CN114414456B - Method and device for calculating saturation of gas hydrate - Google Patents
Method and device for calculating saturation of gas hydrate Download PDFInfo
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- CN114414456B CN114414456B CN202210047808.XA CN202210047808A CN114414456B CN 114414456 B CN114414456 B CN 114414456B CN 202210047808 A CN202210047808 A CN 202210047808A CN 114414456 B CN114414456 B CN 114414456B
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- 238000000034 method Methods 0.000 title claims abstract description 61
- NMJORVOYSJLJGU-UHFFFAOYSA-N methane clathrate Chemical compound C.C.C.C.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O NMJORVOYSJLJGU-UHFFFAOYSA-N 0.000 title claims abstract description 57
- 239000003245 coal Substances 0.000 claims abstract description 223
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 114
- 238000006703 hydration reaction Methods 0.000 claims abstract description 53
- 238000013507 mapping Methods 0.000 claims abstract description 47
- 230000036571 hydration Effects 0.000 claims abstract description 14
- 238000012360 testing method Methods 0.000 claims abstract description 12
- 239000000523 sample Substances 0.000 claims description 71
- 238000006243 chemical reaction Methods 0.000 claims description 43
- 238000002310 reflectometry Methods 0.000 claims description 31
- 238000012545 processing Methods 0.000 claims description 14
- 239000011148 porous material Substances 0.000 claims description 12
- 230000002528 anti-freeze Effects 0.000 claims description 8
- 230000006835 compression Effects 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 3
- 238000007711 solidification Methods 0.000 claims description 2
- 230000008023 solidification Effects 0.000 claims description 2
- 230000002265 prevention Effects 0.000 abstract description 2
- 230000001276 controlling effect Effects 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005065 mining Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000013170 computed tomography imaging Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- -1 salt ions Chemical class 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/221—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance by investigating the dielectric properties
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Abstract
The invention relates to the technical field of disaster prevention and control of coal and gas outburst, in particular to a method and a device for calculating gas hydrate saturation. The method comprises the following steps: measuring the porosity of the coal sample to be measured; carrying out a gas hydration curing test on a coal system to be tested; collecting dielectric constants, pressure and temperatures of a coal system to be tested when the gas hydrate has different saturation degrees; determining a first water content of the coal system to be tested according to the porosity and the pressure and the temperature of the coal system to be tested; constructing a mapping relation between dielectric constant and first water content after hydration reaction; collecting the dielectric constant of a target coal system comprising a target coal sample and the porosity of the target coal sample; and determining the gas hydrate saturation of the target coal system according to the dielectric constant, the mapping relation and the porosity of the target coal sample of the target coal system. The method and the device for calculating the saturation of the gas hydrate can quickly and accurately acquire the saturation of the gas hydrate.
Description
Technical Field
The invention relates to the technical field of disaster prevention and control of coal and gas outburst, in particular to a method and a device for calculating gas hydrate saturation.
Background
Coal and gas outburst is a disaster occurring underground coal mines, and is a phenomenon that broken coal and gas are suddenly sprayed out from the coal body to a large amount of mining space. The hydrate method is an effective method for preventing and curing coal and gas outburst, the hydrate method is used for preventing and curing coal and gas outburst, the synthesis amount of the gas hydrate needs to be accurately obtained, and the saturation degree of the gas hydrate (the volume ratio of solid gas hydrate to the volume of pores of coal in a coal system) needs to be obtained for obtaining the synthesis amount of the gas hydrate.
In the related art, the methods for calculating the saturation of the hydrate include resistivity method, sonic velocity method, computed tomography imaging technology and time domain reflection technology, but the methods and devices for calculating the saturation of the gas hydrate in a coal system are lacked.
Therefore, there is an urgent need for a method and apparatus for calculating the saturation of gas hydrate, which can rapidly and accurately obtain the saturation of gas hydration.
Disclosure of Invention
The embodiment of the invention provides a method and a device for calculating the saturation of gas hydrate, which can rapidly and accurately acquire the saturation of gas hydrate.
