黏土矿物对页岩吸附气量的影响——基于川东南丁山地区龙马溪组页岩样品的实验分析

Effects of Clay Mineral Characteristics on Shale Adsorbed Gas: Based on the Experimental Analysis of Shale Samples in Longmaxi Formation of Dingshan Area, Southeast Sichuan

黏土矿物是页岩的重要矿物组成之一,对页岩微观孔隙的发育具有重要影响。黏土矿物的发育类型及矿物组分有差异,对页岩吸附能力的影响也有所不同。为明确不同黏土矿物及组合特征对页岩吸附气的影响,选取川东南丁山地区龙马溪组富有机质页岩全岩样品及伊利石、高岭石、绿泥石等单矿物样品进行吸附实验。结果显示:单黏土矿物及页岩样品吸附曲线均出现明显的吸附滞后现象,吸附-脱吸附曲线为典型的IV型吸附曲线,表明黏土矿物微观孔隙结构类型主要为“墨水瓶状”及平板线型狭孔。根据不同黏土矿物及含量吸附曲线分析,黏土矿物吸附能力由强到弱依次为蒙脱石、伊蒙混层、伊利石、高岭石。页岩含水率会严重影响黏土矿物的气体吸附能力:当页岩含水率小于58%时,随着含水率的增加,黏土矿物的吸附气量逐渐减少;含水率超过58%以后,随着样品含水率的进一步增加,吸附气量的变化甚微。

The clay minerals are one of the main constituent minerals of the shale, which has an important influence on the development of shale micropores. There are also differences in the influence of clay mineral development types and mineral composition on shale adsorption capacity. In order to clarify the influence of different clay minerals and combination characteristics on shale adsorption gas, single clay minerals such as illite, kaolinite and chlorite, and shale samples of Longmaxi Formation in Dingshan area of southeast Sichuan are selected for shale gas adsorption experiment. The results show that the adsorption hysteresis phenomenon is observed in single clay minerals and shale samples. The adsorption-desorption curve is a typical type IV adsorption curve, indicating that the microscopic pore structure types of clay are mainly “ink bottle-shaped” and flat-line narrow holes. According to the analysis of adsorption curves of different clay minerals and their contents, the adsorption capacity of clay minerals from strong to weak is montmorillonite, illite and kaolinite in turn. The water content of shale seriously affects the adsorption ability of clay minerals to gas. The experimental results show that when the water content is less than 58%, with the increase of water content, the adsorption gas volume also decreases. When the moisture content is over 58%, the adsorption gas volume changes little with the increase of water content.