CN108732329B - Coal seam gas pressure measurement simulation experiment device and method - Google Patents
Coal seam gas pressure measurement simulation experiment device and method Download PDFInfo
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- CN108732329B CN108732329B CN201810497957.XA CN201810497957A CN108732329B CN 108732329 B CN108732329 B CN 108732329B CN 201810497957 A CN201810497957 A CN 201810497957A CN 108732329 B CN108732329 B CN 108732329B
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Abstract
The invention relates to a simulation experiment method, in particular to a simulation experiment device and a simulation experiment method for measuring the pressure of coal seam gas, comprising a coal sample tank, a high-pressure nitrogen cylinder, a conveying pipe and a gas pressure sensor, wherein the coal sample tank comprises a tank body, a sealing cover, an air inlet, an air outlet and a simulation drilling pipeline, the simulation drilling pipeline is vertically arranged in the center of the tank body, the bottom of the simulation drilling pipeline is fixedly connected with the bottom surface of the tank body, and the top of the simulation drilling pipeline penetrates through and is exposed out of the sealing cover; the surface of the simulated drilling pipeline is provided with a plurality of simulated drilling holes; the high-pressure nitrogen bottle is connected with the air inlet of the coal sample tank through a conveying pipe, and the gas pressure sensor is connected with the air outlet of the coal sample tank. The device and the method for the analogue simulation experiment of the coal seam gas pressure measurement are simple in structure, verify the assumption that the smaller the volume of the air chamber is, the faster the pressure balance time is, are simple and convenient in operation process, short in verification time and reliable in experimental result, and can solve the problems that the experimental period is long in a coal mine underground, the achievement is difficult to intuitively embody, and the like.
Description
Technical Field
The invention relates to a simulation experiment method, in particular to a simulation experiment device and method for measuring coal seam gas pressure.
Background
Gas is the product of coalification, and gas in coal is adsorbed in molecular form on the surface of the coal surface due to the presence of Van der Waals forces. The gas contained in the coal is classified into adsorbed gas, free gas, and trace dissolved gas. The gas pressure is a product of movement of free gas, and under the condition that the coal seam is not mined or otherwise acted, the free gas exists in larger pores and cracks in the coal body and is in a dynamic balance state with adsorbed gas. When the coal bed is mined, extracted and manually depressurized, the adsorption and desorption state reaches an equilibrium state with the underground atmospheric pressure again, and the direct method is used for measuring the gas pressure utilization. There is a certain internal link between gas pressure, free gas content and adsorbed gas content.
When the gas pressure is measured downhole by the direct method, the following physical phenomena occur: when the hole is not sealed, the gas desorption and diffusion quantity in the whole hole can be far greater than that in a pressure measuring air chamber at the bottom of the hole after the hole is sealed, but the time for the gas concentration value in the pressure measuring air chamber at the bottom of the hole to reach the peak value after the hole is sealed can be far faster than the time for the hole to reach the peak value after the hole is not sealed. For this phenomenon, the person concerned now proposes an ideality assumption about the gas pressure equalization time and the plenum volume, i.e. the smaller the plenum volume, the shorter the gas pressure equalization time. However, the actual measurement of the drilling site of the coal mine is large in engineering quantity, and the measured pressure is inaccurate due to the influence of various actual conditions, so that the verification effect is difficult to achieve.
Disclosure of Invention
The invention provides a simulation experiment device and a simulation experiment method for measuring coal seam gas pressure in order to solve the technical problems.
The invention provides a coal seam gas pressure measurement similar simulation experiment device, which comprises a coal sample tank, a high-pressure nitrogen cylinder, a conveying pipe and a gas pressure sensor, wherein the coal sample tank comprises a tank body, a sealing cover, an air inlet, an air outlet and a simulation drilling pipeline, the sealing cover is arranged at the top of an opening of the tank body, the air inlet is arranged at the sealing cover, the simulation drilling pipeline is vertically arranged at the center of the tank body, the bottom of the simulation drilling pipeline is fixedly connected with the bottom surface of the tank body, and the top of the simulation drilling pipeline penetrates through and is exposed out of the sealing cover; the surface of the simulated drilling pipeline is provided with a plurality of simulated drilling holes; the high-pressure nitrogen cylinder is connected with the air inlet of the coal sample tank through a conveying pipe, and the gas pressure sensor is connected with the air outlet of the coal sample tank.
Further, the tank body is barrel-shaped, and two opposite sides on the outer wall of the tank body are connected with handles; the sealing cover is round, and is provided with a pull ring.
Preferably, the aperture of the air inlet hole is 5mm-10mm.
Preferably, the diameter of the simulated borehole is 2cm.
The length of the simulated drilling pipeline in the tank body is 35cm.