In a first aspect, the present invention provides a method for calculating gas hydrate saturation comprising the steps of:
measuring the porosity of the coal sample to be measured;
mixing the coal sample to be tested, water and gas to form a coal system to be tested, and performing a gas hydration and solidification test on the coal system to be tested so as to enable the water and the gas to generate hydration reaction to obtain gas hydrate;
collecting dielectric constants, pressures and temperatures of the coal system to be tested of the gas hydrate at different saturation degrees at a first time node; wherein the first time node is a plurality of time nodes in the hydration reflecting process;
determining a first water content of the coal system to be tested after hydration reaction according to the porosity and the pressure and the temperature of the coal system to be tested; the first water content is the volume ratio of the water remained after hydration reaction to the pores of the coal sample to be measured;
constructing a mapping relation between the dielectric constant of the coal system to be tested and the first water content of the coal system to be tested after hydration reaction aiming at different saturation degrees of the gas hydrate;
collecting a dielectric constant of a target coal system comprising a target coal sample, a volume of the target coal sample and a porosity of the target coal sample;
and determining the gas hydrate saturation of the target coal system according to the dielectric constant of the target coal system, the mapping relation, the volume of the target coal sample and the porosity of the target coal sample.
Preferably, the first water content is determined by the porosity of the coal sample to be measured, the volume of the coal sample to be measured and the volume of water in the coal system to be measured.
Preferably, the volume of water in the coal system to be tested is determined by the following formula:
in the method, in the process of the invention,M CH4 the molar mass of the gas is the molar mass of the gas consumed by the hydration reaction,nfor the hydration index to be a function of the hydration index,MH 2 Orepresents the molar mass of water, ρ is the density of water,V 1 the volume of water in the coal system to be tested when hydration reaction does not occur,V 2 is the volume of water in the coal system to be tested.
Preferably, the molar amount of the consumed gas is determined by the following formula:
in the method, in the process of the invention,pfor the pressure, T is the temperature，VFor the volume of the gas in question,Rz is the compression factor, which is the molar gas constant.
Preferably, the determining the gas hydrate saturation of the target coal system according to the dielectric constant of the target coal system, the mapping relation, the volume of the target coal sample and the porosity of the target coal sample includes:
determining a first water content of the target coal system according to the dielectric constant of the target coal system and the mapping relation;
and determining the gas hydrate saturation of the target coal system according to the first water content of the target coal system, the porosity of the target coal sample and the volume of the target coal sample.
Preferably, the dielectric constant is acquired by time domain reflectometry.
Preferably, after the mapping relationship between the dielectric constant of the coal system to be tested and the first water content of the coal system to be tested after the hydration reaction is constructed, the method further comprises:
calculating a second water content of the coal system to be measured at a second time node by using the mapping relation; the second time node is a time node except the first time node;
determining a third water content of the coal system to be tested according to the porosity of the same second time node, the pressure and the temperature of the coal system to be tested;
and checking the mapping relation according to the second water content and the third water content.
In a second aspect, the invention provides a device based on the method of any one of the first aspects, comprising a reaction unit, a sensor unit, a data acquisition processing unit, a temperature control unit, and a gas supply unit;
the reaction unit comprises a reaction cavity and a temperature control cavity, wherein the reaction cavity is arranged in the temperature control cavity and is used for providing a space for hydration reaction in the coal system, and the temperature control cavity is filled with antifreeze;
the sensor unit is connected with the reaction cavity and is used for testing dielectric constants, pressure and temperature in a coal system in the reaction cavity;
the data acquisition processing unit is connected with the sensor unit and is used for receiving and processing the data acquired by the sensor unit;
the temperature control unit is connected with the temperature control cavity and controls the temperature of the reaction cavity by controlling the antifreeze;
the gas supply unit is connected with the reaction cavity, and is used for providing gas for the reaction cavity, and controlling the pressure in the reaction cavity by controlling the amount of the gas introduced into the reaction cavity.
Preferably, the sensor unit comprises a time domain reflectometry probe for conducting electromagnetic waves and a time domain reflectometer for transmitting and receiving electromagnetic waves and converting the received electromagnetic waves into dielectric constant values, the time domain reflectometry probe and the time domain reflectometry probe being connected by a coaxial cable.
Preferably, the data acquisition unit comprises a time domain reflectometry data acquisition unit, the time domain reflectometry data acquisition unit is connected with the time domain reflectometer, and the time domain reflectometry data acquisition unit is used for receiving and storing the dielectric constant output by the time domain reflectometer.
