Terahertz wave testing device and method for correcting co2 diffusion and dissolution parameters

Abstract

This application provides a terahertz wave testing device and a method for correcting CO2 diffusion and solubility parameters, relating to the field of oil and gas field development technology. The device includes: a CO2 storage tank, a reference cylinder, a sample cylinder, a pulsed laser emitter, a beam splitter, a signal delayer, a reflector, a signal generator, a signal receiver, a first reflector, and a second reflector. The CO2 storage tank is connected to the reference cylinder, and the reference cylinder is connected to the sample cylinder. A controllable valve is also installed on the connecting pipeline between the reference cylinder and the sample cylinder to control the on / off state of the connecting pipeline. The beam splitter, signal delayer, and reflector are sequentially arranged in the laser emission direction of the pulsed laser emitter. The terahertz pulse wave generated by the signal generator is incident on the sample cylinder through the first reflector and then reflected to the signal receiver by the second reflector. The terahertz wave testing device of this application can monitor the bulk water content in real time based on terahertz wave time-domain spectroscopy, thereby correcting the diffusion coefficient and solubility of CO2 in heavy oil.

Description

Technical Field

[0001] This application relates to the field of oil and gas field development technology, specifically to a terahertz wave testing device, a CO2 diffusion and dissolution parameter correction method, a CO2 diffusion and dissolution parameter correction device, a computer-readable storage medium, and a terminal device. Background Technology

[0002] my country's heavy oil reservoirs are characterized by deep burial and thin layers, high viscosity, high C-H ratio, and high heteroatom content, making extraction challenging. Given these characteristics, multi-component thermodynamic fluid (MFCF) composite development technology, which involves the synergistic injection of steam, CO2, and N2 into heavy oil reservoirs, has become a research hotspot. This method effectively improves the fluidity of heavy oil based on the effects of heating to reduce viscosity, elastic expansion, and reducing interfacial tension. Compared to simple hot water flooding and steam flooding, MFCF composite development technology offers significant advantages: shorter connection time between injection and production wells, more significant pressure field reduction, wider temperature field influence range, more uniform pressure propulsion, effective expansion of swept volume, reduction of residual oil saturation between injection and production wells, and a substantial increase in heavy oil recovery. The enhanced oil recovery effect of MFCF composite development technology largely depends on the diffusion / dissolution properties of CO2, a key component of the multi-component thermodynamic fluid, in the heavy oil. Therefore, clarifying the diffusion coefficient and solubility of CO2 in the multi-component thermodynamic fluid is crucial for evaluating the feasibility and effectiveness of MFCF composite development technology for heavy oil.

[0003] Currently, indirect methods are commonly used to determine the diffusion / dissolution properties of CO2 in heavy oil. These methods monitor the changes in key system parameters (such as pressure and liquid level) over time, establishing a functional relationship between these parameters and the diffusion coefficient (primarily based on Fick's law of diffusion), ultimately determining the diffusion coefficient and solubility. Among these methods, the PVT method, based on the decay of CO2 pressure in a container, is particularly widely used. For this method, the accuracy of heavy oil volume calibration and the accuracy of CO2 bulk pressure monitoring significantly impact the calculation of CO2 diffusion coefficient and solubility. Currently, this method is often conducted under simulated heavy oil reservoir conditions, with temperatures reaching 373.15-473.15 K. These high temperatures cause water in the heavy oil to precipitate as water vapor, altering the oil volume and affecting the accuracy of CO2 bulk pressure monitoring. However, due to the difficulty in detecting the water content within the experimental system during CO2 diffusion / dissolution, the PVT method assumes a constant sample volume when calculating the CO2 diffusion coefficient and solubility, resulting in data that deviates from actual conditions. Existing methods for analyzing the dynamic changes in the volume of heavy oil during fluid diffusion / dissolution are mostly based on physical and mathematical models for correction. However, existing technologies often neglect the volume changes in heavy oil caused by water precipitation under high-temperature conditions, as well as the influence of precipitated water vapor on the bulk pressure of the injected medium. Therefore, they cannot accurately assess the true diffusion / dissolution performance of the injected medium in heavy oil. Summary of the Invention

[0004] The purpose of this application is to provide a method and apparatus for predicting oil and gas well production based on the sparrow search algorithm, so as to solve the above-mentioned problems.

[0005] To achieve the above objectives, the first aspect of this application provides a terahertz wave testing device, comprising: CO2 storage tank, reference tank, sample tank, pulsed laser emitter, beam splitter, signal delay unit, reflector, signal generator, signal receiver, first reflector and second reflector; The CO2 storage tank is connected to the reference cylinder, the reference cylinder is connected to the sample cylinder, and a controllable valve for controlling the opening and closing of the connection pipeline between the reference cylinder and the sample cylinder is also provided. The beam splitter, signal delayer, and reflector are sequentially arranged in the laser emission direction of the pulsed laser emitter. The pulsed laser emitter is used to generate an ultrashort pulse laser beam. The beam splitter is used to decompose the ultrashort pulse laser beam into a pump beam and a probe beam that are perpendicular to each other. The probe beam is delayed by the signal delayer and then reflected by the reflector to the signal receiver. The signal generator is used to generate terahertz pulse waves when excited by the pump beam. The terahertz pulse waves generated by the signal generator are injected into the sample cylinder through the first reflector and then reflected to the signal receiver through the second reflector.

[0006] Optionally, the device further includes: A booster pump installed between the CO2 storage tank and the reference cylinder is used to boost the low-pressure CO2 gas to the required working pressure. A vacuum pump is installed between the booster pump and the reference cylinder to generate a vacuum negative pressure; A first pressure sensor is used to monitor the pressure inside the reference cylinder; The second pressure sensor is used to monitor the pressure inside the sample cylinder; The controllable valve is a needle valve, the first reflector and the second reflector are both off-axis elliptical mirrors, and the reference cylinder and the sample cylinder are placed in a constant temperature device.

[0007] A second aspect of this application provides a method for correcting CO2 diffusion and dissolution parameters, applied to the aforementioned terahertz wave testing device, the method comprising: When a heavy oil sample is injected into the sample cylinder, the temperature control device is controlled to operate at a specified temperature. The booster pump is controlled to inject CO2 gas into the reference cylinder until the pressure in the reference cylinder reaches pressure equilibrium. The controllable valve is then controlled to open to inject CO2 gas into the sample cylinder through the reference cylinder until the pressure in the sample cylinder reaches a first pressure threshold. Finally, the controllable valve is controlled to close. The real-time terahertz response signal of the fluid in the sample cylinder during the diffusion / dissolution process of CO2 gas in the sample cylinder is obtained by the signal receiver, and the amount of water precipitated from the heavy oil sample during the diffusion / dissolution process of CO2 gas in the heavy oil is determined based on the obtained real-time terahertz response signal. The initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the amount of water precipitated from the heavy oil sample.

[0008] Optionally, before injecting the heavy oil sample into the sample cylinder, the method further includes: Water vapor is injected into the sample cylinder, and the humidity inside the sample cylinder is adjusted by injecting nitrogen gas into the sample cylinder so that the humidity inside the sample cylinder is different at different sampling times; When the signal generator generates a terahertz pulse wave, the relative humidity in the sample cylinder is collected at different sampling times by a hygrometer, and the terahertz response signal of the fluid in the sample cylinder at different sampling times is obtained by the signal receiver. Based on the collected relative humidity and terahertz response signals, a first relationship curve is constructed to characterize the correspondence between different relative humidity and terahertz response signals.

[0009] Optionally, after constructing a first relationship curve characterizing the correspondence between humidity and terahertz signal at different times, the method further includes: Inert gas is injected into the sample cylinder until all nitrogen and water vapor in the sample cylinder are expelled; CO2 gas is injected into the reference cylinder through the CO2 storage tank, and the controllable valve is opened to inject CO2 gas into the sample cylinder through the reference cylinder until the pressure in the sample cylinder reaches a second pressure threshold; and During the process of injecting CO2 gas into the sample cylinder, the pressure inside the sample cylinder is collected at different sampling times by the second pressure sensor, and the terahertz response signal of the fluid inside the sample cylinder at different sampling times is obtained by the signal receiver. Based on the collected pressure and terahertz signals, a second relationship curve is constructed to characterize the correspondence between different CO2 gas pressures and terahertz response signals.

