Multi-well solution mining exploitation of an evaporite mineral stratum

摘要

A method for in situ solution mining of a mineral from an underground evaporite stratum using a set of wells in fluid communication with at least one mineral cavity with some wells operated in solvent injection mode and other wells operated in brine production mode and optionally with some inactive wells, comprising switching the operation mode of one or more wells. The evaporite mineral preferably comprises trona. The at least one cavity may be formed by directionally drilled uncased boreholes or by lithological displacement of the evaporite stratum at a weak interface with an underlying insoluble stratum by application of a lifting hydraulic pressure to create an interfacial gap. The extracted brine can be processed to make valuable products such as soda ash and/or any derivatives thereof. This method can provide more uniform dissolution of mineral in the cavity, minimize flow channeling, minimize sodium bicarbonate blinding for solution mining of incongruent trona ore, and/or may avoid uneven deposit of insolubles.

主权项

1. In an underground formation comprising an evaporite mineral stratum comprising trona, nahcolite, wegscheiderite, or combinations thereof, a method for solution mining an evaporite mineral from at least one cavity having a mineral free face, said method comprising:
a) providing a set of wells in fluid communication with at least one cavity, said set comprising a first subset of wells being operated in injection mode and a second subset of separate wells operated in production mode; b) injecting a solvent into the at least one cavity through the first subset operated in injection mode for the solvent to contact the mineral free face as the solvent flows through the at least one cavity and to dissolve in situ at least a portion of the mineral from the free face into the solvent to form a brine; c) extracting at least a portion of said brine to the ground surface through the second subset of wells operated in production mode; d) switching the operation mode of at least one well from the set after a suitable period of time; and (e) repeating the steps (a) to (d).