当富含沼气的地层直接位于开采煤层上部时,后退式长壁开采通常都存在着沼气问题。随着采空区的形成,上覆岩层中的富集沼气将通过顶板岩层中的裂隙大量流入井下采掘工作面。目前,在美国用新鲜空气将沼气冲淡到安全浓度,或者通过垂直采空区的钻孔抽放。然而,这种方法不言而喻的问题是耗费过多,增加通风费用而使它在经济上没有吸引力。 美国矿业局和皮茨列赫姆煤炭公司正在联合研究穿层钻孔技术,以取代现行的美国长壁开采工作面的沼气控制技术。当长壁盘区回采时,小直径的倾斜钻孔从井下钻窝处打到已产生裂缝的顶板岩层中,蕴藏在裂缝发育地区中的沼气被聚集在穿层钻孔中,然后用真空泵通过井下管路系统抽至地面中 When biogas-rich formations are located directly above the coal seam, biogas problems are commonly associated with reverse longwall mining. With the formation of the goaf, the enriched biogas in the overburden will flow into the underground mining face through the cracks in the roof strata. Currently, biogas is diluted with fresh air to safe concentrations in the United States, or drilled through vertical gobs. However, the self-evident problem with this method is that it is too costly to increase the cost of ventilation to make it economically unattractive. The United States Department of Mines and Pittsley Coal is working on a joint drilling study to replace the existing biogas control technology for longwall mining in the United States. When the longwall panel is recovered, a small diameter inclined borehole is struck from the downhole drill hole into the fractured roof rock formation. Biogas stored in the fracture development area is collected in the borehole through the borehole and then passed through the vacuum pump Downhole pipeline pumping system to the ground