[0010] Optionally, before determining the amount of water precipitated from the heavy oil sample during the diffusion / dissolution of CO2 gas in heavy oil based on the extracted terahertz response signal, the method further includes: A CO2 diffusion / dissolution model and a CO2 solubility model are constructed. The initial diffusion coefficient of CO2 gas in heavy oil is determined based on the CO2 diffusion / dissolution model, and the initial solubility of CO2 gas in heavy oil is determined based on the CO2 solubility model. The amount of water precipitated from the heavy oil sample during the diffusion / dissolution of CO2 gas in heavy oil is determined based on the extracted terahertz response signal, including: Based on the real-time terahertz response signal, the first relationship curve, and the second relationship curve, the relative humidity corresponding to the real-time terahertz response signal is determined, and the partial pressure of the water precipitated from the heavy oil sample is determined based on the relative humidity corresponding to the real-time terahertz response signal. A first relationship function is established between the partial pressure of water precipitated from the heavy oil sample and the amount of water precipitated from the heavy oil sample based on the ideal gas law, and a second relationship function is obtained between the amount of water precipitated from the heavy oil sample and the volume of water precipitated from the heavy oil sample. The amount of water precipitated from the heavy oil sample is calculated based on the first relational function and the second relational function.

[0011] Optionally, the first relational function includes:

[0012] The second relational function includes:

[0013] in, P H2O This refers to the partial pressure of the water that has precipitated from the heavy oil sample. V’ The blank volume after calibration of the sample cylinder. Z H2O The partial pressure coefficient of the water precipitated from the heavy oil sample is given. R Let be the ideal gas constant. T For temperature, V H2O This refers to the volume of water that has separated from the heavy oil sample. n H2O The amount of water precipitated from the heavy oil sample. The density of water, M H2O This is the molar mass of water.

[0014] Optionally, calculating the amount of water precipitated from the heavy oil sample based on the first relational function and the second relational function includes: The initial volume, coefficient of expansion of heavy oil, and pressure inside the sample cylinder at the current moment of the heavy oil sample injected into the sample cylinder are obtained. The volume of the heavy oil sample after expansion is determined based on the initial volume, coefficient of expansion of heavy oil, and pressure inside the sample cylinder at the current moment. The difference between the volume of the swollen heavy oil sample and the volume of water precipitated from the heavy oil sample is taken as the corrected volume of the heavy oil sample. The volume of the sample cylinder is obtained, and the blank volume of the sample cylinder after correction is determined by the difference between the volume of the sample cylinder and the corrected volume of the heavy oil sample. Based on the second relationship function, a third relationship function is determined between the blank volume of the sample cylinder after correction and the amount of water separated from the heavy oil sample, the volume of the sample cylinder, and the volume of the heavy oil sample after expansion. The amount of water precipitated from the heavy oil sample is calculated based on the first relational function and the third relational function.

[0015] Optionally, the initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the amount of water precipitated from the heavy oil sample, including: Based on the amount of water precipitated from the heavy oil sample, the volume of water precipitated from the heavy oil sample is determined according to the second relationship function; The volume fraction of CO2 gas in the sample cylinder is calculated using the following formula:

[0016] in,y CO2 The volume fraction of CO2 gas in the sample cylinder; The pressure inside the sample cylinder at the current moment is obtained, and the product of the volume fraction of CO2 gas in the sample cylinder and the pressure inside the sample cylinder at the current moment is taken as the partial pressure of CO2 gas in the sample cylinder. The initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the partial pressure of CO2 gas in the sample cylinder and the volume of water precipitated from the heavy oil sample.

[0017] Optionally, the CO2 diffusion / dissolution model includes:

[0018] in, β The coefficient of thermal expansion of heavy oil is 1. V 0 represents the initial volume of the heavy oil sample. V C The volume of the sample cylinder ，P (t) for t The pressure inside the sample cylinder at that time P 0( t The initial pressure in the sample cylinder at time t is denoted as . D AB The diffusion coefficient of CO2 gas in heavy oil is given. R Let be the ideal gas constant. T For temperature, Z The compressibility factor of CO2 gas. x eq The equilibrium concentration at the gas-liquid interface, mol / cm³ 3 .

[0019] Optionally, the CO2 solubility model includes:

[0020]

[0021] in, P1 and P3 The values ​​are the equilibrium pressures (MPa) of CO2 in the reference cylinder before and after the controllable valve opens during the diffusion / dissolution of CO2 gas in heavy oil. P2 and P4 These are the equilibrium pressures of CO2 in the sample cylinder before and after the controllable valve is opened, respectively, in MPa; VRC and VSC The blank volumes of the reference cylinder and the sample cylinder are respectively, in m3; Z1, Z2, Z3 and Z4 They are respectivelyP1 , P2 , P3 and P4 The corresponding CO2 compressibility factor, This represents the difference in the amount of CO2 gas before and after diffusion / dissolution in heavy oil. S The solubility of CO2 gas. m The mass of the heavy oil sample is expressed in grams.

[0022] Optionally, the initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the partial pressure of CO2 gas in the sample cylinder and the volume of water precipitated from the heavy oil sample, including: Based on the partial pressure of CO2 gas in the sample cylinder and the volume of water precipitated from the heavy oil sample, the CO2 diffusion / dissolution model and the CO2 solubility model are modified to obtain the modified CO2 diffusion / dissolution model and the modified CO2 solubility model. The initial diffusion coefficient and initial solubility of CO2 gas in heavy oil were corrected based on the modified CO2 diffusion / dissolution model and the modified CO2 solubility model.

[0023] The revised CO2 diffusion / dissolution model includes:

[0024] The modified CO2 solubility model includes:

[0025] in, for t The square of the partial pressure of CO2 gas in the sample cylinder at the specified time. To correct the solubility of CO2 gas, This indicates the partial pressure of CO2 gas in the sample cylinder after the controllable valve is opened.

[0026] A third aspect of this application provides a CO2 diffusion and dissolution parameter correction device, the device comprising: The temperature control module is configured to control the thermostat to operate at a specified temperature when a heavy oil sample is injected into the sample cylinder. The gas injection module is configured to control the booster pump to inject CO2 gas into the reference cylinder until the pressure in the reference cylinder reaches pressure equilibrium, control the controllable valve to open, so as to inject CO2 gas into the sample cylinder through the reference cylinder until the pressure in the sample cylinder reaches a first pressure threshold, and control the controllable valve to close. The signal analysis module is configured to acquire the real-time terahertz response signal of the fluid in the sample cylinder during the diffusion / dissolution process of CO2 gas in the sample cylinder through the signal receiver, and determine the amount of water precipitated from the heavy oil sample during the diffusion / dissolution process of CO2 gas in heavy oil based on the acquired real-time terahertz response signal. The parameter correction module is configured to correct the initial diffusion coefficient and initial solubility of CO2 gas in heavy oil based on the amount of water precipitated from the heavy oil sample.

[0027] In a fourth aspect, this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, causes the processor to perform the CO2 diffusion and dissolution parameter correction method described above.

[0028] In a fifth aspect, this application provides a terminal device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor, when executing the computer program, implements the aforementioned CO2 diffusion and dissolution parameter correction method.

[0029] The embodiments provided in this application have the following beneficial effects: The terahertz wave testing device of this application can monitor the bulk water content in real time based on terahertz wave time-domain spectroscopy, thereby correcting the diffusion coefficient and solubility of CO2 in heavy oil, so as to improve the feasibility of developing heavy oil using multi-element thermal fluid composite technology and the accuracy of the assessment of the enhanced oil recovery effect.

