System and method for monitoring gas front position in a core

Abstract

The application provides a monitoring system and method for the position of a gas front in a core, and belongs to the field of oil development experiments.The monitoring system for the position of the gas front in the core comprises a core displacement experiment device, an electromagnetic wave monitoring module and an analysis module, the electromagnetic wave monitoring module comprises an electromagnetic wave transmitting unit and an electromagnetic wave receiving unit; the core displacement experiment device is used for injecting a displacement medium into a core sample to perform a simulation displacement experiment; the electromagnetic wave transmitting unit is used for transmitting an electromagnetic wave monitoring signal to the inside of the core sample when the core sample is performing the simulation displacement experiment, and the electromagnetic wave monitoring signal propagates from an injection end to an outlet end; and the electromagnetic wave receiving unit is used for receiving the electromagnetic wave monitoring signal and confirming the position of the gas front in the core.The application uses an electromagnetic wave signal to detect the boundary of the gas in the core, so as to determine the position of the gas front in the core in real time, quickly and accurately.

Description

Technical Field

[0001] This invention relates to the field of petroleum development experiments, specifically to a monitoring system and a method for monitoring the position of the gas front in a core. Background Technology

[0002] Petroleum development experiments are an important technical means to solve key problems in oil and gas reservoir development. Among them, core displacement physical simulation experiments can relatively realistically reflect the dynamic development process of oil and gas reservoirs, evaluate the impact of different injection methods and different injection media on oil displacement effects, and provide important theoretical basis for understanding the flow mechanism of oil and gas reservoirs.

[0003] With the widespread application of gas drive technology in oilfield development, one-dimensional core gas drive experiments have become a widely used technique for laboratory mechanism research. It is a primary experimental method for evaluating gas drive effectiveness and studying the migration patterns of the gas injection front, among other key development issues. The key to one-dimensional core gas drive experiments lies in determining the location of the gas injection front within the core. Currently, the main method for determining the gas injection front is the indirect method, which involves collecting pressure changes along the core's flow path to determine the location of the gas injection front. The injected gas generates a pressure rise along its migration path within the core, and the location of the gas injection front is determined by plotting the pressure changes along the core's flow path. However, the accuracy of this method depends on the continuity of the pressure sampling points, which cannot be discontinuous, thus reducing the accuracy of the gas injection front test. Another method involves taking fluid samples along the displacement direction and testing the changes in the gas-oil ratio of the samples to reflect the gas injection front; the point where the gas-oil ratio increases is the front location. However, this method cannot achieve real-time monitoring. Summary of the Invention

[0004] To address one of the aforementioned technical deficiencies, this invention provides a monitoring system and method for the gas front position within a core sample. The monitoring system transmits electromagnetic wave signals to the core sample via an electromagnetic wave module. Based on the differences in propagation speed and attenuation rate of electromagnetic wave signals in different media, the electromagnetic wave signals are used to detect the boundary of the gas within the core, thereby determining the dynamic existence state of the gas inside the core in real time, quickly, and accurately, and thus determining the gas front position inside the core.

[0005] The first aspect of the present invention provides a monitoring system for the location of the gas front in a core, comprising: a core displacement experimental device, an electromagnetic wave monitoring module, and an analysis module; The core displacement experimental device is used to inject a displacement medium into the core sample and conduct a simulated displacement experiment on the core sample through the displacement medium. The electromagnetic wave monitoring module includes: an electromagnetic wave transmitting unit and an electromagnetic wave receiving unit; The electromagnetic wave transmitting unit is used to transmit electromagnetic wave monitoring signals into the interior of the core sample through the injection end of the core sample during the simulated displacement experiment. The electromagnetic wave monitoring signals propagate from the injection end of the core sample to the outlet end of the core sample. The electromagnetic wave receiving unit is used to receive electromagnetic wave monitoring signals from the outlet end of the core sample. The analysis module is used to determine the leading edge position of the gas in the core based on the electromagnetic wave monitoring signal at the outlet end of the core sample.