Compared with the prior art, the invention has at least the following beneficial effects:
in the invention, a coal sample to be measured with known porosity, gas and water are mixed to form a coal system to be measured, the temperature and pressure of the system are adjusted to enable hydration reaction to be carried out in the system, dielectric constant, pressure and temperature data in the coal system to be measured in the hydration reaction process are collected, then a first water content (the volume ratio of the residual water after hydration reaction to the pores of the coal sample to be measured) is calculated according to the collected data and the porosity, and then a mapping relation between the dielectric constant and the first water content is constructed according to the data of the dielectric constant and the obtained data of the first water content. After the mapping relation is obtained, the dielectric constant of any target coal system in the coal mine is measured, then the first water content of the target coal system can be obtained by utilizing the mapping relation, and the gas hydrate saturation of the target coal system can be obtained by combining the porosity of the target coal sample after the first water content is obtained.
In the invention, after the mapping relation is obtained, the gas hydrate saturation can be obtained by only measuring the dielectric constant and the porosity of the target coal system, so that the method provided by the invention can rapidly and accurately obtain the gas hydrate saturation of any target coal system.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for calculating gas hydrate saturation provided by an embodiment of the present invention;
FIG. 2 is a schematic diagram of an apparatus for calculating gas hydrate saturation provided by an embodiment of the present invention;
in the figure:
1. a reaction unit;
2. a time domain reflectometry probe;
3. a temperature sensor;
4. a pressure sensor;
5. a time domain reflectometer;
6. a time domain reflection data collector;
7. an industrial personal computer;
8. a constant temperature water bath box;
9. an air compressor;
10. a booster pump;
11. a gas cylinder.
Description of the embodiments
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of 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, and all other embodiments obtained by those skilled in the art without making any inventive effort based on the embodiments of the present invention are within the scope of protection of the present invention.
In the description of embodiments of the present invention, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying any relative importance unless explicitly specified or limited otherwise; the term "plurality" means two or more, unless specified or indicated otherwise; the terms "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, integrally connected, or electrically connected; can be directly connected or indirectly connected through an intermediate medium. 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.
In the description of the present specification, it should be understood that the terms "upper", "lower", and the like used in the embodiments of the present invention are described in terms of the angles shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In the context of this document, it will also be understood that when an element is referred to as being "on" or "under" another element, it can be directly on the other element or be indirectly on the other element through intervening elements.
As shown in fig. 1, the present invention provides a method for calculating gas hydrate saturation, comprising the steps of:
s1, measuring the porosity of a coal sample to be measured;
s2, mixing a coal sample to be tested, water and gas to form a coal system to be tested, and performing a gas hydration curing test on the coal system to be tested so as to enable the water and the gas to generate hydration reaction to obtain gas hydrate;
s3, collecting dielectric constants, pressure and temperatures of a coal system to be tested when the gas hydrate has different saturation degrees at a first time node; wherein the first time node is a plurality of time nodes in the hydration reflecting process;
s4, determining a first water content of the coal system to be tested after hydration reaction according to the porosity and the pressure and the temperature of the coal system to be tested; the first water content is the volume ratio of the water remained after hydration reaction to the pores of the coal sample to be measured;
s5, constructing a mapping relation between the dielectric constant of the coal system to be tested and the first water content of the coal system to be tested after hydration reaction aiming at different saturation degrees of the gas hydrate;
s6, collecting the dielectric constant of a target coal system comprising a target coal sample, the volume of the target coal sample and the porosity of the target coal sample;
and S7, determining the gas hydrate saturation of the target coal system according to the dielectric constant, the mapping relation, the volume of the target coal sample and the porosity of the target coal sample.
In the invention, a coal sample to be measured with known porosity, gas and water are mixed to form a coal system to be measured, the temperature and pressure of the system are adjusted to enable hydration reaction to be carried out in the system, dielectric constant, pressure and temperature data in the coal system to be measured in the hydration reaction process are collected, then a first water content (the volume ratio of the residual water after hydration reaction to the pores of the coal sample to be measured) is calculated according to the collected data and the porosity, and then a mapping relation between the dielectric constant and the first water content is constructed according to the data of the dielectric constant and the obtained data of the first water content. After the mapping relation is obtained, the dielectric constant of any target coal system in the coal mine is measured, then the first water content of the target coal system can be obtained by utilizing the mapping relation, and the gas hydrate saturation of the target coal system can be obtained by combining the porosity of the target coal sample after the first water content is obtained.
