17. Directional Drilling Open Pit Dewatering Wells – Great Idea

I 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 open pit dewatering wells.   This is an oil field technology from Schlumberger Water Services that was going to be applied to mining.

One of my past roles was engineering for the Diavik diamond mine in northern Canada.  The granitic rock mass was geotechnically very competent with a limited amount of jointing and fracturing.

Groundwater seepage from a partly permafrost pit wall could create a host of operational problems in winter. Most of the groundwater flows were predicted to be along a few main structures or along single open joints.

Generally 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 didn’t.

The use of directional drilling of pumping wells is a great innovation

It gives the opportunity to bend the pumping well to a angled orientation, allowing the well bore to cut across vertical structures rather than paralleling them.   In addition, one could drill pumping wells near the pit crest targeting the ultimate pit bottom.  This may help improve drainage near the operating benches as the pit deepens and may eliminate the need to install inpit pumping wells.

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 replace the need for these high cost drainage galleries.

The bottom line is that the directional drilling innovation makes a lot of sense and mine operators should take a look at it.  It might help improve their pit dewatering systems.

If anyone has experience with directionally drilled dewatering wells, please let us know.

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