The invention also provides a method for measuring the coal seam gas pressure by adopting the analogue simulation experimental device, which comprises the following steps:
(1) Connecting and debugging each instrument and ensuring the good operation of each instrument and equipment and the air tightness of the coal sample tank;
(2) simulating an initial similar state so that the pressure of the gas in the coal sample tank always keeps a stable pressure value, and the gas enters the pressure measuring air chamber to accord with the desorption and emission diffusion rule of the coal bed gas;
(3) Under the condition that coal is not loaded in the coal sample tank, data are recorded in the experimental process, and the relationship between the balance time of a plurality of groups of gas pressure values and the volume of the pressure measuring air chamber is respectively obtained;
(4) And (3) carrying out simulated pressure test on the coal sample, recording data in the experimental process under the condition that the coal sample tank is filled with coal, and respectively obtaining the relationship between the balance time of a plurality of groups of gas pressure values and the volume of the pressure measuring air chamber.
Preferably, the step (1) includes a coal sample tank tightness test, specifically:
connecting the instrument and the equipment, and filling the coal sample into the coal sample tank without filling the coal sample;
coating soapy water on the air inlet and the air outlet of the coal sample tank and the joint of the tank body and the sealing cover;
connecting a gas pressure sensor with the gas outlet, and opening a high-pressure nitrogen bottle to charge gas into the coal sample tank so that the gas injection pressure reaches a certain value;
and observing the positions easy to leak, and if no bubbles are generated and the display reading of the gas pressure sensor is the same as the inflation pressure of the high-pressure nitrogen cylinder, indicating that the gas tightness of the coal sample tank is good.
Preferably, the simulating initial similar state in the step (2) specifically operates as follows:
1) The high-pressure nitrogen cylinder is connected with an air inlet of the coal sample tank through an air injection rubber tube, and a hole is reserved at the connecting part;
2) The simulated coal bed pressure is a certain value A, gas is injected into the coal sample tank according to the pressure value of A+0.12MPa, and after a certain time, the gas pressure in the coal sample tank is always kept within the range of A+/-0.005 MPa;
3) The simulated drilling is processed by the following steps: and coating the cloth polyester fiber on the outer surface of the simulated drilling pipeline, brushing paste on the cloth, continuously coating the cloth on the outer layer of the cloth, winding the cloth on the simulated drilling pipeline by using a nylon ribbon on the last layer, filling cotton into the drilling hole, and preventing coal ash from entering the gas pressure sensor in the pressure measuring process.
Preferably, the specific steps of the empty tank simulation pressure test in the step (3) are as follows:
1) Slowly discharging the gas of the coal sample tank from the gas inlet, wherein the pressure state of the gas in the tank is the same as the atmospheric pressure and is 0MPa after all the gas is discharged;
2) Performing experiments of three groups of pressure values, namely 0.1MPa, 0.3MPa and 0.5MPa, performing full inflation and deflation experiments for a plurality of times, recording the time required for each inflation to the coal sample tank to reach the target pressure value, and finally averaging to obtain the required time;
3) Removing the gas pressure sensor from the top of the simulated drilling pipeline of the coal sample tank, plugging an outlet at the top of the simulated drilling pipeline by using a plug, obtaining average inflation time according to the step 2), inflating, removing the plug after inflation is finished, quickly screwing the pressure sensor on the simulated drilling, and recording the time for observing the sensor to reach each pressure value; changing the volume of the simulated drilling pressure measuring air chamber, and testing the time required for reaching each pressure value under different pressure measuring air chamber volumes according to the method of the step;
4) And drawing a relation chart of the gas pressure balance time and the volume of the pressure measuring air chamber according to the data obtained in the steps, and obtaining the relation of the gas pressure balance time and the volume of the pressure measuring air chamber after analysis.
Further, the method for changing the volume of the pressure measuring air chamber in the step 3) of the empty tank simulation pressure test in the step 3) is as follows: dropping wax oil flowing out of the lighted candle into a drilled hole, and then penetrating a small hole into the solidified wax oil for ventilation; the lengths of the simulated drilling pipelines in the coal sample tank are respectively 30cm, 20cm, 10cm, 5cm, 2cm and 1cm, and the volumes of the corresponding pressure measuring air chambers are respectively 94.2cm 3 、62.8cm 3 、31.4cm 3 、15.7cm 3 、6.28cm 3 、3.14cm 3 Five simulated manometry were performed for each manometric plenum volume.
Further, the specific steps of the step (4) of the simulated pressure test of the coal loading sample are as follows:
1) Loading a coal sample into a coal sample tank, and sealing a sealing cover at an opening at the top of the tank body after loading the coal sample:
2) Performing experiments of three groups of pressure values, namely 0.1MPa, 0.3MPa and 0.5MPa, performing full inflation and deflation experiments for a plurality of times, recording the time required for each inflation to the coal sample tank to reach the target pressure value, and finally averaging to obtain the required time;
3) Removing the gas pressure sensor from the top of the simulated drilling pipeline of the coal sample tank, plugging an outlet at the top of the simulated drilling pipeline by using a plug, obtaining average inflation time according to the step 2), inflating, removing the plug after inflation is finished, quickly screwing the pressure sensor on the simulated drilling, and recording the time for observing the sensor to reach each pressure value; changing the volume of the simulated drilling pressure measuring air chamber, and testing the time required for reaching each pressure value under different pressure measuring air chamber volumes according to the method of the step;
4) And drawing a relation chart of the gas pressure balance time and the volume of the pressure measuring air chamber according to the data obtained in the steps, and obtaining the relation of the gas pressure balance time and the volume of the pressure measuring air chamber after analysis.
