二连盆地群低煤阶煤储层孔隙发育特征研究

Study on pore development characteristics of low rank coal reservoirs in Erlian Basin group

以二连盆地群霍林河盆地和白音华盆地低煤阶煤储层为研究对象,通过对煤储层物性特征、压汞曲线类型、孔径分布特征、孔隙结构类型划分的分析,研究低煤阶煤储层孔隙结构对煤层气吸附解吸的影响。结果表明:二连盆地群低煤阶煤储层孔隙系统发育良好,孔隙度较大,孔隙度Ⅳ煤组<ⅢA煤<3-1煤;孔隙结构以小微孔、大孔为主,孔径小于100 nm的小微孔和孔径大于1000 nm的大孔对孔容贡献最大;基于孔隙孔径分布比例及孔径对煤层气储集和渗流的作用,把研究区孔隙结构类型划分为ⅡC封闭吸附型、ⅡO开放吸附型、ⅠC封闭渗流型、ⅠO开放渗流型4类,其中ⅡO开放吸附型最有利于煤层气的富集和产出;将霍林河盆地Ⅳ煤组、ⅢA煤储层和白音华盆地3-1煤储层相比较,ⅢA煤孔隙结构最有利于煤层气储集和开发。

Taking Huolinhe Basin of Erlian Basin group and the low-rank coal reservoirs of Baiyinhua Basin as the research objects,through the analysis of the physical properties of coal reservoirs,mercury intrusion curve types,pore size distribution characteristics,pore structure types,the effect of the pore structure of low-rank coal reservoirs on coalbed methane adsorption and desorption in Erlian Basin provides a reference for the subsequent development of coalbed methane projects.The results show that the pore system of low coal rank coal reservoirs in Erlian Basin group is well developed and has large porosity.The porosity IV coal group<ⅢA coal<3-1 coal;the pore structure is dominated by small micro-pores and large pores,and the pore size of small pores smaller than 100 nm and large pores larger than 1000 nm contribute the most to pore volume.Based on the pore size distribution ratio and the effect of pore size on coalbed methane storage and seepage,the pore structure types in the study area are divided into four categories:closed adsorption typeⅡC,open adsorption typeⅡO,closed seepage typeⅠC,open seepage typeⅠO,of which the adsorption type is most beneficial to the enrichment and production of coalbed methane.Comparing theⅣcoal formation,ⅢA coal reservoir in Huolinhe Basin and 3-1 coal reservoir in Baiyinhua Basin,the pore structure ofⅢA coal is the most conducive to CBM storage and development.