非煤系瓦斯隧道天然气储渗特征与瓦斯超前预报及参数测试的研究

Research on the Permeability Characteristics of Natural Gas Reservoirs in Tunnels in the Non-Coal Seams,Advanced Gas Forecasting and the Testing of the Corresponding Parameters

隧道施工期间采取超前钻探是补充勘察赋存有害气体特殊地质的最有效方法,常规借鉴煤炭行业的瓦斯压力、绝对瓦斯涌出量等参数测定方法对于非伴煤型天然气地下工程来说不完全适用,针对非伴煤型天然气地下工程,施工阶段现场宜选择简单、易操作、耗时短的钻孔测试参数。结合兰渝铁路梅岭关隧道工程的施工实际,对非煤系地层瓦斯储存和溢出的特征进行了分析,并结合赋存天然气的岩性特点和特殊构造体特征,探索瓦斯涌出初速度等参数测试方法;针对非煤系地层隧道取样进行室内试验,通过对储层孔隙度和围岩渗透性能进行评价,是隧道开挖时瓦斯绝对涌出量预测的基础,并建立了瓦斯绝对涌出量计算模型。由于浅层天然气赋存的复杂性和工程领域研究不足,相关定量计算研究还需深入。

During the construction of a tunnel, drilling holes in advance is one of the most effective additional methods to investi- gate special geological conditions to determine the existence of harmful gases. In this case,the traditional exploring methods in the light of the pressure of gas, the absolute gas emission and other parameters commonly used for the coal industry are found not to be fully applicable to underground natural gas projects in the non-coal seams. With underground natural gas projects in the non-coal seams in mind, the simple,easy-to-operate and time-saving drilling-testing parameters should be chosen at the site during the construction stage. With the practical construction of the Meiling Pass Tunnel of the Lan-Yu Railway as an example, the characteristics of gas reservoirs and the overflowing of gas in the non-coal seams are analyzed, with the parameters-testing methods to determine the initial velocity of gas emission explored upon the basis of taking into consideration the properties of the richly-natural-gas-storing rock and the characteristics of specially-formed rock bodies. The tunnel in non-coal seams is also sampled and indoor-tested. When the tunnel begins to be dug, the forecasting of the absolute gas emission is based on the evalu- ation of the reservoir porosity and the permeability properties of the surrounding rock. Upon this basis,a calculation model for the absolute gas emission quantity is established in the paper. Since the shallow gas occurrence is very complex and scientific studies in the field is far from enough,the related quantitative research still needs to be further deepened.