鄂尔多斯盆地东部煤岩孔隙特征实验分析

煤层气储层孔隙结构特征决定着煤层的吸附能力。利用低温氮吸附法和汞侵入法对鄂尔多斯盆地东部地区煤样的孔隙特征进行测试,并分别对煤样的低温氮吸附孔隙特征和汞侵入孔隙特征进行分析。在此基础上,综合两种实验的测试结果,对煤样的孔隙类型进行分类。压汞实验表明:压汞曲线和退汞曲线相似性较好,两者之间的间距很小,退汞效率达65%~75%;液氮实验表明:低变质煤孔以一端封闭的孔为主,随着煤变质程度的增加,先是较大的孔变为两端开放的孔,接着较小孔变为两端开放的孔,到了无烟煤阶段微孔也变成以两端开放的孔为主。综合两种结果,认为煤样的孔隙中以微孔和过渡孔为主,并且微孔和过渡孔是构成煤样孔隙容积的主要贡献者,大孔和中孔的总孔容所占比例较小。鄂尔多斯盆地东部煤岩的孔隙特征有利于煤层中气体的吸附,是煤层气储层的良好场所。

Experimental Analysis of Coal and Rock Pore Characteristics in Eastern Ordos Basin

The pore structural characteristics of CBM reservoir determine the adsorptive capacity of coal seams. Using low temperature nitrogen adsorption and mercury intrusion methods carried out coal sample pore characteristic test in the eastern Ordos Basin, and ana- lyzed coal sample low temperature nitrogen adsorption and mercury intrusion pore characteristics respectively. On this basis, integrat- ing the results of two methods, carried out classification of coal sample pore types, the mercm＇y injection experiment has shown： low metamorphosed coal pores are mainly closed at one end, along with the increasing metamorphism degree, larger pores changed into pores with two open ends at first, then smaller pores, through to anthracite phase, even the micropores also changed into mainly pores with two open ends. Comprehensively, pores in coal are mainly micropores and transitional pores and they are main contributors to con- stitute coal pore volume, while volume percentage of large and medium pores relatively small. The coal and rock pore characteristics in eastern Ordos Basin are propitious to coal seam gas adsorption, thus the good place to host CBM reservoir.