Rock wave velocity dynamic monitoring test system for simulating gas content change of hydrocarbon source rock

Abstract

The invention belongs to the technical field of rock wave velocity monitoring, and particularly relates to a rock wave velocity dynamic monitoring test system for simulating the gas content change of hydrocarbon source rock, which comprises a rock wave velocity and desorption gas combined monitoring system, a rock wave velocity and desorption gas combined monitoring system, a gas chamber for placing a rock core column sample, and a rock wave velocity and desorption gas combined monitoring system, the air chamber is provided with an air inlet end and an air outlet end, and air pressure in the air chamber is adjustable; the desorption gas recovery systems are matched with the rock wave velocity and desorption gas combined monitoring systems in number, the gas inlet ends of the desorption gas recovery systems are communicated with the gas outlet ends of the rock wave velocity and desorption gas combined monitoring systems, and the desorption gas recovery systems are used for recovering desorption gas; the rock wave velocity and desorption gas combined monitoring system and the desorption gas recovery system are arranged in the constant temperature system; the constant temperature system is used for providing a temperature environment required by the rock wave velocity and desorption gas combined monitoring system; and the gas supply control system is connected with the gas inlet end of the rock wave velocity and desorption gas combined monitoring system and is used for supplying gas and detecting the gas pressure of the gas chamber.

Description

Technical Field

[0001] The invention belongs to the technical field of rock wave velocity monitoring, and in particular relates to a rock wave velocity dynamic monitoring test system for simulating the change of gas content in hydrocarbon source rocks. Background Art

[0002] Rock wave velocity is a very important kinematic characteristic parameter in the field of seismic exploration. Precise geological and geophysical modeling, stratigraphic lithology interpretation, etc. all require accurate formation rock wave velocity.

[0003] Although the existing equipment can well simulate the characteristics of rock wave velocity changes in strata at different burial depths. However, in the actual oil and gas production process, the thickness and depth of the oil and gas reservoirs we are concerned about are often fixed, but with the oil and gas production, the hydrocarbon gas content in the reservoir will show a nonlinear decreasing trend. When the gas in the rock pores escapes, according to the Wyllie equation, the rock wave velocity will change accordingly. However, the existing rock wave velocity detection instruments are unable to monitor the dynamic change trend of rock wave velocity with its gas content, and are unable to obtain the accurate rock wave velocity of oil and gas reservoirs at different gas content stages.

[0004] In summary, the efficient development and high-quality development of unconventional oil and gas reservoirs cannot be separated from the close seismic monitoring of oil and gas reservoirs at different time periods, that is, time-lapse seismic. However, with the drainage of oil and gas from the reservoir, the decrease in the oil and gas content of the reservoir will cause the rock wave velocity to change, and the change in the reservoir rock wave velocity will affect the accuracy of geophysical modeling and stratigraphic lithology interpretation in the seismic exploration link. Therefore, we proposed a rock wave velocity dynamic monitoring test system that simulates the change in gas content of source rocks. Through experimental means, we reveal the changing trend of rock wave velocity with rock oil and gas content, which provides an important scientific reference for more accurate time-lapse seismic monitoring, geological geophysical modeling and stratigraphic lithology interpretation of unconventional oil and gas reservoirs. Summary of the invention

[0005] The purpose of the present invention is to provide a rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks to solve the above problems.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks, comprising:

[0008] At least one rock wave velocity and desorption gas joint monitoring system, wherein the rock wave velocity and desorption gas joint monitoring system is provided with an air chamber for placing a core column sample, the air chamber has an air inlet end and an air outlet end, and the air pressure in the air chamber is adjustable;

[0009] A desorption gas recovery system, the number of which matches the rock wave velocity and desorption gas joint monitoring system, the gas inlet end of the desorption gas recovery system is connected to the gas outlet end of the rock wave velocity and desorption gas joint monitoring system, and is used to recover the desorption gas;

[0010] A constant temperature system, wherein the rock wave velocity and desorption gas joint monitoring system and the desorption gas recovery system are arranged in the constant temperature system; the constant temperature system is used to provide the temperature environment required by the rock wave velocity and desorption gas joint monitoring system;

[0011] The gas supply control system is connected to the gas inlet end of the rock wave velocity and desorption gas joint monitoring system and is used for supplying gas and detecting the gas pressure of the gas chamber.