[0030] Other features and advantages of the embodiments or implementations of this application will be described in detail in the following detailed description section. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. In the drawings: Figure 1 This schematic diagram illustrates the device structure of the terahertz wave testing apparatus according to an embodiment of this application; Figure 2 The schematic diagram illustrates the CO2 bulk pressure change curve and diffusion coefficient and solubility schematic diagram of Example 1 of the present application. Figure 3 The schematic diagram illustrates the CO2 bulk pressure change curve and diffusion coefficient and solubility diagram of Comparative Example 1 of the embodiments of this application. Figure 4 The schematic diagram illustrates the CO2 bulk pressure change curve and diffusion coefficient and solubility diagram of Embodiment 2 of this application; Figure 5 The schematic diagram illustrates the CO2 bulk pressure change curve and diffusion coefficient and solubility diagram of Comparative Example 2 of the embodiments of this application; Figure 6 The schematic diagram illustrates the CO2 bulk pressure change curve and diffusion coefficient and solubility schematic diagram of Example 3 of the present application. Figure 7 The schematic diagram illustrates the CO2 bulk pressure change curve and diffusion coefficient and solubility diagram of Comparative Example 3 of the embodiments of this application; Figure 8 The illustration shows the CO2 bulk pressure change curve and diffusion coefficient and solubility diagram of Example 4 of the present application. Figure 9 The schematic diagram illustrates the CO2 bulk pressure change curve and diffusion coefficient and solubility diagram of Comparative Example 4 of the embodiments of this application. Figure 10 The schematic diagram illustrates a terminal device structure according to an embodiment of this application.

[0032] Explanation of reference numerals in the attached figures 10 - Terminal device, 100 - Processor, 101 - Memory, 102 - Computer program. Detailed Implementation

[0033] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the embodiments of this application.

[0034] To solve the above problems, such as Figure 1As shown, the first aspect of this application provides a terahertz wave testing device, comprising: a CO2 storage tank, a reference cylinder, a sample cylinder, a pulsed laser emitter, a beam splitter, a signal delayer, a reflector, a signal generator, a signal receiver, a first reflector, and a second reflector; the CO2 storage tank is connected to the reference cylinder, the reference cylinder is connected to the sample cylinder, and a controllable valve for controlling the opening and closing of the connecting pipeline between the reference cylinder and the sample cylinder is also provided; the beam splitter, the signal delayer, and the reflector are sequentially arranged in the laser emission direction of the pulsed laser emitter, the pulsed laser emitter is used to generate an ultrashort pulse laser beam, the beam splitter is used to decompose the ultrashort pulse laser beam into a pump beam and a probe beam that are perpendicular to each other, the probe beam is delayed by the signal delayer and then reflected by the reflector to the signal receiver; the signal generator is used to generate a terahertz pulse wave under the excitation of the pump beam, the terahertz pulse wave generated by the signal generator is injected into the sample cylinder through the first reflector and then reflected by the second reflector to the signal receiver. The apparatus includes: a booster pump positioned between the CO2 storage tank and the reference cylinder to pressurize the low-pressure CO2 gas to the required working pressure; a vacuum pump positioned between the booster pump and the reference cylinder to generate a negative vacuum; a first pressure sensor to monitor the pressure inside the reference cylinder; a second pressure sensor to monitor the pressure inside the sample cylinder; a controllable valve (needle valve); and two off-axis elliptical mirrors (first and second reflecting mirrors). The reference cylinder and sample cylinder are placed within a temperature-controlled device. The booster pump pressurizes the CO2 gas to the target pressure, and the temperature-controlled device maintains the experimental temperature. Both the reference cylinder and sample cylinder are equipped with sealed caps, and the sample cylinder's cap also has a fluid inlet. To analyze the terahertz wave signal returned from the sample cylinder, a signal receiver is connected to a signal analysis device, such as a spectrometer.

[0035] As is understandable, terahertz waves are electromagnetic waves with frequencies between 0.10 and 10.00 THz and wavelengths between 0.03 and 3.00 mm. They lie between microwaves and infrared radiation, with energies only in the millielectron volt range, placing them in the transition region between electronics and photonics. Terahertz waves possess high transparency, low energy, transient nature, and water absorption. Under the influence of terahertz waves, the weak interactions between different molecules, macromolecular skeletal vibrations, dipole rotation and vibrational transitions, and the absorption of relative low-frequency vibrations of the crystal lattice in crystals exhibit absorption peaks at different positions or intensities in the spectrum, thus reflecting information such as the conformation and configuration of the substance. For polar water molecules, their hydrogen bond network causes the translational and rotational frequencies of water molecules to fall precisely within the terahertz band, resulting in a strong response to terahertz waves. Based on this characteristic, terahertz waves can be used to determine the moisture content of substances. By acquiring the amplitude and phase information of the terahertz signal pulse when interacting with the sample, and by performing a Fourier transform on the terahertz time-domain pulse, optical parameters such as the absorption coefficient and refractive index of the sample can be obtained, and the internal structural information of the sample can ultimately be determined.

[0036] Thus, based on the testing device of this application, the degree of absorption of terahertz waves by the fluid in the sample cylinder can be monitored in real time. At the same time, the sample cylinder of this application is made of sapphire with high temperature and high pressure resistance and wave transmission properties, which can effectively avoid the interference of the cylinder material on the fluid absorption of terahertz waves while meeting the experimental simulation reservoir conditions.

[0037] In a second aspect, this application provides a method for correcting CO2 diffusion and dissolution parameters, applied to the aforementioned terahertz wave testing apparatus. The method includes: controlling a thermostat to operate at a specified temperature while injecting a heavy oil sample into a sample cylinder; controlling a booster pump to inject CO2 gas into a reference cylinder until the pressure in the reference cylinder reaches pressure equilibrium; controlling a controllable valve to open to inject CO2 gas into the sample cylinder through the reference cylinder until the pressure in the sample cylinder reaches a first pressure threshold; controlling the controllable valve to close; acquiring a real-time terahertz response signal of the fluid in the sample cylinder during the diffusion / dissolution process of CO2 gas using a signal receiver; determining the amount of water precipitated from the heavy oil sample during the diffusion / dissolution process of CO2 gas in the heavy oil based on the acquired real-time terahertz response signal; and correcting the initial diffusion coefficient and initial solubility of CO2 gas in the heavy oil based on the amount of water precipitated from the heavy oil sample.

[0038] Before injecting the heavy oil sample into the sample cylinder, this application also pre-establishes the correspondence between moisture content and terahertz wave response, as follows: 1. Inject water vapor into the sample cylinder and adjust the humidity inside the sample cylinder by injecting nitrogen gas, so that the humidity inside the sample cylinder varies at different sampling times. Specifically, inject a certain amount of water vapor into the blank sample cylinder and adjust the relative humidity inside the sample cylinder by injecting high-purity nitrogen gas (purity ≥99.99%), for example, by gradually increasing or decreasing the humidity inside the sample cylinder.

[0039] 2. With the signal generator producing terahertz pulse waves, the relative humidity inside the sample tank is collected at different sampling times using a hygrometer, and the terahertz response signal of the fluid inside the sample tank at different sampling times is obtained using a signal receiver. Based on the collected relative humidity and terahertz response signal, a first relationship curve characterizing the correspondence between different relative humidities and the terahertz response signal is constructed. The pulsed laser emitter is turned on to enable the signal generator to produce terahertz pulse waves. The terahertz pulse waves generated by the signal generator are reflected into the sample tank by a reflector, and then reflected by the fluid at different humidity levels before entering the signal receiver. Simultaneously, a high-precision hygrometer is used to measure the humidity inside the sample tank to measure the terahertz wave signal at different humidity levels, obtaining the degree of response of the fluid to the terahertz wave at different humidity levels, and establishing a relationship curve between the terahertz wave signal and the degree of response of the fluid in the sample tank to the relative humidity. The terahertz response signal can be the intensity of the received terahertz signal, or optical parameters extracted from the time spectrum of the received terahertz signal, such as refractive index and absorption coefficient, etc., to construct a correspondence between signal intensity or optical parameters and relative humidity. For example, the established relation can be represented as S=f(H) Where S is the terahertz wave response signal and H is the relative humidity.

[0040] After constructing the first relationship curve, a reference curve for the response signal of CO2 gas and terahertz waves is further constructed, as follows: 1. Inject inert gas into the sample cylinder until all nitrogen and water vapor are expelled. Drain the fluid from the blank sample cylinder and purge it with high-purity helium (purity ≥99.99%) for 10 minutes to expel all nitrogen and water vapor.

