CN114414456A - Method and device for calculating gas hydrate saturation - Google Patents
Method and device for calculating gas hydrate saturation Download PDFInfo
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- CN114414456A CN114414456A CN202210047808.XA CN202210047808A CN114414456A CN 114414456 A CN114414456 A CN 114414456A CN 202210047808 A CN202210047808 A CN 202210047808A CN 114414456 A CN114414456 A CN 114414456A
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- 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 56
- 238000000034 method Methods 0.000 title claims abstract description 45
- 239000003245 coal Substances 0.000 claims abstract description 211
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 108
- 238000006703 hydration reaction Methods 0.000 claims abstract description 48
- 238000013507 mapping Methods 0.000 claims abstract description 46
- 238000012360 testing method Methods 0.000 claims abstract description 13
- 230000036571 hydration Effects 0.000 claims abstract description 8
- 238000007711 solidification Methods 0.000 claims abstract description 5
- 230000008023 solidification Effects 0.000 claims abstract description 5
- 239000000523 sample Substances 0.000 claims description 72
- 238000006243 chemical reaction Methods 0.000 claims description 45
- 238000002310 reflectometry Methods 0.000 claims description 21
- 238000012545 processing Methods 0.000 claims description 12
- 239000011148 porous material Substances 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 7
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 3
- 230000002528 anti-freeze Effects 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 3
- 230000006835 compression Effects 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 3
- 230000002265 prevention Effects 0.000 abstract description 2
- 230000008859 change Effects 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000007710 freezing Methods 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
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000002817 coal dust Substances 0.000 description 1
- 238000013170 computed tomography imaging Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000001514 detection 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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- 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
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- G—PHYSICS
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- 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
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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 and solidification test on a coal system to be tested; collecting the dielectric constant, pressure and temperature of a coal system to be measured when the gas hydrate is at different saturation degrees; determining a first water content of the coal system to be detected according to the porosity, the pressure and the temperature of the coal system to be detected; constructing a mapping relation between the dielectric constant and the first water content after hydration reaction; acquiring 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 and the mapping relation of the target coal system and the porosity of the target coal sample. The method and the device for calculating the saturation of the gas hydrate, provided by the invention, can be used for quickly and accurately acquiring 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 which occurs under coal mines, and is a phenomenon that broken coal and gas are suddenly sprayed to a mining space in large quantities from the coal body. The hydrate method is an effective method for preventing and controlling coal and gas outburst, the hydrate method is used for preventing and controlling coal and gas outburst, the synthetic amount of gas hydrate needs to be accurately obtained, and the saturation of the gas hydrate (the volume ratio of the solid gas hydrate to the pore volume of coal in a coal system) needs to be obtained when the synthetic amount of the gas hydrate is obtained.
In the related art, methods for calculating the saturation of the hydrate include a resistivity method, an acoustic velocity method, a computed tomography imaging technology and a time domain reflectometry technology, but methods and devices for calculating the saturation of the gas hydrate in a coal system are lacked.
Therefore, a method and a device for calculating the saturation of gas hydrate are urgently needed, and the saturation of gas hydrate can be rapidly and accurately obtained.
Disclosure of Invention
The embodiment of the invention provides a method and a device for calculating the saturation of a gas hydrate, which can quickly and accurately obtain the saturation of the 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 perform hydration reaction to obtain a gas hydrate;
acquiring the dielectric constant, pressure and temperature of the coal system to be measured when the gas hydrate is 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 detected after hydration reaction according to the porosity, the pressure and the temperature of the coal system to be detected; the first water content is the volume ratio of the water left after hydration reaction to the pores of the coal sample to be detected;
establishing 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;
acquiring 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 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 detected, the volume of the coal sample to be detected and the volume of water in the coal system to be detected.
Preferably, the volume of water in the coal system to be tested is determined by the following formula:
in the formula (I), the compound is shown in the specification,
is the molar mass of the gas, deltan is the molar amount of gas consumed by the hydration reaction, n is the hydration index,
represents the molar mass of water, ρ is the density of water, V1Is the volume of water in the coal system to be measured without hydration reaction, V2The volume of water in the coal system to be measured.
