The environmental risks associated with casing deformation in unconventional(shale)gas wells positioned in abutment pillars of longwall mines is a concern to many in the mining and gas well industry.With the recent in...The environmental risks associated with casing deformation in unconventional(shale)gas wells positioned in abutment pillars of longwall mines is a concern to many in the mining and gas well industry.With the recent interest in shale exploration and the proximity to longwall mining in Southwestern Pennsylvania,the risk to mine workers could be catastrophic as fractures in surrounding strata create pathways for transport of leaked gases.Hence,this research by the National Institute for Occupational Safety and Health(NIOSH)presents an analytical model of the gas transport through fractures in a low permeable stratum.The derived equations are used to conduct parametric studies of specific transport conditions to understand the influence of stratum geology,fracture lengths,and the leaked gas properties on subsurface transport.The results indicated that the prediction that the subsurface gas flux decreases with an increase in fracture length is specifically for a non-gassy stratum.The sub-transport trend could be significantly impacted by the stratum gas generation rate within specific fracture lengths,which emphasized the importance of the stratum geology.These findings provide new insights for improved understanding of subsurface gas transport to ensure mine safety.展开更多
The configuration of an airway(or production drift)in panel cave mines is different from the typical(straight)mine airway designs.The drawpoints are connected to the airway(cross-cuts),which allows airflow from the ca...The configuration of an airway(or production drift)in panel cave mines is different from the typical(straight)mine airway designs.The drawpoints are connected to the airway(cross-cuts),which allows airflow from the cave into the airway or air loss from the airway into the cave due to the ventilation approach and cave porosity.These affect airflow in the production drifts,but it is difficult to investigate these conditions from field or laboratory scaled studies.Therefore,this study develops discrete and continuum computational fluid dynamics(CFD)models to study the effects of the ventilation approach and cave porosity on the airway resistance.Our findings show that:with active undercut ventilation,a unique resistance model is required for the airway in panel cave mines;and an increase in cave porosity decreases the drift’s resistance.These findings provide essential tools for a panel cave ventilation design.展开更多
文摘The environmental risks associated with casing deformation in unconventional(shale)gas wells positioned in abutment pillars of longwall mines is a concern to many in the mining and gas well industry.With the recent interest in shale exploration and the proximity to longwall mining in Southwestern Pennsylvania,the risk to mine workers could be catastrophic as fractures in surrounding strata create pathways for transport of leaked gases.Hence,this research by the National Institute for Occupational Safety and Health(NIOSH)presents an analytical model of the gas transport through fractures in a low permeable stratum.The derived equations are used to conduct parametric studies of specific transport conditions to understand the influence of stratum geology,fracture lengths,and the leaked gas properties on subsurface transport.The results indicated that the prediction that the subsurface gas flux decreases with an increase in fracture length is specifically for a non-gassy stratum.The sub-transport trend could be significantly impacted by the stratum gas generation rate within specific fracture lengths,which emphasized the importance of the stratum geology.These findings provide new insights for improved understanding of subsurface gas transport to ensure mine safety.
基金support from the National Institute for Occupational Safety and Health(NIOSH)(No.200-2014-59613)for conducting this research.
文摘The configuration of an airway(or production drift)in panel cave mines is different from the typical(straight)mine airway designs.The drawpoints are connected to the airway(cross-cuts),which allows airflow from the cave into the airway or air loss from the airway into the cave due to the ventilation approach and cave porosity.These affect airflow in the production drifts,but it is difficult to investigate these conditions from field or laboratory scaled studies.Therefore,this study develops discrete and continuum computational fluid dynamics(CFD)models to study the effects of the ventilation approach and cave porosity on the airway resistance.Our findings show that:with active undercut ventilation,a unique resistance model is required for the airway in panel cave mines;and an increase in cave porosity decreases the drift’s resistance.These findings provide essential tools for a panel cave ventilation design.
