Coal sample bound water sample preparation device and nuclear magnetic detection method thereof

Abstract

The invention relates to the technical field of coal sample bound water determination, in particular to a coal sample bound water sample preparation device and a nuclear magnetic detection method thereof.The coal sample bound water sample preparation device comprises a sample cup used for containing a coal sample needing sample preparation, and valves are arranged at the upper end and the lower end of the sample cup; the sample cup lower end valve is connected with an air source and a water injection pump through a three-way valve, and pressure detectors are arranged on the air source and the water injection pump; the sample cup upper end valve is connected with a vacuum pump and a back-pressure valve through a three-way valve, and the back-pressure valve is connected with a back-pressure pump through a pipeline. By arranging the sample preparation device, related treatment and processing are carried out on a rock sample, a related calculation mode is established by utilizing bound water of the rock sample, and by virtue of detection of the sample preparation device and the nuclear magnetic detector, the rock sample can be accurately detected; therefore, the bound water content of the coal matrix pore fracture can be comprehensively tested without damage.

Description

Technical Field

[0001] The present invention relates to the technical field of coal sample bound water determination, and particularly to a coal sample bound water sample preparation device and a nuclear magnetic detection method thereof. Background Art

[0002] As a new type of clean energy, the development and utilization of coalbed methane is of great significance for environmental protection and alleviating the pressure of China's energy supply. The calibration of the bound water in the matrix pores and fractures of coal reservoirs is crucial for formulating coalbed methane development plans. The current common method is to calculate by detecting the change of the T2 spectrum of a saturated water coal sample before and after centrifugation using a nuclear magnetic resonance instrument. The main problem is that due to the development of coal cleats or soft structure, fragmentation occurs during centrifugation, resulting in the disappearance of some pores and fractures, leading to deviation of the measured value. Summary of the Invention

[0003] The purpose of the present invention is to provide a coal sample bound water sample preparation device and a nuclear magnetic detection method thereof, to achieve non-destructive, comprehensive and accurate detection of the content of coal sample bound water, so as to overcome the problem that due to the development of coal cleats or soft structure, fragmentation occurs during centrifugation, resulting in the disappearance of some pores and fractures, leading to deviation of the measured value.

[0004] The technical solution of the present invention is realized as follows:

[0005] An embodiment of the present invention provides a coal sample bound water sample preparation device, including: a sample cup for containing the coal sample to be prepared, and valves are provided at both the upper and lower ends of the sample cup; a lower valve of the sample cup, the lower valve of the sample cup is connected to a gas source and a water injection pump through a three-way valve, and pressure detectors are provided on both the gas source and the water injection pump; an upper valve of the sample cup, the upper valve of the sample cup is connected to a vacuum pump and a back pressure valve through a three-way valve, and the back pressure valve is connected to a back pressure pump through a pipeline.

[0006] Optionally, the pressure detector is a pressure gauge or a pressure sensor, the back pressure pump is a manual pump or an automatic pump, the sample cup includes a cup body and upper and lower screw caps, pipelines are provided on the upper and lower screw caps, the lower valve and the upper valve of the sample cup are provided on the pipelines, a first valve is provided on the vacuum pump, and a second valve is provided on the back pressure valve.

[0007] Optionally, the gas source uses a gas without nuclear magnetic signal, and the gas without nuclear magnetic signal can be carbon dioxide, carbon monoxide, nitrogen or oxygen.

[0008] Another embodiment of the present invention provides a nuclear magnetic detection method for the content of coal sample bound water, using the above-mentioned coal sample bound water sample preparation device, and the nuclear magnetic detection method includes:

[0009] Determine the lower limit value T of the free water T2 of the sample cup 2Low, based on the transverse relaxation time T detected by the free water T2 of the sample cup in the nuclear magnetic resonance detector 2-1 spectrum as the free water test baseline, based on the case where the sample cup is filled with water, the transverse relaxation time T is detected in the nuclear magnetic resonance detector 2-2 , the T 2-2 minus the T 2-1 and the minimum T2 value after that is the lower limit value T of the free water T2 of the sample cup 2Low ;

[0010] Obtain the sample test baseline. For the dry coal sample placed in the sample cup, perform preliminary processing to obtain the coal sample after the first treatment. Based on the coal sample after the first treatment, detect the transverse relaxation time T in the nuclear magnetic resonance detector 2-3 spectrum, the T 2-3 spectrum is the sample test baseline;

[0011] Obtain the transverse relaxation time T 2-4 spectrum of the saturated water sample. Based on the coal sample after the first treatment, perform secondary processing to obtain the coal sample after the second treatment. Based on the coal sample after the second treatment, detect the transverse relaxation time T in the nuclear magnetic resonance detector 2-4 spectrum, the T 2-4 spectrum is the transverse relaxation time T 2-4 spectrum of the saturated water sample;

[0012] Obtain the T 2-5 spectrum. Based on the coal sample after the second treatment, perform tertiary processing to obtain the coal sample after the third treatment. Based on the coal sample after the third treatment, detect the transverse relaxation time T in the nuclear magnetic resonance detector 2-5 spectrum;

[0013] According to the obtained lower limit value T 2Low , the sample test baseline T 2-3 , the transverse relaxation time T 2-4 spectrum of the saturated water sample and the T 2-5 spectrum, calculate the content of the bound water in the coal sample.

