Device and method for measuring electrical resistance and acoustic wave of core during carbon dioxide displacement

Abstract

A device and method for measuring the electrical resistance and acoustic wave of a core during carbon dioxide displacement. The device comprises: a core holder (1), a displacement device (2), a measurement device (3), and a host computer (4), wherein the displacement device (2) is used for using formation water and supercritical carbon dioxide on the basis of a control signal from the host computer (4) to perform displacement operation on the core; the measurement device (3) is used for measuring the instantaneous produced water volume, electrical resistance, and acoustic wave signal of the core during displacement; and the host computer (4) is used for determining the internal state of the core, when the internal state of the core is a saturated and stable state, sending the control signal to the displacement device (2), and determining whether the obtained instantaneous produced water volume satisfies a preset carbon dioxide saturation condition, and when it is determined that the instantaneous produced water volume satisfies the carbon dioxide saturation condition, obtaining the corresponding electrical resistance and acoustic wave signal. The present invention implements core displacement experiments and precise measurement of parameters such as electrical resistance and acoustic waves, and provides support for using acoustic wave and resistivity logging to quantitatively calculate the supercritical carbon dioxide saturation of actual formations.

Description

A resistivity and acoustic measurement device and method for carbon dioxide-displaced rock cores

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. 202411698467.8, filed on November 25, 2024, and incorporates the entire contents of the aforementioned patent application as part of this disclosure. Technical Field

[0003] This disclosure relates to the field of rock physics technology, and in particular to a device and method for measuring the resistance and acoustic waves of carbon dioxide-displaced rock cores. Background Technology

[0004] CO2 capture, utilization, and sequestration (CCUS / CCS) technology has become an important option for ensuring energy security. Supercritical carbon dioxide (SC-CO2) sequestration in saline aquifers is a technology that captures industrially emitted carbon dioxide and injects it under high pressure into underground saline aquifers. This technology can achieve permanent underground sequestration of carbon dioxide and mitigate the greenhouse effect. During the injection process, the carbon dioxide exists in a supercritical state, with a density close to that of a liquid and a viscosity similar to that of a gas, and a diffusion coefficient nearly a hundred times that of a liquid. Due to its unique physical properties, its density changes are sensitive, and dynamic density correction is complex. In actual sequestration, predicting the distribution range, effectiveness, and sequestration volume of supercritical carbon dioxide injected into saline aquifers is difficult. There is a lack of basic and supporting experimental methods and equipment for well logging interpretation of key parameters such as CO2 saturation. Therefore, conducting rock physics experiments on supercritical carbon dioxide displacement combined with acoustic and electrical parameters, while accurately measuring carbon dioxide saturation, is particularly crucial.

[0005] Currently, research on supercritical carbon dioxide saturation in related technologies is mainly achieved through the following methods:

[0006] One method involves recreating the formation environment in a reactor, enabling the testing of P-wave and S-wave velocities in rock samples with different CO2 and water saturation levels, providing experimental evidence for monitoring the geological sequestration and migration of carbon dioxide. Another method involves accurately characterizing the complex porous media structure and rock conductivity in sandstone reservoirs to obtain the changes in saturated pore size of each phase fluid and supercritical carbon dioxide saturation, thus improving the monitoring accuracy of supercritical carbon dioxide saturation in sandstone reservoirs. A third method involves studying and measuring the relative permeability of supercritical carbon dioxide and saline water in the core.

[0007] However, existing technologies can only be used as a starting point in actual CO2 displacement experiments to study quantitative evaluation methods of supercritical carbon dioxide saturation and related content from the perspective of single parameters such as acoustic transit time or electrical properties. If more test parameters or research perspectives are added to the relevant technologies, it is likely to destroy the temperature and pressure conditions of supercritical CO2 and the in-situ formation simulation environment, resulting in unreliable measurement data and large test errors. Summary of the Invention

[0008] In view of the problems in the related technologies, the present disclosure provides a resistivity and acoustic wave measurement device for carbon dioxide displacement cores, which can at least partially solve the problems existing in the related technologies.

[0009] In a first aspect, this disclosure provides a resistivity and acoustic wave measurement device for carbon dioxide displacement cores, including: a core holder, a displacement device, a measuring device, and a host computer;

[0010] A core holder is used to hold the core to be measured;

[0011] The displacement device is connected to the core holder through the first pipe, and is used to displace the core using formation water and supercritical carbon dioxide according to the control signal from the host computer.

[0012] The measuring device is connected to the core holder through a second pipe and is used to measure the instantaneous water displacement, resistance and acoustic signal of the core during the displacement process.

[0013] The host computer connects to the displacement device and the measuring device to determine the internal state of the core. When the internal state of the core is saturated and stable, a control signal is sent to the displacement device to switch from formation water to supercritical carbon dioxide to displace the core. The host computer also determines whether the instantaneous water displacement meets the preset carbon dioxide saturation condition. When the instantaneous water displacement meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained.

[0014] Furthermore, the displacement device includes a formation water displacement device, a supercritical carbon dioxide displacement device, and a gas-liquid displacement switching valve;

[0015] The gas-liquid displacement switching valve connects the core holder, the formation water displacement device, and the supercritical carbon dioxide displacement device.

[0016] Formation water displacement devices are used to displace core samples using formation water.

[0017] The supercritical carbon dioxide displacement device is used to prepare supercritical carbon dioxide and to use supercritical carbon dioxide to displace core samples.

[0018] The host computer is connected to the gas-liquid displacement switching valve to control the switching between the formation water displacement device and the supercritical carbon dioxide displacement device.

[0019] Furthermore, the host computer includes: a data acquisition unit, a data processing unit, and a signal transmission unit;

[0020] The data acquisition unit is used to obtain the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, and the physical parameters, actual weight, and dry sample weight of the core.

[0021] The data processing unit is used to determine whether the internal state of the core is saturated and stable based on the volume of the first pipe, the volume of the second pipe, the water injection volume, the drainage volume, and the physical parameters, actual weight, and dry sample weight of the core, and outputs the judgment result to the signal transmission module.

[0022] The signal transmitting unit is used to send a control signal to the gas-liquid displacement switching valve when the judgment result is that the internal state of the core is saturated and stable, so as to switch from the formation water displacement device to the supercritical carbon dioxide displacement device.

[0023] Furthermore, the data processing unit includes:

[0024] The saturated weight calculation module is used to calculate the saturated weight of the core based on physical parameters.

[0025] The water inlet weight calculation module is used to calculate the water inlet weight based on the volume of the first pipe.

[0026] The water output weight calculation module is used to calculate the water output weight based on the volume of the second pipe.

[0027] The actual water weight calculation module is used to calculate the actual water weight of the core based on the actual weight and the dry sample weight.

[0028] The first judgment module is used to determine whether the internal state of the core is saturated and stable based on the water injection volume, drainage volume, saturated weight, influent weight, effluent weight, and actual water weight, and outputs the judgment result to the signal transmission module.

[0029] Furthermore, the data acquisition unit is also used to obtain the real-time water discharge volume;

[0030] The data processing unit also includes:

[0031] The theoretical water displacement calculation module is used to calculate the theoretical water displacement from the core based on physical parameters and preset carbon dioxide saturation.

[0032] The second judgment module is used to determine whether the core has reached carbon dioxide saturation based on the real-time water displacement, theoretical water displacement, influent weight, and effluent weight. When the core reaches carbon dioxide saturation, it sends a data acquisition request to the data acquisition unit so that the data acquisition unit can acquire the corresponding resistance and acoustic signals.

[0033] Furthermore, the measuring device includes an instantaneous outflow water measurement device, an acoustic wave acquisition device, and a resistance acquisition device;

[0034] The real-time water displacement measurement device is used to measure the real-time water displacement from the core sample.