[0006] In this embodiment of the invention, the electromagnetic wave monitoring module further includes: a modulation and demodulation unit; The modulation and demodulation unit is connected to the electromagnetic wave transmitting unit and the electromagnetic wave receiving unit; The modulation and demodulation unit is used to modulate the electromagnetic wave monitoring signal, transmit the modulated electromagnetic wave monitoring signal to the electromagnetic wave transmitting unit, receive the electromagnetic wave monitoring signal sent by the electromagnetic wave receiving unit, and demodulate the received electromagnetic wave monitoring signal.

[0007] In this embodiment of the invention, the core displacement experimental device includes: an injection unit, a clamping unit, and a produced fluid metering unit; The clamping unit is used to fix the core sample; The injection unit is used to inject a variety of displacement media into the core sample, and to conduct a simulated displacement experiment on the core sample using the variety of displacement media. The produced fluid metering unit is used to receive the fluid produced after the core sample completes the simulated displacement experiment, and to meter the fluid produced after the core sample completes the simulated displacement experiment.

[0008] In this embodiment of the invention, the clamping unit includes: a core clamp, a core confining sleeve, a first plug, and a second plug; The core holder is used to place and fix the core sample; The core confining sleeve is used to apply confining pressure to the core sample; The first plug is disposed at one end of the core holder, and the first plug is close to the injection end of the core sample; The second plug is located at the other end of the core holder, and the second plug is close to the outlet end of the core sample; The first plug and the second plug are used to seal the core holder.

[0009] In this embodiment of the invention, the injection unit includes: a high-pressure plunger pump and a plurality of intermediate containers; Multiple intermediate containers are used to hold various displacement media respectively, and the output end of the intermediate containers is connected to the injection end of the core sample; The high-pressure plunger pump is used to pump the displacement medium contained in the intermediate container into the core sample.

[0010] In this embodiment of the invention, the output liquid metering unit includes: a gas-liquid separation device and a gas flow meter; The gas-liquid separation device is used to separate the fluid produced after the core sample completes the simulated displacement experiment into gas and liquid, and to measure the separated liquid. The gas flow meter is used to measure the gas separated by the gas-liquid separator.

[0011] In this embodiment of the invention, the core displacement experimental device further includes a confining pressure pump, which is used to apply confining pressure to the core confining pressure sleeve.

[0012] In this embodiment of the invention, the core displacement experimental device further includes: a back pressure control unit, which includes a back pressure valve and a back pressure control pump; The back pressure control pump is connected to the outlet end of the core sample and is used to pump back pressure into the core sample to increase the pressure of the fluid in the pores of the core sample to the experimental pressure. The back pressure valve is located at the outlet end of the back pressure control pump and is used to shut off the back pressure output by the back pressure control pump.

[0013] A second aspect of the present invention provides a method for monitoring the position of the gas front within a core, the method being implemented based on the core gas front position monitoring system described above, comprising: Select the first core sample and the second core sample according to the preset conditions; The first core sample was subjected to a saturated oil test using the core displacement experimental device, and the electromagnetic wave monitoring signal of the first core sample containing oil was obtained by the electromagnetic wave monitoring module. The second core sample was subjected to a saturated gas test using the core displacement experimental device, and the electromagnetic wave monitoring signal of the second core sample containing gas was obtained by the electromagnetic wave monitoring module. The second core sample was subjected to a saturated water test using the core displacement experimental device, and the electromagnetic wave monitoring signal of the second core sample containing water was obtained by the electromagnetic wave monitoring module. The second core sample, after undergoing a saturated water test, was subjected to an oil-water flooding test and a gas-oil flooding test in sequence using the core displacement experimental device. The electromagnetic wave monitoring module was used to obtain the electromagnetic wave monitoring signals of the second core sample at different times during the gas-oil flooding test. Based on the electromagnetic wave monitoring signals of the first core sample when it contained oil, the second core sample when it contained gas, the second core sample when it contained water, and the electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil test, the position of the injected gas front in the second core sample was confirmed.