[0041] 2. Inject high-purity CO2 (purity ≥ 99.99%) into the reference cylinder through the CO2 storage tank. Control the controllable valve to open so that CO2 gas is injected into the sample cylinder through the reference cylinder, allowing it to fully balance until the pressure in the sample cylinder reaches the second pressure threshold, i.e., the preset equilibrium pressure point.

[0042] 3. During the injection of CO2 gas into the sample cylinder, the pressure inside the sample cylinder is collected at different sampling times using a second pressure sensor, and the terahertz response signal of the fluid inside the sample cylinder at different sampling times is acquired using a signal receiver. Based on the collected pressure and terahertz signal, a second relationship curve characterizing the correspondence between different CO2 gas pressures and terahertz response signals is constructed, and this curve is used as the calculation benchmark. For example, a mapping relationship is constructed between the terahertz signal intensity or optical parameters of CO2 gas under different pressures and the corresponding pressure. After the terahertz wave signal of CO2 in the blank sample cylinder is measured, the CO2 in the reference cylinder is emptied.

[0043] After constructing the first and second relationship curves, the bulk water content in the sample tank was monitored in real time during the diffusion / dissolution of CO2 in heavy oil. The specific steps are as follows: 1) Place a certain volume of heavy oil sample in a sample cylinder, connect all components of the measuring device, and place it in a constant temperature device; the experimental temperature range is 150-200°C, which covers the favorable reservoir temperature of heavy oil; the volume of the heavy oil sample is 30±0.1 mL to ensure that the terahertz time-domain spectrometer can only detect the bulk fluid signal in the sample cylinder, so as to avoid the heavy oil sample absorbing terahertz waves and interfering with the identification of water signals; 2) High-purity helium (purity ≥ 99.99%) is introduced into the entire measuring device to test the airtightness of the device. After the test is completed, the helium in the device is purged. 3) Use a booster pump to increase the high-purity CO2 (purity ≥ 99.99%) to the target pressure and inject it into the reference cylinder; 4) After the pressure in the reference cylinder has been balanced for 200 min, slowly open the needle valve connecting the reference cylinder and the sample cylinder to inject CO2 into the reference cylinder. Once the pressure in the sample cylinder reaches the set value, quickly close the needle valve. Record the pressure value after the pressure in the reference cylinder and the sample cylinder has been fully balanced for 200 min. The experimental pressure range is 10-20 MPa, which covers the pressure of favorable heavy oil reservoirs. 5) Monitor the response signal of the fluid in the sample cylinder to the terahertz wave in real time during the above CO2 diffusion / dissolution process, obtain the terahertz band frequency domain spectrum of the fluid in the sample cylinder through fast Fourier transform, and calculate the optical parameters of the fluid in the sample cylinder accordingly; wherein, the frequency of the terahertz wave is 0.1-2.0 THz. 6) Based on the measured optical parameters of the fluid in the sample cylinder, calculate the bulk water content in the sample cylinder during the diffusion / dissolution of CO2 in heavy oil, that is, the amount of water precipitated from the heavy oil sample during the diffusion / dissolution of CO2 gas in heavy oil.

[0044] Before determining the amount of water precipitated from the heavy oil sample during the diffusion / dissolution of CO2 gas in heavy oil based on the extracted terahertz response signal, the method of this application further includes: constructing a CO2 diffusion / dissolution model and a CO2 solubility model; determining the initial diffusion coefficient of CO2 gas in heavy oil based on the CO2 diffusion / dissolution model; and determining the initial solubility of CO2 gas in heavy oil based on the CO2 solubility model. The CO2 diffusion / dissolution model and CO2 solubility model are constructed on the basis of neglecting changes in liquid phase composition, gas-liquid interfacial resistance, temperature changes, and changes in diffusion coefficient during the CO2 diffusion / dissolution process.

[0045] The CO2 diffusion / dissolution model can be expressed as:

[0046] in, β The coefficient of thermal expansion of heavy oil is 1. V 0 represents the initial volume of the heavy oil sample. V C The volume of the sample cylinder , P(t) for t The pressure inside the sample cylinder at all times, P 0( t The initial pressure in the sample cylinder at time t is denoted as . D AB The diffusion coefficient of CO2 gas in heavy oil is given. R Let be the ideal gas constant. T For temperature, Z The compressibility factor of CO2 gas. x eq The equilibrium concentration at the gas-liquid interface, mol / cm³ 3 .

[0047] Alternatively, the CO2 solubility model can be expressed as:

[0048]

[0049] in, P1 and P3 These represent the equilibrium pressure of CO2 in the reference cylinder before and after the controllable valve opens during the diffusion / dissolution of CO2 gas in heavy oil, respectively, in MPa. P2 and P4 These are the equilibrium pressures of CO2 in the sample cylinder before and after the controllable valve is opened, respectively, in MPa; VRC and VSC The blank volumes of the reference cylinder and the sample cylinder are respectively, in m3; Z1, Z2, Z3 and Z4 They are respectively P1 , P2 , P3 and P4 The corresponding CO2 compressibility factor, This represents the difference in the amount of CO2 gas before and after diffusion / dissolution in heavy oil. S The solubility of CO2 gas. m The mass of the heavy oil sample is expressed in grams.

[0050] Specifically, the construction process of the CO2 diffusion / dissolution model and the CO2 solubility model is as follows: 1) According to Fick's second law, we can obtain: In equation (1), x represents the concentration at the gas-liquid interface, in mol / cm³.3 z represents the height of the heavy oil at any time t, in meters. The boundary conditions are: z = z0 (2) t>0 (3) x = x eq (4) In equation (2), z0 is the initial heavy oil height in meters; in equation (4), x eq This refers to the equilibrium concentration at the gas-liquid interface, expressed in mol / cm³. 3 Under constant temperature conditions, it only changes with pressure; The initial conditions are: 0≤z≤z0 (5) t=0 (6) x=0 (7) 2) Based on Fick's second law, a concentration function related to time and location can be established: In equation (8), D AB The diffusion coefficient of CO2 in heavy oil is given in m. 2 / s; 3) According to the law of conservation of mass, the amount of CO2 reduced in the gas phase is equal to the amount that enters the heavy oil through the gas-liquid interface, which can be expressed as: In equation (9), V is the blank volume of the sample cylinder, in m³. 3 Wherein, blank volume refers to the volume of the sample cylinder excluding the heavy oil sample; Z is the compressibility factor of CO2; R is the ideal gas constant, with a value of 8.314 J / mol / K; T is the experimental temperature, in K; P(t) is the pressure of bulk CO2 at time t; and A is the cross-sectional area of ​​the bottom of the sample cylinder, in m². 2 Since CO2 diffusion into heavy oil will cause the heavy oil volume to expand, and thus change the gas phase volume, we have: V h =V0[1+βP(t)] (10) In equation (10), V h The volume of the heavy oil after expansion is expressed in meters (m³). 3 V0 is the initial volume of heavy oil, in m 3 β is the coefficient of thermal expansion of heavy oil; Where, V = V C -V h =V C -V0-βV0P(t) (11) In equation (11), V C This refers to the volume of the sample cylinder, in cubic meters (m³). 3 ; Can be ordered: K = -D AB AZRT (12) Then we have: Integrating time from t0 to t and pressure from P0 to P, we get: because: Can be set as follows: Differentiating equation (16) yields: Then we have: When z = z0: therefore: Right now: In equation (22), the left side of the equation is the pressure correction term, which is related to t. 1 / 2 There is a linear relationship between them. The diffusion coefficient D of CO2 can be calculated by linearly plotting the CO2 bulk pressure change curve in the sample cylinder against the square root of time. AB Among them, the CO2 bulk pressure change curve can be pre-calibrated.

