the interference-free propagation of the evanescent wave. However, if the cladding of the optical fiber 27 is removed, the evanescent wave can interact with the external environment through absorption or scattering, resulting in the loss of the reflected light, thereby generating a weakened total internal reflection in the core of the optical fiber 27. Therefore, when the refractive index of the external environmental medium changes, the propagation characteristics of light in the optical fiber 27 will change; by monitoring the variation law of the reflected light intensity of the cladding-removed section of the optical fiber 27 immersed in the reaction solution with time, the real-time monitoring of the whole process of the CO2-water-rock reaction is realized, filling the gap in the problem that the reaction process cannot be monitored in real time in the previous CO2-water-rock reaction.

[0031] For the reaction kettle described above, in combination with Figure 1 as shown, the reaction kettle includes an autoclave 19, an autoclave lid 20 and a high-pressure clamp 18. The autoclave 19 is a container with an open top. The autoclave lid 20 covers the open top of the autoclave 19, and the autoclave 19 and the autoclave lid 20 are clamped tightly by the high-pressure clamp 18 to form a sealed reaction space. Referring to Figure 2 as shown, the reaction kettle further includes a sealing gasket 22, and the sealing gasket 22 is made of graphite; a through hole is provided on the autoclave lid 20, and both ends of the optical fiber 27 are located in the through hole; the sealing gasket 22 covers the opening of the through hole, and the wires on the light source 13 and the wires on the spectral analyzer 14 respectively pass through the sealing gasket 22 and are connected to both ends of the optical fiber 27. In this embodiment, the light source 13 is a white light halogen lamp. In addition, a magnetic stirrer 25 is arranged inside the autoclave 19 to stir the pure water in the autoclave 19 through the magnetic stirrer 25. The in-situ measurement system for the CO2-water-rock reaction process further includes a waste liquid discharge unit, and the waste liquid discharge unit includes a drain pipe communicated with the inside of the reaction kettle, and a filter 31 and a drain valve 32 are installed on the drain pipe.

[0032] For the CO2 injection unit, in combination with Figure 1 , Figure 2 As shown, the present invention provides a specific embodiment. The CO2 injection unit includes a CO2 gas cylinder 1 and a constant speed and constant pressure pump 5. A pressure gauge 2 and a first CO2 injection control valve 3 are installed at the outlet of the CO2 gas cylinder 1 to respectively monitor the pressure and control the CO2 injection. The main pipeline 8 is connected between the CO2 gas cylinder 1 and the constant speed and constant pressure pump 5, and between the constant speed and constant pressure pump 5 and the autoclave 19. A second CO2 injection control valve 4 and a liquid injection valve 6 of the constant speed and constant pressure pump are sequentially arranged on the main pipeline 8 between the CO2 gas cylinder 1 and the constant speed and constant pressure pump 5. A liquid discharge valve 7 of the constant speed and constant pressure pump is arranged on the main pipeline 8 between the constant speed and constant pressure pump 5 and the autoclave 19. The supercritical CO2 required for the reaction is provided to the reaction kettle through the constant speed and constant pressure pump 5. In addition, for the pure water injection unit, the present invention provides a specific embodiment. The pure water injection unit includes a pure water container 9 and a pure water injection pump 10. The water inlet of the pure water injection pump 10 is connected to the pure water container 9 through a pipeline, and the water outlet of the pure water injection pump 10 is connected to the inside of the reaction kettle. A control valve 11 of the pure water injection pump is arranged on the pure water injection pump 10.

[0033] For the temperature control device, the present invention provides a specific embodiment. The temperature control device includes a hot plate 16 and a thermal insulation cover 17. The thermal insulation cover 17 is fixed on the hot plate 16. The thermal insulation cover 17 has a cavity for accommodating the autoclave 19, and the bottom of the autoclave 19 is in contact with the hot plate 16.