[0014] In this embodiment of the invention, determining the position of the injected gas front in the second core sample based on the electromagnetic wave monitoring signals of the first core sample when it contains oil, the second core sample when it contains gas, the second core sample when it contains water, and the electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil test includes: The first signal characteristic parameter was extracted from the electromagnetic wave monitoring signal when the first core sample contained oil. The second signal characteristic parameters were extracted from the electromagnetic wave monitoring signal when the second core sample contained gas. The third signal characteristic parameter was extracted from the electromagnetic wave monitoring signal when the second core sample was water-bearing. The fourth signal characteristic parameters at multiple different times were extracted from the electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil test; The position of the injected gas front in the second core sample was determined based on the first signal characteristic parameters, the second signal characteristic parameters, the third signal characteristic parameters, and the fourth signal characteristic parameters at multiple different times.

[0015] In this embodiment of the invention, the method further includes: During the oil-drive water test of the second core sample, the fluid produced by the second core sample is obtained, and the bound water saturation and original oil saturation of the second core sample are calculated based on the fluid produced by the second core sample.

[0016] The monitoring system for the gas front position in the core sends electromagnetic wave signals to the core sample through an electromagnetic wave module. Based on the differences in propagation speed and attenuation rate of electromagnetic wave signals in different media, the electromagnetic wave signals are used to detect the boundary of the gas in the core, so as to determine the dynamic existence state of the gas inside the core in real time, quickly and accurately, and thus determine the gas front position inside the core.

[0017] Other features and advantages of the technical solution of the present invention will be described in detail in the following detailed embodiments section. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1This is a schematic diagram of the structure of the monitoring system for the gas front position in the core provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the end face structure of the core holder provided in an embodiment of the present invention; Figure 3 This is a flowchart of a method for monitoring the position of the gas front in a core according to an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures 1—High-pressure plunger pump; 2—Second intermediate container; 3—First intermediate container; 4—Third intermediate container; 5—Core holder; 6—Containing pressure pump; 7—Pressure gauge; 8—Back pressure valve; 9—Back pressure control pump; 10—Gas-liquid separator; 11—Gas flow meter; 12—Electromagnetic wave transmitting antenna; 13—Modulation and demodulation unit; 14—Constant temperature chamber; 15—Electromagnetic wave receiving antenna. Detailed Implementation

[0020] To make the technical solutions and advantages of the embodiments of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0023] In this invention, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] In the process of realizing this invention, the inventors discovered that petroleum development experiments are an important technical means to solve key problems in oil and gas reservoir development. Among them, core displacement physical simulation experiments can relatively realistically reflect the dynamic development process of oil and gas reservoirs, evaluate the impact of different injection methods and different injection media on oil displacement effects, and provide important theoretical basis for understanding the flow mechanism of oil and gas reservoirs.

[0025] With the widespread application of gas drive technology in oilfield development, one-dimensional core gas drive experiments have become a widely used technique for laboratory mechanism research. It is a primary experimental method for evaluating gas drive effectiveness and studying the migration patterns of the gas injection front, among other key development issues. The key to one-dimensional core gas drive experiments lies in determining the location of the gas injection front within the core. Currently, the main method for determining the gas injection front is the indirect method, which involves collecting pressure changes along the core's flow path to determine the location of the gas injection front. The injected gas generates a pressure rise along its migration path within the core, and the location of the gas injection front is determined by plotting the pressure changes along the core's flow path. However, the accuracy of this method depends on the continuity of the pressure sampling points, which cannot be discontinuous, thus reducing the accuracy of the gas injection front test. Another method involves taking fluid samples along the displacement direction and testing the changes in the gas-oil ratio of the samples to reflect the gas injection front; the point where the gas-oil ratio increases is the front location. However, this method cannot achieve real-time monitoring.

