CO_(2)置换CH_(4)强化煤层气开采的试验研究——以韩城矿区煤层气为例

Experimental Study on CO_(2)Replacement CH_(4)Enhanced Coalbed Methane Extraction—Taking Coalbed Methane in Hancheng Mining Area as an Example

煤层气储层普遍渗透率低,吸附性强,基本无自然产能,目前,主要增产技术手段是采用压裂构建复杂的人工裂缝网络,增加采出通道。超临界CO_(2)具有低黏度、高扩散、低表面张力的特性,可应用于压裂改造,增加采出效果。为研究煤样中不同温压、相态条件下CO_(2)对CH_(4)的置换能力,评价超临界CO_(2)压裂强化煤层气高效开发的作用,本文以韩城矿区煤层气为例,开展煤样孔隙结构特征评价及等温吸附试验。结果表明,相比CH_(4),CO_(2)在煤样表面具有更强的吸附性,CO_(2)具有竞争置换能力,可用于强化煤层气高效开发;CO_(2)在煤样中的吸附性随着压强的增加而增加,达到高压时,增加幅度趋于平缓,并表现出极大值;CO_(2)吸附性随着温度的增加而显著减弱。

Coalbed methane reservoirs generally have low permeability,strong adsorption,and almost no natural production capacity,currently,the main production increase technology is to use fracturing to build a complex artificial fracture network and increase production channels.Supercritical CO_(2)has the characteristics of low viscosity,high diffusion,and low surface tension,which can be applied in hydraulic fracturing to increase recovery efficiency.In order to study the displacement ability of CO_(2)on CH_(4)under different temperature-pressure and phase state conditions in coal samples,and evaluate the role of supercritical CO_(2)fracturing in enhancing the efficient development of coalbed methane,this paper takes coalbed methane in the Hancheng Mining Area as an example to carry out evaluation of the pore structure characteristics of coal samples and isothermal adsorption tests.The results show that compared to CH_(4),CO_(2)has stronger adsorption capacity on the surface of coal samples,and CO_(2)has competitive displacement ability,which can be used to enhance the efficient development of coalbed methane;the adsorption capacity of CO_(2)in coal samples increases with the increase of pressure,and when it reaches high pressure,the increase tends to be gentle and shows a maximum value;the CO_(2)adsorption capacity significantly decreases with increasing temperature.