[0034] Continue to refer to Figure 1As shown, the data collector includes a temperature sensor 28, a pressure sensor 29, and a pH meter 30, and the data acquisition and analysis device further includes a computer 15; the temperature sensor 28, the pressure sensor 29, and the pH meter 30 all pass through the autoclave lid 20 and extend into the autoclave 19, and the bottoms of the temperature sensor 28, the pressure sensor 29, and the pH meter 30 are all below the water level of pure water, and their tops are connected to the computer 15 through data transmission lines. Therefore, the temperature data collected by the temperature sensor 28, the pressure data collected by the pressure sensor 29, and the pH value of the reaction solution collected by the pH meter 30 are all transmitted into the computer 15 for data analysis; at the same time, the light of the white light halogen lamp forms an evanescent wave propagating along the surface of the optical fiber core 26. Due to the existence of the exposed part of the optical fiber core 26, the evanescent wave can interact with the external environment through absorption or scattering, resulting in the loss of the reflected light, thereby generating a weakened total internal reflection in the core of the optical fiber 27. The intensity of the reflected light is monitored by the spectral analyzer 14; when the refractive index of the external environmental medium changes, the propagation characteristics of light in the optical fiber 27 will change; by monitoring the change law of the reflected light intensity of the optical fiber core 26 immersed in the reaction solution over time, the real-time monitoring of the whole process of the CO2-water-rock reaction is realized, filling the gap in the problem that the reaction process cannot be monitored in real time in the previous CO2-water-rock reaction.

[0035] In chemical processes involving dissolution and precipitation reactions or phase changes, it is particularly important to monitor, understand, and control the relevant processes, especially to monitor these processes under high temperature and high pressure conditions. However, due to the operating temperature limitations of available electronic components, many traditional sensor systems are difficult to operate normally under such conditions. In recent years, the detection technology based on the total internal reflection principle of the optical fiber 27 has developed rapidly. This technology uses the total internal reflection phenomenon of light in the optical fiber 27 to detect changes in the external environment. In addition, the optical fiber 27 has the characteristics of being tolerant to high temperature and high pressure, small in size, corrosion-resistant, reusable, and capable of remote operation. Therefore, it can be used for the monitoring of environmental solutions in high temperature and high pressure environments. Changes in the refractive index of the environmental solution (possibly caused by changes in temperature, pressure, and solute concentration) will cause changes in the light intensity, phase, or polarization state inside the optical fiber 27. By monitoring these changes, changes in the properties of the solution can be inferred. Based on this, the present invention is based on the total reflection principle of the optical fiber 27, and by integrating the monitoring function of the refractive index of the reaction solution in the reaction kettle under high temperature and high pressure conditions by the optical fiber 27 sensor, the continuous in-situ monitoring of the kinetic process of the CO2-water-rock reaction under high temperature and high pressure conditions can be realized. Compared with the traditional method of only analyzing the composition of two states before and after the reaction, or using the pH meter 30 to measure the pH in the solution, the monitoring using the optical fiber 27 sensor has the characteristics of high reaction sensitivity, high precision, strong durability and corrosion resistance, and is particularly suitable for the monitoring of the CO2-water-rock reaction under high temperature and high pressure conditions.

[0036] Example 2 Combination Figure 1 As shown in the figure, the present invention discloses an in-situ measurement method for CO2-water-rock reaction. Specifically, the method includes the following steps: S10. Calibrate the optical fiber 27 used to establish the standard correspondence between the light intensity and the refractive index; In this embodiment, the optical fiber 27 is placed in a standard sample with a known refractive index, and the light intensity is monitored to establish the standard correspondence between the light intensity and the refractive index.

[0037] S20. Conduct SEM-EDS petrographic composition test analysis before the reaction to obtain the rock mineral composition of the rock sample 23 to be tested before the reaction; SEM (scanning electron microscope)-EDS (X-ray energy spectrometer) is one of the most important composition analysis means at present, and this technology belongs to a very mature solution in the prior art, so it will not be described in detail in this embodiment.

