地勘阶段煤层瓦斯围岩封闭能力评价与应用

Evaluation on CBM Sealing Capability of Coal-enclosing Rocks in Exploring Stages

运用瓦斯地质学理论分析影响煤层瓦斯围岩封闭性能的地质因素,得出煤层顶底板岩性、煤层封闭层泥岩比、有效岩层厚度效应系数为围岩封闭层主控地质因素。提出了有效封闭能力综合指数(ESCI)并建立了煤层瓦斯围岩封闭能力评价模型。以评价模型为基础对马依西一井3号煤层瓦斯围岩封闭能力进行评价。结果表明:研究区3号煤层的封闭层划分为Ⅰ-Ⅳ类,西翼3号煤层围岩封闭类型属于Ⅰ-Ⅱ类,具有强至较强的封闭能力,东翼3号煤层围岩封闭类型主要属于Ⅲ-Ⅳ类,封闭能力中等偏弱,在Ⅲ与Ⅳ类之间,有一小块属于Ⅱ类围岩封闭。总体上,西翼较东翼的围岩条件好,封闭瓦斯能力强,瓦斯含量高,随着围岩封闭条件自南西向北西逐渐变差,围岩封闭瓦斯能力减弱,瓦斯含量降低。

Based on gas geology, CBM sealing capability of coal-enclosing rocks were analyzed to conclude major controlling geological factors of the sealed layers, including the lithology of roof and floor of coal seam, mudstone ratio, and effect coefficient of effective rock thickness. The paper proposes an effective sealing capacity index（ESCI） and establishes an evaluation model on sealing capability of surrounding rock of CBM. Based on the model, No.3 coal seam of No.1 Mayixi Well＇s sealing capability was evaluated. The results show that the sealed layer of No.3 coal seam could be classified into 4 types： from type I to IV. No.3at the west wing belongs to type I and II, with strong to stronger sealing capability; No.3 at the east wing belongs to type III and IV, with medium and weaker capability. Between the type III and IV in the mine is a piece of type II. In general, the condition in the west wing is better than that in the east, with strong sealing capability for CBM and high gas concentration. The sealing condition becomes worse from south-west to north-east part and gas sealing capability and gas concentration decrease gradually.