NGWA TEST PAPER 2025 QUESTIONS AND ANSWERS
RATED A+
✔✔Explain how drill subs are used in the drill string. - ✔✔connect components in the
drill string, facilitate transitions in diameter and thread type, add weight for penetration,
and enable the incorporation of specialized tools for optimized drilling operations.
✔✔Explain how pH can be affected by certain unconsolidated formations. - ✔✔mineral
content
✔✔What are some measures to keep wear down on the kelly bar? - ✔✔maintain
alignment, use lubricants, inspect regularly, apply optimal weight on the bit, and select
suitable drilling fluids.
✔✔How can storage co-efficients be measured in unconsolidated formations? -
✔✔using aquifer tests, where water levels are monitored in observation wells during
pumping, allowing for the calculation of storage based on changes in water levels over
time.
✔✔Assuming you have drilled down to rock and set the casing, what viscosity mud
should you have for continuing the drilling? Explain. - ✔✔30 to 50 centipoise
✔✔What can change rates of penetration in rock formations? - ✔✔rock hardness, bit
design, weight on bit, rotary speed, fluid properties, and the presence of fractures or
faults
✔✔After continuing into rock formations the centrifugal mud pump starts cavitating.
What should you do? - ✔✔reduce the pump speed, check for any blockages in the
suction line, ensure proper mud levels in the pit, and verify that the mud viscosity is
appropriate
✔✔What causes differential sticking? How can you best control against it happening? -
✔✔Differential sticking occurs when a drill pipe gets stuck against the walls of the
borehole.
maintain proper mud weight, ensure good hole cleaning to prevent cuttings buildup,
monitor for pressure changes, and use drilling techniques that minimize contact
between the pipe and the borehole wall
✔✔What are bentonite materials? - ✔✔Bentonite materials are clay minerals rich in
montmorillonite, known for their absorbency and swelling properties, commonly used in
drilling fluids and various industrial applications.
, ✔✔Gel-strength refers to what property in drilling fluid? - ✔✔the ability of drilling fluid to
develop a gel-like consistency when at rest, which helps prevent the settling of solids
and supports the weight of the drill string during pauses in drilling.
✔✔Two holes drilled with mud rotary in the same rock formations have different
penetration rates. Explain the probable causes. - ✔✔variations in bit type, weight on bit,
rotary speed, drilling fluid properties, hole cleaning efficiency, and the presence of
fractures or other geological inconsistencies.
✔✔How do you measure high solids in drilling muds? What methods are used to control
solids build up? - ✔✔measured using centrifuges to assess density and cuttings
volume, while control methods include regular monitoring, using shale shakers and
centrifuges for removal, adding fluid loss additives, and maintaining proper circulation
rates.
✔✔How best can you determine a highly permeable rock formation? - ✔✔best be
determined through well tests, such as pumping tests or slug tests, which measure the
rate of water flow and drawdown in observation wells.
✔✔What type of rock formations are in the sedimentary group? - ✔✔limestone,
sandstone, shale, and conglomerate
✔✔Before drilling into a known water producing rock formation, what should the mud
characteristics be? - ✔✔low density to prevent fracturing, sufficient viscosity for cuttings
suspension, and low fluid loss to minimize water invasion from the formation.
✔✔How is sand content in drilling mud measured? - ✔✔sand content test
✔✔Explain the rating of weight to viscosity in mud rotary drilling. - ✔✔the rating of
weight to viscosity is essential for maintaining proper hydraulic performance; a higher
weight in the drilling mud increases viscosity
✔✔Can annular velocities of the drilling mud be slower or faster in rock formation as
compared to unconsolidated formations? - ✔✔Annular velocities of the drilling mud can
be slower in rock formations compared to unconsolidated formations due to increased
friction and reduced cross-sectional area in the annulus.
✔✔Lost circulation problems in rock formations are usually caused by what conditions?
- ✔✔Lost circulation problems in rock formations are usually caused by conditions such
as high permeability, fractures or faults in the rock, insufficient mud weight, and the
presence of unstable formations.
