| 摘要 |
In-situ solution mining method of an ore bed, particularly containing trona, which comprises exposing to a solvent an ore region inside a borehole drilled in the ore, and dissolving a desired solute within the exposed region to provide a liquor and create a voided ‘undercut’, such undercutting making the ore susceptible to gravitational loading and crushing. Unexposed ore falls into the undercut by gravity without breaking the ore roof resulting in exposure of fresh ore to the solvent and in preventing solvent exposure to contaminating material near the roof. The desired solute is eventually dissolved away in the entire bed from its floor up to its roof. Solvent injection may be delivered through a conduit positioned inside the borehole, and may be moved by retracting or perforating the conduit. The method may employ an advancing undercut initiated up-dip and traveling down-dip, or a retreating undercut initiated down-dip and traveling up-dip. |
| 主权项 |
1. A method for in situ undercut solution mining of a subterranean trona ore bed, said trona ore bed comprising a desired solute being selected from the group consisting of sodium sesquicarbonate, sodium carbonate, and sodium bicarbonate, said trona ore bed having a floor and a trona ore roof, the method comprising the following steps:
injecting a solvent comprising water through a plurality of unlined borehole portions, each of said unlined borehole portions comprising lateral side branches, each of said unlined borehole portions comprising a downhole end positioned within said trona ore bed and above said bed floor, each of said unlined borehole portions being horizontal or being slanted with one of its ends being at a higher elevation than the other end, in order to expose to the solvent a trona ore region within each of said unlined borehole portions or adjacent to said downhole end of said unlined borehole portions; dissolving at least a portion of the desired solute, from said solvent-exposed trona ore region in a manner effective to form a liquor comprising said dissolved desired solute, and to further form an undercut above the bed floor, said undercut comprising at least a section of said unlined borehole portions which have been eroded by dissolution, wherein said lateral side branches of each of said unlined borehole portions favor the lateral widening of said undercut during solvent injection and dissolution; repeating the solvent injection to dissolve additional desired solute from the trona ore thereby enriching the liquor in desired solute, and further in a manner effective to widen the undercut and to trigger the fracture of unexposed trona ore located above said undercut and the downward movement of fractured trona ore rubble by gravity into the undercut, thereby creating fresh surface area of trona ore available for solvent dissolution, wherein said repeating step allows the trona ore roof to sag but not to break so as to minimize chloride contamination of the liquor by preventing exposure of said solvent to chloride-containing material located at or above the trona ore roof; and flowing the liquor towards a subterranean collection zone in order to pass said liquor to a terranean location. |
