Gas Migration in the Aspect of Safety in the Areas of Mines Selected for Closure

Abstract

One of the main hazards occurring in post-mining areas is the uncontrolled migration of gases to the surface, which may pose a serious threat to life and health. These gases are mainly methane and carbon dioxide, in smaller amounts ethane and higher hydrocarbons, carbon oxide, hydrogen sulfide, and radon. Methane migrating into the lower levels of buildings, garages, cable ducts, and sewage systems reaching the concentrations of above 5% may cause an explosion hazard. The concentration of carbon dioxide over 4% also represents a serious threat to life. Moreover, carbon dioxide and methane, emitted into the atmosphere, constitute a considerable source of greenhouse gases. The methane could be utilized, yet it is necessary to develop effective capture and purification methods with the first step of determination being its migration routes. The paper presents the application of numerical modelling with the use of TOUGHv2.0 software, which enabled effective simulation of the multiphase flow, applying adsorption and diffusion phenomena. The results of gas migration modelling were compared to the outcomes of geological tests, and the obtained results were satisfying. It was observed that both geological investigation and computer simulations are proper tools for investigation of the phenomenon of gas migration and identification of gas hazard areas on the surface, constituting the basis for development of effective methane capture methods for further application.

Keywords

• coalbed methane
• risk analysis
• gas migration