In Saskatchewan, the target beds for potash are the potash-bearing members of the Prairie Evaporite sequence contained within the Elk Point Group; a Devonian Aged sedimentary sequence in Western Canada, Montana and North Dakota. There is a total of three (3) significant potash-bearing members that make up the Prairie Evaporite Formation (in descending order): the Patience Lake member (PLM), the Belle Plaine member (BPM) and the Esterhazy member (EZM), which are situated at the top of a halite-dominated sequence, overlying the dolomitic Winnipegosis Formation. The halite-dominated evaporite sequence is itself overlain by the Dawson Bay Formation, another dolomitic-dominated formation, with the Second Red Beds, red dolomitic shales, as the boundary between itself and the underlying evaporites. The potash-bearing members are relatively flat lying, with a very slight regional southward dip. “Mounds” may occur in the Winnipegosis, corresponding to ancient reefs in the carbonates, and are sometimes associated with thinning or “leaching” anomalies in the overlying potash members.

The potash mineralisation within the Prairie Evaporite Formation is relatively uncomplicated. The dominating constituents are halite (NaCl), sylvite (KCl) and carnallite (KMgCl3.6(H2O)); sylvite being the main ore mineral. The salt (i.e., non-clay seam) is generally confined to halite, sylvite and minor anhydrite, as well as carnallite (mostly in the Esterhazy member). The anhydrite content in th ........

Selective solution mining (or “selective dissolution”) of potash consists of using a brine solution mostly consisting of salt (NaCl), and a minor amount of sylvite or potash (KCl), to selectively dissolve the KCl from a potash bed within a solution mining cavern.

Based on geologic data from the six exploration boreholes and 3D seismic survey within KL 245, the Tugaske Project is targeting, as a base case, a continuous potash zone (“sub-member”) at the base of the Patience Lake member, which is being referred to as the “PLM 1”. The PLM 1 averages 3.9 metres thick, with an average potash grade of 43% KCl, across the mining area. Analysis of the relative economics of a range of approaches for the selective dissolution at the Project indicated that the most capital-efficient approach is a multi-lateral horizontal cavern arrangement consisting of a single (1) horizontal injection well that connects to seven (7) horizontal lateral extraction wells (thus forming one cavern system) that are drilled along the base of the target potash bed in a “fan-style” configuration. This method is similar to a current solution mining method that has been utilized by Intrepid Potash at their Cane Creek Mine in Moab, Utah since 2003 (Ryan, 2012).

To attain the design production rate of 250,000 tonnes of KCl product per year (t/y) of saleable MOP, six (6) solution mining caverns are required. On this basis, each cavern will produce about 45,000 t/y of saleable MOP and has a desi ........

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