Testing device for measuring adsorption or desorption amount in coal and strain rule of coal body

Abstract

The invention discloses a testing device for measuring the adsorption or desorption amount in coal and the strain law of a coal body, and relates to the technical field of coal and coal bed gas development, and the key point of the technical scheme is that the testing device comprises a gas steel cylinder, a constant-temperature box, a plurality of groups of experimental testing equipment and a data detection system, and the experimental testing equipment is located in the constant-temperature box; the output end of the gas steel cylinder is connected with a gas injection hose, the gas injection hose is communicated with experimental testing equipment, the experimental testing equipment comprises a reference cylinder and a sample cylinder, pressure sensors are mounted on a top cover of the reference cylinder and the side surface of the sample cylinder, the sensors are hermetically connected with the interior of the steel cylinder, and the pressure sensors are connected with a data monitoring system through acquisition lines. A cylindrical coal sample attached with a strain gauge is placed in the sample cylinder, and the data monitoring system is connected with the strain gauge through an acquisition line. According to the invention, the influence of different gas types, different temperatures and adsorption quantities on the adsorption deformation of the coal body can be tested, and the strain rule of adsorption / desorption of gas in coal under the influence of multiple factors can be conveniently researched.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal and coal bed methane development, more particularly, it relates to a testing device for measuring the amount of gas adsorption or desorption in coal and the strain law of coal body. BACKGROUND

[0002] Methane in coal mainly exists in the pore-fracture system of coal in an adsorbed state. The most commonly used technology for the development of coal bed methane is currently hydraulic fracturing to reduce the pressure of the coal reservoir. The reduction of the reservoir pressure will break the adsorption kinetics of methane, and the methane adsorbed on the surface of the coal pores will desorb, diffuse and seep, and then migrate to the wellbore for production. During the production of coal bed methane, the change in permeability is easily affected by the effective stress effect, matrix shrinkage effect and slippage effect. Research on the matrix shrinkage effect of the coal reservoir can provide theoretical guidance for improving the change in coal bed methane permeability in the later stage.

[0003] The expansion or shrinkage effect of the coal body during the adsorption or desorption process is collectively referred to as adsorption deformation. During the production stage of coal bed methane, the reduction of the reservoir pressure will cause the desorption of the methane adsorbed in the coal matrix, and the coal matrix that originally produces adsorption deformation will gradually shrink and become smaller. There are two main reasons for the adsorption deformation: one is that the gas pressure drives the gas molecules to enter the pore space or microfracture space of the coal or even the interior of the coal body colloidal particles. The gas molecules enter the pores with a diameter comparable to their own, and expand the pore space. The second is that adsorption causes the coal surface energy to decrease, resulting in linear expansion of the coal surface. Adsorption expansion and desorption shrinkage will cause the fracture opening of the coal to decrease or increase, thereby causing the change in the permeability of the coal body, which has an important influence on the effect of coal bed methane extraction.

[0004] The adsorption deformation of the coal body is related to the amount of gas adsorbed by the coal, and the amount of adsorption is affected by the characteristics of the adsorbent (coal rock, coal quality, pore distribution), the type of gas, the adsorption pressure and the adsorption temperature. Past research on the adsorption deformation of coal has mainly focused on the single factor affecting the adsorption deformation of coal, such as the type of gas and the gas pressure. However, there is less research on the adsorption deformation of the coal body under the influence of different gas types, different temperatures and different adsorption amounts, and there is no instrument that can combine the above factors to test the adsorption deformation law of the coal. In view of this, how to test the strain law caused by the adsorption / desorption of methane in coal under the influence of multiple factors is crucial for studying the change law of the permeability of the coal reservoir. SUMMARY

[0005] The purpose of the present application is to provide a testing device for measuring the amount of adsorption or desorption in coal and the strain law of the coal body, which solves the above problems.