[0014] Optionally, for the dry coal sample placed in the sample cup, perform preliminary processing to obtain the coal sample after the first treatment, and detect the transverse relaxation time T in the nuclear magnetic resonance detector 2-3 spectrum, the T 2-3 spectrum is the sample test baseline, including:

[0015] After the coal sample is dried, place it in the sample cup, close the valve at the lower end of the sample cup, open the valve at the upper end of the sample cup, start the vacuum pump to evacuate, and continue to evacuate for 8 hours after the vacuum gauge on the vacuum pump shows zero;

[0016] Close the upper valve of the sample cup, turn off the vacuum pump, set the pressure value of the gas source. There is a valve on the gas source. Open the gas source valve, open the lower valve of the sample cup, inject gas into the sample cup and then close the gas source valve. Observe the pressure value shown on the pressure gauge set at the gas source. When the pressure value shown on the pressure gauge at the gas source is equal to the pressure value set for the conveying gas source, the gas saturation in the sample cup is completed, and then close the lower valve of the sample cup;

[0017] Unload the sample cup and place the sample cup into the nuclear magnetic detector to detect the transverse relaxation time T 2-3 spectrum, and the T 2-3 spectrum is used as the sample test baseline.

[0018] Optionally, based on the coal sample after the first treatment, perform a second processing to obtain a coal sample after the second treatment. Based on the coal sample after the second treatment, detect the transverse relaxation time T 2-4 spectrum in the nuclear magnetic detector, including:

[0019] Take out the sample cup from the nuclear magnetic detector, place the sample cup back into the sample preparation device. The backpressure pump controls the pressure value of the backpressure valve to be greater than the pressure value set for the gas source. Connect the gas source to the second valve, open the gas source valve, open the second valve to make the gas pressure value in the pipeline equal to the pressure value set for the gas source, close the second valve, close the gas source valve, and disconnect the gas source;

[0020] The backpressure pump controls the pressure value of the backpressure valve to be equal to the pressure value set for the gas source. Set the water injection pressure value of the water injection pump, start the water injection pump, open the lower valve of the sample cup, open the upper valve of the sample cup, open the second valve. After water comes out from the backpressure valve, close the lower valve of the sample cup, the upper valve of the sample cup, close the second valve, turn off the water injection pump and turn off the backpressure pump;

[0021] Unload the sample cup and place the sample cup into the nuclear magnetic detector to detect the transverse relaxation time T 2-4 spectrum after saturated water sample, and the T 2-4 spectrum is the transverse relaxation time T 2-4 spectrum of the saturated water sample.

[0022] Optionally, based on the coal sample after the second treatment, perform a third processing to obtain a coal sample after the third treatment. Based on the coal sample after the third treatment, detect the transverse relaxation time T 2-5 spectrum in the nuclear magnetic detector, including:

[0023] Take out the sample cup from the nuclear magnetic resonance detector, place the sample cup back into the sample preparation device, open the upper valve or the lower valve of the sample cup, and close the upper valve or the lower valve of the sample cup when no gas is produced at the outlet end of the sample cup. Unload the sample cup and put it into the nuclear magnetic resonance detector to measure the transverse relaxation time T 2-5 spectrum.

[0024] Optionally, the calculation formula for the water content of the rock sample in the sample cup is:

[0025]

[0026] V 水 represents the water content of the rock sample, with the unit of cubic centimeter (cm 3 ); m i represents the nuclear magnetic resonance T 2-水 spectrum amplitude of the i-th T 2-水 component of the rock sample; M b represents the total amplitude of the T2 spectrum of the standard sample; S b represents the number of scans during NMR data acquisition of the standard sample; S represents the number of scans during NMR data acquisition of the rock sample; G b represents the receive gain during NMR data acquisition of the standard sample; g represents the receive gain during NMR data acquisition of the rock sample; V b represents the total water content of the standard sample, with the unit of cubic centimeter (cm 3 ).

