Directional drilling has several key advantages over traditional non-directional drilling techniques when dewatering strata in advance of mining.  Holes can be maintained within a targeted strata layer or steered to intercept water-bearing features at intentional angles that maximize hydraulic connectivity and drainage.  In addition, sidetracking capabilities allow for maximum coverage from fewer borehole collars and setup locations.  More novel applications include vertical well intercepts to drain water collected in horizontal laterals to a production well.

For thinner interburden distances, MSHA safety regulations require draining of overlying mine workings prior to undermining. REI takes advantage of directional drilling from underground setup locations to install gravity drain boreholes, utilizing the mine’s existing infrastructure as well as preventing the need for surface drilling permits and developments. REI uses pressure tested casing and contained wellheads, including blowout preventers, to fully control water flows at all times.

Directional drilling expands traditional highwall depressurization horizontal drilling capabilities by (1) allowing for longer boreholes, (2) steering to intercept water-bearing features at intentional angles that maximize hydraulic connectivity and drainage, and (3) installing sidetracks to increase coverage area. In addition, the increased design capabilities can allow for more alternative drill setup locations in safer highwall areas that are less intrusive of active mining operations. A more novel application includes vertical well intercepts to drain water collected in horizontal laterals to a production well, shifting the burden of water handling to outside the active mining pit and reducing concerns with freezing at the highwall in colder environments.

REI uses directionally steered holes to place your sensors and monitoring equipment in areas where traditional non-directional holes may not be able to reach. With REI’s focus on directional drilling, our team can assist developing an installation plan using steered boreholes. REI is capable of using directional techniques to install groundwater sensors and monitoring equipment, including vibrating wire piezometers, time-domain reflectometry, fiber optics, wireless piezometers, and spatial location sensors.

With the use of directionally drilled boreholes, REI can install effective grout curtains that shield your workings from high inflows.  Boreholes may be placed in overlying or underlying strata, aligned with projected entries or tunnels, or steered to intercept water-bearing features.  Single boreholes or multi-lateral boreholes may be developed to maximize coverage area and formation of a grout curtain.  High pressure grout pumps are utilized to inject grout into formations through a sealed standpipe or through downhole packers.

Directional drilling equipment can be used with magnetic ranging to intercept specific targets such as vertical wells. In this example REI drilled 2 parallel SIS boreholes in advance of a future longwall mine for degasification. Both boreholes intercepted the same 6.75 in (171 mm) diameter vertical well. Water production (to reduce reservoir pressure) was performed from the vertical well as well as gas production. In this case both SIS boreholes were drilled over-balanced with minimal drilling fluids (clean water) and gas production from the vertical well reached 353,000 ft^3/day (10,000 m^3/day). This project was performed with one of REI’s underground drills.