[0026] To address the aforementioned problems, this invention provides a monitoring system for the gas front position within a core sample, comprising: a core displacement experimental apparatus, an electromagnetic wave monitoring module, and an analysis module. The electromagnetic wave monitoring module includes an electromagnetic wave transmitting unit and an electromagnetic wave receiving unit. The core displacement experimental apparatus is used to inject a displacement medium into the core sample, thereby conducting a simulated displacement experiment on the core sample using the displacement medium. The electromagnetic wave transmitting unit is used to transmit an electromagnetic wave monitoring signal into the interior of the core sample through the injection end during the simulated displacement experiment, and the electromagnetic wave monitoring signal propagates along the injection end to the outlet end of the core sample. The electromagnetic wave receiving unit is used to receive the electromagnetic wave monitoring signal from the outlet end of the core sample. The analysis module is used to determine the gas front position within the core sample based on the electromagnetic wave monitoring signal from the outlet end of the core sample. The monitoring system for the gas front position in the core sends electromagnetic wave signals to the core sample through an electromagnetic wave module. Based on the differences in propagation speed and attenuation rate of electromagnetic wave signals in different media, the electromagnetic wave signals are used to detect the boundary of the gas in the core, so as to determine the dynamic existence state of the gas inside the core in real time, quickly and accurately, and thus determine the gas front position inside the core.

[0027] Figure 1 This is a schematic diagram of the structure of a monitoring system for the location of the gas front in a core, provided in an embodiment of the present invention. Figure 1 As shown in the figure, this embodiment provides a monitoring system for the position of the gas front in a core, including: a core displacement experimental device, an analysis module, and an electromagnetic wave monitoring module. The electromagnetic wave monitoring module includes: an electromagnetic wave transmitting unit and an electromagnetic wave receiving unit. The core displacement experimental device is used to inject a displacement medium into the core sample and conduct a simulated displacement experiment on the core sample through the displacement medium. The electromagnetic wave transmitting unit is used to transmit electromagnetic wave monitoring signals into the interior of the core sample through the injection end of the core sample during the simulated displacement experiment. The electromagnetic wave monitoring signals propagate from the injection end of the core sample to the outlet end of the core sample. The electromagnetic wave receiving unit is used to receive electromagnetic wave monitoring signals from the outlet end of the core sample. The analysis module is used to determine the leading edge position of the gas in the core based on the electromagnetic wave monitoring signal at the outlet end of the core sample.

[0028] In this embodiment, the electromagnetic wave receiving unit is an electromagnetic wave receiving antenna 15, and the electromagnetic wave transmitting unit is an electromagnetic wave transmitting antenna 12.

[0029] Both the electromagnetic wave transmitting antenna 12 and the electromagnetic wave receiving antenna 15 include an electrode main board.

[0030] In this embodiment, the electromagnetic wave monitoring module includes: a modulation and demodulation unit 13; The modulation and demodulation unit 13 is connected to the electromagnetic wave transmitting unit. The modulation and demodulation unit 13 is used to modulate the electromagnetic wave monitoring signal and transmit the modulated electromagnetic wave monitoring signal to the electromagnetic wave transmitting unit. The modulation and demodulation unit 13 is connected to the electromagnetic wave receiving unit. The modulation and demodulation unit 13 is used to receive the electromagnetic wave monitoring signal sent from the electromagnetic wave receiving unit and demodulate the received electromagnetic wave monitoring signal.

[0031] In this embodiment, the core displacement experimental device includes: an injection unit, a clamping unit, and a produced fluid metering unit; The clamping unit is used to fix the core sample; The injection unit is used to inject a variety of displacement media into the core sample, and to conduct a simulated displacement experiment on the core sample using the variety of displacement media. The produced fluid metering unit is used to receive the fluid produced after the core sample completes the simulated displacement experiment, and to meter the fluid produced after the core sample completes the simulated displacement experiment.

