Isothermal absorption curve correction method based on gravimetric method

Abstract

The invention relates to an isothermal adsorption curve correction method based on a gravimetric method. The method comprises steps of carrying out a blank test before a rock core isothermal adsorption test, calculating the volume of a sample barrel under different test pressures, and finely characterizing the dynamic change of the volume of the sample barrel under different test pressures; respectively carrying out pretreatment test, buoyancy test and methane isothermal absorption test of a granular sample which is crushed to a laboratory test standard, in a buoyancy test phase, finely representing the dynamic change characteristics of the sample and the sample barrel under different test pressures, in combination with the dynamic change of the volume of the sample barrel under the same test pressure, constructing a dynamic change mathematical model of the sample volume under different test pressures, realizing fine representation of the sample volume under different test pressures, calculating the adsorbed state methane mass under different test pressures in the methane absorption test stage based on the fine representation, and drawing an accurate isothermal absorption curve based on a gravimetric method. The method can effectively guide evaluation of coal bed gas, shale gas and other unconventional natural gas resources.

Description

technical field [0001] The invention relates to the technical field of unconventional oil and gas development, in particular to a method for correcting an isotherm adsorption curve based on a gravimetric method. Background technique [0002] Unconventional natural gas resources such as coalbed methane and shale gas are used as methane (CH 4 ) as the main component of clean energy, the proportion of the national energy structure is increasing. Coalbed methane and shale gas usually exist in unconventional reservoirs such as coal rock and shale in three different phases: adsorbed state, dissolved state, and free state, especially adsorbed methane is the main occurrence state, and The proportion of adsorbed methane often accounts for more than 85% of the total gas content. Through accurate evaluation of the content of adsorbed methane, relevant parameters such as gas saturation and recovery ratio of coalbed methane and shale gas can be accurately obtained. Studies on the cont...

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Problems solved by technology

[0004] The main problems in the above-mentioned prior art are: (1) Most of the existing studies use improvements to the original isotherm adsorption model to correct the isotherm adsorption curve, but these improved isotherm adsorption models have many idealized assumptions , the correction effect of the improved isothermal adsorption model on the isothermal adsorption curves of different types of coal rocks and shale is very different, that is, the generality of the isothermal adsorption model is poor; In the falling section of the methane adsorption curve, the adsorption phase density is calculated, and then the isotherm adsorption curve is corrected, but the original isotherm adsorption curve after the experimental measurement is not corrected. This will inevitably lead to incorrect calculation of the adsorption phase density and the inability to achieve isothermal adsorption. Accurate correction of curves

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