[0027] Optionally, when calculating the water content of the rock sample in the sample cup, take the values of the T 2-4 and T 2-5 spectra that are less than the values in the T 2Low segment. The T 2-4 -T 2-3 spectrum is the transverse relaxation time T 2-水 spectrum of the saturated water sample, and the T 2-5 -T 2-3 is the transverse relaxation time T 2-解 spectrum after the adsorbed gas of the sample is desorbed.

[0028] Optionally, the calculation formula for the irreducible water content of the rock sample is:

[0029] V 束 =(V 水 / M)×(S1 / S)

[0030] According to the T 2-水 spectrum and the T 2-解 spectrum, determine the T2 cut-off value T 2cutoff , and according to the T 2-水 spectrum diagram, calculate the area under the lower envelope of the T 2-解 spectrum diagram. At T2-水 Find a point above such that the lower envelope area of the left spectral graph is equal to the 2-解 lower envelope area below. The T2 value corresponding to this point is the T2 cut-off value T 2cutoff , V 束 represents the irreducible water content of the rock sample, with the unit of cubic centimeter per gram (cm 3 / g); S1 represents the 2-水 lower envelope area under the immobile peak less than T 2cutoff in T 2-水 ; S represents the lower envelope area of the entire spectrum in T

[0031] The beneficial effects of the present invention are as follows:

[0032] By setting up a sample preparation device, the present invention conducts relevant treatments and processing on the rock sample, establishes relevant calculation methods using the irreducible water of the rock sample, and obtains the irreducible water content of the rock sample through the detection of the sample preparation device and the nuclear magnetic detector, thereby enabling non-destructive and comprehensive testing of the irreducible water content in the pores and fractures of the coal matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 is a schematic structural diagram of a device for preparing a coal sample with irreducible water content according to the present application;

[0035] Figure 2 is a flowchart of the steps of a nuclear magnetic detection method for the irreducible water content of a coal sample according to the present application.

[0036] Reference numerals in the drawings:

[0037] 1. Sample cup; 2. Valve at the lower end of the sample cup; 3. Gas source; 4. Injection water pump; 5. Valve at the upper end of the sample cup; 6. Vacuum pump; 7. Back pressure valve; 8. Back pressure pump; 9. First valve; 10. Second valve; 11. Pressure detector. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments.

[0039] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0040] As Figure 1 described above, this embodiment provides a sample preparation device for coal sample bound water, including: a sample cup 1 for containing the coal sample to be prepared, and valves are provided at both the upper and lower ends of the sample cup 1; a valve 2 at the lower end of the sample cup, which is connected to a gas source 3 and a water injection pump 4 through a three-way valve, and pressure detectors 11 are provided on both the gas source 3 and the water injection pump 4; a valve 5 at the upper end of the sample cup, which is connected to a vacuum pump 6 and a back-pressure valve 7 through a three-way valve, and the back-pressure valve 7 is connected to a back-pressure pump 8 through a pipeline.

[0041] In this embodiment, the pressure detector 11 is a pressure gauge or a pressure sensor, the back-pressure pump 8 is a manual pump or an automatic pump, the sample cup 1 includes a cup body and upper and lower screw caps, pipelines are provided on the upper and lower screw caps, the valve 2 at the lower end of the sample cup and the valve 5 at the upper end of the sample cup are provided on the pipelines, a first valve 9 is provided on the vacuum pump 6, and a second valve 10 is provided on the back-pressure valve 7.

[0042] In this embodiment, the gas source 3 uses a gas without nuclear magnetic signal, and the gas without nuclear magnetic signal can be carbon dioxide, carbon monoxide, nitrogen or oxygen.

[0043] Among them, when measuring the content of bound water in the matrix pores and fractures of a coal reservoir, by sampling, a small amount of rock sample is selected from the coal reservoir, and the rock sample is placed in the sample cup 1. By performing relevant operations on each component in the sample preparation device, the content of bound water in the rock sample is obtained, and the obtained content of bound water in the rock sample is the content of bound water in the matrix pores and fractures of the coal reservoir. The gas source 3 uses a gas without nuclear magnetic signal, and the sample cup 1, the upper and lower screw caps of the sample cup 1, the relevant valves and connecting pipelines are all made of materials without nuclear magnetic signal. Using a gas and materials without nuclear magnetic signal can avoid interference when the sample is placed in a nuclear magnetic detector for detection.

[0044] As Figure 2 described above, this embodiment provides a nuclear magnetic detection method for the content of coal sample bound water, using the above-mentioned sample preparation device for coal sample bound water. The nuclear magnetic detection method includes step S100, step S200, step S300, step S400 and step S500.