Further, the step of loading the coal sample into the coal sample tank in the step (4) -1) comprises the following steps: firstly spreading a coal sample with the grain diameter smaller than 1mm on the bottom layer, then spreading a coal sample layer with the grain diameter of 1mm-3mm and a coal sample layer with the grain diameter of 3mm-5mm upwards in sequence, then mixing and loading the three coal samples with the grain diameter, and finally spreading the coal sample with the grain diameter of 3mm-5mm on the top layer.
By adopting the technical scheme, the method has the following beneficial effects: the analogue simulation experiment device and method for measuring the gas pressure of the coal seam provided by the invention have the advantages of simple structure, simple operation process, short verification time and reliable experiment result, verify the assumption that the smaller the volume of the air chamber is and the faster the pressure balance time is, and can solve the problems of long experiment period, difficult visual achievement and the like of underground experiments of coal mines.
Drawings
FIG. 1 is a schematic diagram of a simulation experiment device for measuring the gas pressure of a coal seam according to an embodiment of the present invention;
FIG. 2 is a graph of the relationship between the volume of the non-coaled plenum and the gas balance time for a pressure value of 0.1 MPa;
FIG. 3 is a graph of the relationship between the volume of the non-coaled plenum and the gas balance time for a pressure value of 0.3 MPa;
FIG. 4 is a graph of the relationship between the volume of the non-coaled plenum and the gas balance time for a pressure value of 0.5 MPa;
FIG. 5 is a graph of the relationship between the volume of a coal-charging pressure measuring air chamber with a pressure value of 0.1MPa and the gas balance time;
FIG. 6 is a graph of the relationship between the volume of a coal-charging pressure measuring air chamber with a pressure value of 0.31MPa and the gas balance time;
FIG. 7 is a graph showing the relationship between the volume and gas balance time of a coal-charging pressure measuring air chamber with a pressure value of 0.31MPa
In the drawing the view of the figure,
1. a high pressure nitrogen cylinder; 2. a delivery tube; 3. a coal sample tank; 3.1, a tank body; 3.2, sealing the cover; 3.3, air inlet; 3.4, an air outlet; 4. a gas pressure sensor; 5. simulating a drilling pipeline; 6. and (5) a coal sample.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the present invention, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate an azimuth or a positional relationship based on that shown in the drawings. These terms are only used to better describe the present invention and its embodiments and are not intended to limit the scope of the indicated devices, elements or components to the particular orientations or to configure and operate in the particular orientations.
Also, some of the terms described above may be used to indicate other meanings in addition to orientation or positional relationships, for example, the term "upper" may also be used to indicate some sort of attachment or connection in some cases. The specific meaning of these terms in the present invention will be understood by those of ordinary skill in the art according to the specific circumstances.
Furthermore, the terms "mounted," "configured," "provided," "connected," and "sleeved" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; may be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements, or components. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
Unless otherwise indicated, the meaning of "a plurality" is two or more.
The invention will now be described in further detail with reference to specific examples thereof in connection with the accompanying drawings.
Examples:
when the gas pressure is measured downhole by the direct method, the following physical phenomena occur: when the hole is not sealed, the gas desorption and diffusion quantity in the whole hole can be far greater than that in a pressure measuring air chamber at the bottom of the hole after the hole is sealed, but the time for the gas concentration value in the pressure measuring air chamber at the bottom of the hole to reach the peak value after the hole is sealed can be far faster than the time for the hole to reach the peak value after the hole is not sealed. According to the phenomenon, an assumption about the gas pressure balance time and the volume of the pressure measuring air chamber is proposed, namely, the smaller the volume of the pressure measuring air chamber is, the shorter the gas pressure balance time is, and the similar simulation experiment is adopted for verification according to the assumption design.
The main research content of the simulation experiment is as follows by a physical simulation method: and (5) researching the relationship between the gas pressure measurement balance time and the volume of the pressure measuring air chamber.
The simulation experiment is a laboratory research method based on a similarity theory and a similarity condition, has the characteristics of simple operation process, short verification time, reliable experimental result and the like, and is the most effective method for solving the problems of long experimental period, difficult visual achievement and the like of underground coal mines. The similarity simulation experiment needs to meet the conditions of geometric similarity, motion similarity, dynamic similarity, initial state similarity, boundary condition similarity and the like. The experiment for simulating and measuring the gas pressure balance is different from the simulation experiment related to the coal mining mechanics, and mainly meets two conditions that the geometric similarity is similar to the initial state, and the two similar conditions are described below.
