注高温过热水蒸汽条件下三轴受压无烟煤单裂缝渗流特性研究

Study on Permeability Characteristics of Single Fracture in the Triaxially Stressed Anthracite Subjected to High-Temperature Superheated Steam Injection

原位注热强化煤层气开采是煤层气高效开采的有效方式之一,为了研究煤层气原位注热开采过程中煤层裂缝渗流特征,利用自主研制的注热式高温高压岩石三轴试验系统,研究了200m和400m埋深地应力条件下,注高温过热水蒸汽前后无烟煤单裂缝渗透率变化特征。研究结果表明,经过12h注热,无烟煤单裂缝渗透率提高,提高幅度与三轴应力大小有关,压力越大,提高幅度越小;注热冷却后,裂缝渗透率受三轴应力压缩影响,渗透率略微降低,但仍高于注热前的数值;通过对比注热前后单裂缝表面微裂隙变化,发现注入高温过热蒸汽后,裂缝表面增加大量微裂隙,已有微裂隙进一步扩展,张开度增加,有效地增强了裂缝导流能力。

In-situ heat injection to enhance coalbed methane mining is one of the effective ways of efficient coalbed methane mining.In order to study the seepage characteristics of coalbed fractures in the process of in-situ heat-injected mining of coalbed methane,the permeability characteristics of single fracture in anthracite before and after high-temperature superheated steam injection under the stress conditions of 200mand 400mburied depth were studied by using the self-developed heat injection rock triaxial experimental system with high temperature and high pressure.It is found that the permeability of single fracture in anthracite increases after 12hours of heat injection.The increase range is related to the magnitude of triaxial stress,and the greater the pressure,the smaller the increase range.After the cooling of heat injection,the permeability of fracture decreases slightly by the affect of triaxial stress compression,but it is still higher than that before heat injection.By comparing the changes of micro cracks on the surface of single fracture before and after heat injection,it is found that after high-temperature superheated steam injection,a large number of micro cracks increase on the fracture surface,the existing micro cracks further expand and the opening increases,which effectively increases the fracture conductivity.