[0035] Acoustic wave acquisition devices are used to acquire acoustic wave signals from rock cores;

[0036] The resistance acquisition device is used to measure the resistance of rock cores.

[0037] Furthermore, the instantaneous water discharge measurement device includes a high-precision electronic balance and a graduated cylinder;

[0038] The acoustic wave acquisition device includes a signal transmitter and an acoustic oscilloscope.

[0039] Furthermore, the core holder has plugs at both ends, and the inner end of the plugs is equipped with electrodes, shear wave transducers and longitudinal wave transducers.

[0040] Furthermore, it also includes: a confining pressure device;

[0041] The confining pressure device is connected to the core holder and is used to apply environmental pressure to the core.

[0042] Furthermore, the supercritical carbon dioxide displacement device includes: a carbon dioxide gas tank, a cryogenic circulator, a liquid constant pressure pump, and a gas heating storage tank;

[0043] The cryogenic circulator is connected to a carbon dioxide tank to liquefy the carbon dioxide in the tank.

[0044] A liquid constant pressure pump is connected to a cryogenic circulator to pressurize liquefied carbon dioxide to a preset pressure;

[0045] A gas heating storage tank is connected to a liquid constant pressure pump to heat the pressurized carbon dioxide to a preset temperature in order to prepare supercritical carbon dioxide.

[0046] Secondly, this disclosure provides a method for measuring the resistivity and acoustic wave properties of carbon dioxide-displaced core samples, applicable to the resistivity and acoustic wave measurement apparatus for carbon dioxide-displaced core samples in any of the above embodiments, comprising:

[0047] The displacement device uses formation water to displace the core sample;

[0048] The host computer determines the internal state of the core. When the internal state of the core is saturated and stable, it sends a control signal to the displacement device.

[0049] The displacement device switches from formation water to supercritical carbon dioxide to displace the core according to the control signal.

[0050] The measuring device measures the instantaneous water displacement, electrical resistance, and acoustic signal of the core during the displacement process;

[0051] The host computer determines whether the acquired instantaneous water discharge volume meets the preset carbon dioxide saturation condition. When it is determined that the instantaneous water discharge volume meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained.

[0052] Furthermore, the displacement device includes a formation water displacement device, a supercritical carbon dioxide displacement device, and a gas-liquid displacement switching valve; the host computer determines the internal state of the core, and when the internal state of the core is saturated and stable, it sends control signals to the displacement device, including:

[0053] The host computer obtains the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, and the physical parameters, actual weight, and dry sample weight of the core.

[0054] The host computer determines whether the internal state of the core is saturated and stable based on the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, the physical parameters of the core, the actual weight, and the dry sample weight.

[0055] When the judgment result is that the internal state of the core is saturated and stable, the host computer sends a control signal to the gas-liquid displacement switching valve to switch from the formation water displacement device to the supercritical carbon dioxide displacement device.

[0056] Furthermore, the host computer determines whether the internal state of the core is saturated and stable based on the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, and the physical parameters, actual weight, and dry sample weight of the core, including:

[0057] The host computer calculates the saturated weight of the core sample based on physical parameters;

[0058] The host computer calculates the weight of the incoming water based on the volume of the first pipe;

[0059] The host computer calculates the weight of the water based on the volume of the second pipe;

[0060] The host computer calculates the actual water weight of the core based on the actual weight and the dry sample weight.

[0061] The host computer determines whether the internal state of the core is saturated and stable based on the water injection volume, drainage volume, weight in saturated state, weight of water entering, weight of water exiting, and actual water weight.

[0062] Furthermore, the host computer determines whether the acquired instantaneous outflow of water meets the preset carbon dioxide saturation condition. When it is determined that the instantaneous outflow of water meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained, including:

[0063] The host computer calculates the theoretical water displacement from the core based on physical parameters and preset carbon dioxide saturation.

[0064] The host computer determines whether the core has reached carbon dioxide saturation based on the real-time water discharge volume, theoretical water discharge volume, influent weight, and effluent weight. When the core reaches carbon dioxide saturation, the corresponding resistance and acoustic signals are acquired.

[0065] The resistivity and acoustic wave measurement device and method for carbon dioxide displacement cores disclosed herein comprises a core holder, a displacement device, a measuring device, and a host computer. The core holder is used to hold the core to be measured. The displacement device is connected to the core holder via a first pipe and is used to perform displacement operations on the core using formation water and supercritical carbon dioxide according to control signals from the host computer. The measuring device is connected to the core holder via a second pipe and is used to measure the instantaneous water displacement, resistivity, and acoustic wave signals of the core during the displacement process. The host computer is connected to the displacement device and the measuring device to determine the internal state of the core. When the internal state of the core is saturated... When the conditions are stable, a control signal is sent to the displacement device to switch from formation water to supercritical carbon dioxide to displace the core. The system then determines whether the instantaneous water displacement meets the preset carbon dioxide saturation condition. When the instantaneous water displacement meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained. This allows for precise measurement of parameters such as resistance and acoustic waves while conducting rock displacement experiments under the simulated in-situ formation environment and supercritical CO2 temperature and pressure conditions. This provides support for quantitatively calculating the supercritical carbon dioxide saturation of actual formations using acoustic and resistivity logging. During the displacement process, only two phases of fluid—supercritical carbon dioxide and formation water—exist within the rock pores. Utilizing the negligible compressibility, unchanged state, and stable phase of formation water, the saturation of supercritical carbon dioxide within the rock pores can be inferred, providing a basis for the quantitative relationship between resistivity, acoustic velocity data, and CO2 saturation. Attached Figure Description

[0066] To more clearly illustrate the technical solutions in the embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0067] Figure 1 is a schematic diagram of the structure of a resistivity and acoustic wave measurement device for carbon dioxide displacement cores provided in an embodiment of this disclosure;

[0068] Figure 2 is a schematic diagram of the structure of a resistivity and acoustic wave measurement device for carbon dioxide displacement cores provided in an embodiment of this disclosure;

[0069] Figure 3 is a schematic diagram of the structure of a host computer provided in an embodiment of this disclosure;

[0070] Figure 4 is a schematic diagram of the structure of a host computer provided in an embodiment of this disclosure;

[0071] Figure 5 is a schematic diagram of the measurement range of inlet water weight and outlet water weight provided in an embodiment of this disclosure;

[0072] Figure 6 is a schematic diagram of the structure of a host computer provided in an embodiment of this disclosure;

[0073] Figure 7 is a graph showing the relationship between the supercritical carbon dioxide displacement time and the resistivity and water content in the acoustic measurement device of the carbon dioxide-displaced core provided in an embodiment of this disclosure.

[0074] Figure 8 is a schematic diagram of acoustic waveforms collected under different supercritical carbon dioxide saturation conditions according to an embodiment of this disclosure;

[0075] Figure 9 is a schematic diagram of the structure of the plug of a core holder provided in an embodiment of this disclosure;

[0076] Figure 10 is a cross-sectional schematic diagram of the inner end of the plug of a core holder provided in an embodiment of the present disclosure;

[0077] Figure 11 is a flowchart illustrating a method for measuring the resistivity and acoustic wave of a carbon dioxide-displaced core according to an embodiment of this disclosure.

[0078] Figure 12 is a schematic flowchart of a method for measuring the resistivity and acoustic wave of a carbon dioxide-displaced core according to an embodiment of the present disclosure.

[0079] Figure 13 is a flowchart illustrating a method for measuring the resistivity and acoustic wave of a carbon dioxide-displaced core according to an embodiment of this disclosure.

[0080] Figure 14 is a schematic flowchart of a method for measuring the electrical resistance and acoustic wave of a carbon dioxide-displaced core according to an embodiment of this disclosure. Detailed Implementation

[0081] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and their descriptions are used to explain this disclosure, but are not intended to limit this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be arbitrarily combined with each other.