[0051] 4) Based on the difference in the amount of CO2 before and after diffusion / dissolution in heavy oil ( Δn The solubility of CO2 (S) can be calculated: (twenty three) (twenty four) Among them, the amount of water precipitated from the heavy oil sample during the diffusion / dissolution of CO2 gas in heavy oil is determined based on the extracted terahertz response signal, including: S10. Based on the real-time terahertz response signal, the first relationship curve, and the second relationship curve, determine the relative humidity corresponding to the real-time terahertz response signal, and determine the partial pressure of water precipitated from the heavy oil sample based on the relative humidity corresponding to the real-time terahertz response signal; for example, compare the real-time terahertz response signal with the terahertz response signal at the corresponding pressure in the second relationship curve, for example, the real-time signal is... S(t) The baseline signal corresponding to the second relationship curve is SIf the value is 0, then the signal change Δ can be calculated. S(t) Based on the mapping relationship between humidity and terahertz response signal established by the first relationship curve, the relative humidity corresponding to the signal change is determined. Based on the conversion relationship between saturated vapor pressure and relative humidity at the current temperature, the partial pressure of water corresponding to the current relative humidity can be determined. This partial pressure is the partial pressure of water precipitated from the heavy oil sample. The saturated vapor pressure at different temperatures can be pre-calibrated. The conversion relationship between saturated vapor pressure and relative humidity is existing technology. For example, it can be expressed as relative humidity = vapor pressure ÷ saturated vapor pressure × 100%, which is not limited here.

[0052] S20. Based on the ideal gas law, establish the first relationship function between the partial pressure of water precipitated from the heavy oil sample and the amount of water precipitated from the heavy oil sample, and obtain the second relationship function between the amount of water precipitated from the heavy oil sample and the volume of water precipitated from the heavy oil sample.

[0053] The first relational function includes: (25) The second relational function includes: (26) in, P H2O This represents the partial pressure of water precipitated from the heavy oil sample. V’ This is the blank volume after the sample cylinder has been calibrated. Z H2O The partial pressure coefficient of water precipitated from the heavy oil sample. R Let be the ideal gas constant. T For temperature, V H2O This represents the volume of water that has precipitated from the heavy oil sample. n H2O This represents the amount of water precipitated from the heavy oil sample. The density of water, M H2O This is the molar mass of water.

[0054] S30. Calculate the amount of water precipitated from the heavy oil sample based on the first and second relational functions. Specifically, this includes: S31. Obtain the initial volume, expansion coefficient and pressure in the sample cylinder of the heavy oil sample injected into the sample cylinder. Determine the expanded volume of the heavy oil sample based on the initial volume, expansion coefficient and pressure in the sample cylinder at the current moment. The expanded volume of the heavy oil sample can be calculated by formula (10). S32. The difference between the volume of the swollen heavy oil sample and the volume of water precipitated from the heavy oil sample is taken as the corrected volume of the heavy oil sample, i.e. ,in, VhThis represents the volume of the heavy oil sample after expansion. This is the corrected volume of the heavy oil sample.

[0055] S33. Obtain the volume of the sample cylinder, and determine the corrected blank volume of the sample cylinder by the difference between the volume of the sample cylinder and the corrected volume of the heavy oil sample. ,in, VC This refers to the volume of the sample cylinder.

[0056] S34. Based on the second relationship function, determine the third relationship function between the blank volume of the sample cylinder after correction and the amount of water separated from the heavy oil sample, the volume of the sample cylinder, and the volume of the heavy oil sample after expansion. V h -( V C - V’ )= n H2O M H2O / ρ H2O .

[0057] S35. Calculate the amount of water precipitated from the heavy oil sample based on the first and third relational functions, and transform the third relational function into... n H2O= ( ρ H2O ( V h -( V C - V’ ))) / M H2O Substituting this into the first relational function allows us to calculate the amount of water precipitated from the heavy oil sample.

[0058] Then, the initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the amount of water precipitated from the heavy oil sample, including: determining the volume of water precipitated from the heavy oil sample according to the second relationship function based on the amount of water precipitated from the heavy oil sample; and calculating the volume fraction of CO2 gas in the sample cylinder using the following formula: ,in, yCO2 The volume fraction of CO2 gas in the sample cylinder is given. The pressure in the sample cylinder at the current moment is obtained as the bulk pressure of CO2 gas in the sample cylinder before correction. Based on Dalton's Law of Partial Pressures, the bulk pressure of CO2 gas in the sample cylinder during the diffusion / dissolution process is corrected. Specifically, the product of the volume fraction of CO2 gas in the sample cylinder and the pressure in the sample cylinder at the current moment is taken as the partial pressure of CO2 gas in the sample cylinder. Where P is the bulk pressure of CO2 gas in the sample cylinder before calibration.P’ To correct for the bulk pressure of CO2 gas in the sample cylinder, the initial diffusion coefficient and initial solubility of CO2 gas in heavy oil were corrected based on the partial pressure of CO2 gas in the sample cylinder and the volume of water precipitated from the heavy oil sample.

[0059] Specifically, the initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the partial pressure of CO2 gas in the sample cylinder and the volume of water precipitated from the heavy oil sample. This includes: correcting the CO2 diffusion / dissolution model and CO2 solubility model based on the partial pressure of CO2 gas in the sample cylinder and the volume of water precipitated from the heavy oil sample, resulting in the corrected CO2 diffusion / dissolution model and the corrected CO2 solubility model; and correcting the initial diffusion coefficient and initial solubility of CO2 gas in heavy oil based on the corrected CO2 diffusion / dissolution model and the corrected CO2 solubility model.

[0060] The revised CO2 diffusion / dissolution model includes:

[0061] The revised CO2 solubility model includes:

[0062] in, for t The square of the partial pressure of CO2 gas in the sample cylinder after time correction. To correct the solubility of CO2 gas, This indicates the partial pressure of CO2 gas in the sample cylinder after the controllable valve is opened, following the calibration.

[0063] The method of this application will be described below through specific embodiments and comparative examples: Example 1 In this embodiment, the volume of the heavy oil sample used was 30±0.1 mL, the CO2 injection pressure was 10 MPa, and the experimental temperature was set at 150℃.

[0064] The terahertz wave testing device of this application is used to monitor the water content precipitated from heavy oil during the diffusion / dissolution of CO2 in heavy oil and to correct the CO2 diffusion coefficient and solubility. The steps are as follows: 1) Establish the relationship between the degree of water response to terahertz waves at a set pressure point; 2) Place the heavy oil sample in the sample cylinder, connect all components of the device, and place it in the constant temperature device; 3) Inject high-purity CO2 (purity ≥99.99%) into the reference cylinder. After the pressure is balanced, slowly open the needle valve connecting the reference cylinder and the sample cylinder to inject CO2 into the sample cylinder. After the pressure in the sample cylinder reaches the set value, quickly close the needle valve. Record the pressure value after the pressure in the reference cylinder and the sample cylinder is fully balanced for 200 minutes. 4) Monitor the response signal of the fluid in the sample cylinder to the terahertz wave in real time during the above CO2 diffusion / dissolution process, obtain the terahertz wave signal of the fluid in the sample cylinder through fast Fourier transform, and estimate the partial pressure and volume of water in the sample cylinder phase based on the relationship between the obtained terahertz wave signal and water content. 5) Based on the volume of water in the sample tank, correct the volume of heavy oil, the blank volume of the sample tank, and the partial pressure of CO2 in the bulk phase, and calculate the diffusion coefficient and solubility of CO2 in the heavy oil accordingly. The corrected CO2 bulk pressure change curve, diffusion coefficient, and solubility in the sample tank are shown below. Figure 2 As shown, Figure 2 In this context, Pressure represents pressure, Time represents time, DAB is the expansion coefficient, S is the solubility, and Parameter represents the parameter.

[0065] Comparative Example 1 The volume of the heavy oil sample used in this comparative example was 30±0.1 mL, the CO2 injection pressure was 10 MPa, and the experimental temperature was set at 150℃.

[0066] Calculations of its diffusion coefficient and solubility in heavy oil were based on the bulk CO2 pressure drop curve: 1) Place the heavy oil sample in the sample cylinder, connect all components of the device, and place it in the constant temperature device; 2) Inject high-purity CO2 (purity ≥99.99%) into the reference cylinder. After the pressure is balanced, slowly open the needle valve connecting the reference cylinder and the sample cylinder to inject CO2 into the sample cylinder. After the pressure in the sample cylinder reaches the set value, quickly close the needle valve. Record the pressure value after the pressure in the reference cylinder and the sample cylinder is fully balanced for 200 minutes. 3) Based on the CO2 pressure decay curve in the bulk phase of the sample cylinder, and using the established mathematical models—the CO2 diffusion / dissolution model and the CO2 solubility model—calculate the diffusion coefficient and solubility of CO2 in heavy oil before correction. Figure 3 As shown.