[0032] In this embodiment, the clamping unit includes: a core clamp 5, a core confining sleeve, a first plug, and a second plug; The core holder 5 is used to place and fix the core sample; The core confining sleeve is used to apply confining pressure to the core sample; The first plug is disposed at one end of the core holder 5, and the first plug is close to the injection end of the core sample; The second plug is located at the other end of the core holder 5, and the second plug is close to the outlet end of the core sample; The first plug and the second plug are used to seal the core holder 5.

[0033] In this embodiment, the core holder 5 is disposed in the holder vessel body.

[0034] In this embodiment, the first intermediate container 3, the second intermediate container 2, the third intermediate container 4, the clamp, and the back pressure valve 8 are all disposed inside the insulation box.

[0035] In this embodiment, the system further includes a pressure gauge 7, which is used to measure the pressure inside the insulation box.

[0036] Figure 2 This is a schematic diagram of the end face structure of the core holder provided in an embodiment of the present invention, as shown below. Figure 2As shown, in this embodiment, an electromagnetic wave transmitting antenna 12 is provided on the first plug, and an electromagnetic wave receiving antenna 15 is provided on the second plug.

[0037] In this embodiment, the injection unit includes: a high-pressure plunger pump 1 and multiple intermediate containers; Multiple intermediate containers are used to hold various displacement media respectively, and the output end of the intermediate containers is connected to the injection end of the core sample; The high-pressure plunger pump 1 is used to pump the displacement medium contained in the intermediate container into the core sample.

[0038] In this embodiment, the high-pressure plunger pump 1 is a high-pressure, high-precision plunger pump, and the intermediate container includes a first intermediate container 3, a second intermediate container 2, and a third intermediate container 4. The first displacement medium is oil, the second displacement medium is water, and the third displacement medium is CO2. The first intermediate container 3 is used to hold oil, the second intermediate container 2 is used to hold water, and the third intermediate container 4 is used to hold CO2.

[0039] In this embodiment, the output liquid metering unit includes: a gas-liquid separator 10 and a gas flow meter 11; The gas-liquid separation device 10 is used to separate the fluid produced after the core sample completes the simulated displacement experiment into gas and liquid, and to measure the separated liquid. The gas flow meter 11 is used to measure the gas separated by the liquid separation device 10.

[0040] In this embodiment, the core displacement experimental device further includes a confining pressure pump 6, which is used to apply confining pressure to the core confining pressure sleeve.

[0041] In this embodiment, the core displacement experimental device further includes a back pressure control unit, which includes a back pressure valve 8 and a back pressure control pump 9. The back pressure control pump 9 is connected to the outlet end of the core sample and is used to pump back pressure into the core sample to increase the pressure of the fluid in the pores of the core sample to the experimental pressure. The back pressure valve 8 is located at the outlet end of the back pressure control pump 9 and is used to shut off the back pressure output by the back pressure control pump 9.

[0042] Figure 3 This is a flowchart illustrating a method for monitoring the location of the gas front within a core, as provided in an embodiment of the present invention. Figure 3 As shown, this embodiment provides a method for monitoring the position of the gas front within a core. This method is based on the core gas front position monitoring system described above and includes: S1. Select the first core sample and the second core sample according to the preset conditions; S2. A saturated oil test is performed on the first core sample using the core displacement experimental device, and the electromagnetic wave monitoring signal when the first core sample contains oil is obtained through the electromagnetic wave monitoring module. S3. A saturated gas test is performed on the second core sample using the core displacement experimental device, and the electromagnetic wave monitoring signal of the second core sample containing gas is obtained through the electromagnetic wave monitoring module. S4. A saturated water test is conducted on the second core sample using the core displacement experimental device, and the electromagnetic wave monitoring signal of the second core sample containing water is obtained through the electromagnetic wave monitoring module. S5. Using the core displacement test device, the second core sample after the saturated water test is subjected to oil-water flooding test and gas-oil flooding test in sequence. The electromagnetic wave monitoring module is used to obtain the electromagnetic wave monitoring signal of the second core sample at different times during the gas-oil flooding test. S6. Based on the electromagnetic wave monitoring signals of the first core sample when it contains oil, the second core sample when it contains gas, the second core sample when it contains water, and the electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil test, confirm the position of the injected gas front in the second core sample.

