侏罗系弱胶结砂岩孔隙介质特征及其保水采煤意义

我国新疆哈密矿区降雨量少、蒸发强烈,属于严重干旱地区,研究区高强度的煤炭资源开采对主要储水含水层的保护极为重要。由于特殊的成岩环境及地下水赋存运移条件,侏罗系弱胶结砂岩为复杂的非常规含水岩系,给研究区煤矿防治水带来了诸多水文地质问题。本文以新疆哈密矿区侏罗系弱胶结砂岩为研究对象,通过渗流实验、实验室测试、理论分析研究弱胶结砂岩微观孔隙结构演变规律。研究表明,弱胶结砂岩属高孔隙度岩石,具有大孔孔喉及中孔孔喉分布频率高的结构特征和强富水性,渗流实验过程中有大量乳白色悬浮物渗出。水相渗流作用下的弱胶结砂岩样出现渗透性突变增大的现象,其孔隙度有明显增大的趋势。通过水质分析及岩矿鉴定分析手段得出可溶盐溶出对渗流实验前后的孔隙度增加贡献率为45.80%～82.28%,悬浮物渗出量计算对孔隙度增大贡献率为14.78%～54.20%,可溶盐及高岭石的溶(渗)出是砂岩渗透性增强的主要因素。鉴于此,提出了有关孔隙结构储水空间变异性以及渗透突变性的保水采煤理念,弱胶结砂岩含水层水体下保水采煤应当遵循"保护性开采、避免大规模扰动"的思路。研究成果对西部地区弱胶结砂岩含水层的开发利用与保护有重要意义,同时可为西部地区受侏罗系弱胶结砂岩水害影响的矿井保水采煤技术的研究提供借鉴。

Pore media characteristics of Jurassic weak cemented sandstone and its significance for water-preserved mining

Hami mining area of Xinjiang has the characteristic of little rainfall and strong evaporation,which is a serious arid area.With the high-intensity coal resources mined in study area,the protection of aquifers is extremely important for coal mining.Due to the special diagenetic environment and migration conditions,Jurassic weak cemented sandstone is a complex water-bearing rock system,which brings many hydrogeological problems to the water control of coal mine in the study area.Taking the Jurassic weak cemented sandstone in Hami mining area as a research topic,the evolution of micropore structure of weak cemented sandstone was studied through seepage experiment,laboratory test and theoretical analysis.The result shows that the weak cemented sandstone is characterized by its large pore and middle pore throat concentrated distribution and strong watery,belonging to high porosity rock,and a large amount of milky suspension is exuded in the seepage experiment.Due to the seepage action,the weak cemented sandstone shows an increase in permeability because of the dissolution of soluble salts and kaolinite and increases in porosity obviously.Through water quality and rock mineral identification analysis,the effect of soluble salt dissolution on the increase of porosity is 45.80%-82.28%,and the effect of suspended solids exudation on the increase of porosity is 14.78%-54.20% after the seepage experiment.The dissolution of soluble salts and kaolinite are the main factors for the enhancement of sandstone permeability.The concept of water-preserved mining was proposed based on the water storage spatial variability of pore structure and permeability mutation,and the idea of “protective mining and avoiding large-scale disturbances” for wa-ter-preserved mining should be followed below the weak cemented sandstone aquifer.The research results have  significance for the development,utilization and protection of weak cemented sandstone aquifers in the western region.At the same time,it can provide a theoretical and practical basis for the study of water-preserved mining technology affected by the Jurassic weak cemented sandstone water damage in the western region in China.