[0082] Figure 1 is a schematic diagram of the structure of a carbon dioxide displacement core resistance and acoustic wave measurement device provided in an embodiment of the present disclosure. As shown in Figure 1, the carbon dioxide displacement core resistance and acoustic wave measurement device provided in the present disclosure includes: a core holder 1, a displacement device 2, a measuring device 3, and a host computer 4.

[0083] Core holder 1 is used to hold the core to be measured;

[0084] Displacement device 2 is connected to core holder 1 through first pipe 5, and is used to displace core using formation water and supercritical carbon dioxide according to control signal from host computer 4.

[0085] The measuring device 3 is connected to the core holder 1 through the second pipe 6, and is used to measure the instantaneous water displacement, resistance and acoustic signal of the core during the displacement process.

[0086] The host computer 4 is connected to the displacement device 2 and the measuring device 3 to determine the internal state of the core. When the internal state of the core is saturated and stable, a control signal is sent to the displacement device 2 to switch the displacement device 2 from formation water to supercritical carbon dioxide to displace the core. The host computer 4 also determines whether the instantaneous water displacement meets the preset carbon dioxide saturation condition. When the instantaneous water displacement meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained.

[0087] Specifically, the core holder 1 is used to securely hold the core to be measured, ensuring that the core does not shift or deform during the entire displacement experiment. The displacement device 2 first uses formation water to displace the core, and then switches to supercritical carbon dioxide to displace the core according to the control signal from the host computer 4. The measuring device 3 has high sensitivity, ensuring the accuracy and reliability of the measurement data. The host computer 4, as the core control unit of the resistivity and acoustic wave measurement device for carbon dioxide displacement of the core, is responsible for coordinating the operation of the displacement device 2 and the measuring device 3, ensuring the flexibility and repeatability of the experimental operation. It adjusts the operation of the displacement device 2 by sending control signals and receives real-time displaced water volume, resistance, and acoustic wave signals from the measuring device 3. When the real-time displaced water volume meets the preset carbon dioxide saturation condition, the host computer 4 records and analyzes the corresponding resistance and acoustic wave signals.

[0088] Figure 2 is a schematic diagram of the structure of a resistivity and acoustic wave measurement device for carbon dioxide displacement core provided in an embodiment of the present disclosure. As shown in Figure 2, the displacement device 2 provided in the present disclosure includes a formation water displacement device 21, a supercritical carbon dioxide displacement device 22, and a gas-liquid displacement switching valve 23.

[0089] The gas-liquid displacement switching valve 23 connects to the core holder 1, the formation water displacement device 21, and the supercritical carbon dioxide displacement device 22.

[0090] Formation water displacement device 21 is used to displace core samples using formation water;

[0091] Specifically, the displacement device 2 is designed to efficiently displace the core sample using different media. It mainly consists of a formation water displacement device 21, a supercritical carbon dioxide displacement device 22, and a gas-liquid displacement switching valve 23, enabling flexible displacement strategies. The formation water displacement device 21 utilizes formation water to displace the core sample, ensuring stability and efficiency during the displacement process. During displacement, the rock sample is first evacuated to remove air, and then pressurized formation water is injected to ensure the pores inside the core are completely filled with liquid. The purpose of this process is to achieve complete saturation of the core sample.

[0092] In one embodiment, the formation water displacement device 21 is a liquid constant pressure pump.

[0093] The supercritical carbon dioxide displacement device 22 is used to prepare supercritical carbon dioxide and use supercritical carbon dioxide to displace the core.

[0094] Specifically, the supercritical carbon dioxide displacement device 22 is responsible for preparing and supplying supercritical carbon dioxide to achieve core displacement operations and ensure the safety and stability of the supercritical operation process. By controlling the temperature and pressure of the supercritical carbon dioxide to reach a supercritical state, its superior solubility and flow characteristics are utilized to effectively displace the core.

[0095] The host computer 4 is connected to the gas-liquid displacement switching valve 23, which is used to control the switching between the gas-liquid displacement switching valve 23 and the formation water displacement device 21 and the supercritical carbon dioxide displacement device 22.

[0096] Specifically, the gas-liquid displacement switching valve 23, as a key component connecting the core holder 1, the formation water displacement device 21, and the supercritical carbon dioxide displacement device 22, features rapid switching and strong sealing performance, preventing impact on the core. This valve, controlled by the host computer 4, enables rapid switching between formation water and supercritical carbon dioxide to meet displacement requirements under different experimental conditions. The host computer 4 is connected to the gas-liquid displacement switching valve 23 and is responsible for real-time monitoring and control of the entire displacement process. By sending control signals, the host computer 4 can flexibly adjust the switching of the displacement medium to ensure the smooth progress of the experiment. In some embodiments, the host computer 4 can be an industrial computer or an embedded system, or other computer system with data acquisition and control functions.

[0097] Figure 3 is a schematic diagram of the structure of the host computer 4 provided in an embodiment of the present disclosure. As shown in Figure 3, the host computer 4 provided in the present disclosure includes: a data acquisition unit 41, a data processing unit 42, and a signal transmission unit 43.

[0098] The data acquisition unit 41 is used to acquire the volume of the first pipe 5, the volume of the second pipe 6, the water injection volume, the drainage volume, and the physical parameters, actual weight, and dry sample weight of the core.

[0099] Specifically, the data acquisition unit 41 is responsible for acquiring multiple key parameters in real time, including the volume, injection volume, and drainage volume of the first pipe 5 and the second pipe 6, as well as the physical parameters, actual weight, and dry sample weight of the core sample. The physical parameters of the core sample include length, diameter, and porosity. This unit ensures the accuracy and timeliness of the data, providing a reliable foundation for subsequent data processing.

[0100] The data processing unit 42 is used to determine whether the internal state of the core is saturated and stable based on the volume of the first pipe 5, the volume of the second pipe 6, the water injection volume, the drainage volume, and the physical parameters, actual weight, and dry sample weight of the core, and outputs the judgment result to the signal transmission module.

[0101] Specifically, the data processing unit 42 comprehensively analyzes the data from the data acquisition unit 41 to determine the stability of the core's internal state. Using a pre-defined algorithm, this unit compares the actual weight with the dry sample weight, and, considering the trends in water injection and drainage, assesses whether the core's moisture distribution and physical properties have reached a stable state. The judgment result is output to the signal transmission module via an interface to facilitate subsequent control operations.

[0102] The signal sending unit 43 is used to send a control signal to the gas-liquid displacement switching valve 23 when the judgment result is that the internal state of the rock core is saturated and stable, so as to switch from the formation water displacement device 21 to the supercritical carbon dioxide displacement device 22.

[0103] Specifically, after receiving the judgment result from the data processing unit 42, the signal transmitting unit 43 is responsible for sending control signals. When the judgment result indicates that the internal state of the core is stable, the signal transmitting unit 43 sends a command to the gas-liquid displacement switching valve 23, prompting it to quickly switch from the formation water displacement device 21 to the supercritical carbon dioxide displacement device 22. The automated design of this process improves the response speed and ensures the accuracy and efficiency of the displacement operation.

[0104] Figure 4 is a schematic diagram of the structure of the host computer 4 provided in an embodiment of the present disclosure. As shown in Figure 4, the data processing unit 42 provided in the present disclosure includes:

[0105] The saturated weight calculation module 421 is used to calculate the saturated weight of the core based on physical parameters.

[0106] Specifically, the physical parameters of the core include length, diameter, and porosity. The saturated weight calculation module 421 calculates the weight of water G required for the core to reach a saturated state using the following formula. 饱 G 饱 =V 孔 ×ρ 水 (1)

[0107] In the formula, V 孔 It is the pore volume of the rock core, ρ 水 It is the density of the groundwater.

[0108] The saturated state weight calculation module 421 first calculates the total volume V of the core using the following formula. 总 :

[0109] In the formula, d is the diameter of the core and h is the length of the core.