[0043] In step S6, determining the position of the injected gas front in the second core sample based on the electromagnetic wave monitoring signals of the first core sample when it contains oil, the second core sample when it contains gas, the second core sample when it contains water, and the electromagnetic wave monitoring signals of the second core sample at different times during the gas-drive oil test, includes: The first signal characteristic parameter was extracted from the electromagnetic wave monitoring signal when the first core sample contained oil. The second signal characteristic parameters were extracted from the electromagnetic wave monitoring signal when the second core sample contained gas. The third signal characteristic parameter was extracted from the electromagnetic wave monitoring signal when the second core sample was water-bearing. The fourth signal characteristic parameters at multiple different times were extracted from the electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil test; The position of the injected gas front in the second core sample was determined based on the first signal characteristic parameters, the second signal characteristic parameters, the third signal characteristic parameters, and the fourth signal characteristic parameters at multiple different times.

[0044] The method further includes: S7. When conducting an oil-drive water test on the second core sample, obtain the fluid produced by the second core sample, and calculate the bound water saturation and original oil saturation of the second core sample based on the fluid produced by the second core sample.

[0045] Specifically, the experimental steps provided in this embodiment are as follows: Step 1: Obtain at least two parallel core samples from the oil and gas reservoir, designated as the first core sample and the second core sample. Prepare sample sizes commonly used in core displacement experiments, including but not limited to cylindrical samples with a diameter of 25mm or 38mm and a length of at least 500mm, or strip-shaped samples with an end face area of ​​at least 40mm × 40mm and a length of at least 500mm, for the purpose of studying one-dimensional flow. Specifically, the first core sample is a cylindrical sample with a diameter of 25mm and a length of 500mm, and the second core sample is a strip-shaped sample with an end face area of ​​40mm × 40mm and a length of 500mm.

[0046] Step 2: Place the first core sample in the holder of the core holder 5, use the confining pressure pump 6 to apply confining pressure to the core confining sleeve, and then use the core confining pressure sleeve to act on the holder to evacuate the first core sample. Then conduct a saturated oil test to test the phase of the electromagnetic wave monitoring signal when the second core sample contains oil.

[0047] Step 3: Place the second core sample in the holder, use the confining pressure pump 6 to apply confining pressure to the core confining sleeve, and then use the core confining pressure sleeve to act on the holder. Use the back pressure control unit to raise the pressure of the fluid in the pores of the second core sample to the preset experimental pressure. Use a high-pressure, high-precision plunger pump to inject CO2 into the core of the second core sample until gas is seen at the outlet end of the second core sample. Test the phase and amplitude of the electromagnetic wave monitoring signal when the second core sample contains gas under this experimental pressure.

[0048] Step 4: Depressurize the second core sample, evacuate the second core sample, and then conduct a saturated water test to test the phase and amplitude of the electromagnetic wave monitoring signal when the second core sample contains water; Step 5: Conduct an oil-flooding experiment on the second core sample and establish a bound water saturation experiment. Calculate the bound water saturation and original oil saturation of the core sample based on the volume of oil and water in the fluid produced from the second core sample. Step Six: Conduct a gas-driven oil injection experiment on the second core sample. The pressure of the pore fluid in the second core sample is again increased to the experimental pressure using the backpressure control unit, and CO2 is injected into the core using the high-pressure plunger pump 1. Electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil injection experiment are obtained through the electromagnetic wave monitoring module. The phase and amplitude of the fluid within the core are demodulated from the electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil injection experiment using the modulation and demodulation unit 13, and compared with the phase and amplitude obtained in Steps Two, Three, and Four (the electromagnetic wave amplitude decays slowly in oil and gas, and is greater than in water; the electromagnetic wave propagation speed in gas is faster than in oil and water, resulting in a smaller phase difference in gas than in oil and water; therefore, the gas occurrence location can be determined by the phase and amplitude), thus determining the injection front position.