[0067] Example 2 In this embodiment, the volume of the heavy oil sample used was 30±0.1 mL, the CO2 injection pressure was 20 MPa, and the experimental temperature was set at 150℃.

[0068] The terahertz wave testing device of this application is used to monitor the water content precipitated from heavy oil during the diffusion / dissolution of CO2 in heavy oil and to correct the CO2 diffusion coefficient and solubility. The steps are as follows: 1) Establish the relationship between the degree of water response to terahertz waves at a set pressure point; 2) Place the heavy oil sample in the sample cylinder, connect all components of the device, and place it in the constant temperature device; 3) Inject high-purity CO2 (purity ≥99.99%) into the reference cylinder. After the pressure is balanced, slowly open the needle valve connecting the reference cylinder and the sample cylinder to inject CO2 into the sample cylinder. After the pressure in the sample cylinder reaches the set value, quickly close the needle valve. Record the pressure value after the pressure in the reference cylinder and the sample cylinder is fully balanced for 200 minutes. 4) Monitor the response signal of the fluid in the sample cylinder to the terahertz wave in real time during the above CO2 diffusion / dissolution process, obtain the terahertz wave signal of the fluid in the sample cylinder through fast Fourier transform, and estimate the partial pressure and volume of water in the sample cylinder phase based on the relationship between the obtained terahertz wave signal and water content. 5) Based on the volume of water in the sample tank, correct the volume of heavy oil, the blank volume of the sample tank, and the partial pressure of CO2 in the bulk phase, and calculate the diffusion coefficient and solubility of CO2 in the heavy oil accordingly. The corrected CO2 bulk pressure change curve, diffusion coefficient, and solubility in the sample tank are shown below. Figure 4 As shown.

[0069] Comparative Example 2 The volume of the heavy oil sample used in this comparative example was 30±0.1 mL, the CO2 injection pressure was 20 MPa, and the experimental temperature was set at 150℃.

[0070] Calculations of its diffusion coefficient and solubility in heavy oil were based on the bulk CO2 pressure drop curve: 1) Place the heavy oil sample in the sample cylinder, connect all components of the device, and place it in the constant temperature device; 2) Inject high-purity CO2 (purity ≥99.99%) into the reference cylinder. After the pressure is balanced, slowly open the needle valve connecting the reference cylinder and the sample cylinder to inject CO2 into the sample cylinder. After the pressure in the sample cylinder reaches the set value, quickly close the needle valve. Record the pressure value after the pressure in the reference cylinder and the sample cylinder is fully balanced for 200 minutes. 3) Based on the CO2 pressure decay curve in the bulk phase of the sample cylinder, calculate the diffusion coefficient and solubility of CO2 in heavy oil before correction using the established mathematical model, such as... Figure 5 As shown.

[0071] Example 3 In this embodiment, the volume of the heavy oil sample used was 30±0.1 mL, the CO2 injection pressure was 10 MPa, and the experimental temperature was set to 200℃.

[0072] The terahertz wave testing device of this application is used to monitor the water content precipitated from heavy oil during the diffusion / dissolution of CO2 in heavy oil and to correct the CO2 diffusion coefficient and solubility. The steps are as follows: 1) Establish the relationship between the degree of water response to terahertz waves at a set pressure point; 2) Place the heavy oil sample in the sample cylinder, connect all components of the device, and place it in the constant temperature device; 3) Inject high-purity CO2 (purity ≥99.99%) into the reference cylinder. After the pressure is balanced, slowly open the needle valve connecting the reference cylinder and the sample cylinder to inject CO2 into the sample cylinder. After the pressure in the sample cylinder reaches the set value, quickly close the needle valve. Record the pressure value after the pressure in the reference cylinder and the sample cylinder is fully balanced for 200 minutes. 4) Monitor the response signal of the fluid in the sample cylinder to the terahertz wave in real time during the above CO2 diffusion / dissolution process, obtain the terahertz wave signal of the fluid in the sample cylinder through fast Fourier transform, and estimate the partial pressure and volume of water in the sample cylinder phase based on the relationship between the obtained terahertz wave signal and water content. 5) Based on the volume of water in the sample tank, correct the volume of heavy oil, the blank volume of the sample tank, and the partial pressure of CO2 in the bulk phase, and calculate the diffusion coefficient and solubility of CO2 in the heavy oil accordingly. The corrected CO2 bulk pressure change curve, diffusion coefficient, and solubility in the sample tank are shown below. Figure 6 As shown.

[0073] Comparative Example 3 The volume of the heavy oil sample used in this comparative example was 30±0.1 mL, the CO2 injection pressure was 10 MPa, and the experimental temperature was set at 200℃.

[0074] Calculations of its diffusion coefficient and solubility in heavy oil were based on the bulk CO2 pressure drop curve: 1) Place the heavy oil sample in the sample cylinder, connect all components of the device, and place it in the constant temperature device; 2) Inject high-purity CO2 (purity ≥99.99%) into the reference cylinder. After the pressure is balanced, slowly open the needle valve connecting the reference cylinder and the sample cylinder to inject CO2 into the sample cylinder. After the pressure in the sample cylinder reaches the set value, quickly close the needle valve. Record the pressure value after the pressure in the reference cylinder and the sample cylinder is fully balanced for 200 minutes. 3) Based on the CO2 pressure decay curve in the bulk phase of the sample cylinder, the diffusion coefficient and solubility of CO2 in heavy oil before correction were calculated using the established mathematical model. Figure 7 As shown.

[0075] Example 4 In this embodiment, the volume of the heavy oil sample used was 30±0.1 mL, the CO2 injection pressure was 20 MPa, and the experimental temperature was set to 200℃.

[0076] The terahertz wave testing device of this application is used to monitor the water content precipitated from heavy oil during the diffusion / dissolution of CO2 in heavy oil and to correct the CO2 diffusion coefficient and solubility. The steps are as follows: 1) Establish the relationship between the degree of water response to terahertz waves at a set pressure point; 2) Place the heavy oil sample in the sample cylinder, connect all components of the device, and place it in the constant temperature device; 3) Inject high-purity CO2 (purity ≥99.99%) into the reference cylinder. After the pressure is balanced, slowly open the needle valve connecting the reference cylinder and the sample cylinder to inject CO2 into the sample cylinder. After the pressure in the sample cylinder reaches the set value, quickly close the needle valve. Record the pressure value after the pressure in the reference cylinder and the sample cylinder is fully balanced for 200 minutes. 4) Monitor the response signal of the fluid in the sample cylinder to the terahertz wave in real time during the above CO2 diffusion / dissolution process, obtain the terahertz wave signal of the fluid in the sample cylinder through fast Fourier transform, and estimate the partial pressure and volume of water in the sample cylinder phase based on the relationship between the obtained terahertz wave signal and water content. 5) Based on the volume of water in the sample tank, correct the volume of heavy oil, the blank volume of the sample tank, and the partial pressure of CO2 in the bulk phase, and calculate the diffusion coefficient and solubility of CO2 in the heavy oil accordingly. The corrected CO2 bulk pressure change curve, diffusion coefficient, and solubility in the sample tank are shown below. Figure 8 As shown.

[0077] Comparative Example 4 The volume of the heavy oil sample used in this comparative example was 30±0.1 mL, the CO2 injection pressure was 20 MPa, and the experimental temperature was set at 200℃.

[0078] Calculations of its diffusion coefficient and solubility in heavy oil were based on the bulk CO2 pressure drop curve: 1) Place the heavy oil sample in the sample cylinder, connect all components of the device, and place it in the constant temperature device; 2) Inject high-purity CO2 (purity ≥99.99%) into the reference cylinder. After the pressure is balanced, slowly open the needle valve connecting the reference cylinder and the sample cylinder to inject CO2 into the sample cylinder. After the pressure in the sample cylinder reaches the set value, quickly close the needle valve. Record the pressure value after the pressure in the reference cylinder and the sample cylinder is fully balanced for 200 minutes. 3) Based on the CO2 pressure decay curve in the bulk phase of the sample cylinder, calculate the diffusion coefficient and solubility of CO2 in heavy oil using the established mathematical model. Figure 9 As shown.