[0110] The total volume V of the core was obtained. 总 Subsequently, the saturated weight calculation module 421 calculates the pore volume V of the core using the following formula. 孔 V 孔 =V 总 ×Porosity(3)

[0111] In one embodiment, the core length h is 4.00 cm, the core diameter d is 2.50 cm, the porosity is 10%, and the formation water density ρ is... 水 It is 1.01 g / cm³ 3 The weight of water G required for the core to reach a saturated state is calculated according to equations (1)-(3). 饱 =1.98g.

[0112] The water inlet weight calculation module 422 is used to calculate the water inlet weight based on the volume of the first pipe 5;

[0113] Specifically, the water inlet weight calculation module 422 calculates the water inlet weight G of the core sample when the inlet end (first pipe 5) is filled with water based on the volume of the first pipe 5 and the formation water density. 入 G 入 =V 入 ×ρ 水 (4)

[0114] In the formula, V 入 It is the volume of the first pipe 5, ρ 水 It is the density of the formation water.

[0115] In one embodiment, as shown in Figure 5, the first pipe 5 is divided into two sections, and the weight of water G when the two sections of the pipe are filled with water is calculated respectively. 入1 and G 入2 To obtain the weight G of the water inlet 入 .

[0116] In one embodiment, the volume V of the first pipe 5 入 =0.99cm 3 Formation water density ρ 水 It is 1.01 g / cm³ 3 The calculated G 入 = 1g.

[0117] The water weight calculation module 423 is used to calculate the water weight based on the volume of the second pipe 6;

[0118] Specifically, the outflow weight calculation module 423 calculates the outflow weight G of the core sample when the outlet end (second pipe 6) is filled with water, based on the volume of the second pipe 6 and the formation water density. 出 G 出 =V 出 ×ρ 水 (5)

[0119] In the formula, V 出 ρ is the volume of the two pipes. 水 It is the density of the formation water.

[0120] In one embodiment, as shown in Figure 5, the second pipe 6 is divided into two sections, and the weight of water G when the two sections of the pipe are filled with water is calculated respectively. 出1 and G 出2 To obtain the weight of the discharged water G 出 .

[0121] In one embodiment, the volume V of the second pipe 6 出 =1.04cm 3 Formation water density ρ 水 It is 1.01 g / cm³ 3 The calculated G 出 =1.05g.

[0122] The actual water weight calculation module 424 is used to calculate the actual water weight of the core based on the actual weight and the dry sample weight.

[0123] Specifically, the actual water weight calculation module 424 calculates the actual water weight G of the core by subtracting the dry sample weight of the core from the actual weight of the core after it has been displaced by formation water. 实 .

[0124] The first judgment module 425 is used to determine whether the internal state of the core is saturated and stable based on the water injection volume, drainage volume, saturated weight, influent weight, effluent weight, and actual water weight, and outputs the judgment result to the signal transmission module.

[0125] Specifically, the saturated core is placed into the core holder 1 and heated to the required formation temperature to simulate actual formation conditions, and further pressurized using the formation water displacement device 21. The outlet valve on the second pipeline 6 is opened, and when a uniform water flow appears at the outlet of the second pipeline 6, the first judgment module 425 obtains the injection volume G. 注 Displacement G 排 And determine the water injection volume G 注 Displacement G 排 Weight in saturated state (G) 饱 Weight in water (G) 入 Water output weight G 出 and actual water weight G 实 Does it satisfy the following formula: G 饱 -G 实 =G 注 -G 排 -G 入 -G 出 (6)

[0126] If equation (6) is satisfied, it ensures that the core and the gaps in the pipe are filled with water and that the internal state of the core is stable. The judgment result is then output to the signal sending module.

[0127] Figure 6 is a schematic diagram of the structure of the host computer 4 provided in an embodiment of the present disclosure. As shown in Figure 6, the data processing unit 42 provided in the present disclosure further includes:

[0128] Theoretical water displacement calculation module 426 is used to calculate the theoretical water displacement of the core based on physical parameters and preset carbon dioxide saturation.

[0129] Specifically, during the displacement experiment, the pore volume inside the core is fixed, and the state and phase of the water within the pores are stable. Therefore, the volume of water displaced from the core pores by supercritical carbon dioxide is also the volume of the core pores occupied by carbon dioxide, from which the carbon dioxide saturation can be calculated. The theoretical water displacement calculation module 426 calculates the theoretical water displacement from the core using the following formula:

[0130] In the formula, V 孔 It is the pore volume of the rock core, S CO2 It is the saturation level of supercritical carbon dioxide, ρ. 水 This refers to the density of formation water. The theoretical water displacement calculation module 426 first uses the following formula to calculate the total volume V of the core. 总:

[0131] In the formula, d is the diameter of the core and h is the length of the core.

[0132] The total volume V of the core was obtained. 总 Subsequently, the theoretical water displacement calculation module 426 calculates the pore volume V of the core using the following formula. 孔 V 孔 =V 总 ×Porosity(3)

[0133] In one embodiment, the core length h is 4.00 cm, the core diameter d is 2.50 cm, the porosity is 10%, and the formation water density ρ is... 水 It is 1.01 g / cm³ 3 Supercritical carbon dioxide saturation S CO2 The theoretical weight of water displaced from the core is calculated based on equations (2), (3), and (7), which is 50%.

[0134] The second judgment module 427 is used to determine whether the core has reached carbon dioxide saturation based on the real-time water discharge volume, theoretical water discharge volume, influent weight and effluent weight. When the core reaches carbon dioxide saturation, it sends a data acquisition request to the data acquisition unit 41 so that the data acquisition unit 41 can acquire the corresponding resistance and acoustic signals.

[0135] Specifically, the data acquisition unit 41 is also used to obtain the real-time displaced water volume. As shown in Figure 7, when supercritical carbon dioxide displaces saturated core, it is easy to break through to the end of the core, causing G... 入 With G 出 The water is first displaced, and then gradually displaced from other pores within the core. Therefore, in the calculation, the instantaneous water displacement volume G is... 即时 First, deduct the weight of the water entering the water, G. 入 With water weight G 出 The second judgment module 427 judges the instantaneous discharge water volume G. 即时 Theoretical water displacement Weight in water (G) 入 and output water weight G 出 Does it satisfy the following formula:

[0136]

[0137] By presetting the supercritical carbon dioxide saturation S CO2 And calculate the theoretical water displacement. And determine G 即时 Does it meet the corresponding theoretical water displacement volume? To determine whether the core sample has reached the preset carbon dioxide saturation level.

[0138] When the core sample reaches a preset carbon dioxide saturation level, the second judgment module 427 sends a data acquisition request to the data acquisition unit 41 so that the data acquisition unit 41 can acquire and record the corresponding resistance and acoustic signals. The above process is repeated for each saturation point to obtain the corresponding resistance and acoustic signals.

[0139] In one embodiment, the real-time supercritical carbon dioxide saturation is calculated according to the following formula obtained from equation (8):

[0140] In one embodiment, G 入 =1g, G 出 =1.05g, preset supercritical carbon dioxide saturation S CO If it is 50%, then the theoretical weight of water displaced is... When G 即时 When the carbon dioxide saturation of the core reaches 50% at 3.04g, the corresponding longitudinal wave velocity is 2800m / s, the transverse wave velocity is 1790m / s, and the resistance is 8KΩ. The calculated resistivity is 60Ω·m.

[0141] In one embodiment, when S CO2 Table 1 shows the corresponding resistance, resistivity, longitudinal wave velocity, and transverse wave velocity for 0%, 25%, 50%, and 75% respectively.

[0142] Table 1

[0143] In one embodiment, when S CO2 The corresponding acoustic waveforms for 0%, 25%, 50%, and 75% are shown in Figure 8.

