鄂尔多斯盆地北部深埋区“地貌—沉积”控水关键要素研究
Key Groundwater Control Factors of Deep Buried Coalfield by Landform and Sedimentation in the Northern Ordos Basin
收稿日期: 2019-01-25 修回日期: 2019-03-27 网络出版日期: 2019-06-11
基金资助: |
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Received: 2019-01-25 Revised: 2019-03-27 Online: 2019-06-11
作者简介 About authors
杨建(1979-),男,江苏盐城人,副研究员,主要从事煤矿防治水方面的研究.E-mail:yangjian@cctegxian.com
鄂尔多斯盆地北部深埋煤田区地表主要有沙漠、基岩台地和黄土沟壑等地貌类型,沙漠区工作面涌水量比其他地貌区大1~2个数量级。为了查清煤层顶板直接充水含水层补给水源、导水通道和充水强度的控制要素,从地形地貌和地质沉积方面开展了研究,结果表明:沙漠地貌地势平缓,降水入渗系数大,第四系厚度大、富水性强,为下伏含水层提供了丰富的补给水源;基岩台地和黄土沟壑地貌,地形起伏大,降水入渗系数极小,浅部地层富水性极弱,是下伏含水层补给能力较弱的水源。陆相沉积形成的砂泥岩互层结构,不存在区域性稳定隔水层,各层段均属于弱—中等富水性含水层,3个矿井的白垩系含水层水位下降了20~130 m,证明浅部与深部含水层存在较密切的水力联系。煤层顶板主要发育七里镇砂岩和真武洞砂岩含水层,为厚度较大的中粗砂岩段,直接充水含水层地质沉积条件相似,但是沙漠区工作面顶板钻孔水量、累计预疏放水量和采空区涌水量均远大于其他地貌区,直接充水含水层富水性主要受地貌控制,深部含水层的水源为大气降水和第四系含水层。沙漠地貌区的不同矿井,工作面顶板钻孔水量、累计预疏放水量、采空区涌水量也存在较大差异,该差异与直接充水含水层厚度和岩性等有关,反映了地质沉积条件也是控制含水层富水性的重要因素。地形地貌和地质沉积是控制直接充水含水层富水性和工作面涌水量的关键要素。
关键词:
There were three landforms (i.e. desert, bedrock platform and loess gully) in deep-buried coalfield of northern Ordos Basin. Water inflow of working face in desert area was 1~2 orders of magnitude larger than that in other landform areas. In order to find out the key controlling factors of the directly water filled aquifers on the roof of the coal seam, we carried out research from the aspects of topography, landform and geological sedimentation. The results showed that desert landform provides abundant recharge water for underlying aquifers because of gentle topography, large precipitation infiltration coefficient, thick and water-rich quaternary system. While bedrock platform and loess gully landform were the water sources with weak recharge capacity of underlying aquifers. The sandstone-mudstone interbedding structure formed by continental deposits resulted in the absence of regional stable aquifers in Jurassic and Cretaceous strata on the roof of coal seams. Pumping tests of boreholes showed that all strata belong to weak to medium water-rich aquifers. The groundwater level of Cretaceous aquifer decreased by 20~130 m in three mines. There was a close hydraulic relationship between shallow and deep aquifers. The Mesozoic strata belonged to fluvial deposits. Qilizhen sandstone and Zhenwudong sandstone aquifers were mainly developed on the roof of the coal seam, which were characterized by thick medium-coarse sandstone sections. The geological and sedimentary conditions of direct water-filled aquifer were similar, but the amount of borehole water, cumulative pre-drainage water and water inflow from goaf in desert geomorphic area were much larger than those in bedrock platform and loess gully geomorphic area. The water-rich of the aquifer was mainly controlled by geomorphology, and the water sources of the deep aquifers were meteoric precipitation and Quaternary aquifer. In different mines with similar Quaternary conditions in Mu Us Desert, there were also great differences in the amount of borehole water, cumulative pre-drainage water and water inflow from goafs. The difference was related to the thickness and lithology of the aquifers. It reflected that the geological sedimentary conditions of the coal seam roof were also important factors to control the water-rich of the aquifers. Topography, landform and geological sedimentation were the key factors to control the water-rich of the aquifer directly and the water inflow from the working face.
Keywords:
本文引用格式
杨建, 刘基, 黄浩, 梁向阳.
Yang Jian, Liu Ji, Huang Hao, Liang Xiangyang.
