Method of exploiting potassium salts from an underground deposit
The present invention pertains to a mineral exploitation method and, more specifically, to a method for extracting potassium salts from underground deposits. In the method according to the present invention, an intermediary stage is carried out between the primary mining and secondary mining stages, and in this intermediary stage sinks ( 8 ) are created that receive the water-immiscible fluid ( 9 ) used in the primary mining stage, exposing an amount of potassium chloride remaining on the cavern ceiling, at the end of the primary mining stage, which will be dissolved by a second solvent during the secondary mining stage.
1. A method for exploiting potassium salts from an underground deposit, comprising:
injecting into a cavity generated in the underground deposit, an aqueous solvent of potassium salt and a water-immiscible fluid through a first pipe into a well in communication with the cavity;
removing a brine comprising dissolved potassium salt through a second pipe in a well in communication with the cavity,
wherein the solvent and the water-immiscible fluid allows for side expansion of the cavity to form a cavern and wherein the water-immiscible fluid forms an insulating interface between the aqueous solvent and a ceiling of the cavern; and
gradually elevating an injection point of the aqueous solvent and of the water-immiscible fluid to allow for vertical expansion of the cavern in a controlled manner, the side expansion being repeated periodically with vertical elevation of the cavern;
wherein, after a final elevation of the injection point and side expansion of the cavern:
water is injected through orifices perforated in the first pipe and the second pipe to form a sink on the cavern ceiling such that the water-immiscible fluid flows from the ceiling of the cavern into the sink, thereby exposing potassium salt at the cavern ceiling; and
a solvent is injected to dissolve the exposed potassium salt after the sink has received the water-immiscible fluid.
2. The method of claim 1 , wherein the first pipe and the second pipe are in a same well.
3. The method of claim 1 , wherein the first pipe is in a first well and the second pipe is in a second well, and the injection of water through the orifices forms a sink around the first pipe and the second pipe.
4. The method of claim 1 , wherein the potassium salt is potassium chloride.
5. The method of claim 4 , wherein the deposit of potassium chloride is associated to sodium chloride, and the aqueous solvent is a solution sub-saturated in potassium chloride and saturated in sodium chloride.
6. The method of claim 1 , wherein the aqueous solvent is water or a solution sub-saturated in potassium chloride and saturated in sodium chloride.
7. The method of claim 1 , wherein the sink comprises a conical cavern.
8. The method of claim 1 , wherein the sink comprises a cylindrical cavern.
9. The method of claim 1 , wherein after the final elevation of the injection point and side expansion of the cavern and before the aqueous solvent is injected through the orifices, the orifices are drilled in a portion of the first pipe and the second pipe adjacent the cavern ceiling.