鄂尔多斯盆地北部直罗组古河道砂体分布区矿井涌水模式

Mine water inflow pattern in the distribution area of paleochannel sand bodies of the Zhiluo Formation in the northern part of the Ordos Basin

近十几年来,鄂尔多斯盆地北部煤矿开采频频受到了直罗组地下水的威胁,甚至出现了突水事故。区内以直罗组地下水为充水水源的大水矿井连片分布,且与直罗组古河道砂体关系密切。为阐释神府南区直罗组古河道砂体分布区矿井涌水模式,在直罗组古河道砂体空间分布及其对地下水赋存控制作用研究的基础上,从研究区尺度、井田尺度和工作面尺度,分析了直罗组古河道砂体与矿井涌水的关系,提出了直罗组古河道砂体下矿井涌水模式。结果表明:神府南区直罗组古河道冲刷带沿红碱淖—尔林兔—锦界一线发育,冲刷带内延安组第5段几乎被冲刷剥蚀殆尽,在局部地区延安组第4段也遭受了冲刷。根据砂分散体系分析和隔水岩组发育特征,将冲刷带内充填沉积的古河道砂体分为3级。直罗组古河道砂体富水性的强弱主要受控于砂体规模、物性特征和风化作用,一级砂体(主河道)区域富水性强于二级砂体(分支河道)及三级砂体(三角洲间湾、分流间湾)区域,当砂体遭受风化后,其富水性将进一步增强。基于不同尺度下砂体分级、风化砂体厚度与矿井涌水关系的分析,提出了研究区东部现阶段古河道砂体下生产矿井的3种涌水模式。强涌水模式,主要位于一级砂体分布区,风化砂体厚度一般≥30 m。中等涌水模式,主要位于一级砂体的边缘或二级砂体区域,风化砂体厚度一般10~30 m。弱涌水模式,主要位于三级砂体区域,风化砂体厚度一般<10 m。

In the past ten years,the coal mining operation in the northern part of the Ordos Basin has been frequently threatened by the groundwater of the Zhiluo Formation,and even some water inrush accidents have occurred.In the area,the mines with the groundwater of the Zhiluo Formation as water source are distributed continuously,and are closely related to the paleochannel sand bodies of the Zhiluo Formation.In order to explain the mine water inflow model in the distribution area of the paleochannel sand bodies of the Zhiluo Formation in the southern area of Shenfu,on the basis of the study of the spatial distribution of paleochannel sand bodies in the Zhiluo Formation and their control effect on groundwater occurrence,the relationship between the paleochannel sand bodies and the mine water inflow in the Zhiluo Formation was analyzed from the scale of the study area,the scale of the well field and the scale of the working face,and the mine water inflow model under the paleochannel sand bodies of the Zhiluo Formation was proposed.The results show that the paleochannel scouring zone of the Zhiluo Formation in the southern area of Shenfu is developed along the line of Hongyannao-Erlintu-Jinjie,and the fifth member of the Yan’an Formation in the erosion zone is almost completely eroded,and the fourth member of the Yan’an Formation is also scoured in some areas.According to the analysis of the sand dispersion system and the development characteristics of the aquifer rock group,the paleochannel sand bodies filled and deposited in the scouring zone are divided into three grades.The water-richness of the paleochannel sand bodies of the Zhiluo Formation is mainly controlled by the scale,physical characteristics and weathering of the sand body,and the water-richness of the first-order sand body(main channel)is stronger than that of the second-class sand body(branch channel)and the third-order sand body(delta bay and tributary bay),and its water richness will be further enhanced when the sand body is weathered.Based on the analysis of the relationship between sand body classification,weathered sand body thickness and mine water inflow at different scales,three water inflow modes of production mines under paleochannel sand bodies in the eastern part of the study area were proposed.The strong water inrush mode is mainly located in the distribution area of the first-class sand body,and the thickness of the weathered sand body is generally≥30 m.Medium water inrush mode is mainly located at the edge of the primary sand body or secondary sand body area,the thickness of the weathered sand body is generally 10-30 m.The weak water inrush mode is mainly located in the tertiary sand body area,and the thickness of the weathered sand body is generally<10 m.