漳村矿峰峰组隔水关键层孔隙性实验研究

Experimental Research on Porosity of Ordovician Fengfeng Formation of Lu'an Coalfield,China

随着诸多华北石炭二叠系煤田进入下组煤开采，研究奥陶系峰峰组地层岩溶发育规律及能否为下组煤开采提供隔水屏障十分重要．以潞安矿区漳村矿下组煤补充勘查漳54号水文地质孔为取样孔，通过岩石薄片鉴定、X射线荧光光谱分析、岩石微结构分析等综合试验，分析了峰峰组岩性、孔隙结构特征及其垂向分布规律．研究表明：峰峰组上段为泥晶至细砂晶灰岩，下段为石膏与白云岩互层；上段灰岩孔隙类型以晶间孔隙、溶蚀孔隙、缝合线等次生孔隙为主，为泥质、方解石、石膏充填，岩溶不发育，平均孔隙度仅1．15％，体积中值孔径0．0288μm，面积中中值孔径0．0098μm，最大连通孔喉直径约0．02～0．04μm，细小和超毛管微孔隙占总孔隙体积的70％以上，重力和毛细水运动微弱，属于低孔隙低渗透性介质；峰峰组上部和下部存在隔水层，中间为弱含水层岩性组合，峰峰组可利用隔水关键层的厚度为142m．为判断、确定奥陶系顶部隔水关键层提供了岩石学和微结构方面实验依据．

Due to the continuing coal excavation of Taiyuan Formation, North China permo-carboniferous coalfield, the evolutionary and engineering features of deep-buried Fengfeng strata have become an interesting and valuable subject for research. Samples taken from Zhang-54, a complementary exploitation borehole of Zhangcun Mine, Lu＇ an Coalfield, China, were observed and measured with thin-section identification, WdXRF, and mercury porosimetry techniques to determine the porosity and lithological features of the Fengfeng Formation. Results show that the upper part of the Fengfeng formation is mainly composed of fine-grained cystalline limestone and the lower part of alternate layers of gypsum and dolomite. The pore types of the upper formation consist chiefly of intercrystalline pores, dissolved pores and stylolites, which are partially filled by clay, calcite, and gypsum. The average porosity of the upper Fengfeng is 1. 15%, volumetric median pore diameter 0. 028 8 μm, area median diameter 0. 009 8 μm, and maximum throat-pore diameter 0.02-0.04 μm. The pore volume of tiny and super-tiny pores accounts for more than 70% of the total pore volume. Aquifuges exist in, both the upper and lower parts of the formation, and an aquitard exists in the middle part of the formation. The thickness of the upper aquifuge that can serve as key-aquifuge is 142 m. The study offers experimental support to the development of key-aquifuge theory and practice.