六盘水煤田杨梅树向斜主要煤层孔隙结构特征研究

Study on pore properties of main coal seams of Yangmeishu syncline in Liupanshui coalfield

为查明六盘水煤田杨梅树向斜上二叠统主要煤层孔隙结构特征,对其进行系统采样,基于压汞、低温液氮吸附试验分析了煤层孔隙发育特征及影响因素,并初步优选有利层段。结果表明:压汞测试各煤层以小孔、微孔为主,且微孔比表面积占绝对优势;低温液氮测试多数煤层以小孔、中孔为主,比表面积占比以微孔、小孔最大;压汞曲线和吸附回线均可划分为3种类型,分别代表一定的孔隙形态和连通性;大致以镜质体反射率Ro,max=1.65%为界,压汞测得孔容和比表面积随煤级先升后降,与无机组分和干燥基灰分含量呈负相关,而Barrett-Joyner-Halenda(BJH)孔容和Branauer-EmmettTeller(BET)比表面积与各影响因素的关系呈正相关,2种试验结果与镜质组含量关系均不明显。经对比分析认为5-2、5-3、13-1、33、34号煤层具有煤层气开发的孔隙条件。

The main coal seams of Upper Permian in Yangmeishu syncline of Liupanshui coalfield were systematically sampled and tested by the low-temperature liquid nitrogen adsorption and mercury intrusion method to analyze pore properties and its influence factors,and favorable intervals were preliminarily selected.The results show that each coal sample tested by mercury intrusion is mainly composed of minipores and micropores,and micropores take the dominant position in pore specific surface area.The low-temperature liquid nitrogen adsorption test mostly consists of minipores and mesopores.The percentage of specific surface area of each coal sample is the largest with micropores and minipores.Mercury intrusion curve and adsorption loop can be divided into three types which represent respectively a certain pore morphology and connectivity.Mercury intrusion pore volume and specific surface area showed a trend of rising first and then falling with the the ratio Ro,max=1.65%as the cut-off point,and they were negatively correlated with the inorganic component and the dry ash content,while the Branauer-Emmett-Teller(BJH)pore volume and Branauer-Emmett-Teller(BET)specific surface area were positively correlated with the influencing factors.The relationship between the two test results and the vitrinite content was not obvious.Considering the pore properties of various coal seams,it is determined that coal seams such as No.5-2、5-3、13-1、33、34 have pore conditions for CBM development.