[0012] Optionally, the rock wave velocity and desorption gas joint monitoring system includes:

[0013] A high-pressure heat-insulating outer cylinder, on which a sample chamber is arranged, and the sample chamber is used to place a core column sample;

[0014] A wave velocity measuring unit, arranged in the sample chamber, for testing the wave velocity of the core column sample;

[0015] An air pressure balance part is arranged on one side of the high-pressure resistant heat-insulating outer cylinder, the air inlet end of the air pressure balance part is connected with the air outlet end of the air supply control system, and the air outlet end of the air pressure balance part is connected with the air inlet end of the sample chamber; the air outlet end of the sample chamber is connected with the air inlet end of the desorption gas recovery system; an electric control valve for controlling the on-off of the pipeline is arranged between the air outlet end of the air pressure balance part and the air inlet end of the sample chamber; an electric control valve for controlling the on-off of the pipeline is arranged between the air outlet end of the sample chamber and the air inlet end of the desorption gas recovery system; a gas pressure sensor is connected in parallel with the air outlet end of the sample chamber, and the gas pressure sensor is electrically connected to the air supply control system;

[0016] The gas supply control system collects the gas pressure data of the gas pressure balance unit and the sample chamber, and collects the wave velocity data of the wave velocity measurement unit.

[0017] Optionally, the air pressure balancing unit includes a reference cylinder, the air inlet end of the reference cylinder is connected to the air supply control system, the air outlet end of the reference cylinder is connected to the sample chamber, the air outlet end of the reference cylinder is connected in parallel with another gas pressure sensor, and the gas pressure sensor is electrically connected to the air supply control system.

[0018] Optionally, the wave velocity measuring unit includes:

[0019] An ultrasonic pulse penetration device is arranged on the top of the sample chamber;

[0020] An ultrasonic receiving device, arranged at the bottom of the sample chamber;

[0021] The core column sample is arranged between the ultrasonic pulse penetrating device and the ultrasonic receiving device;

[0022] The ultrasonic receiving device is signal-connected to the air supply control system.

[0023] Optionally, the ultrasonic pulse penetration device includes:

[0024] A core column sample coupling top plate, wherein the bottom of the core column sample coupling top plate is in contact with the top of the core column sample; a plurality of air inlets are evenly spaced in the circumferential direction on the top of the core column sample coupling top plate;

[0025] An ultrasonic pulser, axially connected to the top of the core column sample coupling top plate; the ultrasonic pulser is electrically connected to a conductive buffer pad through a connecting circuit, the conductive buffer pad is arranged between two adjacent air inlets, and the conductive buffer pad is fixed to the top of the core column sample coupling top plate;

[0026] The bottom end of the conductive elastic part is fixedly connected to the conductive buffer pad, the top end of the conductive elastic part is connected to the top of the sample chamber, and the conductive elastic part is used to connect to the power supply wire.

[0027] Optionally, the conductive elastic part includes a spring, the bottom end of the spring is fixedly connected to the conductive buffer pad, the top end of the spring is fixedly connected to a conductive sheet, the conductive sheet is embedded in the top inner wall of the sample chamber, and the conductive sheet is electrically connected to a power supply.

[0028] Optionally, the ultrasonic receiving device includes:

[0029] A core column sample coupling bottom plate, fixedly connected to the bottom of the sample chamber;

[0030] An ultrasonic receiver is axially connected to the top of the core column sample coupling bottom plate, and the ultrasonic receiver is connected to the gas supply control system signal.

[0031] Optionally, the gas supply control system includes:

[0032] The terminal operation and gas storage system has an air inlet connected to the air outlet of the gas supply system, and the air outlet of the terminal operation and gas storage system is connected to the air inlet of the reference cylinder. The terminal operation and gas storage system is used to control the air supply and feedback the air pressure and wave velocity data.

[0033] Optionally, the terminal operation and gas storage system includes:

[0034] A power supply circuit, used for supplying electric energy, electrically connected to the gas pressure sensor and the conductive sheet;

[0035] A status display, electrically connected to the conductive sheet and the gas pressure sensor, for displaying the power supply status of the gas pressure sensor and the ultrasonic pulser;

[0036] a data processing and display device, electrically connected to the gas pressure sensor, for displaying the gas pressure in the sample chamber and the reference cylinder; the data processing and display device, the data processing and display device is connected to the ultrasonic receiver signal, for displaying wave velocity data;

[0037] A total gas circuit pressure gauge, connected to the gas supply system, for displaying the total input gas pressure;

[0038] The electric control switch is used to control the start and stop of the device and to control the start and close of the electric control valve and the start and stop of the ultrasonic pulser.