[0144] In one embodiment, as shown in FIG2, the measuring device 3 includes an instantaneous water discharge measuring device 31, an acoustic wave acquisition device 33, and a resistance acquisition device 32.

[0145] The real-time water displacement measuring device 31 is used to measure the real-time water displacement from the core.

[0146] Specifically, the real-time water displacement measurement device 31 measures the real-time water displacement generated by the core during the displacement process, ensuring accurate recording of water volume changes. This device collects the water discharged from the core through the second pipe 6. The real-time water displacement data is transmitted to the host computer 4 via a data interface for real-time data analysis.

[0147] The acoustic wave acquisition device 33 is used to acquire acoustic wave signals from the rock core;

[0148] Specifically, the acoustic wave acquisition device 33 is connected to both ends of the core holder 1 via wires to detect changes in acoustic wave signals during the displacement process of the core. It can collect acoustic wave signals caused by changes in the internal structure and pores of the core. The acquired acoustic wave signals are digitally processed and transmitted to the host computer 4 for analysis, providing data support for obtaining the quantitative relationship between acoustic wave velocity data and CO2 saturation.

[0149] The resistance acquisition device 32 is used to measure the resistance of the rock core.

[0150] Specifically, the resistance acquisition device 32 is connected to both ends of the core holder 1 via wires to measure the resistance changes generated in the core during displacement. This device constructs a closed circuit by placing electrodes at both ends of the core to accurately measure its resistance value. Resistance changes are typically related to water distribution and porosity changes within the core; therefore, resistance data can help researchers assess changes in core fluid saturation during displacement.

[0151] In one embodiment, the resistance acquisition device 32 is a resistance tester, which needs to be preheated for 30 minutes before use.

[0152] In one embodiment, the resistance acquisition device 32 is equipped with a signal amplifier and a filter circuit to ensure signal clarity and measurement accuracy.

[0153] In one embodiment, the instantaneous water discharge measurement device 31 includes a high-precision electronic balance and a measuring cylinder;

[0154] The acoustic wave acquisition device 33 includes a signal transmitter and an acoustic oscilloscope.

[0155] Specifically, the real-time water displacement measurement device 31 consists of a high-precision electronic balance and a graduated cylinder, used to accurately measure the amount of water displaced from the core during the displacement process. The device works by measuring the mass change of the water using the electronic balance and recording the volume change of the water using the graduated cylinder, thereby improving measurement accuracy.

[0156] This high-precision electronic balance is used to weigh the amount of water discharged in real time. It has micro-measurement capabilities with an accuracy down to the milligram level. The balance connects to a host computer (4) to transmit the results of each weighing. The electronic balance also features an automatic calibration function to ensure high accuracy during long-term operation.

[0157] The acoustic acquisition device 33, used to acquire acoustic signals during the core displacement process, consists of a signal transmitter and an acoustic oscilloscope. The signal transmitter emits high-frequency ultrasonic waves into the core to ensure penetration and a corresponding acoustic response to the core's internal structure. The transmitter is equipped with adjustment functions to modify the acoustic frequency and intensity to suit different core characteristics. The acoustic oscilloscope receives the acoustic signals reflected or transmitted from the core and converts them into visualized waveforms. The oscilloscope has high sensitivity, enabling it to capture minute changes in the acoustic signal in real time.

[0158] Figure 9 is a schematic diagram of the structure of the plug of the core holder 1 provided in an embodiment of the present disclosure. The core holder 1 has plugs at both ends as shown in Figure 9. The inner end of the plug is provided with an electrode, a transverse wave transducer and a longitudinal wave transducer.

[0159] The core holder 1 has plugs at both ends to seal the core and transmit various signals. The plugs include insulating plugs and insulating rings, possessing high precision and pressure resistance, effectively isolating external interference under high pressure while maintaining a stable grip on the core. As shown in Figure 10, the inner end of the plug is equipped with electrodes, a transverse wave transducer, and a longitudinal wave transducer to achieve resistance measurement and acoustic signal detection.

[0160] The electrode is located at the inner end of the plug and is mainly used to measure the resistivity change of the rock core. The electrode is made of a corrosion-resistant alloy material to ensure stable contact with the rock core for extended periods during displacement experiments. The electrode is connected to the resistance acquisition device 32 via a resistance clamp and connecting wires, transmitting resistance data in real time to ensure the accuracy and stability of the resistance measurement.

[0161] The transverse wave transducer (S-wave transducer) is responsible for transmitting transverse waves into the core and receiving reflected signals, while the longitudinal wave transducer (P-wave transducer) is used to transmit and receive longitudinal wave signals.

[0162] The acoustic wave acquisition device 33 is connected to the transverse wave transducers of the plugs at both ends of the core holder 1 via two wires, and to the longitudinal wave transducers of the plugs at both ends of the core holder 1 via two other wires. The resistance acquisition device 32 is connected to the electrodes of the plugs at both ends of the core holder 1 via two sets of resistance clamps and wires.

[0163] In one embodiment, as shown in FIG2, the resistivity and acoustic wave measurement device for carbon dioxide displacement cores provided in this disclosure further includes: a confining pressure device 7.

[0164] The confining pressure device 7 is connected to the core holder 1 and is used to apply environmental pressure to the core.

[0165] Specifically, the confining pressure device 7 is a device used to apply environmental pressure to the core, ensuring that the core can be tested under conditions close to actual formation conditions during the experiment. This device applies uniform confining pressure to the surface of the core by connecting to the core holder 1, and then sequentially increases the pressure of the confining pressure device 7 and the formation water displacement device 21 until the simulated formation environmental pressure is reached, thereby obtaining more accurate experimental results.

[0166] In one embodiment, researchers can adjust the confining pressure according to experimental needs through a host computer 4 or manual operation, ensuring stable pressure application within a set range.

[0167] In one embodiment, the confining pressure device 7 is a liquid constant pressure pump.

[0168] In one embodiment, as shown in FIG2, the supercritical carbon dioxide displacement device 22 includes: a carbon dioxide gas tank 221, a cryogenic circulator 222, a liquid constant pressure pump 223, and a gas heating storage tank 224.

[0169] Specifically, the supercritical carbon dioxide displacement device 22 is used to prepare and supply supercritical carbon dioxide for use in core displacement experiments. Its main components include a carbon dioxide tank 221, a cryogenic circulator 222, a liquid constant-pressure pump 223, and a gas heating storage tank 224. These parts work closely together to achieve efficient carbon dioxide processing. The carbon dioxide tank 221 stores high-purity carbon dioxide gas, ensuring safety and pressure resistance.

[0170] The cryogenic circulator 222 is connected to the carbon dioxide tank 221 and is used to liquefy the carbon dioxide in the carbon dioxide tank 221.

[0171] Specifically, the cryogenic circulator 222 is connected to the carbon dioxide tank 221 and is responsible for cooling and liquefying gaseous carbon dioxide. The cryogenic circulator 222 works by circulating a coolant to lower the gaseous carbon dioxide to its liquefaction temperature, ensuring that the carbon dioxide is stored in a liquid state for further processing. The cryogenic circulator 222 has a highly efficient heat exchange capacity to accelerate the liquefaction process and improve overall efficiency.

[0172] The liquid constant pressure pump 223 is connected to the cryogenic circulator 222 and is used to pressurize the liquefied carbon dioxide to a preset pressure.

[0173] Specifically, the liquid constant pressure pump 223 is used to pressurize liquefied carbon dioxide to a preset pressure value. This liquid constant pressure pump 223 ensures stable operation under high pressure conditions of liquid carbon dioxide, preventing gasification. The pump's built-in pressure sensor can monitor liquid pressure changes in real time, ensuring the stability and safety of the pressurization process.

[0174] In one embodiment, the liquid constant pressure pump 223 pressurizes the liquefied carbon dioxide to a pressure greater than a preset pressure of 7.39 MPa.