In the invention, after the mapping relation is obtained, the gas hydrate saturation can be obtained by only measuring the dielectric constant of the target coal system, the volume and the porosity of the target coal sample, so that the method provided by the invention can rapidly and accurately obtain the gas hydrate saturation of any target coal system.
It should be noted that, the mapping relationship can only be applied to the coal system for establishing the mapping relationship, and if the saturation of the gas hydrate of other coal seams needs to be obtained, the mapping relationship needs to be established by collecting the coal samples again.
It should be noted that the porosity of the same coal seam is not greatly different, the data of the porosity are not required to be measured each time, if the target coal system is close to the coal system with measured porosity, the porosity is not required to be measured, and only the dielectric constant of the target coal system and the volume of the target coal sample are required to be measured after the mapping relation is obtained.
According to some preferred embodiments, the first moisture content is determined by the porosity of the coal sample to be measured, the volume of the coal sample to be measured, and the volume of water in the coal system to be measured.
In the present invention, the first moisture content can be determined by the following formula:
in the method, in the process of the invention,θ 1 for the first water content,V coal for the volume of the coal body to be measured,P coal is porosity.
According to some preferred embodiments, the volume of water in the coal system to be tested is determined by the following formula:
in the method, in the process of the invention,M CH4 the molar mass of the gas is the molar mass of the gas consumed by the hydration reaction,for the hydration index to be a function of the hydration index,nin the case of 6, the number of the components is,MH 2 Orepresents the molar mass of water, ρ is the density of water,V 1 to measure the volume of water in the coal system when hydration reaction does not occur,V 2 is the volume of water in the coal system to be tested.
In the invention, the water in the coal system gradually decreases along with the progress of the hydration reaction, and under the condition that the molar quantity of the consumed gas is known, the molar quantity of the water participating in the reaction can be calculated according to a chemical reaction formula, and then the volume of the water participating in the hydration reaction is obtained, so that when the coal system to be tested is constructed, the volume of the water in the systemV 1 (the volume of water initially added to the system) is known,V 1 and subtracting the volume of water participating in the hydration reaction to obtain the volume of water in the coal system to be measured.
According to some preferred embodiments, the molar amount of gas consumed is determined by the following formula:
in the method, in the process of the invention,pis the pressure, T is the temperature,Vis the volume of the gas in the gas,Rthe molar gas constant 8.314J/(mol. K), Z is the compression factor.
According to the invention, the consumption molar quantity of the gas at the first time node can be obtained by substituting the pressure and temperature data acquired at the first time node into the formula.
The volume of the gas is as followsVAs the coal system to be measured is in a closed space, only the molar quantity of the gas changes along with the progress of the hydration reaction, therebyVNo change occurs.
According to some preferred embodiments, determining the gas hydrate saturation of the target coal system from the dielectric constant, the mapping relationship, and the porosity of the target coal sample of the target coal system comprises:
determining a first water content of the target coal system according to the dielectric constant and the mapping relation of the target coal system;
and determining the gas hydrate saturation of the target coal system according to the first water content of the target coal system, the porosity of the target coal sample and the volume of the target coal sample.
In the invention, after the mapping relation is obtained, the gas hydrate saturation of any target coal system in the coal seam can be obtained through the mapping relation. Firstly, measuring the dielectric constant of any target coal system, then obtaining a first water content according to a mapping relation, and determining the volume of water in the target coal system through the following formula after obtaining the first water content:
in the method, in the process of the invention,θ 1 for the first water content,V coal for the volume of the target coal body,P coal in order to achieve a degree of porosity, the porous material,V 2 is the volume of water in the target coal system;
after the volume of water in the target coal system is obtained, determining the saturation of the gas hydrate according to the following formula:
in the method, in the process of the invention,S coal in order to achieve the saturation degree of the gas hydrate,V 3 for the volume of the target coal sample,P coal in order to achieve a degree of porosity, the porous material,V 2 is the volume of water in the target coal system.
According to some preferred embodiments, the dielectric constant is acquired by time domain reflectometry.
In the invention, the dielectric constant is obtained by adopting the time domain reflection technology, and the dielectric constant of the target can be rapidly and accurately obtained by utilizing the time domain reflection technology.
According to some preferred embodiments, after constructing the mapping relationship between the dielectric constant of the coal system to be measured and the first water content of the coal system to be measured after the hydration reaction, the method further comprises:
calculating a second water content of the coal system to be measured at a second time node by using the mapping relation; the second time node is a time node except the first time node;
determining a third water content of the coal system to be tested according to the porosity of the same second time node, the pressure and the temperature of the coal system to be tested;
and according to the second water content and the third water content, checking the mapping relation.
