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| Reverse rotary is the standard
technique used to
install large-diameter (boreholes greater than 24 inches) gravel-packed
water supply wells in unconsolidated formations. The
reverse-rotary techniques is similar to the standard mud-rotary
technique in that a rotary-driven drill bit and recirculated drilling
fluid are used to advance and stabilize the boreholes.
However,
in reverse rotary, the drilling fluid is gravity fed down the annular
space of the borehole and the drill string and the return fluid
containing the drill-cutting load is pumped upward through the drill
stem. This reversal in fluid flow allows for the installation
of
larger boreholes compared with direct rotary, since the constant
diameter of the drill string allows for consistent fluid velocity,
regardless of the borehole diameter. The relatively lower velocity of the drilling fluid in the annular space of the drill string and the boreholes reduces the risk of a formation "blow-out." To maintain satisfactory fluid velocity and consistency, reverse-rotary drill use larger pumps, drill rods, compressors and drilling reservoirs (mud pits) than direct-rotary drills. Uni-Tech's fleet of reverse-rotary drills is fully stocked with the tooling and support equipment to handle your most demanding projects. With our truck, trailer and table-mounted reverse-rotary equipment, we can complete boreholes and under-reams from 44 inch diameter to 2,500 feet deep in locations ranging from open fields to inside existing well houses. |