[0038] S30. Place the rock sample 23 to be tested into the reaction kettle, and at the same time place the optical fiber 27 in the reaction kettle. The optical fiber 27 has a part where the outer cladding is removed to expose the optical fiber core 26, and both ends of the optical fiber 27 are respectively connected to the light source 13 and the spectral analyzer 14.

[0039] S40. After sealing the reaction kettle, perform a vacuum treatment, inject pure water into the reaction kettle, so that the rock sample 23 to be tested and the part of the optical fiber core 26 exposed on the optical fiber 27 are below the water level, heat the reaction kettle and keep it constant; inject CO2 into the reaction kettle to increase the pressure in the reaction kettle to the target value and keep it constant; In another specific embodiment, brine can be injected into the reaction kettle; in actual operation, pure water or brine is injected into the reaction kettle according to the actual situation.

[0040] S50. Conduct a CO2-water-rock reaction experiment, continuously monitor the changes of temperature, pressure, pH value and the optical signal parameters in the spectral analyzer 14 with time during the reaction process; during the reaction process, turn on the magnetic stirrer 25 to make the reaction in the reaction kettle sufficient; during the reaction process, monitor the real-time changes of temperature, pressure, pH and the signal of the optical fiber 27 respectively through the temperature sensor, pressure sensor and pH meter 30; the white light halogen lamp emits light, and the light is transmitted through the optical fiber 27. After passing through the optical fiber core 26 without the cladding, the change of the light intensity is monitored by the spectral analyzer 14. When the pH value and the optical signal parameters no longer change, the reaction ends; In step S50, a small amount of reaction solution is taken out through the drain valve at regular intervals during the reaction process for water quality analysis to determine the ion components and contents in the reaction solution.

[0041] S60. Conduct SEM-EDS petrographic composition test and analysis on the rock sample after the reaction, obtain the rock mineral composition of the rock sample 23 to be measured after the reaction, and determine the ionic components and contents in the reaction solution after the reaction; Since in step S50, various parameters have been obtained; in step S60, the ionic components and contents in the reaction solution after the reaction can be determined by means of SEM-EDS petrographic composition test and analysis.

[0042] S70. According to the pH value, light intensity, ionic components of the reaction solution at different times, and rock mineral composition before and after the reaction monitored under different temperature and pressure conditions, calculate the change rules of the ionic components and contents in the reaction solution at different times to determine the reaction rate and reaction process of the CO2-water-rock reaction at different times.

[0043] In this embodiment, step S70 includes the following steps: S701. Determine the refractive index of the reaction solution according to the change of light intensity with time, and use the Lorentz-Lorenz equation to calculate the concentration of the solute in the reaction solution based on the change of the refractive index of the solution. S702. According to the ionic components and contents of the reaction solution at different times, use multiple linear regression analysis or the least squares method to determine the corresponding relationship between multiple groups of ionic contents of the reaction solution and the solute concentration. S703. Combine the changes in the rock mineral composition before and after the reaction to analyze the entire kinetic process of the CO2-water-rock reaction.

[0044] In summary, the present invention provides an in-situ measurement method for the CO2-water-rock reaction. This method uses the change rule of the light intensity signal monitored by the spectral analyzer 14 with the reaction time, and based on the corresponding relationship between the light intensity of the optical fiber 27 and the refractive index of the aqueous solution, calculates the change rule of the refractive index of the aqueous solution in the reaction kettle. By using the Lorentz-Lorenz equation and the detection results of the ionic components in the aqueous solution at different times, and at the same time combining the changes in the rock mineral composition before and after the reaction, the inversion of the CO2-water-rock reaction process can be realized, deeply understanding the CO2-water-rock reaction mechanism, and realizing the prediction and control of the CO2-water-rock reaction process.

[0045] The above is a specific description of the preferred embodiment of the present invention, but the present invention is not limited to the described embodiment. Those skilled in the art can make various equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included in the scope defined by the claims of this application.

