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Drilling Techniques

Uni-Tech utilizes a large range of drilling techniques to advance boreholes for well installation and sampling services. Currently, we offer mud rotary, hollow stem auger, air rotary, reverse rotary, direct push, & drive and wash drilling.

Mud Rotary – In this method, mud is pumped down the drill pipe and out through the jets in the drill bit. The fluid then flows up the annular space between the hole and the drill pipe carrying cuttings in suspension to the surface. This method is the most widely used and versatile drilling method.

Hollow Stem Auger – The advantages of auger drilling include low operating costs, fast penetration rates and no use of fluids. Augers come in continuous flight, short flight/plate augers and bucket augers. Continuous flight augers driven by top head rotary machines carry their cuttings to the surface. Continuous flight augers with hollow stems are often used for sample recovery in environmental and geotechnical operations.

Air Rotary – In air rotary, air alone lifts the cuttings from the borehole. A large compressor provides air that is piped to the swivel hose connected to the top of the Kelly or drill pipe. The air, forced down the drill pipe, escapes through small ports at the bottom of the drill bit, thereby lifting the cuttings and cooling the bit. The cuttings are blown out the top of the hole and collect at the surface around the borehole.

Reverse Rotary – Reverse circulation drilling allows for larger borehole drilling without the limiting factors of drilling fluid pump capacities. Rotary rigs designed for reverse circulation have larger capacity mud pumps and air compressors to allow for increased pressures needed to insure the removal of cuttings from large boreholes. These rigs are far larger than those used for domestic purposes. Reverse circulation drilling is a variant of the mud rotary method in which drilling fluid flows from the mud pit, down the borehole outside the drill rods and passes upward through the bit. Cuttings are carried into the drill rods and discharged back into the mud pit.

Direct Push – Direct push drilling is a method in which a drill string is advanced by pushing or vibrating. This is typically used to gather soil and groundwater samples. Generally, this method is limited to shallow depths and unconsolidated formations.

Drive and Wash – The drive and wash method requires the use of steel casing to maintain an open hole during drilling and sampling operations. The drive and wash method entails driving a casing into the ground with a heavy hammer. After the interval is reached, the soil cuttings are washed out of the casing with a tricone or chopping bit and water. A hardened steel drive shoe is placed on the bottom of the lead casing to aid in penetration and to prevent the casing from splitting and breaking when rocks and cobbles are encountered.