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

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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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 the adsorption test of a single sample, which is very time consuming

At the same time, this method can only measure the amount of methane adsorption at a certain pressure point, and cannot continuously and dynamically detect the amount of adsorption at each pressure point.

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