NGWA EXAM
National Groundwater Association
Water well defined
Drilled, cored, bored, washed, dug, driven, jetted excavation, constructed for extracting
groundwater.
Cable tool drill string
Socket, jars, stem, and drill bit
Drill String
Entire column of string or drill pipe, drill collars, and accessories that transmit fluid and/or
rotational power from Kelly (top head drive) to the drill collars and bit.
Rotary Drill string
Drill bit, Drill collar (stabilizer), Drill pipe, Kelly (top head)
Porosity
The percentage of void spaces or holes in geologic formation. The amount of connected pore
spaces.
Barite
Barium sulfate (BaSO₄), a mineral used to increase the weight of drilling fluid (mud); its
specific gravity is 4.2
Air Rotary Drilling
A method of rotary drilling that uses compressed air as the circulating medium; compressed air
at high uphole velocity removes the cuttings
, Surfactants
Improve flushing of cuttings from bit, produce foam during well drilling, and disaggregate
clays.
2.31
Unit of energy constant to overcome gravity
Examples:
• 2.31 × 40 psi = 92.4' of lift
• 600' ÷ 2.31 = 260 psi
Well Development
A procedure to remove fine solids and materials from the water-bearing zone to optimize
production
Well Development Methods
Chemical, Over pumping, Rawhiding (Washing and backwashing), Mechanical Surging,
Jetting, Air surging
Over Pumping
Pumping well at a much higher rate than normal to develop the well.
Rawhiding
Water pumped to top of well and allowed to flow back, breaking sediment bridges.
Mechanical Surging
Uses surging block on drill rod to force water into aquifer and draw it back to remove
sediments.
Jetting
Jetting nozzles and external water pressure used to clean inside well screen.
National Groundwater Association
Water well defined
Drilled, cored, bored, washed, dug, driven, jetted excavation, constructed for extracting
groundwater.
Cable tool drill string
Socket, jars, stem, and drill bit
Drill String
Entire column of string or drill pipe, drill collars, and accessories that transmit fluid and/or
rotational power from Kelly (top head drive) to the drill collars and bit.
Rotary Drill string
Drill bit, Drill collar (stabilizer), Drill pipe, Kelly (top head)
Porosity
The percentage of void spaces or holes in geologic formation. The amount of connected pore
spaces.
Barite
Barium sulfate (BaSO₄), a mineral used to increase the weight of drilling fluid (mud); its
specific gravity is 4.2
Air Rotary Drilling
A method of rotary drilling that uses compressed air as the circulating medium; compressed air
at high uphole velocity removes the cuttings
, Surfactants
Improve flushing of cuttings from bit, produce foam during well drilling, and disaggregate
clays.
2.31
Unit of energy constant to overcome gravity
Examples:
• 2.31 × 40 psi = 92.4' of lift
• 600' ÷ 2.31 = 260 psi
Well Development
A procedure to remove fine solids and materials from the water-bearing zone to optimize
production
Well Development Methods
Chemical, Over pumping, Rawhiding (Washing and backwashing), Mechanical Surging,
Jetting, Air surging
Over Pumping
Pumping well at a much higher rate than normal to develop the well.
Rawhiding
Water pumped to top of well and allowed to flow back, breaking sediment bridges.
Mechanical Surging
Uses surging block on drill rod to force water into aquifer and draw it back to remove
sediments.
Jetting
Jetting nozzles and external water pressure used to clean inside well screen.