Claims

1. An in-situ measurement system for the CO2-water-rock reaction process, characterized in that, It includes a reactor unit, a CO2 injection unit, a pure water / saline water injection unit, and a data acquisition unit; The reactor unit includes a reactor, a vacuum pump, and a temperature control device. The reactor has a cavity for accommodating a rock sample to be tested. The vacuum pump is connected to the cavity of the reactor and is used to evacuate the inside of the reactor. The temperature control device is located outside the reactor and is used to control the temperature inside the reactor; The CO2 injection unit is connected to the reactor and is used to inject CO2 into the reactor; The pure water / saline water injection unit is connected to the reactor and is used to inject pure water / saline water into the reactor, and the rock sample to be tested is located below the water level of the pure water / saline water; The data acquisition unit includes a light source, an optical fiber, a spectral analyzer, and a data acquisition and analysis device. One end of the optical fiber is connected to the light source, and the other end of the optical fiber is connected to the spectral analyzer. There is a part on the optical fiber where the outer cladding is removed to expose the fiber core, and the optical fiber extends into the reactor so that the exposed fiber core is located below the water level of the pure water / saline water; The data acquisition and analysis device includes a data collector installed on the reactor to realize the acquisition of data during the CO2-water-rock reaction process. The data during the reaction process includes the temperature, pressure, pH value, and the change relationship of the optical signal parameters in the spectral analyzer over time.

2. The in-situ measurement system for the CO2-water-rock reaction process according to claim 1, characterized in that The reactor includes an autoclave, an autoclave lid, and a high-pressure clamp; The autoclave is a container with an open top. The autoclave lid covers the open top of the autoclave, and the autoclave and the autoclave lid are clamped tightly by the high-pressure clamp.

3. The in-situ measurement system for the CO2-water-rock reaction process according to claim 2, characterized in that, The CO2 injection unit includes a CO2 gas cylinder and a constant-speed and constant-pressure pump; A pressure gauge and a first CO2 injection control valve are installed at the outlet of the CO2 gas cylinder; The CO2 gas cylinder and the constant-speed and constant-pressure pump, and the constant-speed and constant-pressure pump and the autoclave are connected through a main pipeline. A second CO2 injection control valve and a constant-speed and constant-pressure pump liquid injection valve are sequentially arranged on the main pipeline between the CO2 gas cylinder and the constant-speed and constant-pressure pump. A constant-speed and constant-pressure pump liquid discharge valve is arranged on the main pipeline between the constant-speed and constant-pressure pump and the autoclave.

4. The in-situ measurement system for the CO2-water-rock reaction process according to claim 2, characterized in that, The data collector includes a temperature sensor, a pressure sensor, and a pH meter. The data acquisition and analysis device further includes a computer; The temperature sensor, the pressure sensor, and the pH meter all pass through the autoclave lid and extend into the autoclave. The bottoms of the temperature sensor, the pressure sensor, and the pH meter are all located below the water level of the pure water / saline water, and their tops are connected to the computer through a data transmission line.

5. The in-situ measurement system for the CO2-water-rock reaction process according to claim 2, characterized in that The reactor further includes a sealing gasket; There is a through hole on the autoclave lid, and both ends of the optical fiber are located in the through hole; The sealing gasket covers the opening of the through hole, and the wires on the light source and the spectral analyzer respectively pass through the sealing gasket and are connected to both ends of the optical fiber.

6. The in-situ measurement system for the CO2-water-rock reaction process according to claim 2, wherein A magnetic stirrer is arranged inside the autoclave to stir the pure water / saline water in the autoclave.

7. The in-situ measurement system for the CO2-water-rock reaction process according to claim 2, wherein, The temperature control device includes a heating plate and a thermal insulation cover; The thermal insulation cover is fixed on the heating plate. The thermal insulation cover has a cavity for accommodating the autoclave, and the bottom of the autoclave is in contact with the heating plate.

8. The in-situ measurement system for the CO2-water-rock reaction process according to claim 1, wherein The light source is a white halogen lamp.