Preferably, the molar amount of the consumed gas is determined by the following formula:
pV＝ΔnZRT
wherein p is the pressure, T is the temperature, V is the volume of the gas, R is the molar gas constant, and Z is the compression factor.
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 permittivity is acquired by a time domain reflectometry technique.
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 hydration reaction is established, the method further includes:
calculating a second water content of the coal system to be detected 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 detected according to the porosity of the same second time node, the pressure and the temperature of the coal system to be detected;
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 in any one of the first aspect, which comprises a reaction unit, a sensor unit, a data acquisition and processing unit, a temperature control unit and an air supply unit;
the reaction unit comprises a reaction cavity and a temperature control cavity, the reaction cavity is arranged in the temperature control cavity, the reaction cavity is used for providing a space for hydration reaction in the coal system, and an antifreezing solution is filled in the temperature control cavity;
the sensor unit is connected with the reaction cavity and used for testing the dielectric constant, the pressure and the temperature in a coal system in the reaction cavity;
the data acquisition and processing unit is connected with the sensor unit and 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 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 includes a time domain reflection probe and a time domain reflectometer, the time domain reflection probe and the time domain reflectometer are connected through a coaxial cable, the time domain reflection probe is used for conducting electromagnetic waves, and the time domain reflectometer is used for transmitting and receiving electromagnetic waves and converting the received electromagnetic waves into a dielectric constant value.
Preferably, the data acquisition unit includes a time domain reflection data collector, the time domain reflection data collector is connected to the time domain reflectometer, and the time domain reflection data collector is configured to receive and store a dielectric constant output by the time domain reflectometer.
Compared with the prior art, the invention at least has 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 the pressure of the system are adjusted to carry out hydration reaction in the system, the dielectric constant, the pressure and the 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 the 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 established according to the data of the dielectric constant and the obtained first water content data. After the mapping relation is obtained, the first water content of the target coal system can be obtained by measuring the dielectric constant of any target coal system in the coal mine and then 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 only by measuring the dielectric constant and the porosity of the target coal system, therefore, the method provided by the invention can quickly 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 used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of a method for calculating gas hydrate saturation according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an apparatus for calculating gas hydrate saturation according to 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 tank;
9. an air compressor;
10. a booster pump;
11. a gas cylinder.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention, and based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the scope of the present invention.
In the description of the embodiments of the present invention, unless explicitly specified or limited otherwise, the terms "first", "second", and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more unless specified or indicated otherwise; the terms "connected," "fixed," and the like are to be construed broadly and may, for example, be fixedly connected, detachably connected, integrally connected, or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the description of the present invention, it should be understood that the terms "upper" and "lower" as used in the description of the embodiments of the present invention are used in the angle shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it will also be understood that when an element is referred to as being "on" or "under" another element, it can be directly on "or" under "the other element or be indirectly on" or "under" the other element via an intermediate element.
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 the coal sample to be measured;
s2, mixing the coal sample to be tested, water and gas to form a coal system to be tested, and carrying out 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 a gas hydrate;
s3, acquiring the dielectric constant, pressure and temperature of the coal system to be measured when the gas hydrate is 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;
s4, determining the first water content of the coal system to be detected after hydration reaction according to the porosity, the pressure and the temperature of the coal system to be detected; wherein the first water content is the volume ratio of the residual water after hydration reaction to the pores of the coal sample to be detected;
s5, aiming at different saturation degrees of the gas hydrate, 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;
s6, acquiring 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 and the mapping relation of the target coal system, 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 the pressure of the system are adjusted to carry out hydration reaction in the system, the dielectric constant, the pressure and the 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 the 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 established according to the data of the dielectric constant and the obtained first water content data. After the mapping relation is obtained, the first water content of the target coal system can be obtained by measuring the dielectric constant of any target coal system in the coal mine and then 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 only by measuring the dielectric constant of the target coal system and the volume and porosity of the target coal sample, so that the gas hydrate saturation of any target coal system can be rapidly and accurately obtained by the method provided by the invention.
It should be noted that the mapping relationship is only applicable to the coal system for establishing the mapping relationship, and if the gas hydrate saturation of other coal seams needs to be obtained, the coal sample needs to be collected again to establish the mapping relationship.