[0039] Optionally, the gas supply system comprises:

[0040] A gas storage tank, wherein a plurality of gas storage tanks are provided, and the plurality of gas storage tanks respectively store different gas sources;

[0041] A pressure gauge is arranged in parallel at the gas outlet of the corresponding gas storage tank; it is used to monitor the gas outlet pressure of the corresponding gas storage tank, the gas outlet ends of several gas storage tanks are connected to the gas inlet end of the reference cylinder through the same pipeline, and the total gas circuit pressure gauge is arranged in parallel on the pipeline.

[0042] Compared with the prior art, the present invention has the following advantages and technical effects:

[0043] When in use, by setting the rock velocity and desorption gas joint monitoring system in a constant temperature system, the constant temperature system provides an experimental environment with different temperatures, and the gas supply control system provides desorption gas for the rock velocity and desorption gas joint monitoring system, and the gas supply control system provides an experimental environment with different air pressures, the above settings can realize the joint determination experiment of gas desorption and rock velocity of source rocks at different temperatures and different air pressures. The present invention can simulate the dynamic monitoring experiment of rock velocity of different source rocks with different gas content changes, and by carrying out isothermal desorption experiments under multi-factor coupling conditions of different temperatures, different air pressures and different lithologies, it can truly simulate the gas desorption rate of source rocks in unconventional natural gas production engineering, as well as the dynamic data determination of the change trend of rock velocity of source rocks with desorption gas content at different production stages. The experimental device is simple and easy to operate, has good use effect, and is easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative labor:

[0045] Figure 1 It is a schematic diagram of the structure of the present invention;

[0046] Figure 2 This is a structural diagram of the rock wave velocity and desorption gas joint monitoring system of the present invention;

[0047] Figure 3 A top view of the ultrasonic pulse penetration device of the present invention;

[0048] Figure 4 A top view of the ultrasonic receiving device of the present invention;

[0049] Figure 5 This is a diagram showing the installation structure of the ultrasonic pulse penetrating device and the ultrasonic receiving device of the present invention;

[0050] Among them, 1. terminal operation and gas storage system; 11. data processing and display device; 12. total gas circuit pressure gauge; 13. electric control switch; 2. gas supply system; 21. pressure gauge; 22. gas storage tank; 3. rock wave velocity and desorption gas joint monitoring system; 31. high pressure insulation outer cylinder; 32. sample chamber; 33. ultrasonic pulse penetration device; 331. ultrasonic pulser; 332. conductive buffer pad; 333. air inlet; 334. connecting circuit; 335. core column sample coupling top plate; 336. pulser latch; 34. ultrasonic receiving device; 341. ultrasonic receiver; 342. core column sample coupling bottom plate; 35. conductive sheet; 36. spring; 37. reference cylinder; 38. gas pressure sensor; 4. status display; 41. gas pressure sensor status light; 42. ultrasonic pulse device status light group; 5. desorption gas recovery system; 6. constant temperature system. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] Reference Figures 1 to 5 The present invention discloses a rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks, comprising:

[0054] At least one rock velocity and desorption gas joint monitoring system 3, wherein the rock velocity and desorption gas joint monitoring system 3 is provided with an air chamber for placing the core column sample, the air chamber has an air inlet end and an air outlet end, and the air pressure in the air chamber is adjustable;

[0055] The desorption gas recovery system 5 has a number matching that of the rock velocity and desorption gas joint monitoring system 3, and the gas inlet of the desorption gas recovery system 5 is connected to the gas outlet of the rock velocity and desorption gas joint monitoring system 3, for recovering the desorption gas;

[0056] The constant temperature system 6, the rock wave velocity and desorption gas joint monitoring system 3 and the desorption gas recovery system 5 are arranged in the constant temperature system 6; the constant temperature system 6 is used to provide the temperature environment required by the rock wave velocity and desorption gas joint monitoring system 3;

[0057] The gas supply control system is connected to the gas inlet end of the rock wave velocity and desorption gas joint monitoring system 3 and is used for supplying gas and detecting the gas pressure of the gas chamber.

