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Glossary of Terms Related to Directional Drilling

Air sparging – remediation technique – typically used to strip volatile contaminants from ground water by injecting air below the water table. Often combined with soil vapor extraction. Some engineers sparge to increase dissolved oxygen in the groundwater and soil to enhance biodegradation. (See bioventing)

The following video shows a downhole video of an air sparge well at system startup. Note that air bursts initially travel past the video camera upon startup. With increased air pressure, the well purged of water and air distribution occurs along the entire perforated section.Follow the link to see the video:

Air stripping – remediation technique – typically used to strip volatile contaminants from ground water by injecting air below the water table. Essentially the same as air sparging. Often combined with soil vapor extraction.

Back reamer – drilling tool – a tool designed to enlarge a pilot hole. Typically employed by attaching to the drill string once it exits the ground (surface to surface installation). Can be used to forward ream a hole.

Bentonite – drilling material – a naturally occurring additive used with water to lubricate, stabilize, and clear drill cuttings from a borehole.

Bioaugmentation – remediation technique – typically used to degrade environmental contaminants by introducing organisms that enhance cleanup.

Bioremediation – remediation technique – typically used to degrade environmental contaminants by using native organisms.

Bioventing – remediation technique – typically used to enhance bioremediation by providing oxygen to native in situ organisms.

Bore or borehole – drilling term – the elongated cavity created by the drilling process. Often the borehole is not a void, but rather a hole filled with drilling mud and cuttings.

BOREGEL™ – drilling material – a drilling mud manufactured by BAROID consisting of bentonite, polymer, and soda ash. Typically used in horizontal directional drilling for utilities. Because it contains bentonite, BOREGEL is usually not suitable for environmental applications.

Box – drilling term – the female thread portion of a drill rod.

Bubbling pressure or air entry value or threshold pressure – remediation term – the pressure at which air will enter the saturated zone.

Cable sonde – drilling tool – a downhole transmitter or probe that is powered by electricity generated at the surface.

Chinese finger – drilling equipment – a woven wire device typically used to pull materials into a bore. The finger is placed over the material and when it is pulled, it tightens on the material, becoming tighter the harder it pulls.

Compactor reamer – drilling tool – a tool used to enlarge the borehole by compressing the soil. Since this type of tool typically will decrease the permeability of the soil, it may not be suitable for horizontal wells.

CON DET® – drilling material – a water-soluble anionic surfactant manufactured by BAROID used to prevent formation materials from sticking to drilling tools.

Deflection – drilling term – the amount of flex exhibited by the drill rods. The drill head is typically steered by pushing it into the formation without rotation. There are limits to which the rods can be pushed before they deflect excessively.

Dry hole – drilling term – a condition that occurs when the drilling tools advance beyond the drilling mud. Typically caused by trying to drill too fast.

EZ MUD® – drilling material – a polymer additive used to increase viscosity and gel strength of bentonite drilling mud.

Filter cake – drilling term – the wall cake that forms from the platelets in bentonite-based drilling mud. Filter cake is the barrier between the borehole and the formation, limiting the amount of drilling mud needed to complete the borehole.

Frac out – drilling term – during normal drilling operations, drilling fluid travels up the borehole into a pit. When the borehole becomes obstructed or the pressure becomes too great inside the borehole, the ground fractures and fluid escapes to the surface.

Front locate point – drilling term – walkover locating systems determine the azimuth of the drill head using the magnetic field created by the down hole transmitter. This magnetic field is hourglass in shape, and the magnetic field changes at the top and bottom of the hourglass. The point at the front of the hourglass is the front locate point.

Gel strength – drilling term – the property of drilling fluid that permits it to suspend and transport drill cuttings from the borehole.

High Density Polyethylene (HDPE) – well screen material – HDPE is often used for horizontal environmental wells because of its flexibility, chemical resistance, and high tensile strength.

Hydro-lock – drilling term – A condition where the well casing and screens become “locked” in the borehole during pullback. This occurs when fluid becomes trapped inside the borehole behind the well materials. Suction increases to the point where the drill can no longer pull the casing into the hole.

Locator – drilling equipment – The above-ground component of a walkover locating system. The locator includes one or more antennae and a receiver to detect the signal transmitted by the downhole transmitter, and a microprocessor to decipher and display the downhole data

Lubricity – drilling term – the lubrication properties of a given material. Certain drilling mud additives improve the lubricity in a borehole.

Negative locate – drilling term – the locate point midway between the forward and rear locate points, at the center point of the “hourglass”. See front locate point.

Pitch – drilling term –The deviation from a horizontal plane is measured as pitch. When the drill is directed downward, the pitch is negative. When it is directed toward the surface, the pitch is positive.

Pothole – drilling term – a small hole excavated from the surface to a buried utility in order to provide positive verification of its location..

Rear locate – drilling term – the point along the drilling path opposite the front locate point.

Remote – drilling equipment – walkover equipment typically includes a direct reading receiver held by the locating technician and a remote unit that is a repeater for the locator. The remote is located at the drilling machine and enables the driller to see the same information as the locator.

Rod wiper – drilling equipment – A rubber or synthetic grommet placed over the drill rods during pullback to strip excess mud from the rods before they are stowed.

Sonde – drilling equipment – The downhole component of an electronic locating system. Same as a transmitter.

Strike alert – drilling equipment – A protective device used while drilling that sounds an alarm if the drill string contacts a buried electrical utility.

Swivel – drilling equipment – the fitting at the top of the drill string that enables the flow of drilling mud into the drill rods while simultaneously permitting them to rotate.

Thread compound – drilling material – An anti-seizing compound, frequently a high-pressure, copper-based grease, used to prevent the drill rod’s threads from seizing.

Transmitter – drilling equipment – The downhole component of an electronic locating system. Same as a sonde.

Wing cutter – drilling equipment – A reaming tool with wing-shaped extensions, used to expand the pilot hole to its final diameter.

API – American Petroleum Institute
ASTM – American Society of Testing and Materials