[0045] Step S100: Determine the lower limit value T of the free water T2 of the sample cup 1. Based on the transverse relaxation time T detected by the free water T2 of the sample cup 1 in the nuclear magnetic resonance detector as the free water test baseline, when the sample cup 1 is filled with water, detect the transverse relaxation time T in the nuclear magnetic resonance detector. The minimum T2 value after subtracting the above T is the lower limit value T of the free water T2 of the sample cup 1; 2Low , based on the transverse relaxation time T detected by the free water T2 of the sample cup 1 in the nuclear magnetic resonance detector as the free water test baseline, when the sample cup 1 is filled with water, detect the transverse relaxation time T in the nuclear magnetic resonance detector. The minimum T2 value after subtracting the above T is the lower limit value T of the free water T2 of the sample cup 1; 2-1 , based on the transverse relaxation time T detected by the free water T2 of the sample cup 1 in the nuclear magnetic resonance detector as the free water test baseline, when the sample cup 1 is filled with water, detect the transverse relaxation time T in the nuclear magnetic resonance detector. The minimum T2 value after subtracting the above T is the lower limit value T of the free water T2 of the sample cup 1; 2-2 , the T 2-2 minus the above T 2-1 and the minimum T2 value is the lower limit value T of the free water T2 of the sample cup 1; 2Low ;

[0046] Step S200: Obtain the sample test baseline. For the dry coal sample placed in the sample cup 1, perform preliminary processing to obtain the coal sample after the first processing. Based on the coal sample after the first processing, detect the transverse relaxation time T spectrum in the nuclear magnetic resonance detector. The T spectrum is the sample test baseline; 2-3 , based on the transverse relaxation time T detected by the free water T2 of the sample cup 1 in the nuclear magnetic resonance detector as the free water test baseline, when the sample cup 1 is filled with water, detect the transverse relaxation time T in the nuclear magnetic resonance detector. The minimum T2 value after subtracting the above T is the lower limit value T of the free water T2 of the sample cup 1; 2-3 spectrum is the sample test baseline;

[0047] Step S300: Obtain the transverse relaxation time T spectrum of the saturated water sample. Based on the coal sample after the first processing, perform second processing to obtain the coal sample after the second processing. Based on the coal sample after the second processing, detect the transverse relaxation time T spectrum in the nuclear magnetic resonance detector. The T spectrum is the transverse relaxation time T spectrum of the saturated water sample; 2-4 , based on the transverse relaxation time T detected by the free water T2 of the sample cup 1 in the nuclear magnetic resonance detector as the free water test baseline, when the sample cup 1 is filled with water, detect the transverse relaxation time T in the nuclear magnetic resonance detector. The minimum T2 value after subtracting the above T is the lower limit value T of the free water T2 of the sample cup 1; 2-4 , based on the transverse relaxation time T detected by the free water T2 of the sample cup 1 in the nuclear magnetic resonance detector as the free water test baseline, when the sample cup 1 is filled with water, detect the transverse relaxation time T in the nuclear magnetic resonance detector. The minimum T2 value after subtracting the above T is the lower limit value T of the free water T2 of the sample cup 1; 2-4 spectrum is the transverse relaxation time T spectrum of the saturated water sample; 2-4 spectrum;

[0048] Step S400: Obtain the T 2-5 spectrum. Based on the coal sample after the second processing, perform third processing to obtain the coal sample after the third processing. Based on the coal sample after the third processing, detect the transverse relaxation time T spectrum in the nuclear magnetic resonance detector; 2-5 spectrum;

[0049] Step S500: Calculate the content of the bound water in the coal sample according to the obtained lower limit value T 2Low , the sample test baseline T 2-3 , the transverse relaxation time T spectrum of the saturated water sample 2-4 spectrum and the T 2-5 spectrum.

[0050] In step S200 of the present embodiment, for the dry coal sample placed in the sample cup 1, performing preliminary processing to obtain the coal sample after the first processing and detecting the transverse relaxation time T spectrum in the nuclear magnetic resonance detector, the T spectrum is the sample test baseline, including: 2-3 , based on the transverse relaxation time T detected by the free water T2 of the sample cup 1 in the nuclear magnetic resonance detector as the free water test baseline, when the sample cup 1 is filled with water, detect the transverse relaxation time T in the nuclear magnetic resonance detector. The minimum T2 value after subtracting the above T is the lower limit value T of the free water T2 of the sample cup 1; 2-3 spectrum is the sample test baseline, including:

[0051] Step S210: After drying the coal sample, place it in the sample cup 1, close the valve 2 at the lower end of the sample cup, open the valve 5 at the upper end of the sample cup, start the vacuum pump 6 to pump vacuum, and continue to pump for 8 hours after the vacuum gauge on the vacuum pump 6 shows zero;