[0079] As can be seen from the above examples and comparative examples, after correcting for the volume of heavy oil and the bulk pressure of CO2 during the diffusion / dissolution process of CO2 in heavy oil, the diffusion coefficient of CO2 in heavy oil decreases but the solubility increases. This indicates that without considering the water separation of heavy oil under high temperature conditions, the effect of CO2 on enhancing the fluidity of heavy oil cannot be accurately evaluated. Therefore, correcting for the volume change of heavy oil and the change of bulk CO2 pressure during the diffusion / dissolution process helps to more reasonably and effectively evaluate the viscosity reduction and oil recovery effects of multi-element thermal fluid composite extraction technology on heavy oil.

[0080] like Figure 10 As shown, in a third aspect of this application, a CO2 diffusion and dissolution parameter correction device is provided, the device comprising: The temperature control module is configured to control the thermostat to operate at a specified temperature when a heavy oil sample is injected into the sample cylinder. The gas injection module is configured to control the booster pump to inject CO2 gas into the reference cylinder until the pressure in the reference cylinder reaches pressure equilibrium, then control the controllable valve to open so as to inject CO2 gas into the sample cylinder through the reference cylinder until the pressure in the sample cylinder reaches the first pressure threshold, then control the controllable valve to close. The signal analysis module is configured to acquire the real-time terahertz response signal of the fluid in the sample cylinder during the diffusion / dissolution process of CO2 gas in the sample cylinder through a signal receiver, and determine the amount of water precipitated from the heavy oil sample during the diffusion / dissolution process of CO2 gas in heavy oil based on the acquired real-time terahertz response signal. The parameter correction module is configured to correct the initial diffusion coefficient and initial solubility of CO2 gas in heavy oil based on the amount of water precipitated from the heavy oil sample.

[0081] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application.

[0082] In a fourth aspect, this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, causes the processor to perform the CO2 diffusion and dissolution parameter correction method described above.

[0083] In a fifth aspect, this application provides a terminal device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor, when executing the computer program, implements the aforementioned CO2 diffusion and dissolution parameter correction method.

[0084] like Figure 10 The diagram shown is a schematic representation of a terminal device provided in an embodiment of this application. Figure 10 As shown, the terminal device 10 of this embodiment includes a processor 100, a memory 101, and a computer program 102 stored in the memory 101 and executable on the processor 100. When the processor 100 executes the computer program 102, it implements the steps in the above method embodiments. Alternatively, when the processor 100 executes the computer program 102, it implements the functions of each module / unit in the above device embodiments.

[0085] For example, computer program 102 may be divided into one or more modules / units, one or more of which are stored in memory 101 and executed by processor 100 to complete this application. One or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 102 in terminal device 10.

[0086] Terminal device 10 may be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. Terminal device 10 may include, but is not limited to, a processor 100 and a memory 101. Those skilled in the art will understand that... Figure 10 This is merely an example of terminal device 10 and does not constitute a limitation on terminal device 10. It may include more or fewer components than shown, or combine certain components, or different components. For example, terminal device may also include input / output devices, network access devices, buses, etc.

[0087] The processor 100 can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0088] The memory 101 can be an internal storage unit of the terminal device 10, such as a hard disk or RAM of the terminal device 10. The memory 101 can also be an external storage device of the terminal device 10, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or FlashCard equipped on the terminal device 10. Furthermore, the memory 101 can include both internal and external storage units of the terminal device 10. The memory 101 is used to store computer programs and other programs and data required by the terminal device 10. The memory 101 can also be used to temporarily store data that has been output or will be output.

[0089] In summary, this application addresses the calculation deviations in diffusion coefficient and solubility caused by dynamic changes in sample volume during the diffusion / dissolution of CO2 in water-containing heavy oil. Based on terahertz time-domain spectroscopy, it corrects for the volume of heavy oil and the diffusion coefficient and solubility of CO2 within it. This correction can rectify the dynamic changes in heavy oil volume caused by water leaching during the diffusion / dissolution of CO2 in heavy oil under high-temperature conditions, as well as the corresponding changes in CO2 bulk partial pressure, thereby correcting the diffusion coefficient and solubility of CO2 in heavy oil. The corrected CO2 diffusion coefficient and solubility reflect the viscosity-reducing and flow-enhancing effects of CO2, a key component of multi-component thermal fluids, on in-situ heavy oil under actual heavy oil reservoir conditions. Compared to existing technologies, the corrected CO2 diffusion coefficient and solubility obtained in this application have higher accuracy.

[0090] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0091] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0092] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A terahertz wave testing apparatus characterized by comprising: include: CO2 storage tank, reference tank, sample tank, pulsed laser emitter, beam splitter, signal delay unit, reflector, signal generator, signal receiver, first reflector and second reflector; The CO2 storage tank is connected to the reference cylinder, the reference cylinder is connected to the sample cylinder, and a controllable valve for controlling the opening and closing of the connection pipeline between the reference cylinder and the sample cylinder is also provided. The beam splitter, signal delayer, and reflector are sequentially arranged in the laser emission direction of the pulsed laser emitter. The pulsed laser emitter is used to generate an ultrashort pulse laser beam. The beam splitter is used to decompose the ultrashort pulse laser beam into a pump beam and a probe beam that are perpendicular to each other. The probe beam is delayed by the signal delayer and then reflected by the reflector to the signal receiver. The signal generator is used to generate terahertz pulse waves when excited by the pump beam. The terahertz pulse waves generated by the signal generator are injected into the sample cylinder through the first reflector and then reflected to the signal receiver through the second reflector.

2. The terahertz wave testing apparatus according to claim 1, wherein The device further includes: A booster pump installed between the CO2 storage tank and the reference cylinder is used to boost the low-pressure CO2 gas to the required working pressure. A vacuum pump is installed between the booster pump and the reference cylinder to generate a vacuum negative pressure; A first pressure sensor is used to monitor the pressure inside the reference cylinder; The second pressure sensor is used to monitor the pressure inside the sample cylinder; The controllable valve is a needle valve, the first reflector and the second reflector are both off-axis elliptical mirrors, and the reference cylinder and the sample cylinder are placed in a constant temperature device.

3. A method of CO2 diffusion and dissolution parameter correction, characterized by, The method, applied to the terahertz wave testing apparatus of claim 2, comprises: When a heavy oil sample is injected into the sample cylinder, the temperature control device is controlled to operate at a specified temperature. The booster pump is controlled to inject CO2 gas into the reference cylinder until the pressure in the reference cylinder reaches pressure equilibrium. The controllable valve is then controlled to open to inject CO2 gas into the sample cylinder through the reference cylinder until the pressure in the sample cylinder reaches a first pressure threshold. Finally, the controllable valve is controlled to close. The real-time terahertz response signal of the fluid in the sample cylinder during the diffusion / dissolution process of CO2 gas in the sample cylinder is obtained by the signal receiver, and the amount of water precipitated from the heavy oil sample during the diffusion / dissolution process of CO2 gas in the heavy oil is determined based on the obtained real-time terahertz response signal. The initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the amount of water precipitated from the heavy oil sample.

4. The method of CO2 diffusion and dissolution parameter correction of claim 3, wherein, Before injecting the heavy oil sample into the sample cylinder, the method further includes: Water vapor is injected into the sample cylinder, and the humidity inside the sample cylinder is adjusted by injecting nitrogen gas into the sample cylinder so that the humidity inside the sample cylinder is different at different sampling times; When the signal generator generates a terahertz pulse wave, the relative humidity in the sample cylinder is collected at different sampling times by a hygrometer, and the terahertz response signal of the fluid in the sample cylinder at different sampling times is obtained by the signal receiver. Based on the collected relative humidity and terahertz response signals, a first relationship curve is constructed to characterize the correspondence between different relative humidity and terahertz response signals.

