BRISBANE, AUSTRALIA -- (Marketwired) -- 06/10/13 -- Orocobre Limited (TSX: ORI)(ASX: ORE) (the Company or Orocobre) reports completion of long-term pump tests at the 85% owned Salinas Grandes Potash-Lithium project ("Salinas Grandes") in Salta Province, North West Argentina.
Salinas Grandes has an inferred resource, to a depth of 13.3m, estimated to contain 56.5 million cubic metres of brine at 795 mg/L lithium and 9,550 mg/L potassium, which is equivalent to 239,200 tonnes of lithium carbonate and 1.03 million tonnes of potash (potassium chloride) based on 5.32 tonnes of lithium carbonate being equivalent to 1 tonne of lithium and 1.91 tonnes of potash being equivalent to one tonne of potassium.
To view Figure 1, please visit the following link: http://media3.marketwire.com/docs/orl0610fig1.pdf.
Following completion of the resource estimate in 2012 the company has conducted long-term pump tests on five test production wells and two trenches within the central area of the salar. The purpose of the test work was:
-- to ascertain whether a sufficiently high pumping rate could be achieved from the aquifer (being only to 13.3m depth)-- to investigate changes in permeability over the salar and to determine whether there are preferred areas for possible future extraction-- to ascertain whether the brine would maintain a stable grade during extraction and not be diluted by brackish water beneath the brine body
An extensive array of monitoring wells was established around test production wells and trenches. These provided information on the drawdown cones of wells and variations in brine chemistry with time.
Drilling and Geology
Orocobre previous drilled a total of 12 diamond drill holes in the Salinas Grandes salar to an average depth of 71.4 metres, with certain holes as deep as 180 metres and 47 shallow auger holes to a typical depth of 12m.
The shallow brine body is hosted in a sequence of silt and clay units, with minor intercalated sand - which generally increase in proportion towards the north of the salar. Halite extends to a maximum thickness of 0.5 metres below surface in the center-south of the salar. Drilling established there are higher permeability zones within the salar, associated with intervals of higher sand content and as channels within lower permeability silts and clays.
Pump Testing Methodology
To evaluate the potential for long term brine extraction from the Salinas Grandes salar pump testing was completed on five purpose-constructed test production wells. These wells were drilled to between 12.5 and 13.5 m below surface, using a rotary drilling rig, with the wells reamed to an outside diameter of 18 inches. Well casing with a diameter of 12 or 8 inches was installed in the wells, with the length of the casing perforated throughout. A clean well sorted 1-2 mm sand pack was installed as a filter around the casing in the holes. The location of the wells is shown in figure 2.
To view Figure 2, please visit the following link: http://media3.marketwire.com/docs/orl0610fig2.pdf.