In the present invention, after the mapping relationship is obtained, the obtained mapping relationship may be verified by the above method. The mapping relation is obtained through data obtained by the first time node, the second water content is reversely deduced by the mapping relation according to the dielectric constant measured by the second time node, and the third water content is determined according to the porosity collected by the same second time node and the data of the pressure and the temperature of the coal system to be measured, and if the values of the second water content and the third water content are consistent, the mapping relation is correct.
As shown in fig. 2, the invention also provides a device based on any one of the above methods, which comprises a reaction unit 1, a sensor unit, a data acquisition processing unit, a temperature control unit and a gas supply unit;
the reaction unit 1 comprises a reaction cavity and a temperature control cavity, wherein the reaction cavity is arranged in the temperature control cavity and is used for providing space for hydration reaction in a coal system, and the temperature control cavity is filled with antifreeze;
the sensor unit is connected with the reaction cavity and is used for testing dielectric constant, pressure and temperature in a coal system in the reaction cavity;
the data acquisition processing unit is connected with the sensor unit and is used for receiving the data acquired by the sensor unit and processing the data;
the temperature control unit is connected with the temperature control cavity and controls the temperature of the reaction cavity by controlling the antifreeze;
the gas supply unit is connected with the reaction cavity and is used for providing gas for the reaction cavity and controlling the pressure in the reaction cavity by controlling the amount of the gas introduced into the reaction cavity.
According to the device provided by the invention, the coal system to be tested can be constructed in the reaction cavity, the temperature and the pressure are provided for the coal system to be tested through the temperature control unit and the air supply unit, so that the coal system to be tested is subjected to hydration reaction, and the sensor unit acquires the dielectric constant, the pressure and the temperature in the coal system and transmits data to the data acquisition and processing unit.
In the invention, the sensor unit also comprises a temperature sensor 3 and a pressure sensor 4, wherein the temperature sensor 3 adopts a temperature sensor 3 with high-precision platinum resistor, the pressure sensor adopts a pressure sensor with a specific diaphragm sensor, and the sensor can detect and stably collect the temperature and the pressure of a test in real time, and has the excellent effects of higher accuracy and simplicity and convenience in operation.
In the present invention, the reaction unit 1 is provided with a high-pressure transparent window, and the withstand voltage is 20 Mpa. The temperature control unit comprises a constant-temperature water bath box 8 and a circulating pump, wherein the constant-temperature water bath box 8 is filled with antifreeze, the constant-temperature water bath box 8 is connected with the temperature control cavity, and the circulating pump enables the antifreeze to circulate between the constant-temperature water bath box 8 and the temperature control cavity so as to achieve the temperature control effect.
In the invention, the air supply unit comprises a constant temperature water bath box 9, a booster pump 10 and a gas cylinder 11. The constant-temperature water bath box 9 mainly has the function of providing driving gas for the booster pump 10 and the gas cylinder 11. The gas booster pump 10 is used as a reciprocating type single-acting gas drive pump, the difference of the large area and the small area of the two ends of a piston is utilized in the gas booster pump, low gas pressure acts on the large area end of a gas pressure piston, and high-pressure low-flow gas is output at the small area end of the piston to provide a sufficient pressure gas source for a test.
In the invention, the ultrasonic detecting instrument is additionally arranged on the device, so that the saturation of the gas hydrate and acoustic parameters can be effectively monitored in real time, and the system error is avoided, so that the measurement is more accurate and effective.
According to some preferred embodiments, the sensor unit comprises a time domain reflectometry probe 2 and a time domain reflectometer, the time domain reflectometry probe 2 and the time domain reflectometry probe are connected by a coaxial cable, the time domain reflectometry probe 2 is used for conducting electromagnetic waves, and the time domain reflectometry probe is used for transmitting electromagnetic waves and receiving electromagnetic waves and converting the received electromagnetic waves into dielectric constant values.