[0006] The above technical purpose of the present application is achieved by the following technical scheme:

[0007] The present application provides a kind of measuring coal adsorption or desorption amount and coal body strain law testing device, including gas cylinder, thermostat, multiple experimental test equipment and data detection system, the experimental test equipment is located in thermostat, the output end of the gas cylinder is connected with gas injection hose, the gas injection hose is communicated with experimental test equipment, the experimental test equipment includes reference cylinder and sample cylinder, the reference cylinder top cover and sample cylinder side are equipped with pressure sensor, the sensor is sealedly connected between steel bottle interior, the pressure sensor is connected with data monitoring system by acquisition line, the sample cylinder is placed into columnar coal sample with strain gauge, the data monitoring system is connected with strain gauge by acquisition line.

[0008] The present application is further provided that: the experimental test equipment has 4 groups.

[0009] The present application is further provided that: the reference cylinder top is equipped with gas delivery pipeline one, the gas injection hose is connected with gas delivery pipeline one, the gas delivery pipeline one is equipped with gas inlet end and gas outlet end, the gas inlet end is communicated with sample cylinder, the gas inlet end and gas outlet end are both equipped with gas control valve, the reference cylinder and sample cylinder are equipped with gas delivery pipeline two, the gas delivery pipeline two is also equipped with gas control valve.

[0010] The present application is further provided that: the data monitoring system is composed of data acquisition instrument and computer, the computer receives the information recorded by data acquisition instrument through data line, the data acquisition instrument is composed of pressure sensor collector and strain gauge data collector.

[0011] The present application is further provided that: pressure sensor collector is connected with pressure sensor through pressure data acquisition line, and the pressure change data in the whole experiment process is collected.

[0012] The present application is further provided that: strain gauge data collector is connected with strain gauge through strain data acquisition line, and strain data in the process of gas adsorption / desorption is recorded.

[0013] The present application is further provided that: the top end of the thermostat is equipped with circulating heater.

[0014] In conclusion, the present application has the following beneficial effects: the present application can test the influence of different gas types, different temperatures and adsorption amount size on coal body adsorption deformation, and facilitate to study the strain law caused by coal methane adsorption / desorption under the influence of multiple factors. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a kind of measuring coal adsorption or desorption amount and coal body strain law testing device composition diagram in the embodiment of the present application;

[0016] Figure 2 It is coal sample size diagram in the embodiment of the present application.

[0017] Figure 3 is a coal sample processing diagram in the embodiment of the present application;

[0018] Figure 4 is a diagram of the experimental test equipment in the embodiment of the present application.

[0019] In the figure: 1, gas cylinder; 2, pressure valve; 3, gas filling hose; 4, gas control valve; 5, pressure sensor; 6, reference cylinder; 7, sample device; 8, sample cylinder; 9, coal sample; 10, strain gauge; 11, thermostat; 12, circulating heater; 13, pressure sensor collector; 14, strain gauge data collector; 15, data acquisition instrument; 16, computer; 17, pressure data acquisition line; 18, strain data acquisition line; 19, data line. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0021] Embodiment:

[0022] A test device for measuring the adsorption or desorption amount in coal and the strain regularity of coal, as shown in Figure 1 , Figure 2 , Figure 3 and Figure 4 , comprises a gas cylinder, a thermostat 11, multiple sets of experimental test equipment and a data detection system. The experimental test equipment is located in the thermostat 11. The output end of the gas cylinder is connected with a gas filling hose, and the gas filling hose is in communication with the experimental test equipment.

[0023] The gas cylinder is provided with a pressure valve 2, which can adjust the gas pressure during the gas filling process.

[0024] In the embodiment, four sets of experimental test equipment are set up to test CH4, CO2, N2 and He respectively. The experimental test equipment comprises a reference cylinder 6 and a sample cylinder 8. Both the reference cylinder 6 and the sample cylinder 8 are composed of steel material. The reference cylinder 6 and the sample cylinder 8 are connected with a gas conveying pipeline which is a metal pipe and is provided with multiple gas control valves 4 to ensure the circulation of gas between the sample cylinder 8, the reference cylinder 6 and the atmosphere.