[0049] In this embodiment, the experimental pressure was 10 MPa and the experimental temperature was room temperature. The sandstone core #1 had a gas permeability of 127 md, a porosity of 19.2%, a core diameter of 2.54 cm, and a length of 10 cm. The experimental oil was simulated oil with a viscosity of 1.5 mPa·s and a density of 0.751 cm³ / g. The experimental water was distilled water, and the experimental gas was 99.9% pure CO₂. First, the core was evacuated from the saturated distilled water, resulting in a core pore volume of 9.50 mL. Then, the distilled water was displaced with the experimental oil, achieving a bound water saturation of 25.2%, a water volume of 2.4 mL, and an oil volume of 7.1 mL. When the CO₂ injection volume was 1.94 mL (approximately 0.2 pore volumes), the injection front was located 4.6 cm from the injection end. When the CO₂ injection volume was 3.21 mL (0.35 pore volumes), the injection front reached the core outlet, indicating that CO₂ channeling occurred under this injection volume condition.

[0050] This invention not only meets the experimental conditions of high temperature and high pressure, but also enables real-time, rapid and accurate study of the dynamic occurrence state of gas inside the core without damaging the core, providing an important technical means for monitoring the gas injection front of the core.

[0051] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0052] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0053] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details described above. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. Furthermore, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. As long as such combination does not violate the spirit of the embodiments of the present invention, it should also be considered as the content disclosed by the embodiments of the present invention.

Claims

1. A monitoring system for the position of the gas front in a core sample, characterized in that, include: Core displacement experimental apparatus, electromagnetic wave monitoring module, and analysis module; The core displacement experimental device is used to inject a displacement medium into the core sample and conduct a simulated displacement experiment on the core sample through the displacement medium. The electromagnetic wave monitoring module includes: an electromagnetic wave transmitting unit and an electromagnetic wave receiving unit; The electromagnetic wave transmitting unit is used to transmit electromagnetic wave monitoring signals into the interior of the core sample through the injection end of the core sample during the simulated displacement experiment. The electromagnetic wave monitoring signals propagate from the injection end of the core sample to the outlet end of the core sample. The electromagnetic wave receiving unit is used to receive electromagnetic wave monitoring signals from the outlet end of the core sample. The analysis module is used to determine the leading edge position of the gas in the core based on the electromagnetic wave monitoring signal at the outlet end of the core sample.

2. The monitoring system for the location of the gas front in the core according to claim 1, characterized in that, The electromagnetic wave monitoring module further includes: a modulation and demodulation unit; The modulation and demodulation unit is connected to the electromagnetic wave transmitting unit and the electromagnetic wave receiving unit; The modulation and demodulation unit is used to modulate the electromagnetic wave monitoring signal, transmit the modulated electromagnetic wave monitoring signal to the electromagnetic wave transmitting unit, receive the electromagnetic wave monitoring signal sent by the electromagnetic wave receiving unit, and demodulate the received electromagnetic wave monitoring signal.

3. The monitoring system for the position of the gas front in the core according to claim 1, characterized in that, The core displacement experimental device includes: an injection unit, a clamping unit, and a produced fluid metering unit; The clamping unit is used to fix the core sample; The injection unit is used to inject a variety of displacement media into the core sample, and to conduct a simulated displacement experiment on the core sample using the variety of displacement media. The produced fluid metering unit is used to receive the fluid produced after the core sample completes the simulated displacement experiment, and to meter the fluid produced after the core sample completes the simulated displacement experiment.

4. The monitoring system for the location of the gas front in the core according to claim 3, characterized in that, The clamping unit includes: a core clamp, a core confining sleeve, a first plug, and a second plug; The core holder is used to place and fix the core sample; The core confining sleeve is used to apply confining pressure to the core sample; The first plug is disposed at one end of the core holder, and the first plug is close to the injection end of the core sample; The second plug is located at the other end of the core holder, and the second plug is close to the outlet end of the core sample; The first plug and the second plug are used to seal the core holder.

