Water Well Drilling Terms

Water Well Drilling Terms

Annulus

The space between the drill string (drill pipe) or casing and the wall of the borehole.

Aquifer Stimulation

A type of development that is done in semi consolidated and completely consolidated formations to alter the formation physically to improve its hydraulic properties. (Commonly called Well Development)

Aquifer

A formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield economical quantities of water to wells.

Aquifer test/Recovery/Drawdown Test

A test involving the withdrawal of measured quantities of water from an aquifer and the measurement of resulting changes in the head in the aquifer both during and after the period of discharge or addition.

Artesian well

A well deriving its water from a confined aquifer in which the water level stands above the ground surface, synonymous with a flowing artesian well.

Bedrock

A general term for rock, usually solid, that underlies soil or other unconsolidated material.

Bentonite

A colloidal clay, largely made up of the mineral sodium montmorillonite. Used as drilling mud or in a dried hard “chip” style for sealing formation.

Drill Bit

The cutting tool attached to the bottom of the drill string or pipe.

Chlorine

Widely used in the disinfection of water.

Confined Aquifer

A formation in which the groundwater is isolated from the atmosphere at the point of discharge by impermeable geologic formations. Confined groundwater is generally subject to a pressure greater than atmospheric.

Cone of Depression

A depression in the groundwater table that has the shape of an inverted cone and develops around the well from which water is being withdrawn. It defines the area of influence of a well.

Corrosion

The act or process of dissolving or wearing away metals.

Development

The act of repairing damage to the formation caused by the drilling process and increasing the porosity and permeability of the materials surrounding the intake portion of the well.

Drawdown

The distance between the static water level and the surface of the cone of depression.

Drilling Fluid

A water - or air-based fluid used in the water well drilling operation to remove cuttings from the hole, to clean and cool the bit, to reduce friction between the drill string and the sides of the hole.

Filter pack

Sand or gravel that is smooth, uniform, clean and well-rounded. It is placed in the annuals of the well between the borehole wall and the well screen to prevent formation material from entering the screen.

Groundwater Table

The surface between the zone of saturation and the zone of aeration; the surface of an unconfined aquifer.

Grout

A fluid mixture of cement and water (neat cement) of a consistency that can be forced through a pipe and placed as required. Various additives, such as sand, bentonite and hydrated lime, may be included in the mixture to meet certain requirements. Bentonite and water are sometimes used for grout. Used to seal off the

Hardness

A property of water causing the formation of an insoluble residue when the water is used with soap. It is primarily caused by calcium and magnesium ions.

Naturally Developed Well

A well in which the screen is placed in direct contact with the aquifer materials; no filter pack is used.

Observation Well

A well drilled in a selected location for the purpose of observing parameters such as water levels and pressure changes.

Overburden

The loose soil, silt, sand, gravel or other unconsolidated material overlying bedrock.

Oxidation

The combining of an element with oxygen.

Permeability

The property or capacity of porous rock, sediment, or soil for transmitting a fluid. The measure of the relative ease of fluid to flow under equal pressure. (The ability of water to flow through a formation)

Porosity

The percentage of the bulk volume of a rock or soil that is occupied by interstices, whether isolated or connected. (The space between rock or soil that may contain water)

Pumping Test

A test that is conducted to determine aquifer or well characteristics.

Recharge

The addition of water to the zone of saturation. (Water adding to a formation or aquifer)

Sandstone

A sedimentary rock composed of abundant rounded or angular fragments of sand set in a fine-grained matrix (silt or clay) and more or less firmly united by a cementing material.

Sedimentary Rocks

Rocks resulting from the consolidation of loose sediment that has accumulated in layers.

Shale

A fine-grained sedimentary rock, formed by the consolidation of clay, silt or mud. It is characterized by finely laminated structure and is sufficiently indurated so that it will not fall apart on wetting.

Static Water Level

The level of water in a well that is not being affected by the withdrawal of groundwater.

Well Screen

A filtering device used to keep sediment from entering a Waterwell.

Well Yield

The volume of water discharged from a well in gallons per minute or cubic meters per day