It should also be noted that the porosity of the same coal seam is not greatly different, the data of the porosity does not need to be measured each time, if the target coal system is closer to the coal system with the measured porosity, the porosity does not need to be measured, and only the dielectric constant of the target coal system and the volume of the target coal sample need to be measured after the mapping relationship is obtained.
According to some preferred embodiments, the first moisture content is determined by the porosity of the coal sample to be tested, the volume of the coal sample to be tested, and the volume of water in the coal system to be tested.
In the present invention, the first water content can be determined by the following formula:
in the formula, theta1Is a first water content, VcoalIs the volume of the coal body to be measured, PcoalIs porosity.
According to some preferred embodiments, the volume of water in the coal system under test is determined by the following formula:
in the formula (I), the compound is shown in the specification,
is the molar mass of the gas, deltan is the molar amount of gas consumed by the hydration reaction, n is the hydration index, n is 6,
represents the molar mass of water, ρ is the density of water, V1Is the volume of water, V, in the coal system to be measured without hydration reaction2Is the volume of water in the coal system to be measured.
In the present invention, the water in the coal system is gradually reduced as the hydration reaction proceeds, and when the molar amount of the consumed gas is known, the molar amount of the water participating in the hydration reaction is calculated by a chemical reaction formula, and the volume of the water participating in the hydration reaction is determined, and the volume V of the water in the system is determined to construct the coal system to be measured1(volume of water initially added to the system) is known, V1And subtracting the volume of the water participating in the hydration reaction to obtain the volume of the 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:
pV＝ΔnZRT
wherein p is pressure, T is temperature, V is volume of gas, R is molar gas constant 8.314J/(mol K), and Z is compression factor.
In the invention, the consumption molar quantity of the gas at the time node can be obtained by substituting the pressure and temperature data acquired by the first time node into the formula.
The volume V of the gas is the volume of the gas in the coal system to be measured, and since the coal system to be measured is in a closed space, only the molar amount of the gas changes as the hydration reaction proceeds, and V does not change.
According to some preferred embodiments, determining the gas hydrate saturation of the target coal system from the dielectric constant of the target coal system, the mapping and the porosity of the target coal sample comprises:
determining a first water content of a 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 bed 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 by the following formula after obtaining the first water content:
in the formula, theta1Is a first water content, VcoalIs the volume of the target coal body, PcoalIs porosity, V2Is the volume of water in the target coal system;
and determining the saturation of the gas hydrate according to the following formula after the volume of water in the target coal system is obtained:
in the formula, ScoalIs gas hydrate saturation, V3Is the volume of the target coal sample, PcoalIs porosity, V2Is the volume of water in the target coal system.
According to some preferred embodiments, the dielectric constant is acquired by a time domain reflectometry technique.
In the invention, the dielectric constant is obtained by adopting a 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 tested and the first water content of the coal system to be tested after 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 detected according to the porosity of the same second time node and the pressure and temperature of the coal system to be detected;
and checking the mapping relation according to the second water content and the third water content.
In the present invention, after the mapping relationship is obtained, the obtained mapping relationship may be verified by using the above method. The mapping relation is obtained through data obtained by a first time node, a second water content is reversely deduced by using the mapping relation according to the dielectric constant measured by a second time node, a third water content is determined according to the porosity, the pressure and the temperature of the coal system to be measured which are collected by the same second time node, and if the second water content is consistent with the third water content in value, the mapping relation is correct.
As shown in fig. 2, the present invention further provides a device based on any one of the above methods, comprising a reaction unit 1, a sensor unit, a data acquisition and processing unit, a temperature control unit, and an air 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, the reaction cavity is used for providing a space for hydration reaction in a coal system, and an antifreezing solution is filled in the temperature control cavity;
the sensor unit is connected with the reaction cavity and used for testing the dielectric constant, the pressure intensity and the temperature in a coal system in the reaction cavity;
the data acquisition and processing unit is connected with the sensor unit and 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 used for providing gas for the reaction cavity and controlling the pressure intensity in the reaction cavity by controlling the amount of the gas introduced into the reaction cavity.