[0025] The experimental test equipment provides a stable high pressure environment for coal rock adsorption-desorption process, is made of steel material, and can bear a maximum pressure of 25 MPa. The reference cylinder 6, the sample cylinder 8 and the atmosphere are connected by metal pipelines, have good sealing property, and the gas flow therebetween is controlled by the gas control valve 4. The pressure sensor 5 is installed near the reference cylinder 6 and the sample cylinder 8, and is used for recording the free gas pressure changes in the reference cylinder 6 and the sample cylinder 8 during the whole experiment.

[0026] With reference to Figure 1 and Figure 4 , the reference cylinder 6 is provided with a gas conveying pipeline 1, a gas injection hose is connected with the gas conveying pipeline 1, the gas conveying pipeline 1 is provided with an air inlet end and an air outlet end, the air inlet end is communicated with the sample cylinder 8, the air inlet end and the air outlet end are both provided with the gas control valve 4, the gas conveying pipeline 2 is arranged between the reference cylinder 6 and the sample cylinder 8, and the gas conveying pipeline 2 is also provided with the gas control valve 4. In the device, the reference cylinder 6 placed in the thermostat 11 is injected by the gas injection cylinder, the gas is injected through the gas injection hose, and the pressure valve 2 on the gas injection cylinder can adjust the gas pressure during the injection.

[0027] The pressure sensor 5 is installed on the top cover of the reference cylinder 6 and the side surface of the sample cylinder 8, is sealingly connected between the sensor and the inside of the cylinder, is connected with the data monitoring system through the acquisition line, and monitors the pressure change in the cylinder. The columnar coal sample 9 with the strain gauge 10 attached is placed in the sample cylinder 8, the data monitoring system is connected with the strain gauge 10 through the acquisition line, and can record the strain of the coal sample 9 during the adsorption / desorption process.

[0028] The data monitoring system is composed of the data acquisition instrument 15 and the computer 16, the data acquisition instrument 15 is composed of the pressure sensor collector 13 and the strain gauge data collector 14, the pressure sensor collector 13 is connected with the pressure sensor 5 through the pressure data acquisition line 17, and collects the pressure change data during the whole experiment. The strain gauge data collector 14 is connected with the strain gauge 10 through the strain data acquisition line 18, and records the strain data during the gas adsorption / desorption process. The computer 16 receives the information recorded by the data acquisition instrument 15 through the data line 19.

[0029] The circulating heater 12 is installed at the top end of the thermostat 11, the circulating pump of the heater circulates the heated air in the thermostat 11, and ensures that the temperature in the box is uniformly distributed.

[0030] Coal sample processing

[0031] The experimental coal sample 9 is selected, a circular coal column is drilled by a sample drilling machine, and the diameter and height of the coal column are accurately measured by a vernier caliper: the diameter is 50 mm, and the radial length is 100 mm Figure 2 The top and bottom of the coal sample 9 are cut flat, and the strain gauges 10 are attached to the top, bottom and surrounding of the coal sample 9, and then the coal sample 9 is placed in a drying box to remove the water in the coal.

[0032] As Figure 3 shown, the cyano acrylate is pasted on the ground and side of the coal sample 9 with resistance strain gauges 10 to avoid bubbles during the process of pasting and ensure the strain gauges 10 are intact. Figure 3 The strain gauges 10 have data collection lines connected to an external strain gauge data collector 14, and the strain tester has an accuracy error of ±2% and a collection rate of not less than 2KHz.

[0033] Experimental process

[0034] 1) Before the experiment, the volume of the sample cylinder 8 (V1) and the reference cylinder 6 (V2) are measured, and helium gas is injected into the reference cylinder 6 and the sample cylinder 8 through the gas storage cylinder 1 to measure the volume of the reference cylinder 6 and the sample cylinder 8. Helium is a non-adsorbed gas with a very small kinetic diameter, which can easily enter the small pore space in the coal. Then the sample is placed in the sample cylinder 8, and after checking the sealing, helium is continuously injected to measure the free gas space volume (V3) in the sample cylinder 8. Figure 4

[0035] 2) Experimental environment: the constant temperature oven 11-11 is set to 25℃, 35℃ and 45℃, etc.

[0036] 3) Gas tightness: the gas storage cylinder 1-1 and the pressure boosting control system inject 2-20MPa of helium gas into the reference cylinder 6 and the sample cylinder 8, and record the pressure change for 24 hours.