[0052] Step S220: Close the valve 5 at the upper end of the sample cup, turn off the vacuum pump 6, set the pressure value of the gas source 3. There is a valve on the gas source 3. Open the gas source valve, open the valve 2 at the lower end of the sample cup, inject gas into the sample cup 1 and then close the gas source valve. Observe the pressure value shown on the pressure gauge set at the gas source 3. When the pressure value shown on the pressure gauge at the gas source 3 is equal to the set pressure value of the conveying gas source 3, the gas saturation in the sample cup 1 is completed, and then close the valve 2 at the lower end of the sample cup;

[0053] Step S230: Unload the sample cup 1, and put the sample cup 1 into a nuclear magnetic resonance detector to detect the transverse relaxation time T 2-3 spectrum, and the T 2-3 spectrum is used as the sample test baseline.

[0054] Among them, the related operations for the first treatment of the coal sample are as follows: First, after drying the coal sample, place it in the sample cup 1, close the valve 2 at the lower end of the sample cup, open the valve 5 at the upper end of the sample cup, start the vacuum pump 6 to pump vacuum, and continue to pump for 8 hours after the vacuum gauge on the vacuum pump 6 shows zero. Close the valve 5 at the upper end of the sample cup, turn off the vacuum pump 6, set the pressure value of the gas source 3. There is a valve on the gas source 3. Open the gas source valve, open the valve 2 at the lower end of the sample cup, inject gas into the sample cup 1 and then close the gas source valve. Observe the pressure value shown on the pressure gauge set at the gas source 3. When the pressure value shown on the pressure gauge at the gas source 3 is equal to the set pressure value of the conveying gas source 3, the gas saturation in the sample cup 1 is completed, and then close the valve 2 at the lower end of the sample cup. Unload the sample cup 1, and put the sample cup 1 into a nuclear magnetic resonance detector to detect the transverse relaxation time T 2-3 spectrum, and the T 2-3 spectrum is used as the sample test baseline.

[0055] In step S300 of this embodiment, based on the coal sample after the first treatment, a second processing is performed to obtain a coal sample after the second treatment. Based on the coal sample after the second treatment, the transverse relaxation time T 2-4 spectrum is detected in a nuclear magnetic resonance detector, including:

[0056] Step S310: Take out the sample cup 1 from the nuclear magnetic detector, place the sample cup 1 back into the sample preparation device. The backpressure pump 8 controls the pressure value of the backpressure valve 7 to be greater than the pressure value set by the gas source 3. Connect the gas source 3 to the second valve 10, open the gas source valve, open the second valve 10 to make the gas pressure value in the pipeline equal to the pressure value set by the gas source 3, close the second valve 10, close the gas source valve, and disconnect the gas source 3.

[0057] Step S320: The backpressure pump 8 controls the pressure value of the backpressure valve 7 to be equal to the pressure value set by the gas source 3. Set the water injection pressure value of the water injection pump 4, start the water injection pump 4, open the lower valve 2 of the sample cup, open the upper valve 5 of the sample cup, open the second valve 10. After water comes out from the backpressure valve 7, close the lower valve 2 of the sample cup, the upper valve 5 of the sample cup, close the second valve 10, turn off the water injection pump 4 and turn off the backpressure pump 8.

[0058] Step S330: Unload the sample cup 1, put the sample cup 1 into the nuclear magnetic detector to detect the transverse relaxation time T 2-4 spectrum of the saturated water sample, and the T 2-4 spectrum is the transverse relaxation time T 2-4 spectrum of the saturated water sample.

[0059] Among them, the related operations for the second treatment of the coal sample are as follows: Based on the coal sample after the first treatment, continue to perform related operations on the coal sample. Put the sample cup 1 into the nuclear magnetic detector to detect the transverse relaxation time T 2-3 spectrum, and place the obtained coal sample back into the sample preparation device. At this time, the backpressure pump 8 controls the pressure value of the backpressure valve 7 to be greater than the pressure value set by the gas source 3. Connect the gas source 3 to the second valve 10, open the gas source valve, open the second valve 10 to make the gas pressure value in the pipeline equal to the pressure value set by the gas source 3, close the second valve 10, close the gas source valve, and disconnect the gas source 3. The backpressure pump 8 controls the pressure value of the backpressure valve 7 to be equal to the pressure value set by the gas source 3. Set the water injection pressure value of the water injection pump 4, start the water injection pump 4, open the lower valve 2 of the sample cup, open the upper valve 5 of the sample cup, open the second valve 10. After water comes out from the backpressure valve 7, close the lower valve 2 of the sample cup, the upper valve 5 of the sample cup, close the second valve 10, turn off the water injection pump 4 and turn off the backpressure pump 8. Unload the sample cup 1, put the sample cup 1 into the nuclear magnetic detector to detect the transverse relaxation time T 2-4 spectrum of the saturated water sample, and the T 2-4 spectrum is the transverse relaxation time T 2-4 spectrum of the saturated water sample, thereby obtaining the coal sample after the second treatment.

