Millennial Lithium (I) – Extended Pumping Tests indicate Robust Pastos Grandes Lithium Aquifer

Millennial Lithium Corp. reported encouraging results from an extended pumping test of the first production scale well at its Pastos Grandes Project in Salta. Pumping well PGPW16-01 was installed in late 2016 to complete extended pumping of the lithium brine to determine the robustness and chemical variation of the aquifer over an extended period. At a pumping rate of 27.7 litres/second (l/s), the lithium content remained very consistent over the 60 hour period. The drawdown over 24 hours was approximately 9 metres (m) with very rapid recovery.

Millennial CEO, Farhad Abasov, commented: “Millennial is very pleased with the results of this first pumping test. The test indicates strong brine flow rates of 27.7 l/s at the maximum capacity of the pumping equipment with only minor draw-down, and consistent lithium concentrations suggest a robust aquifer. Strong lithium values remained relatively consistent throughout the duration of the pumping test suggesting lithium distribution is widespread. Brine from well PGPW16-01 is now being used to feed a series of trial evaporation ponds as part of Millennial’s ongoing development of the Pastos Grandes project.”

Well PGPW16-01 was drilled at a diameter of 17 inches to a depth of 125m and then 13.5 inches to the total depth of 351m. The well was completed with slotted casing (screen) at 10 inch and 6 inch diameters with gravel pack from top to bottom in the annulus in order to capture brine from the numerous permeable layers. The pumping rate for the test period was 27.7 l/s, the capacity of the equipment on site. Table 1 contains a summary of the main results of the test work.

 

WELL ID	PUMPING DURATION (hours)	AVERAGE PUMPING RATE (l/s)	DRAWDOWN AFTER 24 HOURS OF PUMPING (metres)
PGPW16-01	60	27.7	9.04

Table 1. Summary of Pumping Test at Well PGPW16-01

 

Measurements of brine levels during the pumping test indicate a drawdown of approximately 9m over a 24 hour period. In addition, continued measurements after termination of the pumping test showed a recovery of the brine level to within 0.5m of its original position after the 60 hour recovery period. The drawdown data is the basis for the calculation of the aquifer transmissivity, the rate at which the brine moves through the aquifer. Based on early testing, the transmissivity of Pastos Grandes is conservatively estimated to be very good at 550 square metres per day (m2/d).

Brine sampling during the pumping test was completed every 6 hours for a better understanding of the variation in brine chemical composition as the aquifer was tested. In general, the chemistry is consistent over the 60 hour period with lithium only dropping 8.2 mg/l from an initial 438.7 mg/l to 430.5 mg/l. Lithium to magnesium (Li/Mg), sulphate to lithium (SO4/Li) and potassium to lithium (K/Li) ratios also remain fairly constant over the test period.

A second pumping well is being constructed at hole PGMW17-04b where recent drilling has intersected extensive lithium-bearing brine and testing is expected to commence in the near future.