[0037] 4) Measurement and calculation of the volume of the sample cylinder 8, the reference cylinder 6 and the free gas in the sample cylinder 8.

[0038] 5) Vacuum pumping. Open the vacuum pump and open all valves between the sample cylinder 8 and the reference cylinder 6 to perform vacuum treatment on the sample cylinder 8 and the reference cylinder 6 to remove impurity gases.

[0039] 6) Gas adsorption. Select CO2, CH4 and N2 as the adsorbed gas. Close the valve between the sample cylinder 8 and the reference cylinder 6, and sequentially inject different types of gas into the reference cylinder 6 at 2MPa, 4MPa, 6MPa, 8MPa, 10MPa, 12MPa……20MPa, open the valve between the reference cylinder 6 and the sample cylinder 8, and after the pressure of the two cylinders is balanced, close the valve to make the coal sample 9 adsorb for 24 hours to reach adsorption equilibrium. Repeat the process of gas injection and pressure increase in sequence until the highest pressure set in the experiment, then record the pressure change of the sample cylinder 8 and the reference cylinder 6 through the pressure sensor collector 13, and record the adsorption expansion data through the strain gauge data collector 14.

[0040] ​7) Gas desorption. After the highest pressure adsorption equilibrium is reached, open the valve of reference cylinder 6, and exhaust the gas to atmospheric pressure. Note that the methane should be exhausted slowly and separately to avoid open flame for safety. After the gas of reference cylinder 6 is exhausted, close the valve, open the valve between sample cylinder 8 and reference cylinder 6, and desorb for 24 hours. Record the pressure data and strain data during the desorption process.

[0041] 8) Data processing. Convert the pressure data to adsorption amount at different pressures, and convert the strain data to strain size.

[0042] Finally, it should be noted that the above only for the preferred embodiments of the present application, and is not intended to limit the present application, although the foregoing embodiments of the present application have been described in detail, for those skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement of the technical solutions described in the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included within the scope of the present application.

Claims

1. A testing device for measuring the amount of adsorption or desorption in coal and the strain law of coal body, characterized in that: The utility model relates to a gas adsorption / desorption experimental test device, including gas cylinder, thermostat, multiple sets of experimental test equipment and data detection system, experimental test equipment is located in thermostat, the output of gas cylinder is connected with gas injection hose, gas injection hose communicates with experimental test equipment, experimental test equipment includes reference cylinder and sample cylinder, reference cylinder top cover and sample cylinder side are equipped with pressure sensor, sensor is sealedly connected between steel bottle inside, pressure sensor is connected with data monitoring system through acquisition line, sample cylinder is placed into columnar coal sample with strain gauge, data monitoring system is connected with strain gauge through acquisition line.

2. The testing device for measuring the adsorption or desorption amount and the strain regularity of coal according to claim 1, characterized in that: The experimental test equipment has 4 groups.

3. The testing device for measuring the adsorption or desorption amount and the strain regularity of coal according to claim 1, characterized in that: The reference cylinder top is equipped with gas delivery pipeline no.

4. The testing device for measuring the adsorption or desorption amount and the strain regularity of coal according to claim 1, characterized in that: The data monitoring system is composed of a data acquisition instrument and a computer.

5. The testing device for measuring the adsorption or desorption amount and the strain regularity of coal according to claim 4, characterized in that: The pressure sensor collector is connected with the pressure sensor through a pressure data acquisition line to collect pressure change data during the whole experiment.

6. The testing device for measuring the adsorption or desorption amount and the strain regularity of coal according to claim 4, characterized in that: The strain gauge data collector is connected with the strain gauge through a strain data acquisition line to record strain data during the gas adsorption / desorption process.

7. The testing device for measuring the adsorption or desorption amount and the strain regularity of coal according to claim 1, characterized in that: The top of the thermostat is provided with a circulating heater.

8. The testing device for measuring the adsorption or desorption amount and the strain regularity of coal according to claim 1, characterized in that: The gas injection cylinder is provided with a pressure valve.

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