1. Geometric similarity conditions
Geometric similarity is a fundamental condition of the whole physical similarity simulation model, and the model must be required to be similar to the physical geometry, so the designed model must be enlarged or reduced to a certain extent according to the size of the original model. Taking the length L of the model as an example, LM is the length of the mould, LH is the length of a real object, alpha L is the ratio of LM to LH, which is also commonly called a scale, and the geometric scale conditions are as follows:
generally, the larger the model is, the closer the model is to the prototype, the better the underground actual situation of the coal mine can be reflected, but due to the condition limitation of each aspect, the model is necessarily obtained by reducing the prototype according to the proportion, the model similar to the experiment is a drilled pressure measuring air chamber, and the value of the model alpha L of the roadway is 50-100. The length of the simulated drilling hole is the length of the underground drilling hole of the coal mine
2. Initial state similarity
By initial state similarity is meant that the model and the natural state of the prototype should remain as similar as possible during the experiment. The initial state to be maintained in the simulation experiment is similar to two points, wherein the first point is that the pressure of the gas in the model is always kept to be a stable pressure value, and the second point is that the gas enters the pressure measuring air chamber and is in accordance with the analysis gushing diffusion rule of the coal seam gas. The operation method is to change the air inflow and further process the simulation drilling, and the experimental steps of the specific operation process are described in detail.
From the previous study, after the gas pressure is measured by a direct method to form a hole, the gas in the coal bed is desorbed and diffused into the pressure measuring air chamber to generate gas pressure, and the pressure balance time is deduced:
the equilibrium model differential pressure is:
wherein PAO and PBO are respectively the initial pressures of a sealed coal sample tank and a pressure measuring air chamber in a simulated drilling hole; and PA and PB are the pressures of the coal sample tank and the pressure measuring air chamber at a certain moment in the balancing process respectively.
The flow from the coal sample tank to the pressure measuring air chamber is as follows:
the conductance is as follows:
i.e. V A dp A ＝-U(p A -p B )dt (4-4)
The gas in the high-pressure gas cylinder and the pressure measuring gas chamber are regarded as ideal gas, and an ideal state equation is respectively applied:
subtracting (4-6) from (4-5)
Assuming that the gas leakage of the high-pressure gas cylinder and the gas pressure gas chamber and the pipeline communicated between the high-pressure gas cylinder and the gas pressure gas chamber is negligible, the total mass of the gas of the two gas chambers is unchanged.
Bringing formula (4-8) into formula (4-7)
And due to RTdm A ＝V A dp A With (4-9)
Substituting formula (4-4) into formula (4-10)
Integrate (4-11)
Finishing to obtain 4-13
From formulas 4-13, the trend in gas equilibration times is that the smaller VB, the faster the equilibration time.
The following example verifies the correctness of the formula derivation by a simulation experiment:
the embodiment provides a coal seam gas pressure measurement similar simulation experiment device, referring to fig. 1, comprising a coal sample tank 3, a high-pressure nitrogen gas bottle 1, a conveying pipe 2 and a gas pressure sensor 4, wherein the coal sample tank 3 comprises a tank body 3.1, a sealing cover 3.2, an air inlet 3.3, an air outlet 3.3 and a simulation drilling pipeline 5, the sealing cover 3.2 is arranged at the top of an opening of the tank body, the air inlet is arranged at the sealing cover, the simulation drilling pipeline is vertically arranged at the center of the tank body, the bottom of the simulation drilling pipeline is fixedly connected with the bottom surface of the tank body, and the top of the simulation drilling pipeline penetrates through and is exposed out of the sealing cover; the surface of the simulated drilling pipeline is provided with a plurality of simulated drilling holes 5.1; the high-pressure nitrogen cylinder 1 is connected with an air inlet of the coal sample tank 3 through a conveying pipe 2, and the gas pressure sensor is connected with an air outlet of the coal sample tank.
In this embodiment, the tank body is barrel-shaped, and the design parameters of the tank body are as follows: the height is 30cm, the diameter is 30cm, the wall thickness is 2.5mm, the weight is 65kg, and handles (not shown in the figure) are connected to two opposite sides of the outer wall of the tank body;
the sealing cover is circular and is provided with a pull ring (not shown in the figure). The top of the tank body is reinforced by screws, and the tank body is pulled up by a top pull ring during detachment. The coal sample tank is provided with an air inlet hole and an air outlet hole, the aperture of the air inlet hole is 5mm, a simulated drilling pipeline is arranged in the coal sample tank, the drilling length for measuring the gas pressure by a direct method is generally 30-35m, so that the design length of the simulated drilling pipeline in the tank body is 35cm, and a gas pressure sensor is further connected to the air outlet at the top of the simulated drilling pipeline.
