煤解吸二氧化碳和甲烷的特性曲线及其应用

二氧化碳与甲烷的吸附与解吸机理决定了二氧化碳在煤中的螯合和强化甲烷产出的能力，是近期人们所关注的焦点。根据对大量甲烷和二氧化碳吸附/解吸等温线和吸附特性曲线的研究结果，从吸附势角度探讨了两者的吸附/解吸机理，并将解吸特性曲线归纳为3类：①两者的吸附-解吸等温线不相交，二氧化碳的吸附势大于等于甲烷的，在两者接近的中压阶段不利于注二氧化碳驱甲烷，高压、低压阶段均有利；②因甲烷的吸附-解吸等温线相交造成两者的吸附特性曲线相交，高压下利于注二氧化碳驱甲烷；③因二氧化碳的吸附-解吸等温线相交造成两者的吸附特性曲线相交，高压下利于注二氧化碳驱甲烷。这一结论为二氧化碳驱甲烷实验所证实。吸附势理论的引入为定量评价注入二氧化碳驱甲烷工艺参数和有利储层的选择提供了方法。

DESORPTION CHARACTERISTIC CURVES OF CARBON DIOXIDE AND METHANE IN COAL AND THEIR APPLICATION

Mechanisms of adsorption and desorption of carbon dioxide and methane determine the chelation capacity of carbon dioxide in coal. How to enhance the deliverability of methane is the focus of research at present. Based on study of a large amount of adsorption/desorption isotherms and adsorption characteristic curves of methane and carbon dioxide, their mechanisms of adsorption/desorption are discussed in the context of adsorption potential, and desorption curves are concluded into 3 types: ① when their adsorption/desorption curves do not intersect and the adsorption potential of carbon dioxide is equal to or larger than that of methane, intermediate pressure at which their potential values are close is unfavorable for displacing methane through injection of carbon dioxide, while both high and low pressure are favorable; ② when their adsorption curves intersect due to the intersecting of adsorption/desorption curves of methane, high pressure is favorable for displacement of methane through injection of carbon dioxide; ③ when their adsorption curves intersect due to the intersecting of adsorption/desorption curves of carbon dioxide, high pressure is favorable for displacement of methane through injection of carbon dioxide. These understandings have been verified by experiment of methane displacement by injecting carbon dioxide. The introduction of adsorption potential theory provides a methodology for evaluation of process parameters of displacing methane through injection of carbon dioxide and selection of favorable reservoirs.