Method for measuring coal sample methane adsorbing capacity through low-field nuclear magnetic resonance

A technology of low-field nuclear magnetic resonance and coal sample methane, which is applied in the direction of analysis by nuclear magnetic resonance, and can solve the problems of continuous adsorption, time-consuming, dynamic detection, etc.

Active Publication Date: 2013-12-04
CHINA UNIV OF GEOSCIENCES (BEIJING)
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Problems solved by technology

[0004] Conventional methane isothermal adsorption experiments usually measure the adsorption capacity at 6-9 pressure points, and it usually takes about 8-12 hours to achieve adsorption equilibrium at each pressure point. Therefore, it usually takes about a week to complete

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  • Method for measuring coal sample methane adsorbing capacity through low-field nuclear magnetic resonance
  • Method for measuring coal sample methane adsorbing capacity through low-field nuclear magnetic resonance
  • Method for measuring coal sample methane adsorbing capacity through low-field nuclear magnetic resonance

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Embodiment Construction

[0051] The invention mainly measures the unit mass adsorption gas content of the coal sample under the corresponding pressure through the NMR T2 spectrum after the methane adsorption of the powdery coal sample is balanced. The low-field nuclear magnetic resonance technology of the present invention detects H nuclei in methane, and its signal amplitude is proportional to the mass of methane within the detection range. Methane in powdered coal samples has different NMR characteristics from free methane; the presence of coal samples accelerates the relaxation rate of methane, and there are roughly three peaks in the methane NMR T2 spectrum, from left to right are adsorbed methane Peak (Q1 peak, about less than 10ms), inter-particle / pore methane peak (Q2 peak, between 10-100ms) and free-state methane peak (Q3 peak, between 400-1000ms) such as Figure 4 shown.

[0052] In order to prove that the Q1 peak is the adsorption peak, when coal adsorbs methane at different pressure points...

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Abstract

The invention discloses a method for measuring coal sample methane adsorbing capacity through low-field nuclear magnetic resonance. According to the method, selected measuring parameters are used for carrying out low-field nuclear magnetic resonance measurement on powder coal samples after methane adsorption balance under set pressure, the nuclear magnetism T2 spectrum of methane in the coal samples is obtained, then signal amplitude integrals of the first spectrum peak (in the range of 0.1-4ms spectrum) on the left of the T2 spectrum are substituted to a hydrogen content index reticle equation of methane under the standard condition built through an experiment, the standard condition size of methane adsorbed by the coal samples is obtained, and therefore the methane adsorbing capacity of unit mass of coal under the set pressure is obtained. According to the method, the scale relation of methane mass and nuclear magnetic resonance 1H nuclear signals is built, the quantitative assay of methane adsorbing capacity under the same temperature and different pressures is achieved, and the novel method can be used for measuring coal methane absorbing capacity in a real-time, home-position and dynamic mode.

Description

technical field [0001] The invention relates to a method for measuring the methane adsorption capacity of coal samples by using low-field nuclear magnetic resonance, and belongs to the technical field of methane adsorption capacity of coal and coal bed gas content measurement. Background technique [0002] Coalbed methane mainly exists in the coal seam in the state of adsorption. In the field of coalbed methane exploration and development, accurate determination of the adsorbed methane gas content of coal is of great significance for reservoir evaluation, coalbed methane reserve estimation and development effect evaluation. [0003] At present, the method of measuring the methane adsorption capacity of coal mainly adopts the national standard method "High pressure isothermal adsorption test method of coal - capacity method" (GB / T19560) jointly drafted by China United Coalbed Methane Co., Ltd. -2004). This method measures the methane adsorption volume under a typical adsorp...

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Application Information

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IPC IPC(8): G01N24/08
Inventor 姚艳斌谢松彬刘大锰李振涛
Owner CHINA UNIV OF GEOSCIENCES (BEIJING)
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