In another aspect, the embodiment provides a method for measuring a coal seam gas pressure by using the simulation experiment device, which comprises the following steps:
s1, connecting and debugging each instrument and ensuring good operation of each instrument and equipment and air tightness of a coal sample tank;
the high-pressure nitrogen bottle is used as an air source, is connected with an air inlet of the coal sample tank through a rubber tube, is inflated into the coal sample tank, and an air outlet of the coal sample tank is connected with a pressure sensor for debugging equipment and measuring gas pressure
The HH316 normal temperature pressure sensor is adopted in the experiment, the pressure sensor adopts diffused silicon as a pressure sensitive element, and the HH316 normal temperature pressure sensor has wide application range and can accurately measure and transmit the pressure of liquid, gas and steam. The HH316 normal temperature pressure sensor has the advantages that the mechanical protection level reaches IP65 and explosion protection is also realized, and the pressure sensor is better suitable for coal seam pressure measurement compared with other pressure sensors. The power supply of the experiment adaptive gas pressure sensor is 220v alternating current to 24v direct current power supply
The method also comprises the step of testing the tightness of the coal sample tank, and specifically comprises the following steps:
connecting the instrument and the equipment, and filling the coal sample into the coal sample tank without filling the coal sample;
coating soapy water on the air inlet and the air outlet of the coal sample tank and the joint of the tank body and the sealing cover;
connecting a gas pressure sensor with the gas outlet, opening a high-pressure nitrogen bottle to charge gas into the coal sample tank, so that the gas injection pressure reaches a certain value, for example, 0.1MP;
and observing the positions easy to leak, and if no bubbles are generated and the display reading of the gas pressure sensor is the same as the inflation pressure of the high-pressure nitrogen cylinder, indicating that the gas tightness of the coal sample tank is good.
S2, simulating an initial similar state to enable the pressure of gas in the coal sample tank to always keep a stable pressure value, wherein the gas enters the pressure measuring air chamber to accord with the desorption and emission diffusion rule of coal bed gas;
the initial state of the simulation experiment is similar to the two-point requirement that the pressure of the gas in the coal sample tank always keeps a stable pressure value, and the gas entering the pressure measuring air chamber accords with the desorption emission diffusion rule of the coal bed gas. Aiming at the two requirements, the following experimental operation is carried out:
1) The high-pressure nitrogen cylinder is connected with the air inlet of the coal sample tank through an air injection rubber tube, and a hole is reserved at the connecting part
A gap; because the volume of the coal sample tank is limited, the gas tightness of the tank body is good, if the gas is always injected into the tank at a certain pressure, the pressure in the tank continuously rises, and the constant pressure cannot be maintained. Therefore, when the gas injection rubber pipe is connected with the gas inlet hole in the operation process, a certain hole is required to be reserved, and part of injected gas needs to be leaked.
2) The simulated coal bed pressure is a certain value A, gas is injected into the coal sample tank according to the pressure value of A+0.12MPa, and after a certain time, the gas pressure in the coal sample tank is always kept within the range of A+/-0.005 MPa;
if the experimental simulation coal bed pressure is 0.1MPa, when gas is injected into the coal sample tank according to 0.12MPa, the gas pressure in the coal sample tank is always kept at about 0.1MPa after a period of time, the error is not more than 0.005MPa, and the method is in an allowable error range, meets the condition that the initial states of the similarity simulation are similar, and other pressure values are similar. By using the method, the valve on the high-pressure gas cylinder is not closed, and the gas pressure in the coal sample tank is always at a stable pressure value.
3) The simulated drilling is processed by the following steps: and coating the cloth polyester fiber on the outer surface of the simulated drilling pipeline, brushing paste on the cloth, continuously coating the cloth on the outer layer of the cloth, winding the cloth on the simulated drilling pipeline by using a nylon ribbon on the last layer, filling cotton into the drilling hole, and preventing coal ash from entering the gas pressure sensor in the pressure measuring process.
The gas pressure in the pressure measuring air chamber does not reach equilibrium instantaneously, and the dynamic equilibrium is achieved by desorbing and diffusing free gas in the coal seam for a certain time. The simulated drilling holes of the coal sample tank are directly ventilated, so that the pressure value of the air chamber can reach the balance value quickly in the simulated pressure measurement process, and the actual pressure measurement rule can not be simulated. The simulated drilling is processed by the following steps: preparing a plurality of fabrics with poor air permeability, such as polyester fibers, taking a layer of fabric, coating the fabric with paste, continuously coating the fabric with the fabric, drilling, winding the gauze on the simulated drilling by using a nylon ribbon on the last layer, filling cotton into the drilling, and preventing coal ash from entering the pressure sensor in the pressure measuring process.
S3, performing empty tank simulation pressure test, recording data in the experimental process under the condition that coal is not filled in the coal sample tank, and respectively obtaining the relationship between the balance time of a plurality of groups of gas pressure values and the volume of the pressure measuring air chamber;
the simulated pressure measurement experiment is a comparison experiment of control variables, and the experimental variables are the volumes of the pressure measurement air chambers in the simulated drilling holes. In order to find out problems existing in the experiment as much as possible and ensure the smooth progress of the experiment, the experiment firstly carries out a simulation pressure test by not filling coal into a coal sample tank.
The method for testing the simulated pressure of the empty tank comprises the following specific steps:
1) Slowly discharging the gas of the coal sample tank from the gas inlet, wherein the pressure state of the gas in the tank is the same as the atmospheric pressure and is 0MPa after all the gas is discharged;
2) Performing experiments of three groups of pressure values, namely 0.1MPa, 0.3MPa and 0.5MPa, and performing complete inflation and deflation experiments for multiple times to record the time required by each time when the gas in the coal sample tank reaches the target pressure value in order to ensure that the gas pressure in the coal sample tank is constant and reaches the inflation time required by each pressure value as accurate as possible, and finally obtaining the required time by averaging; the experimental data are shown in Table 4-1.
