17. Directional Drilling Open Pit Dewatering Wells – Great Idea
Date: May 16, 2015Author: Ken Kuchling
I recently read an interesting article in the Mining Magazine May 2015 edition called “Top 10 Technologies”. One of the new technologies that jumped out at me is the capability to directionally drill pit dewatering wells. This is an oil field technology from Schlumberger Water Services that is being applied to mining. More information is at this link (see Well Placement Technology for Mine Dewatering).
One of my past projects was a diamond mine in northern Canada. The granitic rock mass was geotechnically very competent with limited jointing and fracturing. Groundwater seepage into a partly permafrost could create a host of operational problems in winter as well as affect pit wall stability. Most of the groundwater flows were predicted to be along a few main structures or along single open joints. These structures were near vertical, which created a problem when trying to intercept them with vertically drilled pumping wells. Either you hit one or you don’t.
The use of directional drilling of pumping wells can be a great innovation. It gives the opportunity to bend the pumping well to a more horizontal orientation, allowing the well bore to cut across vertical structures rather than parallel to them. In addition, one can drill wells near the pit crest bending them in towards the ultimate pit bottom. This may help improve drainage near the operating benches in the pit as it deepens and may eliminate the need to install inpit pumping wells.
In addition, some open pits have constructed underground drainage galleries around the pit circumference to help intercept groundwater seepage. Possibly directionally drilling aligned parallel to the pit wall can replicate these drainage galleries at a much lower cost.
My bottom line is that the directional drilling innovation makes a lot of sense to me and mine operators should take a look at it, it might improve their pit dewatering systems.