In 2017 a new shaft was being constructed in a mine in Poland. The shaft was being sunk at 8.7m diameter by conventional blind sinking methods. The shaft sink was at around 1067m deep and, while conducting standard probe drilling in advance of the shaft floor, the probe holes intersected very high pressure – high inflow rate water. This water inflow was up to 1800L per minute with a static pressure of 75bar. The water was 47°C, highly mineralized and brought with it toxic concentrations of H2S gas. The water and gas were contained in a fairly well-defined 5m thick dolomite rock layer (the aquifer) at approx. 28-33m below the shaft floor. The shaft sink could not continue through this saline aquifer without first sealing the water and gas inflows.
For the next 18 months, the shaft-sinking contractor tried diligently to seal this aquifer by using a variety of different grout products from within the shaft and from the surface. This water-sealing effort had a massive impact on the project financially, and the construction schedule was 1.5 years behind schedule which also had an impact on the mine operator.
Ordinary Portland Cement (OPC) and some 15 different grout products such as ultra fine, resins, polyurethanes, acrylics were tried and all had little to no effect as the dolomite rock mass was very tight, and the static head pressure would eject the grout projects before they could take effect.
In January 2019, the shaft-sinking contractor contacted Sovereign Hydroseal to see if its proprietary grouting technology could successfully control the shaft water. An inspection was conducted by Sovereign in February 2019, and an NOH2O® grouting trial program was negotiated. Sovereign mobilized staff from Australia, the U.S. and South Africa and equipment and grout products from the United States and Australia in April 2019. In less than 4 weeks the water and gas inflow had been sealed to well below the required minimum with only the trial volume of grout products used.
