NGWA Exam 4 Rated A+ 2025
Explain percentage retention in designing a screen for a gravel well. - ANSWER-The
proportion of gravel or formation particles that the screen is designed to retain, ensuring
proper filtration while allowing water flow without clogging.
Explain various methods for setting casing using air rotary equipment. - ANSWER-
Driving: Use a hammer or rig to drive the casing down.
Rotating: Rotate the casing into place using the drill rig.
Pushing: Use the rig's hydraulic system to push the casing down.
Explain why soft formations require low annular velocities. - ANSWER-To prevent
erosion, collapse, or destabilization of the borehole due to excessive cuttings removal or
formation washout.
How are air rotary rigs sized? - ANSWER-Air compressor capacity (CFM/PSI)
drilling depth capacity
mast height
How are screen lengths determined? - ANSWER-By the thickness of the water-bearing
formation and the desired water yield.
How could a crooked hole be corrected using air rotary? - ANSWER-using stabilizers,
reducing weight on the bit, and adjusting the drilling angle.
How does weight (density) of the drilling fluid affect the down hole conditions during
driilling? - ANSWER-Controls downhole pressure, stabilizes the borehole, prevents
formation collapse, and helps control fluid loss or blowouts.
How is mud weight controlled? What factors enter into the viscosity of mud? -
ANSWER-Mud weight is controlled by adding materials like barite or bentonite.
Viscosity factors: Type of additives, fluid composition, and solids content.
How is the DHH drill bit sharpened? - ANSWER-By grinding the worn or rounded edges
of the bit's cutting surfaces, usually with specialized grinding tools.
If up hole velocities decrease, what could be the probable cause? - ANSWER-Reduced
air pressure
blockage in the air stream
increased hole diameter.
In using mud rotary in unconsolidated formations, what is the relationship of speed in
RPMs and feeds? - ANSWER-In mud rotary drilling for unconsolidated formations,
higher RPMs require lower feeds to avoid collapsing the borehole, while lower RPMs
can tolerate higher feeds for better penetration.
Explain percentage retention in designing a screen for a gravel well. - ANSWER-The
proportion of gravel or formation particles that the screen is designed to retain, ensuring
proper filtration while allowing water flow without clogging.
Explain various methods for setting casing using air rotary equipment. - ANSWER-
Driving: Use a hammer or rig to drive the casing down.
Rotating: Rotate the casing into place using the drill rig.
Pushing: Use the rig's hydraulic system to push the casing down.
Explain why soft formations require low annular velocities. - ANSWER-To prevent
erosion, collapse, or destabilization of the borehole due to excessive cuttings removal or
formation washout.
How are air rotary rigs sized? - ANSWER-Air compressor capacity (CFM/PSI)
drilling depth capacity
mast height
How are screen lengths determined? - ANSWER-By the thickness of the water-bearing
formation and the desired water yield.
How could a crooked hole be corrected using air rotary? - ANSWER-using stabilizers,
reducing weight on the bit, and adjusting the drilling angle.
How does weight (density) of the drilling fluid affect the down hole conditions during
driilling? - ANSWER-Controls downhole pressure, stabilizes the borehole, prevents
formation collapse, and helps control fluid loss or blowouts.
How is mud weight controlled? What factors enter into the viscosity of mud? -
ANSWER-Mud weight is controlled by adding materials like barite or bentonite.
Viscosity factors: Type of additives, fluid composition, and solids content.
How is the DHH drill bit sharpened? - ANSWER-By grinding the worn or rounded edges
of the bit's cutting surfaces, usually with specialized grinding tools.
If up hole velocities decrease, what could be the probable cause? - ANSWER-Reduced
air pressure
blockage in the air stream
increased hole diameter.
In using mud rotary in unconsolidated formations, what is the relationship of speed in
RPMs and feeds? - ANSWER-In mud rotary drilling for unconsolidated formations,
higher RPMs require lower feeds to avoid collapsing the borehole, while lower RPMs
can tolerate higher feeds for better penetration.
