陕北侏罗系砂岩沉积控水规律研究

The law of sedimentary water control of Jurassic system in northern Shaanxi Province

为了科学高效地指导矿井防治水工作,保障煤炭资源安全开采,分别采用地学信息统计联合灰色关联理论、微观孔隙结构测试、沉积微相划分等手段从砂岩岩性及其组合、微观孔隙结构、沉积相3个方面研究了榆神府矿区中部侏罗系直罗组、延安组、风化基岩含水层的沉积控水规律。侏罗系砂岩含水层中粗砂岩、中砂岩等粗碎屑岩厚度越大,富水性越强,泥岩与砂质泥岩等细碎屑岩厚度越大,富水性越弱。依据含水层岩性、孔隙大小、分布、连通性等将侏罗系砂岩微观孔隙结构划分为大孔粗喉型、中孔-中-细喉型、小孔细喉型、小-微孔-微细喉型等4种类型,认为风化程度相同时,砂岩微观孔隙结构分类级别越低,粒度越粗,含水层富水性越强,风化程度不同时,同时代地层风化程度越强,砂岩微观孔隙结构分类级别越低,粒度越粗,含水层富水性越强。侏罗系直罗组含水层主要为河流沉积体系,曲流河、辫状河沉积相,河道、河漫滩沉积微相,相同沉积相条件下河道较河漫滩沉积微相富水性强,河道岩性以砾岩、粗砂岩、中砂岩为主;延安组上部地层以三角洲沉积体系为主,三角洲平原沉积相,分流河道与分流间湾沉积微相,分流河道较分流间湾沉积微相富水性强,分流河道岩性以中砂岩为主,偶见粉砂岩。

In order to guide water prevention and control scientifically and efficiently and ensure safe mining of coal resources, the law of sedimentary water control of Zhiluo formation aquifers, Yan’an formation aquifers, and weathered bedrock aquifers were researched from three aspects of lithology and its combination, microscopic pore structure, and sedimentary facies by means of geological information statistics combined with gray correlation theory, microscopic pore structure test, and sedimentary microfacies division. The thicker the coarse clastic the fine clastic rocks such as mudstone and sandy rocks such as coarse sandstone and middle sandstone are, the better the water-abundance is;the thicker mudstone are, the weaker the water-abundance is. According to lithology, pore size, distribution, and connectivity, the microscopic pore structure can be divided into four types: large pore and coarse throat, mesopore and middle-fine throat, r keyhole and fine throat, and small-microporous and micro-fine throat. When the degree of weathering are the same, the lower the classification level of sandstone microscopic pore structure and the coarser the grains are, the better the water-abundance is in the aquifers;when the degree of weathering are different and the stratigraphic age is the same, the stronger the weathering is, the lower the classification level of sandstone microscopic pore structure, and the coarser the grains are, the better the water-abundance is in the aquifers. The Zhiluo formation aquifers are mainly fluvial sedimentary system with meandering river and braided river as sedimentary facies and channel and floodplain as sedimentary microfacies. Under the same sedimentary facies in Zhiluo formation aquifers, water-abundance of channel sedimentary microfacies are stronger than that of floodplain sedimentary microfacies, and lithology of channel sedimentary is mainly conglomerate, coarse sandstone and middle sandstone. The upper strata of Yan’an formation aquifers are mainly delta sedimentary system with delta plain as sedimentary facies, and distributary channel, and distributary bay as sedimentary microfacies, and water-abundance of distributary channel is better than that of distributary bay sedimentary microfacies, and distributary channel is mainly composed of middle sandstone, occasionally siltstone.