TABLE 4-1 charging time Table for unbacked gas
3) Removing the gas pressure sensor from the top of the simulated drilling pipeline of the coal sample tank, plugging an outlet at the top of the simulated drilling pipeline by using a plug, obtaining average inflation time according to the step 2), inflating, removing the plug after inflation is finished, quickly screwing the pressure sensor on the simulated drilling, and recording the time for observing the sensor to reach each pressure value; changing the volume of the simulated drilling pressure measuring air chamber, and testing the time required for reaching each pressure value under different pressure measuring air chamber volumes according to the method of the step;
the method for changing the volume of the pressure measuring air chamber comprises the following steps: dropping wax oil flowing out of the lighted candle into a drilled hole, and then penetrating a small hole into the solidified wax oil for ventilation; the lengths of the simulated drilling pipelines in the coal sample tank are 30cm and 20cm respectively,10cm, 5cm, 2cm and 1cm, and the volumes of the corresponding pressure measuring air chambers are 94.2cm respectively 3 、62.8cm 3 、31.4cm 3 、15.7cm 3 、6.28cm 3 、3.14cm 3 Five simulated manometry were performed for each manometric plenum volume.
4) And drawing a relation chart of the gas pressure balance time and the volume of the pressure measuring air chamber according to the data obtained in the steps, and obtaining the relation of the gas pressure balance time and the volume of the pressure measuring air chamber after analysis.
Through the three steps, the analysis data are recorded, and the experiment of simulating the gas pressure measurement without coal filling of the coal sample tank is completed.
The experimental data are recorded, tables 4-3 are non-coaled gas balance time recording tables with the pressure value of 0.1MPa, and the relation diagram of the gas pressure balance time and the volume of the pressure measuring air chamber is drawn according to the data in the tables, and refer to fig. 2.
TABLE 4-3 non-coal-charging balance time record Table
Tables 4-4 are tables for recording the balance time of the unburnt coal gas with the pressure value of 0.3MPa, and the relationship between the balance time of the gas pressure and the volume of the pressure measuring air chamber is drawn according to the data in the tables, and refer to fig. 3.
Tables 4-4 non-coal-charging balance time record table
Tables 4-5 are tables for recording the balance time of the unburnt coal gas with the pressure value of 0.5MPa, and the relationship between the balance time of the gas pressure and the volume of the pressure measuring air chamber is drawn according to the data in the tables, and refer to fig. 4.
Tables 4-5 non-coal-charging balance time record table
S4, simulating pressure test of the coal sample, recording data in the experimental process under the condition that the coal sample tank is filled with coal, and respectively obtaining the relationship between the balance time of a plurality of groups of gas pressure values and the volume of the pressure measuring air chamber.
1) Loading a coal sample into a coal sample tank, and sealing a sealing cover at an opening at the top of the tank body after loading the coal sample:
in order to ensure that the experiment can achieve the effect of simulating the measurement of the gas pressure of the coal seam, the freshly collected coal samples of the coal mine at the cliff bottom are selected for treatment, the coal samples are crushed and screened by a standard sieve, the prepared particle sizes of the coal samples are divided into three types, namely 2Kg of the coal samples with the particle sizes of 3mm-5mm, 2Kg of the coal samples with the particle sizes of 1mm-3mm and 2Kg of the coal samples with the particle sizes of less than 1mm, and the coal samples with the particle sizes of three pore diameters are required to be mixed when being filled into a sealed coal sample tank, so that the pore structure of the coal body is ensured to be close to the original coal seam.
Further, the step of loading the coal sample into the coal sample tank in the step (4) -1) comprises the following steps: firstly spreading a coal sample with the grain diameter smaller than 1mm on the bottom layer, then spreading a coal sample layer with the grain diameter of 1mm-3mm and a coal sample layer with the grain diameter of 3mm-5mm upwards in sequence, then mixing and loading the three coal samples with the grain diameter, and finally spreading the coal sample with the grain diameter of 3mm-5mm on the top layer.
2) Performing experiments of three groups of pressure values, namely 0.1MPa, 0.3MPa and 0.5MPa, performing full inflation and deflation experiments for a plurality of times, recording the time required for each inflation to the coal sample tank to reach the target pressure value, and finally averaging to obtain the required time;
3) Removing the gas pressure sensor from the top of the simulated drilling pipeline of the coal sample tank, plugging an outlet at the top of the simulated drilling pipeline by using a plug, obtaining average inflation time according to the step 2), inflating, removing the plug after inflation is finished, quickly screwing the pressure sensor on the simulated drilling, and recording the time for observing the sensor to reach each pressure value; changing the volume of the simulated drilling pressure measuring air chamber, and testing the time required for reaching each pressure value under different pressure measuring air chamber volumes according to the method of the step;
4) And drawing a relation chart of the gas pressure balance time and the volume of the pressure measuring air chamber according to the data obtained in the steps, and obtaining the relation of the gas pressure balance time and the volume of the pressure measuring air chamber after analysis.
Recording the data obtained in the experimental process, and preparing the analysis experimental result.
