IN-SITU GASIFICATION OF EAST TEXAS LIGNITE: FIELD RESEARCH, 1980 FIELD TEST (UNDERGROUND, COAL, CONVERSION)

Field testing demonstrates technical feasibility for gasification of lignite in-situ in East Texas hydrogeological conditions with minimal environmental changes. Problem areas in technology development are direct control of direction and placement of linkage channels and demonstrated resource recovery. These problems must be solved before economical feasibility is determined.; During the summer of 1980 an Underground Lignite Gasification (ULG) field test was done by the Petroleum Engineering Department of Texas A&M University. This experiment was an attempt to gasify lignite in a two-dimensional gas generator at the Alcoa/Rockdale site in Milam County, Texas. The array consisted of 11 process wells arranged in a 60 x 60-foot square. Operational problems related primarily to well construction prevented generation of product gas with sufficiently high heating value for the test to be considered successful from a product quality view-point. However, insight was gained into the methodology for constructing inexpensive process wells which are capable of withstanding the stresses generated by high temperature. Evidence suggests that reverse burn linkage channels occurred at, or near, the top of the seam even though efforts were made to propogate linkage paths at the bottom. Also, linkage channels did not occur in-line between wells as intended by design and by operations.; There is no evidence of rock movement in the area of the gas generator, and there is no change in water quality in the major aquifer (Unit 2). Water quality changes did occur in Unit 5 inside and outside the area of the gas generator.; Total lignite gasified is 156.7 tons from 16 individual gasification experiments. This represents 7.8% recovery of the 2100 tons within the area of the gas generator. Gas heating values ranged from 7 to 94 Btu/scf. The experiments consisted of 10 reverse burn linkages and 17 forward gasification tests.