In the invention, the device provided by the application can be used for constructing a coal system to be detected in the reaction cavity, the temperature and the pressure are provided for the coal system to be detected through the temperature control unit and the gas supply unit so as to enable the coal system to be detected to generate hydration reaction, and the sensor unit is used for acquiring the dielectric constant, the pressure and the temperature in the coal system and transmitting the 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 high-precision platinum resistor temperature sensor 3, the pressure sensor adopts a specific diaphragm sensor pressure sensor, the sensors can detect the temperature and the pressure of the test in real time and stably collect the temperature and the pressure, and the sensor has the excellent effects of higher accuracy, simple operation and convenient collection.
In the present invention, the reaction unit 1 is provided with a high pressure transparent window and the pressure resistance is 20 MPa. The temperature control unit comprises a constant temperature water bath box 8 and a circulating pump, wherein an anti-freezing solution is filled in the constant temperature water bath box 8, the constant temperature water bath box 8 is connected with the temperature control cavity, and the circulating pump enables the anti-freezing solution to circulate between the constant temperature water bath box 8 and the temperature control cavity, so that the temperature control effect is realized.
In the invention, the gas supply unit comprises a constant temperature water bath box 9, a booster pump 10 and a gas cylinder 11. The constant temperature water bath tank 9 mainly functions to supply driving gas to the booster pump 10 and the gas cylinder 11. The gas booster pump 10 is used as a reciprocating single-action gas-driven pump, the inside of the gas booster pump utilizes the large and small area difference of two ends of a piston, low pressure acts on the large area end of a pneumatic 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 device is additionally provided with the ultrasonic detection instrument, so that the saturation and the acoustic parameters of the gas hydrate can be effectively monitored in real time, the system error is avoided, and the measurement is more accurate and effective.
According to some preferred embodiments, the sensor unit comprises a time domain reflection probe 2 and a time domain reflectometer, the time domain reflection probe 2 and the time domain reflectometer being connected by a coaxial cable, the time domain reflection probe 2 being for conducting electromagnetic waves, the time domain reflectometer being for emitting electromagnetic waves and receiving electromagnetic waves and converting the received electromagnetic waves into a value of a dielectric constant.
In the invention, the dielectric constant value of the target can be rapidly obtained by adopting the time domain reflection probe 2 and the time domain reflectometer. The coaxial cable adopted by the invention can fully reduce the attenuation of electromagnetic wave signals. The time domain reflection probe 2 can be regarded as a waveguide, and the impedance of the probe changes along with the change of the dielectric constant of the coal system gas hydrate. The time domain reflectometer can accurately measure the dielectric constant and the conductivity of the gas hydrate by self-defining a calibration 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 reflection data collector 6, the time domain reflection data collector 6 is connected to the time domain reflectometer, and the time domain reflection data collector 6 is configured to receive and store a dielectric constant output by the time domain reflectometer.
In the invention, one time domain reflection data acquisition unit 6 can control a plurality of time domain reflectometers, the time domain reflection data acquisition unit 6 can store the dielectric constant value provided by the time domain reflectometers, and the first water content can be directly output according to the dielectric constant measured by the time domain reflectometers after the mapping relation is obtained.
In the invention, the time domain reflectometry system consisting of the time domain reflectometry probe 2, the time domain reflectometry and the time domain reflectometry data acquisition unit 6 is distinguished by high speed, high precision, reliability and durability, and can provide suitable and flexible selection for tests by using complex configurations of various sensors even under a severe coal mining environment. In the measuring process, the time domain reflection data collector 6 can process data in real time, automatically and independently operate, does not depend on an alternating current power supply, a computer and manual control, and can compile 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 excel tables, thereby facilitating the drawing processing at the later stage. 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 change trend of the water content change waveform.