✔✔Setting and developing screens in most rock formations are not necessary. Explain
why. - ✔✔Setting and developing screens in most rock formations are not necessary
RATED A+
✔✔Explain how drill subs are used in the drill string. - ✔✔connect components in the
drill string, facilitate transitions in diameter and thread type, add weight for penetration,
and enable the incorporation of specialized tools for optimized drilling operations.
✔✔Explain how pH can be affected by certain unconsolidated formations. - ✔✔mineral
content
✔✔What are some measures to keep wear down on the kelly bar? - ✔✔maintain
alignment, use lubricants, inspect regularly, apply optimal weight on the bit, and select
suitable drilling fluids.
✔✔How can storage co-efficients be measured in unconsolidated formations? -
✔✔using aquifer tests, where water levels are monitored in observation wells during
pumping, allowing for the calculation of storage based on changes in water levels over
time.
✔✔Assuming you have drilled down to rock and set the casing, what viscosity mud
should you have for continuing the drilling? Explain. - ✔✔30 to 50 centipoise
✔✔What can change rates of penetration in rock formations? - ✔✔rock hardness, bit
design, weight on bit, rotary speed, fluid properties, and the presence of fractures or
faults
✔✔After continuing into rock formations the centrifugal mud pump starts cavitating.
What should you do? - ✔✔reduce the pump speed, check for any blockages in the
suction line, ensure proper mud levels in the pit, and verify that the mud viscosity is
appropriate
✔✔What causes differential sticking? How can you best control against it happening? -
✔✔Differential sticking occurs when a drill pipe gets stuck against the walls of the
borehole.
maintain proper mud weight, ensure good hole cleaning to prevent cuttings buildup,
monitor for pressure changes, and use drilling techniques that minimize contact
between the pipe and the borehole wall
✔✔What are bentonite materials? - ✔✔Bentonite materials are clay minerals rich in
montmorillonite, known for their absorbency and swelling properties, commonly used in
drilling fluids and various industrial applications.
, ✔✔Gel-strength refers to what property in drilling fluid? - ✔✔the ability of drilling fluid to
develop a gel-like consistency when at rest, which helps prevent the settling of solids
and supports the weight of the drill string during pauses in drilling.
✔✔Two holes drilled with mud rotary in the same rock formations have different
penetration rates. Explain the probable causes. - ✔✔variations in bit type, weight on bit,
rotary speed, drilling fluid properties, hole cleaning efficiency, and the presence of
fractures or other geological inconsistencies.
✔✔How do you measure high solids in drilling muds? What methods are used to control
solids build up? - ✔✔measured using centrifuges to assess density and cuttings
volume, while control methods include regular monitoring, using shale shakers and
centrifuges for removal, adding fluid loss additives, and maintaining proper circulation
rates.
✔✔How best can you determine a highly permeable rock formation? - ✔✔best be
determined through well tests, such as pumping tests or slug tests, which measure the
rate of water flow and drawdown in observation wells.
✔✔What type of rock formations are in the sedimentary group? - ✔✔limestone,
sandstone, shale, and conglomerate
✔✔Before drilling into a known water producing rock formation, what should the mud
characteristics be? - ✔✔low density to prevent fracturing, sufficient viscosity for cuttings
suspension, and low fluid loss to minimize water invasion from the formation.
✔✔How is sand content in drilling mud measured? - ✔✔sand content test
✔✔Explain the rating of weight to viscosity in mud rotary drilling. - ✔✔the rating of
weight to viscosity is essential for maintaining proper hydraulic performance; a higher
weight in the drilling mud increases viscosity
✔✔Can annular velocities of the drilling mud be slower or faster in rock formation as
compared to unconsolidated formations? - ✔✔Annular velocities of the drilling mud can
be slower in rock formations compared to unconsolidated formations due to increased
friction and reduced cross-sectional area in the annulus.
✔✔Lost circulation problems in rock formations are usually caused by what conditions?
- ✔✔Lost circulation problems in rock formations are usually caused by conditions such
as high permeability, fractures or faults in the rock, insufficient mud weight, and the
presence of unstable formations.
✔✔Setting and developing screens in most rock formations are not necessary. Explain
why. - ✔✔Setting and developing screens in most rock formations are not necessary
