The Areal Sweep Efficiency of the In-Situ Recovery of Subbituminous Coal

Abstract

emphasisis being placed on the development of processeswhich produce a maximumamount lhis paper presentsthe resultsof of the in place energy. The followingmisapplyingparticletrackingtechniquesto the cussiondescribesa simple approachto predictionof areal sweep for the in-situ determiningthe areal sweep efficiencyfor recoveryof subbituminous coal. Comparison UCG and comparesthe resultswith field of field data with calculatedvalues indicate experimentalresults. that these techniquesare applicableand support the theory that the in-siturecoveky BACKGROUND of subbituminous coal as encounteredat Hanna, Wyoming,is a permeationprocess. TheThe processbeing utilizedby LERC model predictsbreakthroughof the flame front in the ongoingexperimentation near Hanna, at the productionwell and intermediatepoints Wyoming,is known as the linkedvertical with sufficientaccuracyfor preliminary well process. This processuses reverse design purposes.combustionto modify the naturalpermeability such that gasificationin the forwardmode

Underground coal gasification: Development of theory, laboratory experimentation, interpretation, and correlation with the Hanna field tests: Final report

“…For this reason, the initial version of the spa 11 i ng-enhanced-dryi ng mode 1 for water influx reported in and Camp et al (1980) used the simplest possible two-dimensional sweep model, namely that of a radially expanding right-circular cylinder. In a later version of this water-influx model, Levie et al (1981) employed the more realistic two-dimensional sweep model of Jennings et al (1976). This latter refinement in the model had no effect on the •water-influx predictions for the reason just given; however, it did change the mndP.l predictions for the shape of the cavity which is formed because of spalling.…”

“…Based on the above considerations, Jennings et al (1976) developed the first successful sweep model to describe the instantaneous resource recovery for the UCG process. Jennings et al' assumed that the lateral growth of the gasification cavity was a permeation process.…”

“…As mentioned above, Lhe input data and inl"ofllldliurt required to utilize the areal sweep model of Jennings et al (1976) are the instantaneous downhole production-well pressure and effective air-injection rate (the rate corrected for the amount of air 1 ost to the formation which is not available for combustion), as well as the (assumed) isotropic permeability of the cual and the relationship between the flame front velocity and air flux determined from the solution of Gunn and Whitman (1976). The Jennings et al model then determines the instantaneous areal or lateral sweep of the gasification process which is uniquely related to the amount of coal consumed.…”

“…The Jennings et al model then determines the instantaneous areal or lateral sweep of the gasification process which is uniquely related to the amount of coal consumed. Figure V-1 shows the sweep contours predicted by Jennings et al (1976) for the Hanna II Phase II UCG field test. The legend in this figure indicates the number of days after gasification commenced corresponding to each of the twelve contours.…”

“…Again, the maximum cavity height is predicted well, althOU!=Jh somewhat more gas1f1cat1on occurred along the sidewalls then is predicted by the model. Note that this shortcoming in the model appears to arise because of the inaccuracies in the lateral cavity growth or areal sweep model of Jennings et al (1976), not because of deficiencies in the spalling model.…”