[0058] When in use, by setting the rock velocity and desorption gas joint monitoring system 3 in the constant temperature system 6, the constant temperature system 6 provides an experimental environment with different temperatures, and the gas supply control system provides desorption gas for the rock velocity and desorption gas joint monitoring system 3, and the gas supply control system provides an experimental environment with different air pressures, the above settings can realize the joint determination experiment of gas desorption and rock velocity of source rocks at different temperatures and different air pressures. The present invention can simulate the dynamic monitoring experiment of rock velocity of different source rocks with different gas content changes, and by carrying out isothermal desorption experiments under multi-factor coupling conditions of different temperatures, different air pressures and different lithologies, it can truly simulate the gas desorption rate of source rocks in unconventional natural gas production engineering, and the dynamic data determination of the change trend of rock velocity of source rocks with desorption gas content at different production stages. The experimental device is simple and easy to operate, has good use effect, and is easy to promote.

[0059] The constant temperature system 6 is composed of a top open heating box and methyl silicone oil. When conducting desorption and rock wave velocity measurement experiments, the rock wave velocity and desorption gas joint monitoring system 3 and the desorption gas recovery system 5 are immersed in methyl silicone oil, which can play a role in temperature control and heat preservation during the experiment.

[0060] As an optional implementation, the rock wave velocity and desorption gas joint monitoring system 3 includes:

[0061] A high pressure resistant heat preservation outer cylinder 31, a sample chamber 32 is arranged on the high pressure resistant heat preservation outer cylinder 31, and the sample chamber 32 is used to place the core column sample;

[0062] The wave velocity measuring part is arranged in the sample chamber 32 and is used to test the wave velocity of the core column sample;

[0063] The air pressure balance part is arranged on one side of the high-pressure heat-insulating outer cylinder 31, the air inlet end of the air pressure balance part is connected with the air outlet end of the air supply control system, and the air outlet end of the air pressure balance part is connected with the air inlet end of the sample chamber 32; the air outlet end of the sample chamber 32 is connected with the air inlet end of the desorption gas recovery system 5; an electric control valve for controlling the on-off of the pipeline is arranged between the air outlet end of the air pressure balance part and the air inlet end of the sample chamber 32; an electric control valve for controlling the on-off of the pipeline is arranged between the air outlet end of the sample chamber 32 and the air inlet end of the desorption gas recovery system 5; a gas pressure sensor 38 is connected in parallel with the air outlet end of the sample chamber 32, and the gas pressure sensor 38 is electrically connected to the air supply control system;

[0064] The gas supply control system collects the gas pressure data of the gas pressure balance part and the sample chamber 32, and collects the wave velocity data of the wave velocity measurement part.

[0065] As an optional embodiment, the air pressure balancing part includes a reference cylinder 37, the air inlet end of the reference cylinder 37 is connected to the air supply control system, the air outlet end of the reference cylinder 37 is connected to the sample chamber 32, and another gas pressure sensor 38 is connected in parallel to the air outlet end of the reference cylinder 37, and the gas pressure sensor 38 is electrically connected to the air supply control system.

[0066] As an optional implementation, the wave velocity measuring unit includes:

[0067] An ultrasonic pulse penetrating device 33 is arranged on the top of the sample chamber 32;

[0068] An ultrasonic receiving device 34 is disposed at the bottom of the sample chamber 32;

[0069] The core column sample is arranged between the ultrasonic pulse penetrating device 33 and the ultrasonic receiving device 34;

[0070] The ultrasonic receiving device 34 is connected to the air supply control system signal.

[0071] As an optional embodiment, the ultrasonic pulse penetration device 33 includes:

[0072] The core column sample is coupled with a top plate 335, the bottom of which is in contact with the top of the core column sample; a plurality of air inlets 333 are arranged at equal intervals in the circumferential direction on the top of the core column sample coupling top plate 335;

[0073] The ultrasonic pulser 331 is axially connected to the top of the core column sample coupling top plate 335; the ultrasonic pulser 331 is electrically connected to a conductive buffer pad 332 through a connecting circuit 334, the conductive buffer pad 332 is arranged between two adjacent air inlets 333, and the conductive buffer pad 332 is fixed to the top of the core column sample coupling top plate 335;

[0074] The bottom end of the conductive elastic part is fixedly connected to the conductive buffer pad 332 , and the top end of the conductive elastic part is connected to the top of the sample chamber 32 . The conductive elastic part is used to connect to the power supply wire.

[0075] As an optional embodiment, the conductive elastic part includes a spring 36, the bottom end of the spring 36 is fixed to the conductive buffer pad 332, the top end of the spring 36 is fixed with a conductive sheet 35, the conductive sheet 35 is embedded in the top inner wall of the sample chamber 32, and the conductive sheet 35 is electrically connected to the power supply.

