CA Well Driller key terms

The impermeable material placed in the space between the borehole wall and the outside of the well casing, intended to prevent surface water and shallow groundwater from moving down along the casing.

The gap between the drilled borehole wall and the casing, or between two concentric casings, that must be filled or sealed to protect the well and groundwater.

A standardized tapered pipe thread used on some well casings and couplings, defined by the American Petroleum Institute, that seals by thread interference rather than by an added gasket.

A well in which the water level rises above the top of the producing aquifer because the aquifer is confined under pressure, sometimes flowing at the surface without pumping.

A clay composed mainly of montmorillonite that swells when wet, used as a drilling fluid additive and as a component of grout and seal mixtures in wells.

Casing without openings, screens, or perforations, installed to conduct water to the surface and to isolate the borehole from unwanted formations.

An uncontrolled release of water, gas, or drilling fluid from a well up through the borehole, often caused by encountering an unexpected zone of high pressure.

The nominal or actual inside or outside measurement of a well casing, which determines the pump size, screen size, and annular clearance that can be accommodated.

A mixture of cement and water, often with bentonite or additives, placed in the annular space to form a hard, low-permeability seal around the casing.

A layer of low-permeability material such as clay or dense rock that restricts the movement of groundwater and can separate an aquifer from shallower water.

A short threaded or welded sleeve used to join two lengths of casing or pipe end to end so the string is continuous and watertight.

The process of removing drilling fluid, cuttings, and fine sediment from the borehole and surrounding aquifer so the well produces clear water at its expected capacity.

Treating a well, pump, and appurtenances with a chlorine solution to kill bacteria and other microorganisms before the well is placed into service.

The drop in water level in a well caused by pumping, measured as the difference between the static water level and the pumping water level.

A liquid, usually water mixed with clay or polymers, circulated during drilling to cool the bit, carry cuttings to the surface, and stabilize the borehole wall.

A hardened steel ring attached to the bottom of casing to cut through soil and protect the casing edge as it is driven or advanced into the ground.

Sorted gravel or sand placed in the annular space around a well screen to filter formation material and improve the flow of water into the well.

A pumpable mixture of cement, bentonite, or other approved material used to fill and seal the annular space or to abandon a well.

A development technique in which water is injected under high pressure to open and clean fractures in rock or to break down drilling mud near the borehole.

A hole or slot cut through casing or liner so water can enter the well from a selected interval of the formation.

A small-diameter observation well or tube used to measure the water level or pressure head at a specific depth in the ground.

The imaginary level to which water in a confined aquifer would rise under its own pressure if a well were drilled into it.

The water level measured in a well while it is being pumped at a steady rate, after drawdown has stabilized.

The watertight seal at the top of a well, typically a grouted annular space and a sealed well cap, that keeps surface water and contaminants out.

The yield of a well divided by the drawdown produced by that pumping rate, expressed as flow per unit of water-level drop, used to compare well performance.

The level of water in a well when it is not being pumped and has had time to recover to its natural, undisturbed position.

A well development method that alternately forces water into and out of the screen or formation to loosen and remove fine material and drilling mud.

The upper portion of the annular seal, extending from the ground surface down a required depth, that blocks downward movement of surface water along the casing.

A pipe lowered into the annular space to place grout or seal material from the bottom upward, avoiding voids and contamination from the fluid above.

The permanent closure of a well that is no longer in use, carried out by sealing the borehole and removing or cutting off casing so it cannot act as a pathway for contamination.

A tight-fitting cover on top of the casing that keeps out surface water, debris, insects, and small animals while allowing access for measurement and service.

The pipe installed in a borehole to keep the hole open, protect the pump, and prevent unwanted water or contaminants from entering the well.

The complete removal or sealing of a well and its casing so the borehole no longer exists as a well, sometimes required where the well cannot be properly abandoned.

The set of operations performed after drilling and casing to clean the well and improve its hydraulic connection with the surrounding aquifer.

A record of the geologic formations, depths, casing, screen, and seal intervals encountered in a borehole, required to document well construction.

A slotted or perforated section of casing installed opposite a producing formation to let water in while holding back sand and gravel.

A controlled pumping test that measures the rate and drawdown of a well to determine its safe yield and performance characteristics.

The volume of water a well can produce per unit of time under a stated pumping condition, usually expressed in gallons per minute.