9. The in-situ measurement system for the CO2-water-rock reaction process according to claim 1, wherein The pure water / salt water injection unit includes a pure water / salt water container and a pure water / salt water injection pump. The water inlet of the pure water / salt water injection pump is connected to the pure water / salt water container through a pipeline, and the water outlet of the pure water / salt water injection pump is connected to the inside of the reaction kettle.

10. The in-situ measurement system for the CO2-water-rock reaction process according to claim 1, wherein The in-situ measurement system for the CO2-water-rock reaction process further includes a waste liquid discharging unit. The waste liquid discharging unit includes a liquid discharging pipeline connected to the inside of the reaction kettle, and a filter and a liquid discharging valve are installed on the liquid discharging pipeline.

11. An in-situ measurement method for CO2-water-rock reaction, characterized in that, This method includes the following steps: Calibrate the optical fiber used to establish the standard correspondence between the light intensity and the refractive index; Conduct SEM-EDS petrographic composition test analysis before the reaction to obtain the rock mineral composition of the rock sample to be tested before the reaction; Place the rock sample to be tested into the reaction kettle, and at the same time place the optical fiber into the reaction kettle. There is a part on the optical fiber where the outer cladding is removed to expose the fiber core. The two ends of the optical fiber are respectively connected to a light source and a spectral analyzer; After sealing the reaction kettle, conduct a vacuum treatment, inject pure water / salt water into the reaction kettle, so that the rock sample to be tested and the part of the fiber core exposed on the optical fiber are below the horizontal plane, heat the reaction kettle and keep it constant; inject CO2 into the reaction kettle to increase the pressure in the reaction kettle to the target value and keep it constant; Conduct a CO2-water-rock reaction experiment, and continuously monitor the relationships between the temperature, pressure, pH value during the reaction process and the optical signal parameters in the spectral analyzer changing with time; Conduct SEM-EDS petrographic composition test analysis after the reaction to obtain the rock mineral composition of the rock sample to be tested after the reaction, and determine the ionic components and contents in the reaction solution after the reaction; According to the pH value, light intensity, ionic components in the reaction solution at different times, and rock mineral compositions before and after the reaction monitored under different temperature and pressure conditions, calculate the change rules of the ionic components and contents in the reaction solution at different times to determine the reaction rate and reaction process of the CO2-water-rock reaction at different times.

12. A method for in-situ measurement of CO2-water-rock reaction according to claim 11, characterized in that, The calibration of the optical fiber used to establish the standard correspondence between the light intensity and the refractive index further includes: Place the optical fiber into a standard sample with a known refractive index, monitor the light intensity, and thus establish the standard correspondence between the light intensity and the refractive index.

13. A method for in-situ measurement of CO2-water-rock reaction according to claim 11, characterized in that, The continuous monitoring of the relationships between the temperature, pressure, pH value during the reaction process and the optical signal parameters in the spectral analyzer changing with time further includes: During the reaction process, take out a small amount of the reaction solution at regular intervals for water quality analysis to determine the ionic components and contents in the reaction solution.

14. A method for in-situ measurement of CO2-water-rock reaction according to claim 13, characterized in that, Calculating the variation law of ionic components and contents in the reaction solution at different times based on the pH value, light intensity, ionic components of the reaction solution at different times, and rock mineral components before and after the reaction under different temperature and pressure conditions monitored, so as to determine the reaction rate and reaction process of the CO2-water-rock reaction at different times, including: Determining the refractive index in the reaction solution according to the change of light intensity with time, and calculating the concentration of solute in the reaction solution according to the change of solution refractive index by using the Lorentz-Lorenz equation; According to the ionic components and contents of the reaction solution at different times, using multiple linear regression analysis or the least square method to determine the corresponding relationship between the ionic contents of multiple groups of reaction solutions and the solute concentration; Combining the changes in rock mineral components before and after the reaction to realize the analysis of the whole kinetic process of the CO2-water-rock reaction.

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