晋城成庄井田煤层气直井开发后煤层底板突水危险性评价

以晋城矿区成庄井田为依托,分析煤层气开发后煤层底板岩石破裂压力、地应力、煤层底板含水层水压和隔水层有效厚度等条件,建立了煤层气开发后煤层底板突水危险性评价理论与方法,揭示煤层气直井开发对煤炭开采底板突水影响机制。研究结果表明:煤层气井煤层底板完井深度和采动矿压与承压水的水压使煤层底板隔水层形成贯通的破裂,如果隔水层中的最小水平主应力大于承压水的水压,从应力方面,就不会发生突水,如果相反,就会发生突水;煤层气井煤层底板完井深度和采动矿压与承压水的水压未能使底板隔水层形成贯通的破裂,开采煤层承受的水压与煤层到主要含水层间有效隔水层厚度之比,决定了煤层底板突水危险性。根据煤层底板隔水层岩石破裂压力、水压和水压与隔水层厚度比值等关键参数,将煤层底板突水危险性划分为安全(Ⅰ)、中等安全(II)、安全性差或有危险(III)和安全性极差或极有危险(Ⅳ)4类。成庄井田太原组15号煤层距奥灰含水层间距小,且变化大,煤层气垂直井开发后煤炭开采受奥灰水威胁。如果9号煤层气完井深度与煤炭开采底板破坏深度15 m相同计算,煤层底板突水危险性主要为中等安全,仅在深部存在突水危险性;煤层气开发后3号煤层开采过程中不会发生底板突水。

Assessment of water inrush risk of coal floor after CBM development using vertical wells at Chengzhuang mine field in Jincheng

At Chengzhuang mine field in Jincheng mining area，the fracture pressure of coal floor rock，in situ stress，the hydraulic pressure of aquifer in the coal floor and the aquifuge thickness were analyzed after coal-bed methane (CBM) development.The theory and method for evaluating water inrush risk in coal floor after CBM development were developed.The influence mechanism of CBM vertical wells development on coal floor water inrush during coal mining was obtained.The results show that the completion depth of CBM wells，the underground pressure in coal mining and the water pressure make the aquifuge in the coal floor break through rupture.If the minimum horizontal stress in aquifuge is greater than the hydrostatic pressure of confined water，the water inrush would not occur，otherwise，the water inrush would occur.If the completion depth of CBM wells and the underground pressure in mining and the water pressure of confined water do not make coal floor aquifuge break through rupture，the ratio of water pressure of the aquifer in the coal floor to effective aquifuge thickness between coal seam and the aquifer determines the water inrush risk of the coal floor.According to key parameters of the fracture pressure of coal floor rock，water pressure and the ratio of water pressure to aquifuge thickness，the water inrush risk in the coal floor is divided into four types：safety (I)，medium safety (II)，poor safety or danger (III) and extremely dangerous (IV).The distance between No.15 coal seam of Taiyuan formation and the Ordovician limestone aquifer is small，and the variation is large.The coal mining after CBM vertical wells development is threatened by the confined water in Ordovician limestone.Water inrush from No.3 coal floor does not occur in coal mining after CBM development.If the completion depth of CBM wells for No.9 coal seam and the coal floor damage depth caused by the coal mining are same according to the calculation under coal floor 15 m，the water inrush risk of coal floor is mainly the type of medium safety，however，there is a water inrush risk in the deep area.