Potash at the Milestone Project area occurs conformably within Middle Devonian-age sedimentary rocks, and is found in total thicknesses ranging from approximately 30 to 40 m at a depth of approximately 1,350 to 1,450 m. Evaporites are generally formed by seawater flowing into landlocked basins, followed by the evaporation of the seawater and precipitation of the dissolved salts. Progressive solar distillation of these salt-rich brines results in sequentially precipitated beds of limestone (CaCO3), dolomite (CaCO3·MgCO3), anhydrite (CaSO4), halite (NaCl), carnallite (KCl·MgCl2·6H2O), sylvite (KCl), kieserite (MgSO4.H2O), and other calcium and magnesium salts.

In the KLSA 008 Lease area, the Esterhazy, Belle Plaine, and Patience Lake Members are present. Also present is the “White Bear Marker Beds,” which is a distinctive unit of thin interbedded clay, halite, and sylvinite beds between the Belle Plaine and Esterhazy Members but is of insufficient thickness and grade to be attractive for mining.

The typical sylvinite interval within the Prairie Evaporite Formation consists of a mass of interlocked sylvite crystals that range from pink to translucent, and which may be rimmed by greenish-grey clay or bright-red iron insolubles, with minor halite randomly disseminated throughout the interval. Local large (greater than 2.0–2.5 centimeters [cm]) cubic translucent to cloudy halite crystals may be present within the sylvite groundmass, and overall, the sylvinite ........

The Milestone Project will extract potash from the Prairie Evaporite Formation using solution mining. The Phase I Project has drilled, connected and operated 3 horizontal solution mining caverns for a period of approximately 18 months from October 2019 – May 2021.

Milestone Phase I Plant Operation
Western Potash successfully completed the drilling of 3 horizontal injection wells which intersected high grade potash in all wells, as demonstrated by the downhole logs and core assay of well W001-2. The directional drilling was able to target the bottom of the target potash bed. The project then drilled and successfully connected all 3 production wells.

The target geological horizon for Caverns 1 and 3 was the Belle Plaine (BP) Member with a true vertical depth of approximately 1,750 m below the surface, and Cavern 2 in the Esterhazy (EH) Member at a depth of approximately 1,770 m. In each cavern, the production well was designed to intersect with the injection well at the bottom of the potash seam with both wells cased approximately to the intersection point. The injection well was extended horizontally for approximately 850 m from the junction point. An injection tubular was inserted into the injection well and set to the far end of the injection well.

After the wells were completed, water from the crystallization pond was circulated into the injection well and back out the production well in all three caverns.

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