[0175] The gas heating storage tank 224 is connected to the liquid constant pressure pump 223, which is used to heat the pressurized carbon dioxide to a preset temperature in order to prepare supercritical carbon dioxide.

[0176] Specifically, the gas heating storage tank 224 is connected to the liquid constant pressure pump 223, which is responsible for heating the pressurized liquid carbon dioxide to the temperature required for supercritical state. The storage tank is equipped with heating elements and temperature sensors, enabling precise control of the heating process. By adjusting the heating power and time, the preparation of supercritical carbon dioxide can be effectively achieved.

[0177] In one embodiment, the gas heating storage tank 224 heats the pressurized carbon dioxide to a temperature greater than a preset temperature of 31.06°C.

[0178] This disclosure provides a resistivity and acoustic wave measurement device for carbon dioxide displacement core samples, comprising a core holder, a displacement device, a measuring device, and a host computer. The core holder is used to hold the core sample to be measured. The displacement device is connected to the core holder via a first pipe and is used to perform displacement operations on the core sample using formation water and supercritical carbon dioxide according to control signals from the host computer. The measuring device is connected to the core holder via a second pipe and is used to measure the instantaneous water displacement, resistivity, and acoustic wave signals of the core sample during the displacement process. The host computer is connected to the displacement device and the measuring device to determine the internal state of the core sample. When the internal state of the core sample is saturated... When the conditions are stable, a control signal is sent to the displacement device to switch from formation water to supercritical carbon dioxide to displace the core. The system then determines whether the instantaneous water displacement meets the preset carbon dioxide saturation condition. When the instantaneous water displacement meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained. This allows for precise measurement of parameters such as resistance and acoustic waves while conducting rock displacement experiments under the simulated in-situ formation environment and supercritical CO2 temperature and pressure conditions. This provides support for quantitatively calculating the supercritical carbon dioxide saturation of actual formations using acoustic and resistivity logging. During the displacement process, only two phases of fluid—supercritical carbon dioxide and formation water—exist within the rock pores. Utilizing the negligible compressibility, unchanged state, and stable phase of formation water, the saturation of supercritical carbon dioxide within the rock pores can be inferred, providing a basis for the quantitative relationship between resistivity, acoustic velocity data, and CO2 saturation.

[0179] In addition, this disclosure also provides a method for measuring the resistance and acoustic waves of carbon dioxide-displaced cores, which completes the measurement of the resistance and acoustic waves of carbon dioxide-displaced cores by using the resistance and acoustic wave measuring device of carbon dioxide-displaced cores described in the above embodiments.

[0180] Figure 11 is a flowchart illustrating a method for measuring the resistivity and acoustic waves of a carbon dioxide-displaced core according to an embodiment of this disclosure. As shown in Figure 11, the method for measuring the resistivity and acoustic waves of a carbon dioxide-displaced core according to this disclosure includes:

[0181] S1101: Displacement device uses formation water to displace the core sample;

[0182] S1102: The host computer determines the internal state of the core. When the internal state of the core is saturated and stable, it sends a control signal to the displacement device.

[0183] S1103: The displacement device switches from formation water to supercritical carbon dioxide to displace the core according to the control signal;

[0184] Specifically, the core holder is used to securely hold the core sample to be measured, ensuring that the core does not shift or deform during the entire displacement experiment. The displacement device first uses formation water to displace the core, and then switches to supercritical carbon dioxide to displace the core according to the control signal from the host computer. The measuring device has high sensitivity, ensuring the accuracy and reliability of the measurement data.

[0185] S1104: The measuring device measures the instantaneous water displacement, resistance, and acoustic signal of the core during the displacement process;

[0186] S1105: The host computer determines whether the acquired instantaneous water discharge volume meets the preset carbon dioxide saturation condition. When it is determined that the instantaneous water discharge volume meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained.

[0187] Specifically, the host computer, as the core control unit of the resistivity and acoustic wave measurement device for carbon dioxide displacement cores, is responsible for coordinating the operation of the displacement device and the measurement device, ensuring the flexibility and repeatability of the experimental operation. It adjusts the operation of the displacement device by sending control signals and receives real-time displaced water volume, resistance, and acoustic wave signals from the measurement device. When the real-time displaced water volume meets the preset carbon dioxide saturation condition, the host computer records and analyzes the corresponding resistance and acoustic wave signals.

[0188] Figure 12 is a flowchart illustrating a method for measuring the resistivity and acoustic wave of a carbon dioxide-displaced core according to an embodiment of this disclosure. As shown in Figure 12, step S1102 includes:

[0189] S1201: The host computer obtains the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, and the physical parameters, actual weight, and dry sample weight of the core sample.

[0190] Specifically, the host computer is responsible for acquiring multiple key parameters in real time, including the volume, injection volume, and drainage volume of the first and second pipes, as well as the physical parameters, actual weight, and dry weight of the core sample. The physical parameters of the core sample include length, diameter, and porosity. The host computer ensures the accuracy and timeliness of the data, providing a reliable foundation for subsequent data processing.

[0191] S1202: The host computer determines whether the internal state of the core is saturated and stable based on the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, and the physical parameters, actual weight, and dry sample weight of the core.

[0192] Specifically, the host computer comprehensively analyzes the acquired data to determine the stability of the core's internal state. Using a pre-defined algorithm, it compares the actual weight with the dry sample weight, and considers the trends in water injection and drainage to assess whether the core's moisture distribution and physical properties have reached a stable state. The judgment result is output to the signal transmission module via an interface to ensure smooth subsequent control operations.

[0193] S1203: When the judgment result is that the internal state of the core is saturated and stable, the host computer sends a control signal to the gas-liquid displacement switching valve to switch from the formation water displacement device to the supercritical carbon dioxide displacement device.

[0194] Specifically, when the assessment indicates that the internal state of the core is stable, the host computer sends a command to the gas-liquid displacement switching valve, prompting it to quickly switch from the formation water displacement device to the supercritical carbon dioxide displacement device. This automated design improves response speed and ensures the accuracy and efficiency of the displacement operation.

[0195] Figure 13 is a flowchart illustrating a method for measuring the resistivity and acoustic wave of a carbon dioxide-displaced core according to an embodiment of this disclosure. As shown in Figure 13, step S1202 includes:

[0196] S1301: The host computer calculates the saturated weight of the core sample based on physical parameters;

[0197] Specifically, the physical parameters of the core include length, diameter, and porosity. The host computer uses the following formula to calculate the weight of water G required for the core to reach a saturated state. 饱 G 饱 =V 孔 ×ρ 水 (1)

[0198] In the formula, V 孔 It is the pore volume of the rock core, ρ 水 It is the density of the formation water.

[0199] The host computer first calculates the total volume V of the core using the following formula.总 :

[0200] In the formula, d is the diameter of the core and h is the length of the core.

[0201] The total volume V of the core was obtained. 总 Then, the host computer uses the following formula to calculate the pore volume V of the core. 孔 V 孔 =V 总 ×Porosity(3)

[0202] In one embodiment, the core length h is 4.00 cm, the core diameter d is 2.50 cm, the porosity is 10%, and the formation water density ρ is... 水 It is 1.01 g / cm³ 3 The weight of water G required for the core to reach a saturated state is calculated according to equations (1)-(3). 饱 =1.98g.

[0203] S1302: The host computer calculates the weight of the incoming water based on the volume of the first pipe;

[0204] Specifically, the host computer calculates the water weight G when the inlet end (first pipe) of the core sample is filled with water based on the volume of the first pipe and the formation water density. 入 G 入 =V 入 ×ρ 水 (4)

[0205] In the formula, V 入 ρ is the volume of the first pipe. 水 It is the density of the formation water.

[0206] In one embodiment, as shown in Figure 5, the first pipe is divided into two sections, and the weight G of water when each section of the pipe is filled with water is calculated. 入1 and G 入2 To obtain the weight G of the water inlet 入 .

