Status Of The Fourth Underground Coal Gasification Experiment At Hanna, Wyoming
Authors: Bartke Theodore C. , Dockter Leroy , Sterner Thomas E. , Virgona Joseph E. 
Published: December 2007

Abstract
The fourth underground coal gasification experiment conducted by the Laramie Energy Technology Center is currently underway at a site near Hanna, Wyoming. The Hanna IV experiment, as originally conceived, was significantly larger than the three previous experiments. The experiment was designed to meet the following objectives: determination of the interrelationships of well spacing, air injection rate, and areal sweep efficiency; demonstration of the ability toconduct reverse combustion linkage over distances up to 45.7 m (150 feet);determination of pressure and gas composition gradients within the coal seamduring process operation; determination of gasification zone progress as a function of time; and demonstration of relaying the process down a row of process wells.
A portion of the technology development has involved environmental assessment of the process. This assessment included characterization of the effluents from the process as well as initiation of biological effects studies and determination of the fate of pollutants from the process. Major concerns associated with the process are impacts on air and ground water quality and the effects of subsidence.
This paper describes the initial phase of the Hanna IV experiment in which difficulties were encountered and a sustained gasification process could not be maintained. An override situation across the 30.5 m (100-foot) well spacing resulted in a premature shutdown of the experiment. Preparations are being made to continue the experiment and recover from the override situation.

Introduction
The recent development of shortages of inexpensive petroleum fuels has resulted in renewed interest in research on efficient gasification of coal in the United States. The U.S. Bureau of Mines initiated an assessment of underground coal gasification (UCG) in 1971.1 This study concluded that a renewed field effort was appropriate in view of recent advances in drilling technology and instrumentation. Since 1972, the Laramie Energy Technology Center (LETC), of the U.S. Department of Energy (DOE), has been conducting field experiments2 of UCG near Hanna, Wyoming, on property of the Rocky Mountain Energy Company, a subsidiary of the Union Pacific Railroad.
Three experiments, involving five gasification tests, have been completed with significant technical success and have yielded average production rates of 321 km3/day (12 MM scf/day) of 6.7 MJ/m3 (170 Btu/scf) gas.
Hanna I was conducted from March 1973 through February 1974.3 It yielded an average production rate of 42.9 km3/day (1.6 MM scf/day)of 5.0 MJ/m 3 (126 Btu/scf) gas during six of its 12-monthduration.
Hanna II, conducted in three phases, was designed to improve on the results of Hanna I in terms of gas quality and resource utilization. Phase 1, conducted from April through August 1975,4 utilized 1143 tonnes (1260 tons) of coal with an average production rate of 72.3 km3/day (2.7 MMscf/day) of 6.0 MJ/m3 (152 Btu/scf) gas. Phases 2 and 3 were conducted from April through July 1976.5 Phase 2 utilized 2268tonnes (2500 tons) of coal with an average production rate of 228km3 /day (8.5 MM scf/day) of 6.7 MJ/m 3 (171 Btu/scf)gas. Phase 3 utilized 3810 tonnes (4200 tons) of coal with a maximum production rate of 321 km3/day (12 MM scf/day) of 6.7 MJ/m3 (170Btu/scf) gas. The average heating value of the process gas during Hanna II -Phase 3 was only 5.4 MJ/m3 (138 Btu/scf) due to excessive groundwater influx into the reaction zone.6
Hanna III, conducted during June and July 1977, was designed to provide information on the potential impacts of UCG on ground water quality and the environmental control technology implications of those impacts. 7–9The gasification phase utilized 2601 tonnes (2867 tons) of coal with an average production rate of 268 km3/day (10 MM scf/day) of 5.4MJ/m3 (138 Btu/scf) gas. Pre-operational ground water characterization and monitoring were completed, and ground water sampling and analyses will continue until apparent equilibrium conditions have been reached.