鄂尔多斯盆地煤层以厚和特厚煤层为主,煤田地质构造简单[12],煤层赋存稳定,煤层倾角2°~5°,很少有断层和褶曲,一般认为水文地质条件简单。但是位于蒙陕接壤区的深埋煤田区在矿井建设和生产过程中发生了类型多样的水害问题,其中最主要的问题来源于毛乌素沙漠区的主采煤层顶板直接充水含水层(包括延安组三段和直罗组一段)富水性较强。由于之前普遍将安定组视为区域性稳定隔水层[13],对于本地区深部侏罗系含水层地下水的来源,认为来自侧向补给或深部循环[14],但是随着深部矿井生产活动的持续,工作面涌水量大小与地貌密切相关,涌水量变化过程则与顶板直接充水含水层岩性和岩相特征有关,因此地貌和沉积是控制鄂尔多斯盆地北部深埋煤田区顶板直接充水含水层富水性的关键要素。开展地形地貌和地质沉积与工作面涌水之间的关系研究,以期查清研究区煤层顶板直接充水含水层的补给水源、导水通道和储水空间,为鄂尔多斯盆地北部深埋煤田区矿井防治水提供科学依据。
1 研究区概况
鄂尔多斯盆地北部侏罗纪煤田区位于陕北与晋西北黄土高原及内蒙古鄂尔多斯高原的接壤地带,主要包括新街、呼吉尔特、纳林河和榆横等矿区,地势总体由西北向东南降低,局部起伏较大,海拔1 100~1 500 m,盆地北部的东胜—盐池梁海拔1 500 m左右;研究区内南北地势较高、中间相对低平(图1)。区内河流主要有黄河水系和陕西省唯一的内陆水系,多以羽状和树枝状排列,其中黄河一级支流无定河流经纳林河和榆横矿区;内陆水系为红碱淖,系风蚀洼地所成,湖水依赖季节性河流、湖面降水和地下水补给,入湖主要季节性河流共有7条,无出流,系内陆封闭湖盆。研究区地处中纬度地区的中温带区,冬季干燥寒冷、降水稀少,夏季降水增多,易产生暴雨和冰雹天气;春季易出现寒潮大风、扬沙和沙尘暴等天气;秋季降温明显,属典型大陆性季风气候。本地区多年平均降水量在400 mm左右,差异不大;蒸发量一般为降水量的4~6倍。
图1
2 补给水源
研究区从北向南,地貌特征大致可以分为3类(图2和表1):
图2
表1 地貌及第四系相关参数表
Table 1
3 导水通道
3.1 地层结构
进入中新生代,构造作用导致鄂尔多斯盆地逐渐成为大型陆相盆地,以河流、河湖和三角洲相沉积为主,且受构造格架控制,陆相沉积具有物源多、相带窄、相变快、水域面积小等特点,形成了延安组煤层顶板数十层甚至上百层的砂泥岩互层地质特征(图3),不存在区域性稳定隔水层。根据沙漠地貌区巴彦高勒、葫芦素等矿开展的水文地质补充勘探结果,也证明各段地层属于多层含水层夹薄层隔水透镜体,且抽水试验结果显示,在煤层顶板基岩段,随着地层埋深的增加,单位涌水量(q)呈减小趋势(图4),白垩系含水层q=0.114~0.304 L/(s·m),属于中等富水性;安定组、直罗组和延安组的单位涌水量分别为0.0227~0.1200,0.027~0.034和0.0033~0.177 L/(s·m),属于弱到—中等富水性。白垩系和安定组渗透系数(K)分别为0.0335~0.453和0.1357~0.4512 m/d,显著高于下伏直罗组和延安组。另外,在延安—直罗、安定—白垩和白垩—第四系地质不整合面,由于地层抬升、河流冲刷和风化剥蚀等作用,形成了古风化带和上覆厚层中粗砂岩层的中—强富水性含水层,例如延安组顶构造与直罗组底部七里镇砂岩共同构成的含水层段。
图3
图3
煤层顶板砂泥岩互层结构(以纳林河二号矿为例)
Fig.3
Cross-section of sand-mudstone interbedding on coal seam roof
图4
图4
各段地层抽水试验水文地质参数结果
Fig.4
Hydrogeological parameters of formation pumping test in each section
(a)单位涌水量;(b)渗透系数
(a)Unit inflow;(b)Permeability coefficient
3.2 含水层水力联系
从2008年开始,研究区范围内纳林河二号、巴彦高勒、母杜柴登等前期建设生产矿井,截止2016年累计疏放顶板含水层水超过1 000×104 m3,但中生代砂泥岩互层结构条件下,地下水的下渗和越流是个长期而缓慢的过程,白垩系含水层水位基本未受到影响;但随着煤层顶板导水裂缝带范围内直接充水含水层的持续大流量疏放,从2017年开始,红庆河、石拉乌素和营盘壕后期开采矿井的白垩系含水层水位分别下降了20,130(图5)和70 m,表明白垩系含水层与下伏侏罗系地层(包括安定组、直罗组和延安组)存在较密切的水力联系。
图5
图5
工作面回采过程中白垩系水位变化特征
Fig.5
