Method to minimize brine contamination and/or gas migration during in situ trona solution mining

摘要

A method for in situ solution mining of trona in which an aqueous solvent dissolves trona and forms a brine, which comprises: applying a hydraulic pressure greater than the overburden pressure at an interface between trona roof and overburden to lithologically displace the overburden from the trona roof and form a gap; flowing a liquid settable and/or sealing composition into such interface gap and allowing such composition to solidify inside such gap to form a water-impermeable and optionally gas-impermeable barrier inside. This technique should limit contamination from the overburden; should seal or plug fractures transversing the trona roof; should prevent water infiltration from overburden; and/or should minimize gas migration into the overburden from the cavity. The lithological displacement whereby the interface gap is formed may be carried out at the same time as the composition is flowed inside the gap being formed.

主权项

1. In an underground formation containing a trona stratum comprising sodium sesquicarbonate lying above one or more substantially-insoluble strata containing water-soluble contaminants selected from the group consisting of chloride, sulfate, and water-soluble organics, said trona stratum comprising an ore roof with a parting upper interface above which is defined an overburden up to the ground and below which an aqueous solvent is to injected in a cavity to dissolve trona and to form a brine which is recovered at least in part at the ground surface,
a method for minimizing brine contamination from overburden during in situ trona solution mining of a cavity formed in the trona stratum, comprising: (a) applying a hydraulic pressure which is greater than the overburden pressure at the upper interface to lithologically displace the overburden from the trona ore roof, thereby forming an interface gap; (b) flowing a composition selected from the group consisting of a liquid settable composition, a sealing agent, and combinations thereof, into the upper interface gap; and (c) allowing such composition to stay for a time sufficient to form a barrier inside said upper interface gap, said barrier being water-impermeable and optionally gas-impermeable.