And recording pressure balance time data of different pressure measuring air chamber volumes under the condition of canning coal samples to obtain tables 4-6, and drawing a relation chart of the gas pressure balance time and the pressure measuring air chamber volumes according to the table data, wherein the relation chart is shown in fig. 5.
Tables 4 to 6 coal gas balance time recording tables
Tables 4-7 are gas balance time record tables with the pressure value of 0.3MPa, and the relation diagram of the gas pressure balance time and the volume of the pressure measuring air chamber is drawn according to the data in the tables, and refer to fig. 6.
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Tables 4-7 coal gas balance time recording tables
Tables 4-8 are coal-charging gas balance time recording tables with pressure value of 0.5MPa, and the relation diagram of gas pressure balance time and pressure measuring air chamber volume is drawn according to the data in the tables, and refer to fig. 7.
Tables 4-8 coal gas balance time recording tables
By analyzing the relationship diagram of the volume of the pressure measuring air chamber and the gas balance time, the following conclusion can be obtained:
(1) From the relation between the volume of the pressure measuring air chamber and the gas balance time, whether the coal sample tank is filled with coal or not, the smaller the volume of the air chamber is, the shorter the gas reaches balance time, and the correctness of the imaginary provided in the summary of the chapter is verified;
(2) The result of the simulation experiment can deduce that in the actual hole sealing, the length of the pressure measuring air chamber is less than two meters, and the gas pressure balancing time is fastest;
(3) The balance time is shortened in a nonlinear relation along with the reduction of the volume of the air chamber, the time shortening amount from the point 6 to the point 5 in all the figures is very small, when the underground actual measurement of the gas pressure is carried out, if the hole sealing distance is too short, the air chamber is too long, the pressure measuring period is far longer than the normal balance time, the pressure measuring failure is very easy, and the similar simulation experiment also proves the effectiveness of the two-stage hole sealing in the pressure measuring of the ultra-long drilling hole from the other aspect.
In the coal seam gas pressure measurement simulation experiment device provided by the embodiment, in the ultra-long drilling gas pressure measurement technology, the accuracy of pressure measurement can be ensured by effective hole sealing, and the pressure measurement speed can be increased by reasonable air chamber volume. By designing a gas pressure measurement simulation experiment, the assumption that the smaller the volume of the air chamber is, the faster the pressure balance time is verified, the length of the optimal pressure measurement air chamber is determined according to an experimental result, the feasibility of two-stage hole sealing is proved in the aspect of experiments, and a theoretical basis is provided for on-site pressure measurement.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. The coal bed gas pressure measurement simulation method is characterized by adopting a coal bed gas pressure measurement simulation experiment device, wherein the coal bed gas pressure measurement simulation experiment device comprises: the coal sample tank (3), the high-pressure nitrogen gas cylinder (1), the conveying pipe (2) and the gas pressure sensor (4), wherein the coal sample tank (3) comprises a tank body (3.1), a sealing cover (3.2), an air inlet (3.3), an air outlet (3.4) and a simulated drilling pipeline (5), the sealing cover (3.2) is arranged at the top of an opening of the tank body (3.1), the air inlet (3.3) is arranged at the sealing cover (3.2), the simulated drilling pipeline (5) is vertically arranged at the inner center of the tank body (3.1), the bottom of the simulated drilling pipeline is fixedly connected with the inner bottom surface of the tank body (3.1), and the top of the simulated drilling pipeline penetrates through and is exposed out of the sealing cover (3.2); the surface of the simulated drilling pipeline (5) is provided with a plurality of simulated drilling holes (5.1); the high-pressure nitrogen cylinder (1) is connected with an air inlet (3.3) of the coal sample tank (3) through a conveying pipe (2), and the gas pressure sensor (4) is connected with an air outlet (3.4) of the coal sample tank (3);
the method comprises the following steps:
(1) Connecting and debugging each instrument and ensuring the good operation of each instrument and equipment and the air tightness of the coal sample tank;
(2) Simulating an initial similar state to ensure that the pressure of the gas in the coal sample tank always keeps a stable pressure value, and the gas entering the pressure measuring air chamber accords with the desorption and emission diffusion rule of the coal bed gas;
(3) Under the condition that coal is not loaded in the coal sample tank, data are recorded in the experimental process, and the relationship between the balance time of a plurality of groups of gas pressure values and the volume of the pressure measuring air chamber is respectively obtained, wherein the method comprises the following specific steps of:
1) Slowly discharging the gas of the coal sample tank from the gas inlet, wherein the pressure state of the gas in the tank is the same as the atmospheric pressure and is 0MPa after all the gas is discharged;
2) Performing experiments of three groups of pressure values, namely 0.1MPa, 0.3MPa and 0.5MPa, performing full inflation and deflation experiments for a plurality of times, recording the time required for each inflation to the coal sample tank to reach the target pressure value, and finally averaging to obtain the required time;
3) Removing the gas pressure sensor from the top of the simulated drilling pipeline of the coal sample tank, plugging an outlet at the top of the simulated drilling pipeline by using a plug, obtaining average inflation time according to the step 2), inflating, removing the plug after inflation is finished, quickly screwing the pressure sensor on the simulated drilling, and recording the time for observing the sensor to reach each pressure value; changing the volume of the simulated drilling pressure measuring air chamber, and testing the time required for reaching each pressure value under different pressure measuring air chamber volumes according to the method of the step;
the method for changing the volume of the simulated drilling pressure measuring air chamber in the step (3) of the empty tank simulated pressure test comprises the following steps: dropping wax oil flowing out of the lighted candle into a drilled hole, and then penetrating a small hole into the solidified wax oil for ventilation; the lengths of the simulated drilling pipelines in the coal sample tank are respectively 30cm, 20cm, 10cm, 5cm, 2cm and 1cm, and the volumes of the corresponding pressure measuring air chambers are respectively 94.2cm 3 、62.8cm 3 、31.4cm 3 、15.7cm 3 、6.28cm 3 、3.14cm 3 Five simulated pressure measurements are carried out on the volume of each pressure measuring air chamber;
4) Drawing a relation chart of gas pressure balance time and the volume of the pressure measuring air chamber according to the data obtained in the steps, and obtaining the relation of the gas pressure balance time and the volume of the pressure measuring air chamber after analysis;
(4) And (3) carrying out simulated pressure test on the coal sample, recording data in the experimental process under the condition that the coal sample tank is filled with coal, and respectively obtaining the relationship between the balance time of a plurality of groups of gas pressure values and the volume of the pressure measuring air chamber.