In the invention, the porosity of the coal dust particles is obtained by using a full-automatic mercury porosimeter. Before using the device, deionized water is needed to clean the reaction cavity, the line connection is checked, and whether the temperature and pressure readings are normal is checked; using a time domain reflection measurement system to test the dielectric constant of water and air to check whether the system is normal or not, checking whether the waveform change collected by the time domain reflection data collector 6 is abnormal or not, and judging whether a waveform diagram can be exported or not; after the device is checked, putting the coal sample to be detected into the reaction cavity, adding pure water to fill the pores of the coal sample to be detected, sealing the reaction cavity cover, and checking whether the reaction cavity is sealed; after the device and the closure are checked, determining phase equilibrium temperature and pressure according to a gas hydrate phase equilibrium curve, adjusting the temperature of the coal system to be measured to the equilibrium temperature by using a temperature control unit, and adjusting the pressure of the coal system to be measured by using an air supply unit after the temperature is stable to enable the coal system to be measured to carry out hydration and solidification reaction; then, the data are collected and processed according to the method provided by the invention, the collected data are sorted, and then the Matlab software regression analysis is utilized to establish the mapping relation. The device provided by the invention is simple to operate, the measurement is not influenced by the concentration of salt ions in pore water, the temperature and the pressure, and the accurate measurement of the saturation of the gas hydrate in a coal system can be realized
It should be noted that after the mapping relationship is obtained, the first water content can be obtained by using the 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 examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present 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 solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
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 perform hydration reaction to obtain a gas hydrate;
acquiring the dielectric constant, pressure and temperature of the coal system to be measured when the gas hydrate is 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 detected after hydration reaction according to the porosity, the pressure and the temperature of the coal system to be detected; the first water content is the volume ratio of the water left after hydration reaction to the pores of the coal sample to be detected;
establishing 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;
acquiring 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 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.
2. The method of claim 1, wherein the first moisture content is determined by a porosity of the coal sample to be tested, a volume of the coal sample to be tested, and a volume of water in the coal system to be tested.
3. The method of claim 2, wherein the volume of water in the coal system under test is determined by the following equation:
in the formula (I), the compound is shown in the specification,
is the molar mass of the gas, deltan is the molar amount of gas consumed by the hydration reaction, n is the hydration index,
represents the molar mass of water, ρ is the density of water, V1Is the volume of water in the coal system to be measured without hydration reaction, V2The volume of water in the coal system to be measured.
4. The method according to claim 3, wherein the molar amount of gas consumed is determined by the following formula:
pV＝ΔnZRT
wherein p is the pressure, T is the temperature, V is the volume of the gas, R is the molar gas constant, and Z is the compression factor.
5. The method of claim 1, wherein determining the gas hydrate saturation of the target coal system from the dielectric constant of the target coal system, the mapping, the volume of the target coal sample, and the porosity of the target coal sample comprises:
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.
6. The method of claim 1, wherein the permittivity is acquired by a time domain reflectometry technique.
7. The method of claim 1, wherein after the mapping of the dielectric constant of the coal system to be tested to the first water content of the coal system to be tested after the hydration reaction, the method further comprises:
calculating a second water content of the coal system to be detected 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 detected according to the porosity of the same second time node, the pressure and the temperature of the coal system to be detected;
and checking the mapping relation according to the second water content and the third water content.
8. The device based on the method of any one of claims 1 to 7, which is characterized by comprising a reaction unit, a sensor unit, a data acquisition and processing unit, a temperature control unit and a gas supply unit;
the reaction unit comprises a reaction cavity and a temperature control cavity, the reaction cavity is arranged in the temperature control cavity, the reaction cavity is used for providing a space for hydration reaction in the coal system, and an antifreezing solution is filled in the temperature control cavity;
the sensor unit is connected with the reaction cavity and used for testing the dielectric constant, the pressure and the temperature in a coal system in the reaction cavity;
the data acquisition and processing unit is connected with the sensor unit and 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 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.
9. The apparatus of claim 8, wherein the sensor unit comprises a time domain reflectometry probe and a time domain reflectometry probe, the time domain reflectometry probe and the time domain reflectometry probe connected by a coaxial cable, the time domain reflectometry probe for conducting electromagnetic waves, the time domain reflectometry probe for transmitting and receiving electromagnetic waves and converting the received electromagnetic waves into a value of dielectric constant.
10. The apparatus of claim 9, wherein the data acquisition unit comprises a time domain reflectometry data collector, the time domain reflectometry data collector is connected to the time domain reflectometry, and the time domain reflectometry data collector is configured to receive and store a dielectric constant output by the time domain reflectometry.
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