Hydrologic Site Selection for Mining of Deep Basin Lignite in Texas. Final Report

摘要

Population and industrial growth within the state of Texas during the remainder of this century and into the 21st century will result in a significant increase in the demand for energy. Because of the depletion of the state's oil and gas reserves for use in energy production and because of the universal scrubbing requirements which have removed the primary advantage of low-sulfur western coal, it is expected that Texas lignite will be the fuel preferred by many of the state's utilities and industries. Near surface lignite reserves are adequate to meet the needs of the early decades of the 21st century. Meeting the demands of the decades beyond will require the recovery of deep basin lignite or a transition to alternative energy fuels. The subject of this research is the hydrological and geomechanical feasibility and impact of open pit mining and underground coal gasification for recovery of deep basin Texas lignite. Of major concern are the quantities and uses of water from site dewatering and depressurizing operations, the stability of open pit mine slopes and how it is influenced by water, and the regional hydrologic impacts of lignite mining. A summary of the conclusions from this research follows. Water use from open pit mine dewatering and depressurizing operations is significant, though the amounts are very much site specific and dependent on the mine plan. The major variables which influence the total system discharge are the geometry of the mine cut, the required drawdown and dewatering time, aquifer hydraulic and storage parameters, and local stratigraphy. Mathematical models are presented which quantitatively show how these variables influence the water quantities. In general, the quantities of water associated with dewatering can greatly exceed those associated with depressurization of an underlying aquifer. (ERA citation 09:004345)