2. The method according to claim 1, characterized in that the tank (3.1) is barrel-shaped and that opposite sides of its outer wall are connected with handles; the sealing cover is round, and is provided with a pull ring.
3. Method according to claim 1, characterized in that the length of the simulated drilling conduit (5) in the tank is 35cm.
4. The method according to claim 1, wherein the step (1) comprises a coal sample tank tightness test, in particular:
connecting the instrument and the equipment, and filling the coal sample into the coal sample tank without filling the coal sample;
coating soapy water on the air inlet and the air outlet of the coal sample tank and the joint of the tank body and the sealing cover;
connecting a gas pressure sensor with the gas outlet, and opening a high-pressure nitrogen bottle to charge gas into the coal sample tank so that the gas injection pressure reaches a certain value;
and observing the positions easy to leak, and if no bubbles are generated and the display reading of the gas pressure sensor is the same as the inflation pressure of the high-pressure nitrogen cylinder, indicating that the gas tightness of the coal sample tank is good.
5. The method of claim 1, wherein the simulating initial similar state in step (2) is specifically operative to:
1) The high-pressure nitrogen cylinder is connected with an air inlet of the coal sample tank through an air injection rubber tube, and a hole is reserved at the connecting part;
2) The pressure of the simulated coal bed is a certain value A, gas is injected into the coal sample tank according to the pressure value of A+0.12MPa, and after a certain time, the gas pressure in the coal sample tank is always kept within the range of A+/-0.005 MPa;
3) The simulated drilling is processed by the following steps: and coating the cloth polyester fiber on the outer surface of the simulated drilling pipeline, brushing paste on the cloth, continuously coating the cloth on the outer layer of the cloth, winding the cloth on the simulated drilling pipeline by using a nylon ribbon on the last layer, filling cotton into the drilling hole, and preventing coal ash from entering the gas pressure sensor in the pressure measuring process.
6. The method of claim 1, wherein the step (4) of simulating the pressure test of the coal sample comprises the following specific steps:
1) Loading a coal sample into a coal sample tank, and sealing a sealing cover at the top opening of the tank body after loading the coal sample;
2) Performing experiments of three groups of pressure values, namely 0.1MPa, 0.3MPa and 0.5MPa, performing full inflation and deflation experiments for a plurality of times, recording the time required for each inflation to the coal sample tank to reach the target pressure value, and finally averaging to obtain the required time;
3) Removing the gas pressure sensor from the top of the simulated drilling pipeline of the coal sample tank, plugging an outlet at the top of the simulated drilling pipeline by using a plug, obtaining average inflation time according to the step 2), inflating, removing the plug after inflation is finished, quickly screwing the pressure sensor on the simulated drilling, and recording the time for observing the sensor to reach each pressure value; changing the volume of the simulated drilling pressure measuring air chamber, and testing the time required for reaching each pressure value under different pressure measuring air chamber volumes according to the method of the step;
4) And drawing a relation chart of the gas pressure balance time and the volume of the pressure measuring air chamber according to the data obtained in the steps, and obtaining the relation of the gas pressure balance time and the volume of the pressure measuring air chamber after analysis.
7. The method according to claim 6, wherein the step of loading the coal sample into the coal sample tank in the step (4) -1) is specifically: firstly spreading a coal sample with the grain diameter smaller than 1mm on the bottom layer, then spreading a coal sample layer with the grain diameter of 1mm-3mm and a coal sample layer with the grain diameter of 3mm-5mm upwards in sequence, then mixing and loading the three coal samples with the grain diameter, and finally spreading the coal sample with the grain diameter of 3mm-5mm on the top layer.
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| CN112903519B (en) * | 2021-01-19 | 2023-08-22 | 河南理工大学 | Rapid measuring system and method for desorbable amount of coal bed gas |
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