[0076] As an optional implementation, the ultrasonic receiving device 34 includes:

[0077] The core column sample coupling bottom plate 342 is fixed to the bottom of the sample chamber 32;

[0078] The ultrasonic receiver 341 is axially connected to the top of the core column sample coupling bottom plate 342, and the ultrasonic receiver 341 is connected to the gas supply control system signal.

[0079] The rock velocity and desorption gas joint monitoring system 3 includes a high-pressure insulation outer cylinder 31, a sample chamber 32, an ultrasonic pulse penetration device 33, an ultrasonic receiving device 34, a conductive sheet 35, a spring 36, a reference cylinder 37, and a gas pressure sensor 38. The gas pressure sensor 38 is connected to the reference cylinder 37 and the ends of each branch gas path of the sample chamber 32 to monitor the gas pressure changes of different units in real time. The ultrasonic pulse penetration device 33 is connected to the spring 36 and the conductive sheet 35. Through the spring 36, the ultrasonic pulse penetration device 33 can be tightly coupled to the top of the core column sample to ensure the accuracy of the rock velocity measurement.

[0080] The ultrasonic pulse penetration device 33 includes an ultrasonic pulser 331, a conductive buffer pad 332, an air inlet 333, a connecting circuit 334, a core column sample coupling top plate 335, and a pulser latch 336. The ultrasonic receiving device 34 includes an ultrasonic receiver 341 and a core column sample coupling bottom plate 342.

[0081] The ultrasonic pulser 331 is fixed to the core column sample coupling top plate 335 through the pulser latch 336. The coupling top plate is connected to the sample chamber 32 through the spring 36, and the relative position of the core column sample coupling top plate 335 inside the cylinder body is controlled by the spring 36 to ensure that the core column sample coupling top plate 335 is tightly connected to the top of the core column sample; the core column sample coupling bottom plate 342 is fixed to the bottom of the sample chamber to ensure that it is tightly connected to the bottom of the core column sample.

[0082] The conductive buffer pad 332 on the core column sample coupling top plate 335 can reduce the impact of the instantaneous release of spring kinetic energy on the coupling top plate, avoid longitudinal displacement of the coupling top plate, and reduce experimental errors; the four circular air inlets 333 of the coupling top plate can ensure the smoothness of the air path when the coupling top plate is closely connected with the core column sample.

[0083] The desorption gas recovery system 5 is connected to the sample chamber 32 through the unit gas path, which can temporarily store the desorption gas of the source rock, and finally connect it to the main gas path. After the experiment is completed, the desorption waste gas is directly discharged, or connected to the gas chromatograph for further desorption gas composition analysis.

[0084] As an optional implementation, the air supply control system includes:

[0085] The terminal operation and gas storage system 1, the air inlet end is connected to the air outlet end of the gas supply system 2, the air outlet end of the terminal operation and gas storage system 1 is connected to the air inlet end of the reference cylinder 37, and the terminal operation and gas storage system 1 is used to control the air supply and feedback the air pressure and wave speed data.

[0086] As an optional implementation, the terminal operation and gas storage system 1 includes:

[0087] A power supply circuit, used for supplying electric energy, electrically connected to the gas pressure sensor 38 and the conductive sheet 35;

[0088] A status display 4, electrically connected to the conductive sheet 35 and the gas pressure sensor 38, for displaying the power supply status of the gas pressure sensor 38 and the ultrasonic pulser 331;

[0089] The data processing and display device 11 is electrically connected to the gas pressure sensor 38 and is used to display the gas pressure in the sample chamber 32 and the reference cylinder 37; the data processing and display device 11 is signal-connected to the ultrasonic receiver 341 and is used to display wave velocity data;

[0090] A total gas circuit pressure gauge 12, connected to the gas supply system 2, for displaying the total input gas pressure;

[0091] The electric control switch 13 is used to control the start and stop of the device and the start and stop of the electric control valve and the start and stop of the ultrasonic pulser 331.

[0092] As an optional embodiment, the gas supply system 2 includes:

[0093] A gas storage tank 22, wherein a plurality of gas storage tanks 22 are provided, and the plurality of gas storage tanks 22 respectively store different gas sources;

[0094] The pressure gauge 21 is arranged in parallel at the outlet end of the corresponding gas storage tank 22; it is used to monitor the outlet pressure of the corresponding gas storage tank 22. The outlet ends of several gas storage tanks 22 are connected to the inlet end of the reference cylinder 37 through the same pipeline, and the total gas circuit pressure gauge 12 is arranged in parallel on the pipeline.

