In-situ leaching of south Texas uranium ores: Part 3-post-leach assessment of recovery and sweep efficiency

This paper reports results of a post-leach study following nearly 3 years' uranium in-situ leaching in a south Texas ore body. Wells drilled in strategic locations were logged (including delayed fission neutron (DFN) and gamma ray logs) and cored and the recovered core chemically analyzed. Overall uranium recovery for the total 11.9-m (39-ft) ore zone was about 70%, estimated from core and log data. Although ammonia analyses gave evidence of some leachate contact at some time over the whole interval, uranium recovery was not uniform over the total 11.9 m (39 ft). The upper half of the ore zone appears to have been leached exhaustively, showing not only complete uranium depletion but zero reducing capacity. In the lower half of the interval, however, there was evidence of severe reservoir stratification. There were two narrow, visually oxidized bands from which uranium had been leached. These were interposed between three zones containing strong uranium shows, which had been totally or partially bypassed by the leaching fluid. Lithological cross sections suggested that, in the bypassed zones, a higher degree of sand compaction or the presence of clayballs or clay streaks caused lower permeability, thereby severely limiting the accessibility of the uranium mineral tomore » the injected fluids.« less