[0207] In one embodiment, the volume V of the first pipe 入 =0.99cm 3 Formation water density ρ 水 It is 1.01 g / cm³ 3 The calculated G 入 = 1g.

[0208] S1303: The host computer calculates the weight of the water based on the volume of the second pipe;

[0209] Specifically, the host computer calculates the weight of the water exiting the core sample (second pipe) when it is filled with water, G, based on the volume of the second pipe and the density of the formation water. 出 G 出 =V 出 ×ρ 水 (5)

[0210] In the formula, V 出 ρ is the volume of the two pipes. 水 It is the density of the formation water.

[0211] In one embodiment, as shown in Figure 5, the second pipe is divided into two sections, and the weight G of water when each section of the pipe is filled with water is calculated. 出1 and G 出2 To obtain the weight of the discharged water G 出 .

[0212] In one embodiment, the volume V of the second pipe 出 =1.04cm 3 Formation water density ρ 水 It is 1.01 g / cm³ 3 The calculated G 出 =1.05g.

[0213] S1304: The host computer calculates the actual water weight of the core based on the actual weight and the dry sample weight;

[0214] Specifically, the host computer subtracts the dry sample weight of the core from the actual weight of the core after it has been displaced by formation water to obtain the actual water weight G of the core. 实 .

[0215] S1305: The host computer determines whether the internal state of the core is saturated and stable based on the water injection volume, drainage volume, saturated weight, influent weight, effluent weight, and actual water weight.

[0216] Specifically, the saturated core is placed in a core holder and heated to the required formation temperature to simulate actual formation conditions, and then pressurized further using a formation water displacement device. The outlet valve on the second pipeline is opened, and when a uniform water flow appears at the outlet of the second pipeline, the host computer obtains the injection volume G. 注 Displacement G 排 And determine the water injection volume G 注 Displacement G 排 Weight in saturated state (G) 饱 Weight in water (G) 入 Water output weight G 出 and actual water weight G 实 Does it satisfy the following formula: G 饱 -G 实 =G注 -G 排 -G 入 -G 出 (6)

[0217] If equation (6) is satisfied, it ensures that the core and the pores of the pipe are filled with water and that the internal state of the core is stable.

[0218] Figure 14 is a flowchart illustrating a method for measuring the resistivity and acoustic wave of a carbon dioxide-displaced core according to an embodiment of this disclosure. As shown in Figure 14, step S1145 includes:

[0219] S1401: The host computer calculates the theoretical water displacement from the core based on physical parameters and preset carbon dioxide saturation.

[0220] Specifically, during the displacement experiment, the pore volume inside the core is fixed, and the state and phase of the water within the pores are stable. Therefore, the volume of water displaced from the core pores by supercritical carbon dioxide is also the volume of the core pores occupied by carbon dioxide, from which the carbon dioxide saturation can be calculated. The host computer uses the following formula to calculate the theoretical water displacement from the core:

[0221] In the formula, V 孔 It is the pore volume of the rock core, S CO2 It is the saturation level of supercritical carbon dioxide, ρ. 水 It is the density of the formation water.

[0222] The host computer first calculates the total volume V of the core using the following formula. 总 :

[0223] In the formula, d is the diameter of the core and h is the length of the core.

[0224] The total volume V of the core was obtained. 总 Then, the host computer uses the following formula to calculate the pore volume V of the core. 孔 V 孔 =V 总 ×Porosity(3)

[0225] In one embodiment, the core length h is 4.00 cm, the core diameter d is 2.50 cm, the porosity is 10%, and the formation water density ρ is... 水 It is 1.01 g / cm³ 3 Supercritical carbon dioxide saturation S CO2 The theoretical weight of water displaced from the core is calculated based on equations (2), (3), and (7), which is 50%.

[0226] S1402: The host computer determines whether the core has reached carbon dioxide saturation based on the acquired real-time water discharge volume, theoretical water discharge volume, influent weight, and effluent weight. When the core reaches carbon dioxide saturation, the corresponding resistance and acoustic signals are acquired.

[0227] Specifically, the host computer also obtains the real-time water displacement volume. As shown in Figure 7, when supercritical carbon dioxide displaces saturated core, it is easy to exceed the core end, leading to the removal of G... 入 With G 出 The water is first displaced, and then gradually displaced from other pores within the core. Therefore, in the calculation, the instantaneous water displacement volume G is... 即时 First, deduct the weight of the water entering the water, G. 入 With water weight G 出 The host computer determines the real-time water discharge volume G. 即时 Theoretical water displacement Weight in water (G) 入 and output water weight G 出 Does it satisfy the following formula:

[0228] By presetting the supercritical carbon dioxide saturation S CO2 And calculate the theoretical water displacement. And determine G 即时 Does it meet the corresponding theoretical water displacement volume? To determine whether the core sample has reached the preset carbon dioxide saturation level.

[0229] When the core sample reaches the preset carbon dioxide saturation level, the host computer acquires and records the corresponding resistance and acoustic signals. The above process is repeated for each saturation point to obtain the corresponding resistance and acoustic signals.

[0230] In one embodiment, the real-time supercritical carbon dioxide saturation is calculated according to the following formula obtained from equation (8):

[0231] In one embodiment, G 入 =1g, G 出 =1.05g, preset supercritical carbon dioxide saturation S CO2 If it is 50%, then the theoretical weight of water displaced is... When G 即时 When the carbon dioxide saturation of the core reaches 50% at 3.04g, the corresponding longitudinal wave velocity is 2800m / s, the transverse wave velocity is 1790m / s, and the resistance is 8KΩ. The calculated resistivity is 60Ω·m.

[0232] In one embodiment, when S CO2Table 1 shows the corresponding resistance, resistivity, longitudinal wave velocity, and transverse wave velocity for 0%, 25%, 50%, and 75% respectively.

[0233] Table 1

[0234] In one embodiment, when S CO2 The corresponding acoustic waveforms for 0%, 25%, 50%, and 75% are shown in Figure 8.

[0235] This disclosure provides a method for measuring the resistivity and acoustic wave of a core sample displaced by carbon dioxide. The method involves using a displacement device to displace the core sample with formation water. A host computer determines the internal state of the core sample; when the internal state is saturated and stable, a control signal is sent to the displacement device. The displacement device switches from formation water to supercritical carbon dioxide to displace the core sample according to the control signal. A measuring device measures the instantaneous water displacement, resistivity, and acoustic wave signals of the core sample during the displacement process. The host computer determines whether the instantaneous water displacement meets the preset carbon dioxide saturation condition. When the instantaneous water displacement meets the carbon dioxide saturation condition, the corresponding resistivity and acoustic wave signals are obtained. This method enables precise measurement of parameters such as resistivity and acoustic wave while conducting rock displacement experiments under the simulated in-situ formation environment and supercritical CO2 temperature and pressure conditions. This provides support for quantitatively calculating the supercritical carbon dioxide saturation of actual formations using acoustic wave and resistivity logging. During the displacement process, the rock pores contain only two-phase fluids: supercritical carbon dioxide and formation water. By taking advantage of the negligible compressibility coefficient, unchanged state, and stable phase of formation water in the rock, the saturation of supercritical carbon dioxide in the rock pores can be inferred, providing a basis for the quantitative relationship between resistivity, acoustic velocity data, and CO2 saturation.

[0236] In the description of this specification, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0237] The terms "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. The order of steps involved in the various embodiments is used to illustrate the implementation of this disclosure, and the order of steps is not limited and may be adjusted as needed.

[0238] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art will understand the specific meaning of the above terms in this disclosure based on the specific circumstances.