[0060] In step S400 of this embodiment, based on the coal sample after the second treatment, perform a third processing to obtain a coal sample after the third treatment. Based on the coal sample after the third treatment, detect the transverse relaxation time T in the nuclear magnetic detector2-5 Spectrum, including:

[0061] Step S410: Take out the sample cup 1 from the nuclear magnetic resonance detector, place the sample cup 1 back into the sample preparation device, open the upper valve 5 or the lower valve 2 of the sample cup. When no more gas is produced from the outlet end of the sample cup 1, close the upper valve 5 or the lower valve 2 of the sample cup, unload the sample cup 1, and put it into the nuclear magnetic resonance detector to detect the transverse relaxation time T 2-5 spectrum.

[0062] Among them, place the coal sample obtained after the second treatment back into the sample preparation device again, open the upper valve 5 or the lower valve 2 of the sample cup. When no more gas is produced from the outlet end of the sample cup 1, close the upper valve 5 or the lower valve 2 of the sample cup, unload the sample cup 1, and put it into the nuclear magnetic resonance detector to detect the transverse relaxation time T 2-5 spectrum, and then obtain the coal sample after the third treatment.

[0063] In step S500 of this embodiment,

[0064] Step S510: The calculation formula for the water content of the rock sample in the sample cup 1 is:

[0065]

[0066] V 水 represents the water content of the rock sample, with the unit of cubic centimeter (cm 3 ); m i represents the nuclear magnetic resonance T 2-水 spectrum amplitude of the i-th T 2-水 component of the rock sample; M b represents the total amplitude of the T2 spectrum of the standard sample; S b represents the number of scans during NMR data acquisition of the standard sample; S represents the number of scans during NMR data acquisition of the rock sample; G b represents the receive gain during NMR data acquisition of the standard sample; g represents the receive gain during NMR data acquisition of the rock sample; V b represents the total water content of the standard sample, with the unit of cubic centimeter (cm 3 ).

[0067] Among them, the water content of the rock sample is the water content calculated from a small amount of rock sample selected from the coal reservoir. The obtained bound water content of the rock sample is the content of the bound water in the matrix pores and fractures of the coal reservoir, thereby obtaining the bound water content of the coal sample.

[0068] In this embodiment, when calculating the water content of the rock sample in the sample cup 1, take the values of T 2-4 and T 2-5 spectra to be less than T 2LowThe value of the segment, T 2-4 -T 2-3 The spectrum is the transverse relaxation time T of the saturated water sample 2-水 Spectrum, T 2-5 -T 2-3 Is the transverse relaxation time T after the adsorbed gas of the sample is desorbed 2-解 Spectrum.

[0069] Step S520, the calculation formula for the irreducible water content of the rock sample is:

[0070] V 束 =(V 水 / M)×(S1 / S)

[0071] According to the T 2-水 Spectrum and T 2-解 Spectrum, determine the T2 cut-off value T 2cutoff , according to the T 2-水 Spectrum diagram, calculate the lower envelope area of the T 2-解 Spectrum diagram, find a point on the T 2-水 So that the lower envelope area of the left spectrum diagram is equal to the lower envelope area of the T 2-解 The T2 value corresponding to this point is the T2 cut-off value T 2cutoff , V 束 Represents the irreducible water content of the rock sample, with the unit of cubic centimeter per gram (cm 3 / g); S1 represents the lower envelope area of the immobile peak less than T 2-水 In the T 2cutoff ; S represents the lower envelope area of the entire T 2-水 Spectrum; M represents the sample mass, with the unit of g.

[0072] The present invention realizes non-destructive and comprehensive testing of the irreducible water content in the pores and fractures of the coal matrix by setting up a sample preparation device to perform relevant processing and machining on the rock sample, establishing a relevant calculation method using the irreducible water in the rock sample, and obtaining the irreducible water content of the rock sample through the detection of the sample preparation device and the nuclear magnetic detector.

[0073] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A sample preparation device for bound water in coal samples, characterized in that, Comprising: A sample cup (1) for containing coal samples to be prepared for testing. Valves are provided at both the upper and lower ends of the sample cup (1). A valve (2) at the lower end of the sample cup. The valve (2) at the lower end of the sample cup is connected to a gas source (3) and a water injection pump (4) through a three-way valve. Pressure detectors (11) are provided on both the gas source (3) and the water injection pump (4). A valve (5) at the upper end of the sample cup. The valve (5) at the upper end of the sample cup is connected to a vacuum pump (6) and a back-pressure valve (7) through a three-way valve. The back-pressure valve (7) is connected to a back-pressure pump (8) through a pipeline.