5. The method of CO2 diffusion and dissolution parameter correction of claim 4, wherein, After constructing a first relationship curve representing the correspondence between humidity and terahertz signal at different times, the method further includes: Inert gas is injected into the sample cylinder until all nitrogen and water vapor in the sample cylinder are expelled; CO2 gas is injected into the reference cylinder through the CO2 storage tank, and the controllable valve is opened to inject CO2 gas into the sample cylinder through the reference cylinder until the pressure in the sample cylinder reaches a second pressure threshold; and During the process of injecting CO2 gas into the sample cylinder, the pressure inside the sample cylinder is collected at different sampling times by the second pressure sensor, and the terahertz response signal of the fluid inside the sample cylinder at different sampling times is obtained by the signal receiver. Based on the collected pressure and terahertz signals, a second relationship curve is constructed to characterize the correspondence between different CO2 gas pressures and terahertz response signals.

6. The method of CO2 diffusion and dissolution parameter correction of claim 5, wherein, Before determining the amount of water precipitated from the heavy oil sample during the diffusion / dissolution of CO2 gas in heavy oil based on the extracted terahertz response signal, the method further includes: A CO2 diffusion / dissolution model and a CO2 solubility model are constructed. The initial diffusion coefficient of CO2 gas in heavy oil is determined based on the CO2 diffusion / dissolution model, and the initial solubility of CO2 gas in heavy oil is determined based on the CO2 solubility model. The amount of water precipitated from the heavy oil sample during the diffusion / dissolution of CO2 gas in heavy oil is determined based on the extracted terahertz response signal, including: Based on the real-time terahertz response signal, the first relationship curve, and the second relationship curve, the relative humidity corresponding to the real-time terahertz response signal is determined, and the partial pressure of the water precipitated from the heavy oil sample is determined based on the relative humidity corresponding to the real-time terahertz response signal. A first relationship function is established between the partial pressure of water precipitated from the heavy oil sample and the amount of water precipitated from the heavy oil sample based on the ideal gas law, and a second relationship function is obtained between the amount of water precipitated from the heavy oil sample and the volume of water precipitated from the heavy oil sample. The amount of water precipitated from the heavy oil sample is calculated based on the first relational function and the second relational function.

7. The method of CO2 diffusion and dissolution parameter correction of claim 6, wherein, The first relational function includes: The second relational function includes: wherein, P H2O Pw is the partial pressure of water evolved from the heavy oil sample, V’ Vc is the corrected blank volume for the sample cylinder, Z H2O Cw is the coefficient of partial pressure of water evolved from the heavy oil sample, R R is the ideal gas constant, T T is the temperature, V H2O Vw is the volume of water evolved from the heavy oil sample, n H2O W is the amount of water evolved from the heavy oil sample, D is the density of water, M H2O M is the molar mass of water.

8. The method of CO2 diffusion and dissolution parameter correction of claim 7, wherein, The amount of water precipitated from the heavy oil sample is calculated based on the first relational function and the second relational function, including: The initial volume, coefficient of expansion of heavy oil, and pressure inside the sample cylinder at the current moment of the heavy oil sample injected into the sample cylinder are obtained. The volume of the heavy oil sample after expansion is determined based on the initial volume, coefficient of expansion of heavy oil, and pressure inside the sample cylinder at the current moment. The difference between the volume of the swollen heavy oil sample and the volume of water precipitated from the heavy oil sample is taken as the corrected volume of the heavy oil sample. The volume of the sample cylinder is obtained, and the blank volume of the sample cylinder after correction is determined by the difference between the volume of the sample cylinder and the corrected volume of the heavy oil sample. Based on the second relationship function, a third relationship function is determined between the blank volume of the sample cylinder after correction and the amount of water separated from the heavy oil sample, the volume of the sample cylinder, and the volume of the heavy oil sample after expansion. The amount of water precipitated from the heavy oil sample is calculated based on the first relational function and the third relational function.

9. The method of CO2 diffusion and dissolution parameter correction of claim 8, wherein, The initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the amount of water precipitated from the heavy oil sample, including: Based on the amount of water precipitated from the heavy oil sample, the volume of water precipitated from the heavy oil sample is determined according to the second relationship function; The volume fraction of CO2 gas in the sample cylinder is calculated using the following formula: wherein, y CO2 the volume fraction of CO2 gas within the sample cylinder; The pressure inside the sample cylinder at the current moment is obtained, and the product of the volume fraction of CO2 gas in the sample cylinder and the pressure inside the sample cylinder at the current moment is taken as the partial pressure of CO2 gas in the sample cylinder. The initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the partial pressure of CO2 gas in the sample cylinder and the volume of water precipitated from the heavy oil sample.

10. The method of CO2 diffusion and dissolution parameter correction of claim 9, wherein, The CO2 diffusion / dissolution model includes: wherein, β is the dilatation coefficient of the heavy oil, V 0 is the initial volume of the heavy oil sample, V C is the volume of the sample cylinder , P(t) is the initial concentration of CO2 in the heavy oil sample, t is the pressure in the sample cylinder at time t, P 0( t ) is the initial pressure in the sample cylinder at time t, D AB is the diffusion coefficient of CO2 gas in heavy oil, R is the ideal gas constant, T is the temperature, Z is the compressibility factor of CO2 gas, x eq is the equilibrium concentration at the gas-liquid interface, mol / cm 3 .

11. The method for correcting CO2 diffusion and dissolution parameters according to claim 10, characterized in that, The CO2 solubility model includes: in, P1 and P3 The values ​​are the equilibrium pressures (MPa) of CO2 in the reference cylinder before and after the controllable valve opens during the diffusion / dissolution of CO2 gas in heavy oil. P2 and P4 These are the equilibrium pressures of CO2 in the sample cylinder before and after the controllable valve is opened, respectively, in MPa; VRC and VSC The blank volumes of the reference cylinder and the sample cylinder are respectively, in m3; Z1、 Z2, Z3 and Z4 They are respectively P1 , P2 , P3 and P4 The corresponding CO2 compressibility factor, This represents the difference in the amount of CO2 gas before and after diffusion / dissolution in heavy oil. S The solubility of CO2 gas. m The mass of the heavy oil sample is expressed in grams.

12. The CO2 diffusion and dissolution parameter correction method according to claim 11, characterized in that, The initial diffusion coefficient and initial solubility of CO2 gas in heavy oil are corrected based on the partial pressure of CO2 gas in the sample cylinder and the volume of water precipitated from the heavy oil sample, including: Based on the partial pressure of CO2 gas in the sample cylinder and the volume of water precipitated from the heavy oil sample, the CO2 diffusion / dissolution model and the CO2 solubility model are modified to obtain the modified CO2 diffusion / dissolution model and the modified CO2 solubility model. The initial diffusion coefficient and initial solubility of CO2 gas in heavy oil were corrected based on the modified CO2 diffusion / dissolution model and the modified CO2 solubility model. The revised CO2 diffusion / dissolution model includes: The modified CO2 solubility model includes: in, for t The square of the partial pressure of CO2 gas in the sample cylinder at the specified time. To correct the solubility of CO2 gas, This indicates the partial pressure of CO2 gas in the sample cylinder after the controllable valve is opened.

13. A CO2 diffusion and dissolution parameter correction device, characterized in that, The device includes: The temperature control module is configured to control the thermostat to operate at a specified temperature when a heavy oil sample is injected into the sample cylinder. The gas injection module is configured to control the booster pump to inject CO2 gas into the reference cylinder until the pressure in the reference cylinder reaches pressure equilibrium, control the controllable valve to open, so as to inject CO2 gas into the sample cylinder through the reference cylinder until the pressure in the sample cylinder reaches a first pressure threshold, and control the controllable valve to close. The signal analysis module is configured to acquire the real-time terahertz response signal of the fluid in the sample cylinder during the diffusion / dissolution process of CO2 gas in the sample cylinder through the signal receiver, and determine the amount of water precipitated from the heavy oil sample during the diffusion / dissolution process of CO2 gas in heavy oil based on the acquired real-time terahertz response signal. The parameter correction module is configured to correct the initial diffusion coefficient and initial solubility of CO2 gas in heavy oil based on the amount of water precipitated from the heavy oil sample.

14. A computer-readable storage medium storing a computer program that, when executed by a processor, causes the processor to perform the CO2 diffusion and dissolution parameter correction method as described in any one of claims 3-12.

15. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the CO2 diffusion and dissolution parameter correction method according to any one of claims 3-12.

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