[0095] The main circuit is responsible for connecting the terminal operation and gas storage system 1, the ultrasonic pulse penetration device 33, and the gas pressure sensor 38. It can transmit the monitored air pressure and rock wave velocity data to the terminal operation and gas storage system 1, and display them in real time on the data processing and display device 11, so as to facilitate the experimental operators to carry out data proofreading and analysis.

[0096] The gas supply system 2 includes three independent gas storage tanks 22, each of which is independently connected to a pressure gauge 21, which can flexibly adjust the content ratio of the experimental gas. In actual use, in conventional experiments, the three independent gas storage tanks store 99.9% high-purity gases of three different components, namely low-pressure helium (3Mpa), high-pressure methane (12Mpa), and high-pressure carbon dioxide (12Mpa). Low-pressure helium is an inert gas and is not adsorbed by the pores of the source rock. It can be used to measure the free space volume of the reference cylinder and the sample chamber; high-pressure methane and carbon dioxide can be mixed in the terminal operation and gas storage system 1, and the content ratio of the mixed gas can be flexibly adjusted according to the experimental requirements and the type of core samples. At the same time, the terminal operation and gas storage system 1 is equipped with a total gas circuit pressure gauge 12 and an electric control switch 13, which can adjust the gas pressure finally delivered to each experimental unit.

[0097] The status display 4 includes a gas pressure sensor status light 41 and an ultrasonic pulse device status light group 42, which are connected to the ultrasonic pulse penetration device 33, the gas pressure sensor 38, the terminal operation and gas storage system 1 through a circuit to monitor the working status of the ultrasonic pulse penetration device 33 and the gas pressure sensor 38 in real time to ensure the normal operation of the instrument and the effective recovery of data.

[0098] The working principle and process of the present invention are as follows:

[0099] When conducting the experiment, the volume parameters of the core column sample are first measured and recorded, the cover of the sample chamber 32 is opened, and then the core column sample is vertically placed in the sample chamber 32 to ensure that the bottom of the core column sample is closely connected to the core column sample coupling bottom plate 342; the cover of the sample chamber 32 is pressed tightly to ensure that the core column sample coupling top plate 335 is closely connected to the top of the core column sample under the action of the spring 36. After the core sample is placed, the rock wave velocity and desorption gas joint monitoring system 3 and the desorption gas recovery system 5 are placed in the constant temperature system 6.

[0100] The ultrasonic pulse penetration device 33 is turned on to continuously monitor the rock wave velocity of the core column sample until the end of the experiment. The elastic wave velocity of the ultrasonic wave passing through the experimental sample is obtained by measuring the time taken for the ultrasonic wave to pass through the core column sample and dividing the core column length by the time (Formulas 2 and 3). Finally, the measured rock wave velocity is viewed in real time through the data processing and display device 11.

[0101] Vp= L / tp (2)

[0102] Vs= L / ts (3)

[0103] Where Vp is the rock longitudinal wave velocity, Vs is the rock shear wave velocity, L is the length of the core column sample, tp and ts represent the time it takes for the longitudinal wave and shear wave to pass through the rock sample, respectively.

[0104] The experimental temperature is set by the constant temperature system 6. After the system temperature is stable, the helium tank of the gas supply system 2 is opened and the pressure is adjusted to 0.5MPa. The first gas circuit and the second gas circuit electric control valve are opened to fill helium into the terminal operation and gas storage system 1 and the reference cylinder 37 to make the gas pressure reach 0.5MPa, and the gas pressure values ​​of the reference cylinder 37 and the sample chamber 32 are recorded at this time; then the first gas circuit and the second gas circuit electric control valve are closed, and the electric control valve of the unit gas circuit between the reference cylinder 37 and the sample chamber 32 is opened to keep the reference cylinder 37 connected to the sample chamber 32. Let it stand for 20 minutes, wait for the gas pressure of the reference cylinder 37 and the sample chamber 32 to be stable and balanced, and record the gas pressure values ​​of the two cylinders at this time. Repeat the above steps 3-5 times, take the average value of the gas pressure measured before and after the balance, and substitute it into the corresponding formula to calculate the free space volume of the sample chamber 32. After the free space volume is measured, close the first gas circuit electric control valve, open all the electric control valves of the second gas circuit and the unit gas circuit, and discharge all the helium from the experimental device.