Change of Cretaceous water level in mining process of working face
4 储水空间
4.1 导水裂缝带发育高度
导水裂缝带发育高度是顶板水防治的重要技术参数,在呼吉尔特矿区巴彦高勒煤矿01和03工作面辅运顺槽,采用井下仰孔分段注水测漏法和钻孔电视探测法,开展了顶板导水裂缝带发育高度实测,共施工采前和采后孔3个(图6a),T1为采前对比孔,T2和T3为采后导水裂缝带实测孔,以T2钻孔的分段注水结果显示(图6b):垂高大于130 m的地层无法将水压入,表明裂隙不发育;垂高小于80 m的地层,由于裂隙极为发育,该段含水层水大量从钻孔流出,导致压水试验难以开展;垂高在80~130 m的地层,压水试验结果呈齿状,且注入水量随着垂高增加而减小,表明该段地层裂隙发育具有不均一性和逐渐减小特征。结合冲洗液漏失量和孔内窥视结果,最终确定导水裂缝带发育高度为126 m(即裂采比22.03倍)。研究区内煤层顶板覆岩主要由砂岩和泥岩组成的侏罗系中硬岩层,工作面采用较大跨度开采的条件下,根据多个矿井的导水裂缝带发育高度实测结果,总体上导水裂缝带高度(H)随采厚(M)的增加而增大,满足二项式关系(图7):H=-0.304 M 2+10.824M+58.015(R2= 0.7945,P=0.00045)。
图6
图6
钻孔布置及覆岩探测结果
Fig.6
Borehole design and overburden detection results
(a)钻孔布置;(b)压力探测
(a)Layout of drill hole;(b)Pressure water detection
图7
图7
研究区导水裂缝带实测值
Fig.7
Measured value of water conduction fracture zone in study area
4.2 储水空间岩性特征
从北部红庆河煤矿到南部魏墙煤矿(表2),各矿井首采区主采的3-1煤层厚度分别为5.5~7.2(红庆河)、5.5~6.5(巴彦高勒)、4.5~6.5(纳林河二号)和3.0~3.4 m(魏墙),开采过程中导水裂缝带发育高度则分别为108.4~120.2(红庆河)、126.0(巴彦高勒)、103.2(纳林河二号)和87.8~91.3 m(魏墙),对比延安组三段厚度可以发现,研究区内所有煤矿3-1煤开采过程中,导水裂缝带都将贯穿延安组三段地层,延安组三段发育了曲流河沉积形成的灰白略带黄色中细粒长石砂岩含水层(真武洞砂岩);导水裂缝带还可发育至直罗组地层(图8),直罗组底部发育了曲流河沉积形成的灰绿色、青灰色(含砾)中—粗长石砂岩含水层(七里镇砂岩),红庆河煤矿所在的新街矿区则发育了辫状河沉积形成的粗砂—砾岩含水层,具有厚度大、粒径粗、砂地比(砂岩总厚度/地层厚度)高等特征;红庆河煤矿导水裂缝带则局部可以发育至安定组。因此研究区内煤层开采过程中直接充水含水层为延安组三段真武洞砂岩和直罗组底部七里镇砂岩,这2段含水层是影响煤层开采的重要顶板储水空间要素,其地质沉积环境决定的储水能力:红庆河>巴彦高勒≈纳林河二号>魏墙。
图8
图8
研究区地层结构柱状图
Fig.8
Stratigraphic structural cylindrical diagram of the research area
表2 研究区主采煤层顶板地层结构
Table 2
指标 | 新街 | 呼吉尔特 | 纳林河 | 榆横南 |
---|---|---|---|---|
红庆河 | 巴彦高勒 | 纳林河二号 | 魏墙 | |
3-1煤厚度/m | 5.5~7.2 | 5.5~6.5 | 4.5~6.5 | 3.0~3.4 |
延安组三段厚度/m | 7.0~12.0 | 80.0~90.0 | 80.0~95.0 | 44.9~63.7 |
直罗组厚度/m | 79.5~153.2 | 70.9~115.2 | 105.1~223.3 | 88.3~149.1 |
导水裂缝带高度/m | 108.4~120.2 | 126.0 | 103.2 | 87.8~91.3 |
真武洞砂岩厚度/m | 5.0~10.0 | 3.2~14.0 | 2.8~16.0 | 1.9~33.7 |
真武洞砂岩孔隙率/% | 13.2~17.9 | 11.2~18.1 | 21.7~24.9 | — |
七里镇砂岩厚度/m | 20.0~40.0 | 14.6~31.0 | 17.0~36.0 | 2.7~17.2 |
七里镇砂岩孔隙率/% | 12.6~23.3 | 25.94~26.9 | 24.6~26.8 | — |