5. The monitoring system for the position of the gas front in the core according to claim 3, characterized in that, The injection unit includes: a high-pressure plunger pump and multiple intermediate containers; Multiple intermediate containers are used to hold various displacement media respectively, and the output end of the intermediate containers is connected to the injection end of the core sample; The high-pressure plunger pump is used to pump the displacement medium contained in the intermediate container into the core sample.

6. The monitoring system for the position of the gas front in the core according to claim 3, characterized in that, The output liquid metering unit includes: a gas-liquid separator and a gas flow meter; The gas-liquid separation device is used to separate the fluid produced after the core sample completes the simulated displacement experiment into gas and liquid, and to measure the separated liquid. The gas flow meter is used to measure the gas separated by the gas-liquid separator.

7. The monitoring system for the location of the gas front in the core according to claim 4, characterized in that, The core displacement experimental apparatus further includes a confining pressure pump, which is used to apply confining pressure to the core confining pressure sleeve.

8. The monitoring system for the location of the gas front in the core according to claim 4, characterized in that, The core displacement experimental device also includes: a back pressure control unit, which includes a back pressure valve and a back pressure control pump; The back pressure control pump is connected to the outlet end of the core sample and is used to pump back pressure into the core sample to increase the pressure of the fluid in the pores of the core sample to the experimental pressure. The back pressure valve is located at the outlet end of the back pressure control pump and is used to shut off the back pressure output by the back pressure control pump.

9. A method for monitoring the position of the gas front within a core, wherein the method is implemented based on the monitoring system for the position of the gas front within a core as described in any one of claims 1-8, characterized in that, include: Select the first core sample and the second core sample according to the preset conditions; The first core sample was subjected to a saturated oil test using the core displacement experimental device, and the electromagnetic wave monitoring signal of the first core sample containing oil was obtained by the electromagnetic wave monitoring module. The second core sample was subjected to a saturated gas test using the core displacement experimental device, and the electromagnetic wave monitoring signal of the second core sample containing gas was obtained by the electromagnetic wave monitoring module. The second core sample was subjected to a saturated water test using the core displacement experimental device, and the electromagnetic wave monitoring signal of the second core sample containing water was obtained by the electromagnetic wave monitoring module. The second core sample, after undergoing a saturated water test, was subjected to an oil-water flooding test and a gas-oil flooding test in sequence using the core displacement experimental device. The electromagnetic wave monitoring module was used to obtain the electromagnetic wave monitoring signals of the second core sample at different times during the gas-oil flooding test. Based on the electromagnetic wave monitoring signals of the first core sample when it contained oil, the second core sample when it contained gas, the second core sample when it contained water, and the electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil test, the position of the injected gas front in the second core sample was confirmed.

10. The method for monitoring the position of the gas front in a core according to claim 9, characterized in that, The determination of the injected gas front position within the second core sample based on the electromagnetic wave monitoring signals of the first core sample when it contained oil, the second core sample when it contained gas, the second core sample when it contained water, and the electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil test includes: The first signal characteristic parameter was extracted from the electromagnetic wave monitoring signal when the first core sample contained oil. The second signal characteristic parameters were extracted from the electromagnetic wave monitoring signal when the second core sample contained gas. The third signal characteristic parameter was extracted from the electromagnetic wave monitoring signal when the second core sample was water-bearing. The fourth signal characteristic parameters at multiple different times were extracted from the electromagnetic wave monitoring signals of the second core sample at different times during the gas-driven oil test; The position of the injected gas front in the second core sample was determined based on the first signal characteristic parameters, the second signal characteristic parameters, the third signal characteristic parameters, and the fourth signal characteristic parameters at multiple different times.

11. The method for monitoring the position of the gas front in a core according to claim 9, characterized in that, The method further includes: During the oil-drive water test of the second core sample, the fluid produced by the second core sample is obtained, and the bound water saturation and original oil saturation of the second core sample are calculated based on the fluid produced by the second core sample.

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