[0105] Open the methane gas tank and carbon dioxide gas tank of the gas supply system 2, and adjust the pressure to obtain the mixed gas ratio required for the experiment (except the helium gas tank, the other two gases can be flexibly replaced according to the experimental requirements), open the first gas circuit and the second gas circuit electric control valve, fill the terminal operation and gas storage system 1 and the reference cylinder 37 with experimental gas, so that the gas pressure reaches 12MPa, and record the gas pressure and rock wave velocity values ​​of the reference cylinder 37 and the sample chamber 32 at this time; then close the first gas circuit and the second gas circuit electric control valve, open the electric control valve of the unit gas circuit between the reference cylinder 37 and the sample chamber 32, keep the reference cylinder 37 connected to the sample chamber 32, let it stand for 12 hours, wait for the core sample in the sample chamber 32 to reach the adsorption saturation state, and record the gas pressure and rock wave velocity values ​​of the core sample when it reaches the adsorption saturation state.

[0106] After the core sample is saturated with adsorbed gas, close the electric control valve of the unit gas path between the reference cylinder 37 and the sample chamber 32, and use the experimentally designed desorption pressure gradient as the threshold value (e.g., 10MPa, 8MPa, 6MPa, 4MPa, 2MPa, 0MPa), repeatedly open and close the electric control valve of the unit gas path between the sample chamber 32 and the desorption gas recovery system 5, so that the gas pressure of the sample chamber 32 drops to the designed pressure gradient threshold value, and stand for 12 hours until the negative pressure desorption is completed, and record the gas pressure and rock wave velocity values ​​of the core sample at the desorption pressure point. Repeat the above steps to the lowest set pressure of 0Mpa to ensure that the adsorbed gas of the core sample has been completely desorbed, record the gas pressure and rock wave velocity values ​​after the core sample desorption is completed, and calculate the gas content of the core sample at different desorption pressures through the corresponding formula, and finally characterize the dynamic change trend of the rock wave velocity of the core sample at different desorption pressures with its gas content through the terminal operation and the gas storage system 1.

[0107] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0108] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks, characterized in that: include: At least one rock wave velocity and desorption gas combined monitoring system (3), wherein the rock wave velocity and desorption gas combined monitoring system (3) is provided with an air chamber for placing a core column sample, the air chamber has an air inlet end and an air outlet end, and the air pressure in the air chamber is adjustable; a desorption gas recovery system (5), the number of which matches that of the rock velocity and desorption gas combined monitoring system (3); an air inlet of the desorption gas recovery system (5) is connected to an air outlet of the rock velocity and desorption gas combined monitoring system (3) for recovering desorption gas; A constant temperature system (6), wherein the rock wave velocity and desorption gas joint monitoring system (3) and the desorption gas recovery system (5) are arranged in the constant temperature system (6); the constant temperature system (6) is used to provide a temperature environment required by the rock wave velocity and desorption gas joint monitoring system (3); A gas supply control system is connected to the gas inlet end of the rock wave velocity and desorption gas joint monitoring system (3) and is used for supplying gas and detecting the gas pressure of the gas chamber.

2. A rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks according to claim 1, characterized in that: The rock wave velocity and desorption gas joint monitoring system (3) comprises: A high-pressure resistant heat-insulating outer cylinder (31), a sample chamber (32) being arranged on the high-pressure resistant heat-insulating outer cylinder (31), and the sample chamber (32) being used for placing a core column sample; A wave velocity measuring unit, arranged in the sample chamber (32), for testing the wave velocity of the core column sample; A gas pressure balance part is arranged on one side of the high-pressure resistant heat-insulating outer cylinder (31); the gas inlet end of the gas pressure balance part is connected to the gas outlet end of the gas supply control system, and the gas outlet end of the gas pressure balance part is connected to the gas inlet end of the sample chamber (32); the gas outlet end of the sample chamber (32) is connected to the gas inlet end of the desorption gas recovery system (5); an electric control valve for controlling the on-off of the pipeline is arranged between the gas outlet end of the gas pressure balance part and the gas inlet end of the sample chamber (32); an electric control valve for controlling the on-off of the pipeline is arranged between the gas outlet end of the sample chamber (32) and the gas inlet end of the desorption gas recovery system (5); a gas pressure sensor (38) is connected in parallel to the gas outlet end of the sample chamber (32), and the gas pressure sensor (38) is electrically connected to the gas supply control system; The gas supply control system collects the gas pressure data of the gas pressure balance unit and the sample chamber (32), and collects the wave velocity data of the wave velocity measurement unit.