4.3 直接充水含水层富水特征
中生代地质沉积形成的真武洞砂岩和七里镇砂岩,为这2段地层储水提供了必要条件,但是结合导水裂缝带发育特征,在回采工作面顶板施工“探查+预疏放”钻孔,并开展采前顶板水预疏放,结果发现(表3):
图9
图9
呼吉尔特矿区总涌水量历时曲线
Fig.9
Diachronic curve of total water inflow in Hujirt mining area
表3 直接充水含水层富水特征表
Table 3
指标 | 新街 | 呼吉尔特 | 纳林河 | 榆横南 |
---|---|---|---|---|
红庆河 | 巴彦高勒 | 纳林河二号 | 魏墙 | |
真武洞钻孔水量/(m3/h) | 0 | 0.1~40.0 | 20.0~110.0 | 0 |
七里镇钻孔水量/(m3/h) | 0.6~9.4 | 0.2~60.0 | 30.0~144.0 | 0.1~8.8 |
首采面总疏放水量/m3 | 9 348.7 | 179 000.0 | 1 426 000.0 | 19 894.6 |
首采面涌水量/(m3/h) | 70.0 | 492.0 | 354.5 | 40.0 |
5 结 论
(1)沙漠地貌地势平缓,降水入渗系数大,第四系厚度大、富水性强,为下伏含水层提供了丰富的补给水源;基岩台地和黄土沟壑地貌,地形起伏大,降水入渗系数极小,浅部地层富水性极弱,是下伏含水层补给能力较弱的水源。
(2)陆相沉积形成的砂泥岩互层结构,导致煤层顶板延安组、直罗组、安定组和白垩系未发育区域性稳定隔水层,钻孔抽水试验显示各层段均属于弱—中等富水性含水层,且红庆河、石拉乌素和营盘壕等煤矿在首采工作面回采过程中,白垩系含水层水位下降了20~130 m,证明浅部与深部含水层存在较密切的水力联系。
(3)研究区中生代地层属于河流相沉积,在煤层顶板主要发育了七里镇砂岩和真武洞砂岩含水层,均表现为厚度较大的中粗砂岩段,表明煤炭开采的直接充水含水层地质沉积条件相似,但是沙漠地貌区工作面顶板钻孔水量、累计预疏放水量、采空区涌水量均远大于基岩台地和黄土沟壑地貌区,显示研究区煤层顶板直接充水含水层富水性主要受地貌控制。
(4)沙漠地貌区第四系条件相似的不同矿井,工作面顶板钻孔水量、累计预疏放水量和采空区涌水量也存在较大差异,该差异与直接充水含水层厚度、岩性等有关,反映了煤层顶板地质沉积的岩性岩相条件也是控制含水层富水性的重要因素。
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[J].
鄂尔多斯聚煤盆地的形成及构造环境
[J]. ,
Ordos basin tectonic evolution and structural control of coal
[J].
鄂尔多斯盆地构造演化和构造控煤作用
[J]. ,
Underground coal gasification and its strategic significance to the development of natural gas industry in China
[J].
煤炭地下气化及对中国天然气发展的战略意义
[J]. ,
Coalbed Methane (CBM) development potential of low rank coal: A case study from Ordos Basin
[J].
低变质煤的煤层气开发潜力——以鄂尔多斯盆地侏罗系为例
[J]. ,
Hydrogeological and hydrogeochemical characteristics of deep buried coal seam roof in Shaanxi and Inner Mongolia Contiguous area
[J].
蒙陕接壤区深埋型煤层顶板水文地质及水文地球化学特征
[J]. ,
Discussion on the origin of groundwater in the Ordos Basin
[J].
鄂尔多斯自流盆地地下水来源争议问题讨论
[J]. ,
Research on Vegetation Evolution Risk Assessment Based on Groundwater Development in Inner Mogaolian Energy Basement of Ordos Basin
[D].
鄂尔多斯盆地内蒙古能源基地地下水开发与植被演化风险评价研究
[D].
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