Mine Site Greenhouse Gas Mitigation » Mine Site Greenhouse Gas Mitigation
Gas emissions and problems in the Australian coalmines have increased significantly in recent years with some mines reaching greater depths and with a steep rise in longwall production levels and panel sizes. Traditionally, the main objective of the gas drainage operations is to meet the safety requirements of the underground coalmines. However, with the recent focus on reducing greenhouse gas (GHG) emissions from the mining industry, gas drainage and improved gas capture has become one of the critical GHG mitigation strategies. ACARP identified that the wider application of gas drainage as a mitigation strategy depends on achieving drainage costs that are less than the combined value of the associated safety, greenhouse and gas revenue benefits.
The main objective of the project was to carry out detailed investigations of the pre-mining gas recovery technologies and to optimise the design and operational parameters, paying particular attention to the emerging medium radius drilling technology (MRD). The main focus was on maximising gas capture and reducing total gas drainage costs and fugitive greenhouse gas emissions.
The major benefit of the project is the provision to the coal industry of an optimum and/or an alternative predrainage strategy to combat the ever-increasing gas emissions in coal mines. Surface predrainage allows substantially more lead time for effective gas drainage of the coal seams than other methods currently in use and improves the quality and consistency of mine gas production, which will enable the effective utilisation of mine gas and results in reduced GHG emissions. The successful completion of the project also results in substantial productivity, safety and cost benefits to the underground coalmines, by way of reduced gateroad development requirements, in addition to the benefits of GHG mitigation for the industry.
The project studied field sites (coal mines) in the Bowen Basin as a basis for modelling and optimisation. The project was carried out in close collaboration with the mine management. The work program consisted of the following components:
- Geological modelling and geotechnical assessment, including 3D Visualisation
- Review studies of the data obtained from previous surface to inseam gas drainage trials
- Gas reservoir modelling studies to optimise the following design parameters
- Length of wells, (and diameter, if found to be critical)
- Water pumping rate with respect to gas desorption characteristics
- Layouts and directions – with respect to cleat orientation
- Timing – with respect to both gas drainage and investment
- Multiple seams drainage options and their effect on Specific gas emissions (SGE)
- Development of economic models and investigation of various options (including u/g and surface)
- A 3-D Visualisation of the MRD technique
- Development of guidelines and technology transfer