3. The rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks according to claim 2 is characterized by: The air pressure balancing unit comprises a reference cylinder (37), the air inlet end of the reference cylinder (37) is connected to the air supply control system, the air outlet end of the reference cylinder (37) is connected to the sample chamber (32), the air outlet end of the reference cylinder (37) is connected in parallel with another gas pressure sensor (38), and the gas pressure sensor (38) is electrically connected to the air supply control system.

4. A rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks according to claim 3, characterized in that: The wave velocity measuring unit comprises: An ultrasonic pulse penetration device (33) is arranged on the top of the sample chamber (32); An ultrasonic receiving device (34) is arranged at the bottom of the sample chamber (32); The core column sample is arranged between the ultrasonic pulse penetration device (33) and the ultrasonic receiving device (34); The ultrasonic receiving device (34) is connected to the air supply control system signal.

5. A rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks according to claim 4, characterized in that: The ultrasonic pulse penetration device (33) comprises: A core column sample coupling top plate (335), wherein the bottom of the core column sample coupling top plate (335) contacts the top of the core column sample; a plurality of air inlets (333) are arranged at equal intervals in the circumferential direction on the top of the core column sample coupling top plate (335); An ultrasonic pulser (331) is axially connected to the top of the core column sample coupling top plate (335); the ultrasonic pulser (331) is electrically connected to a conductive buffer pad (332) via a connecting circuit (334); the conductive buffer pad (332) is arranged between two adjacent air inlets (333); and the conductive buffer pad (332) is fixed to the top of the core column sample coupling top plate (335); The bottom end of the conductive elastic part is fixedly connected to the conductive buffer pad (332), the top end of the conductive elastic part is connected to the top of the sample chamber (32), and the conductive elastic part is used to connect to the power supply wire.

6. The rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks according to claim 5, characterized in that: The conductive elastic part includes a spring (36), the bottom end of the spring (36) is fixedly connected to the conductive buffer pad (332), the top end of the spring (36) is fixedly connected to a conductive sheet (35), the conductive sheet (35) is embedded in the top inner wall of the sample chamber (32), and the conductive sheet (35) is electrically connected to a power source.

7. A rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks according to claim 4, characterized in that: The ultrasonic receiving device (34) comprises: A core column sample coupling bottom plate (342) fixedly connected to the bottom of the sample chamber (32); An ultrasonic receiver (341) is axially connected to the top of the core column sample coupling base plate (342), and the ultrasonic receiver (341) is connected to the gas supply control system signal.

8. A rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks according to claim 7, characterized in that: The air supply control system comprises: The terminal operation and gas storage system (1) has an air inlet connected to an air outlet of a gas supply system (2), and the air outlet of the terminal operation and gas storage system (1) is connected to an air inlet of the reference cylinder (37). The terminal operation and gas storage system (1) is used to control the air supply and feedback air pressure and wave velocity data.

9. A rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks according to claim 8, characterized in that: The terminal operation and gas storage system (1) comprises: A power supply circuit, used for supplying electric energy, electrically connected to the gas pressure sensor (38) and the conductive sheet (35); a status display (4), electrically connected to the conductive sheet (35) and the gas pressure sensor (38), and used to display the power supply status of the gas pressure sensor (38) and the ultrasonic pulser (331); A data processing and display device (11) is electrically connected to the gas pressure sensor (38) and is used to display the gas pressure in the sample chamber (32) and the reference cylinder (37); the data processing and display device (11) is signal-connected to the ultrasonic receiver (341) and is used to display wave velocity data; A total gas circuit pressure gauge (12), connected to the gas supply system (2) and used to display the total input gas pressure; The electric control switch (13) is used to control the start and stop of the device and control the start and close of the electric control valve and the start and stop of the ultrasonic pulser (331).

10. A rock wave velocity dynamic monitoring test system for simulating the change of gas content in source rocks according to claim 9, characterized in that: The gas supply system (2) comprises: A gas storage tank (22), wherein a plurality of the gas storage tanks (22) are provided, and the plurality of gas storage tanks (22) respectively store different gas sources; A pressure gauge (21) is arranged in parallel at the gas outlet end of the corresponding gas storage tank (22); it is used to monitor the gas outlet pressure of the corresponding gas storage tank (22); the gas outlet ends of several gas storage tanks (22) are connected to the gas inlet end of the reference cylinder (37) through the same pipeline, and the total gas circuit pressure gauge (12) is arranged in parallel on the pipeline.

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