2. The sample preparation device for bound water in coal samples according to claim 1, characterized in that, The pressure detector (11) is a pressure gauge or a pressure sensor. The back-pressure pump (8) is a manual pump or an automatic pump. The sample cup (1) includes a cup body and upper and lower screw caps. Pipelines are provided on the upper and lower screw caps. The valve (2) at the lower end of the sample cup and the valve (5) at the upper end of the sample cup are provided on the pipeline. A first valve (9) is provided on the vacuum pump (6), and a second valve (10) is provided on the back-pressure valve (7).

3. The sample preparation device for bound water in coal samples according to claim 2, characterized in that, The gas source (3) uses a gas without nuclear magnetic signal, and the gas without nuclear magnetic signal can be carbon dioxide, carbon monoxide, nitrogen or oxygen.

4. A nuclear magnetic detection method for the content of bound water in coal samples, using any one of the sample preparation devices for bound water in coal samples according to claims 1 - 3, characterized in that, The nuclear magnetic detection method includes: Determine the lower limit value T of the free water T2 of the sample cup (1) 2Low , based on the transverse relaxation time T detected by the free water T2 of the sample cup (1) in the nuclear magnetic detector 2-1 spectrum as the free water test baseline, based on the case where the sample cup (1) is filled with water, the transverse relaxation time T is detected in the nuclear magnetic detector 2-2 , the T 2-2 subtract the T 2-1 The minimum T2 value after that is the lower limit value T of the free water T2 of the sample cup (1) 2Low ; Obtain a sample test baseline. For the dry coal sample placed in the sample cup (1), perform preliminary processing to obtain the coal sample after the first treatment. Based on the coal sample after the first treatment, detect the transverse relaxation time T in a nuclear magnetic resonance detector 2-3 spectrum, and the T 2-3 spectrum is the sample test baseline; Obtain the transverse relaxation time T2 spectrum of the saturated water sample. Based on the coal sample after the first treatment, perform a second processing to obtain the coal sample after the second treatment. Based on the coal sample after the second treatment, detect the transverse relaxation time T2 spectrum in a nuclear magnetic detector. The T2 spectrum is the transverse relaxation time T2 spectrum of the saturated water sample. 2-4 spectrum. Based on the coal sample after the first treatment, perform a second processing to obtain the coal sample after the second treatment. Based on the coal sample after the second treatment, detect the transverse relaxation time T2 2-4 spectrum, where the T2 2-4 spectrum is the transverse relaxation time T2 2-4 spectrum; Obtain the T 2-5 spectrum. Based on the coal sample after the second treatment, perform a third processing to obtain a coal sample after the third treatment. Based on the coal sample after the third treatment, detect the transverse relaxation time T 2-5 spectrum; According to the obtained down-line value T 2Low , the sample test baseline T 2-3 , the transverse relaxation time T of the saturated water sample 2-4 spectrum and the T 2-5 spectrum, the content of the bound water in the coal sample is calculated.

5. The nuclear magnetic detection method for the content of bound water in coal samples according to claim 4, characterized in that, The dried coal sample placed in the sample cup (1) is subjected to preliminary processing to obtain a coal sample after the first treatment, and the transverse relaxation time T is measured in a nuclear magnetic resonance detector 2-3 spectrum, and the T 2-3 spectrum is the sample test baseline, including: After the coal sample is dried, it is placed in the sample cup (1). The valve (2) at the lower end of the sample cup is closed, the valve (5) at the upper end of the sample cup is opened, and the vacuum pump (6) is started to pump vacuum. After the vacuum gauge on the vacuum pump (6) shows zero, continue to pump for 8 hours. The valve (5) at the upper end of the sample cup is closed, the vacuum pump (6) is closed, the pressure value of the gas source (3) is set. A valve is provided on the gas source (3). The gas source valve is opened, the valve (2) at the lower end of the sample cup is opened, gas is injected into the sample cup (1), and then the gas source valve is closed. Observe the pressure value shown on the pressure gauge provided at the gas source (3). When the pressure value shown on the pressure gauge at the gas source (3) is equal to the set pressure value of the gas source (3) for transportation, the gas saturation in the sample cup (1) is completed, and the valve (2) at the lower end of the sample cup is closed. Unload the sample cup (1) and place the sample cup (1) in a nuclear magnetic resonance detector to detect the transverse relaxation time T 2-3 spectrum, and the T 2-3 spectrum serves as the sample test baseline.