In the present invention, the dielectric constant value of the target can be rapidly obtained using the time domain reflectometry probe 2 and the time domain reflectometer. The coaxial cable adopted by the invention can sufficiently reduce the attenuation of electromagnetic wave signals. The time domain reflectometry probe 2 can be considered as a waveguide, and the impedance of the probe changes with the change of the dielectric constant of the gas hydrate of the coal system. The time domain reflectometer can accurately measure the dielectric constant and the conductivity of the gas hydrate by self-defining and calibrating the time domain. The time domain reflectometer has the advantages of low power consumption, firmness, durability, high sensitivity, low noise and the like.
According to some preferred embodiments, the data acquisition unit comprises a time domain reflectometry data acquisition unit 6, the time domain reflectometry data acquisition unit 6 being connected to the time domain reflectometer, the time domain reflectometry data acquisition unit 6 being adapted to receive and store the dielectric constant of the time domain reflectometer output.
In the present invention, one time domain reflection data collector 6 may control a plurality of time domain reflectometers, and the time domain reflection data collector 6 may store a dielectric constant value provided by the time domain reflectometers, and may directly output the first water content according to the dielectric constant measured by the time domain reflectometers after obtaining the mapping relation.
In the present invention, the time domain reflectometry system consisting of the time domain reflectometry probe 2, the time domain reflectometer and the time domain reflectometry data collector 6 is distinguished by high speed, high precision, reliability and durability, and the complex configuration of various sensors can be used to provide a suitable and flexible choice for experiments even in severe coal mining environments. The time domain reflection data collector 6 can process data instantly in the measuring process, automatically and independently operate, does not depend on alternating current power supply, a computer and manual control, and can write programs and collect data by using software compatible with a PC.
In the invention, the data acquisition processing unit also comprises an industrial personal computer 7 which is used for collecting the data of the time domain reflection data acquisition unit 6 and exporting the data in the form of an excel table so as to facilitate the later drawing processing. The industrial personal computer 7 can also directly observe the electromagnetic wave reflection waveform in real time through P-TDR software, and can clearly compare the variation trend of the water content variation waveform.
In the present invention, the porosity of the pulverized coal particles is obtained using a fully automatic mercury porosimeter. Before the device is used, deionized water is needed to be used for cleaning the reaction cavity, and the connection of a circuit is checked to see whether the temperature and pressure indication number is normal or not; using a time domain reflectometry system to test the dielectric constants of water and air to check whether the system is normal or not, checking whether the waveform change acquired by the time domain reflectometry data acquisition unit 6 is abnormal or not, and deriving a waveform diagram or not; after the device is inspected, placing the coal sample to be inspected into a reaction cavity, adding pure water to fill the pores of the coal sample to be inspected, closing a reaction cavity cover, and inspecting whether the reaction cavity is closed; after the device and the sealing performance are checked, determining phase equilibrium temperature and pressure according to a gas hydrate phase equilibrium curve, regulating the temperature of the coal system to be tested to the equilibrium temperature by using a temperature control unit, and regulating the pressure of the coal system to be tested by using a gas supply unit after the temperature is stable so as to carry out hydration curing reaction in the coal system to be tested; then collecting and processing data according to the method provided by the invention, sorting the collected data, and establishing a mapping relation by utilizing Matlab software regression analysis. The device provided by the invention is simple to operate, and the measurement is not influenced by the concentration of pore water salt ions, the temperature and the pressure, so that the accurate measurement of the saturation of the gas hydrate in a coal system can be realized
After the mapping relation is obtained, the first water content can be obtained by using a time domain reflectometry system, and then the gas hydrate saturation of the target coal sample can be obtained by combining the porosity and the volume of the target coal sample.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (6)
1. A method for calculating gas hydrate saturation comprising the steps of:
measuring the porosity of the coal sample to be measured;
mixing the coal sample to be tested, water and gas to form a coal system to be tested, and performing a gas hydration and solidification test on the coal system to be tested so as to enable the water and the gas to generate hydration reaction to obtain gas hydrate;
collecting dielectric constants, pressures and temperatures of the coal system to be tested of the gas hydrate at different saturation degrees at a first time node; wherein the first time node is a plurality of time nodes in the hydration reaction process;
determining a first water content of the coal system to be tested after hydration reaction according to the following steps; the first water content is the volume ratio of the water remained after hydration reaction to the pores of the coal sample to be measured;
step (1), determining the molar quantity of the gas consumed by the hydration reaction according to the pressure and the temperature of the coal system to be tested:
in the method, in the process of the invention,for the molar amount of gas consumed by the hydration reaction,pfor said pressure, T is said temperature,Vfor the volume of the gas in question,Rz is a compression factor and is a molar gas constant;
step (2), determining the volume of water in the coal system to be tested according to the molar quantity of the gas consumed by the hydration reaction:
in the method, in the process of the invention, nfor the hydration index to be a function of the hydration index,MH 2 Orepresents the molar mass of water, ρ is the density of water,V 1 the volume of water in the coal system to be tested when hydration reaction does not occur,V 2 for the to-be-measuredThe volume of water in the coal system;
step (3), determining the first water content according to the porosity of the coal sample to be detected, the volume of the coal sample to be detected and the volume of water in the coal system to be detected:
in the method, in the process of the invention,θ 1 for the first water content,V coal for the volume of the coal body to be measured,P coal is porosity;
constructing a mapping relation between the dielectric constant of the coal system to be tested and the first water content of the coal system to be tested after hydration reaction aiming at different saturation degrees of the gas hydrate;
collecting a dielectric constant of a target coal system comprising a target coal sample, a volume of the target coal sample and a porosity of the target coal sample;
determining the gas hydrate saturation of the target coal system according to the dielectric constant of the target coal system, the mapping relation, the volume of the target coal sample and the porosity of the target coal sample;
the determining the gas hydrate saturation of the target coal system according to the dielectric constant of the target coal system, the mapping relation, the volume of the target coal sample and the porosity of the target coal sample comprises the following steps:
determining a first water content of the target coal system according to the dielectric constant of the target coal system and the mapping relation;
determining a gas hydrate saturation of the target coal system according to the first water content of the target coal system, the porosity of the target coal sample and the volume of the target coal sample;
firstly measuring the dielectric constant of any target coal system, then obtaining the first water content according to the mapping relation, and determining the volume of water in the target coal system through the following formula after obtaining the first water content:
in the method, in the process of the invention,θ 1 for the first water content,V coal for the volume of the target coal body,P coal in order to achieve a degree of porosity, the porous material,V 2 is the volume of water in the target coal system;
determining the gas hydrate saturation according to the following formula:
in the method, in the process of the invention,S coal in order to achieve the saturation degree of the gas hydrate,V 3 for the volume of the target coal sample,P coal in order to achieve a degree of porosity, the porous material,V 2 is the volume of water in the target coal system.
2. The method of claim 1, wherein the dielectric constant is acquired by time domain reflectometry.
3. The method of claim 1, further comprising, after said constructing a mapping of the dielectric constant of the test coal system to the first moisture content of the test coal system after the hydration reaction:
calculating a second water content of the coal system to be measured at a second time node by using the mapping relation; the second time node is a time node except the first time node;
determining a third water content of the coal system to be tested according to the porosity of the same second time node, the pressure and the temperature of the coal system to be tested;
and checking the mapping relation according to the second water content and the third water content.
4. A device based on the method of any one of claims 1-3, characterized by comprising a reaction unit, a sensor unit, a data acquisition processing unit, a temperature control unit, a gas supply unit;
the reaction unit comprises a reaction cavity and a temperature control cavity, wherein the reaction cavity is arranged in the temperature control cavity and is used for providing a space for hydration reaction in the coal system, and the temperature control cavity is filled with antifreeze;
the sensor unit is connected with the reaction cavity and is used for testing dielectric constants, pressure and temperature in a coal system in the reaction cavity;
the data acquisition processing unit is connected with the sensor unit and is used for receiving and processing the data acquired by the sensor unit;
the temperature control unit is connected with the temperature control cavity and controls the temperature of the reaction cavity by controlling the antifreeze;
the gas supply unit is connected with the reaction cavity, and is used for providing gas for the reaction cavity, and controlling the pressure in the reaction cavity by controlling the amount of the gas introduced into the reaction cavity.
5. The apparatus of claim 4, wherein the sensor unit comprises a time domain reflectometry probe and a time domain reflectometer, the time domain reflectometry probe and the time domain reflectometer being connected by a coaxial cable, the time domain reflectometry probe being configured to conduct electromagnetic waves, the time domain reflectometer being configured to transmit and receive electromagnetic waves and to convert the received electromagnetic waves to a dielectric constant value.
6. The apparatus of claim 5, wherein the data acquisition processing unit comprises a time domain reflectometry data acquisition device coupled to the time domain reflectometer, the time domain reflectometry data acquisition device configured to receive and store a dielectric constant of an output of the time domain reflectometer.
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