[0239] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit the scope of protection of this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores, characterized in that, include: Core holder, displacement device, measuring device and host computer; The core holder is used to hold the core to be measured; The displacement device is connected to the core holder through a first pipe, and is used to perform displacement operations on the core using formation water and supercritical carbon dioxide according to the control signal of the host computer. The measuring device is connected to the core holder through a second pipe and is used to measure the instantaneous water displacement, resistance and acoustic signal of the core during the displacement process. The host computer connects to the displacement device and the measuring device to determine the internal state of the core. When the internal state of the core is saturated and stable, a control signal is sent to the displacement device to switch the displacement device from formation water to supercritical carbon dioxide to displace the core. The host computer also determines whether the instantaneous water displacement meets the preset carbon dioxide saturation condition. When the instantaneous water displacement meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained.

2. The resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores according to claim 1, characterized in that, The displacement device includes a formation water displacement device, a supercritical carbon dioxide displacement device, and a gas-liquid displacement switching valve. The gas-liquid displacement switching valve is connected to the core holder, the formation water displacement device and the supercritical carbon dioxide displacement device. The formation water displacement device is used to displace the core using formation water. The supercritical carbon dioxide displacement device is used to prepare supercritical carbon dioxide and to use the supercritical carbon dioxide to displace the core. The host computer is connected to the gas-liquid displacement switching valve and is used to control the gas-liquid displacement switching valve to switch between the formation water displacement device and the supercritical carbon dioxide displacement device.

3. The resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores according to claim 2, characterized in that, The host computer includes: a data acquisition unit, a data processing unit, and a signal transmission unit; The data acquisition unit is used to obtain the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, and the physical parameters, actual weight, and dry sample weight of the core. The data processing unit is used to determine whether the internal state of the core is saturated and stable based on the volume of the first pipe, the volume of the second pipe, the water injection volume, the drainage volume, and the physical parameters, actual weight, and dry sample weight of the core, and outputs the determination result to the signal transmission module. The signal transmitting unit is used to send a control signal to the gas-liquid displacement switching valve to switch from the formation water displacement device to the supercritical carbon dioxide displacement device when the judgment result is that the internal state of the core is saturated and stable.

4. The resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores according to claim 3, characterized in that, The data processing unit includes: The saturated weight calculation module is used to calculate the saturated weight of the core based on the physical parameters. The water inlet weight calculation module is used to calculate the water inlet weight based on the volume of the first pipe. The water weight calculation module is used to calculate the water weight based on the volume of the second pipe. The actual water weight calculation module is used to calculate the actual water weight of the core based on the actual weight and the dry sample weight. The first judgment module is used to determine whether the internal state of the core is saturated and stable based on the water injection volume, the drainage volume, the saturated weight, the influent weight, the effluent weight, and the actual water weight, and outputs the judgment result to the signal sending module.

5. The resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores according to claim 4, characterized in that, The data acquisition unit is also used to acquire the real-time water discharge volume; The data processing unit further includes: The theoretical water displacement calculation module is used to calculate the theoretical water displacement of the core based on the physical parameters and the preset carbon dioxide saturation. The second judgment module is used to determine whether the core has reached the carbon dioxide saturation level based on the real-time water discharge volume, the theoretical water discharge volume, the influent weight, and the effluent weight. When the core reaches the carbon dioxide saturation level, it sends a data acquisition request to the data acquisition unit so that the data acquisition unit can acquire the corresponding resistance and acoustic signals.

6. The resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores according to claim 1, characterized in that, The measuring device includes an instantaneous water discharge measuring device, an acoustic wave acquisition device, and a resistance acquisition device. The instantaneous water displacement measurement device is used to measure the instantaneous water displacement of the core. The acoustic wave acquisition device is used to acquire acoustic wave signals from the rock core; The resistance acquisition device is used to measure the resistance of the rock core.

7. The resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores according to claim 6, characterized in that, The instantaneous water discharge measurement device includes a high-precision electronic balance and a measuring cylinder. The acoustic wave acquisition device includes a signal transmitter and an acoustic oscilloscope.

8. The resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores according to claim 1, characterized in that, The core holder is equipped with plugs at both ends; The inner end of the plug is provided with an electrode, a transverse wave transducer, and a longitudinal wave transducer.

9. The resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores according to claim 1, characterized in that, Also includes: Confining pressure device; The confining pressure device is connected to the core holder and is used to apply environmental pressure to the core.

10. The resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores according to claim 2, characterized in that, The supercritical carbon dioxide displacement device includes: a carbon dioxide tank, a cryogenic circulator, a liquid constant pressure pump, and a gas heating storage tank. The cryogenic circulator is connected to the carbon dioxide tank and is used to liquefy the carbon dioxide in the carbon dioxide tank; The liquid constant pressure pump is connected to the cryogenic circulator and is used to pressurize the liquefied carbon dioxide to a preset pressure; The gas heating storage tank is connected to the liquid constant pressure pump, which is used to heat the pressurized carbon dioxide to a preset temperature in order to prepare the supercritical carbon dioxide.

11. A method for measuring the resistivity and acoustic wave properties of carbon dioxide-displaced rock cores, applied to the resistivity and acoustic wave measurement device for carbon dioxide-displaced rock cores as described in any one of claims 1-10, characterized in that, include: The displacement device uses formation water to displace the core sample. The host computer determines the internal state of the core, and when the internal state of the core is saturated and stable, it sends a control signal to the displacement device. The displacement device switches from formation water to supercritical carbon dioxide to perform displacement operations on the core according to the control signal. The measuring device measures the instantaneous water displacement, resistance, and acoustic signal of the core during the displacement process; The host computer determines whether the acquired instantaneous water discharge volume meets the preset carbon dioxide saturation condition. When it is determined that the instantaneous water discharge volume meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained.

12. The method for measuring the resistivity and acoustic wave of carbon dioxide-displaced core samples according to claim 11, characterized in that, The displacement device includes a formation water displacement device, a supercritical carbon dioxide displacement device, and a gas-liquid displacement switching valve. The host computer determines the internal state of the core sample. When the internal state of the core sample is saturated and stable, it sends a control signal to the displacement device, including: The host computer obtains the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, and the physical parameters, actual weight, and dry sample weight of the core. The host computer determines whether the internal state of the core is saturated and stable based on the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, and the physical parameters, actual weight, and dry sample weight of the core. When the judgment result is that the internal state of the core is saturated and stable, the host computer sends a control signal to the gas-liquid displacement switching valve to switch from the formation water displacement device to the supercritical carbon dioxide displacement device.

13. The method for measuring the resistivity and acoustic wave of carbon dioxide-displaced core samples according to claim 12, characterized in that, The host computer determines whether the internal state of the core is saturated and stable based on the volume of the first pipe, the volume of the second pipe, the water injection volume, the water drainage volume, and the physical parameters, actual weight, and dry sample weight of the core, including: The host computer calculates the saturated weight of the core sample based on the physical parameters. The host computer calculates the weight of the incoming water based on the volume of the first pipe; The host computer calculates the weight of water based on the volume of the second pipe; The host computer calculates the actual water weight of the core based on the actual weight and the dry sample weight. The host computer determines whether the internal state of the core is saturated and stable based on the water injection volume, the drainage volume, the saturated weight, the influent weight, the effluent weight, and the actual water weight.

14. The method for measuring the resistivity and acoustic wave of carbon dioxide-displaced core samples according to claim 13, characterized in that, The host computer determines whether the acquired instantaneous water discharge volume meets the preset carbon dioxide saturation condition. When it is determined that the instantaneous water discharge volume meets the carbon dioxide saturation condition, the corresponding resistance and acoustic signals are obtained, including: The host computer calculates the theoretical water displacement from the core based on the physical parameters and the preset carbon dioxide saturation. The host computer determines whether the core has reached the carbon dioxide saturation level based on the acquired real-time water discharge volume, the theoretical water discharge volume, the influent weight, and the effluent weight. When the core reaches the carbon dioxide saturation level, the corresponding resistance and acoustic signals are acquired.

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