6. The nuclear magnetic detection method for the content of bound water in coal samples according to claim 5, characterized in that, Based on the coal sample after the first treatment, a second processing treatment is carried out to obtain a coal sample after the second treatment. Based on the coal sample after the second treatment, the transverse relaxation time T is detected in a nuclear magnetic detector 2-4 spectrum, including: Take out the sample cup (1) from the nuclear magnetic detector, place the sample cup (1) back into the sample preparation device. The back-pressure pump (8) controls the pressure value of the back-pressure valve (7) to be greater than the set pressure value of the gas source (3). Connect the gas source (3) to the second valve (10), open the gas source valve, open the second valve (10) to make the gas pressure value in the pipeline equal to the set pressure value of the gas source (3), close the second valve (10), close the gas source valve, and disconnect the gas source (3). The back-pressure pump (8) controls the pressure value of the back-pressure valve (7) to be equal to the set pressure value of the gas source (3). Set the water injection pressure value of the water injection pump (4). Start the water injection pump (4), open the valve (2) at the lower end of the sample cup, open the valve (5) at the upper end of the sample cup, open the second valve (10). After water comes out from the back-pressure valve (7), close the valve (2) at the lower end of the sample cup, the valve (5) at the upper end of the sample cup, close the second valve (10), close the water injection pump (4) and the back-pressure pump (8). Unload the sample cup (1), place the sample cup (1) in a nuclear magnetic resonance detector to detect the transverse relaxation time T of the saturated water sample 2-4 spectrum, and the T 2-4 spectrum is the transverse relaxation time T of the saturated water sample 2-4 spectrum.

7. The nuclear magnetic detection method for the content of bound water in coal samples according to claim 6, characterized in that, Based on the coal sample after the second treatment, a third processing treatment is carried out to obtain a coal sample after the third treatment. Based on the coal sample after the third treatment, the transverse relaxation time T is detected in a nuclear magnetic detector 2-5 spectrum, including: Take out the sample cup (1) from the nuclear magnetic detector, place the sample cup (1) back into the sample preparation device, open the upper valve (5) or the lower valve (2) of the sample cup, and close the upper valve (5) or the lower valve (2) of the sample cup when no more gas is produced at the outlet end of the sample cup (1). Unload the sample cup (1) and put it into the nuclear magnetic detector to measure the transverse relaxation time T 2-5 spectrum.

8. The nuclear magnetic detection method for the content of bound water in coal samples according to claim 7, characterized in that, The calculation formula for the water content of the rock sample in the sample cup (1) is: V 水 represents the water content of the rock sample, with the unit of cubic centimeter (cm 3 ); m i represents the nuclear magnetic resonance T 2-水 spectrum amplitude of the i-th T 2-水 component of the rock sample; M b represents the total amplitude of the T2 spectrum of the standard sample; S b represents the number of scans during NMR data acquisition of the standard sample; S represents the number of scans during NMR data acquisition of the rock sample; G b represents the receive gain during NMR data acquisition of the standard sample; g represents the receive gain during NMR data acquisition of the rock sample; V b represents the total water content of the standard sample, with the unit of cubic centimeter (cm 3 ).

9. The nuclear magnetic detection method for the content of bound water in coal samples according to claim 8, characterized in that, When calculating the water content of the rock sample in the sample cup (1), the values of the T 2-4 and T 2-5 spectra are taken to be less than the value in the T 2Low section. The T 2-4 -T 2-3 spectrum is the transverse relaxation time T 2-水 spectrum of the saturated water sample, and the T 2-5 -T 2-3 is the transverse relaxation time T 2-解 spectrum after the adsorbed gas of the sample is desorbed.

10. A nuclear magnetic detection method for the bound water content of coal samples according to claim 9, characterized in that, The calculation formula for the irreducible water content of the rock sample is: V 束 = (V 水 / M) × (S1 / S) According to the T 2-水 spectrum and the T 2-解 spectrum, determine the T2 cut-off value T 2cutoff , according to the T 2-水 spectrum, calculate the T 2-解 spectrum lower envelope area. On the T 2-水 , find a point such that the left lower envelope area of the spectrum is equal to the T 2-解 lower envelope area. The T2 value corresponding to this point is the T2 cut-off value T 2cutoff , V 束 represents the irreducible water content of the rock sample, with the unit of cubic centimeter per gram (cm 3 / g); S1 represents the lower envelope area under the immobile peak in the T 2-水 that is less than T 2cutoff ; S represents the lower envelope area of the entire T 2-水 spectrum; M represents the sample mass, with the unit of g.

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