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NGWA CWD practice questions

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Question 1Drilling general exam

Which drilling method uses a rapidly rotating bit on the end of a drill string to advance a borehole, with cuttings typically removed by circulating fluid or air?

  1. Jetting
  2. Hand augering
  3. Cable tool drilling
  4. Rotary drilling Correct answer.

Explanation

Rotary drilling turns a bit mounted on the end of the drill string while circulating fluid or air lifts cuttings to the surface. This method dominates modern water well construction because it is fast and works in many formations. Cable tool drilling instead lifts and drops a heavy bit on a wire rope.

Question 2Drilling general exam

In a mud rotary system, what is the primary purpose of the drilling fluid returning up the annulus?

  1. To carry cuttings to the surface and stabilize the borehole wall Correct answer.
  2. To cool the drill bit only
  3. To lubricate the hoist drum
  4. To seal the pump packing

Explanation

Returning drilling fluid lifts rock cuttings out of the hole and exerts hydrostatic pressure that helps hold the borehole wall open. Cooling and lubrication of the bit are secondary benefits, not the main reason for circulation. Without adequate annular velocity, cuttings settle and can stick the string.

Question 3Drilling general exam

A driller is running a cable tool rig and wants to check that the hole is being kept vertical. Which practice best supports that goal?

  1. Keeping the tools properly dressed and using a straight, well-aligned string Correct answer.
  2. Increasing the stroke rate to maximum
  3. Rotating the casing while drilling
  4. Adding water only after the tools reach total depth

Explanation

Cable tool holes stay vertical when the bit is properly dressed and the string is straight and aligned with the derrick. A dull or uneven bit tends to drift and produce a crooked hole. Operators also check with a plumb line or similar device during drilling.

Question 4Drilling general exam

What does the term 'make-up torque' refer to on a drill string?

  1. The torque needed to break a connection loose
  2. The torque generated by the mud pump
  3. The torque limit of the hoist brake
  4. The torque applied to tighten a threaded connection to its specified value Correct answer.

Explanation

Make-up torque is the controlled torque applied when tightening a tool joint or coupling so the connection seals and carries load without overstressing threads. Too little torque risks a connection backing off downhole; too much can gall or yield the threads. Breaking out a connection requires break-out torque, which is a separate value.

Question 5Drilling general exam

Which casing material is most commonly specified for aggressive corrosive groundwater with high chloride and low pH where carbon steel would fail quickly?

  1. Thermoplastic such as PVC or HDPE Correct answer.
  2. Black steel
  3. Cast iron
  4. Galvanized steel

Explanation

Thermoplastic casing such as PVC or HDPE resists chloride-driven and low-pH corrosion that attacks ferrous metals. Selection still depends on collapse strength, temperature, and diameter requirements. Galvanizing and coatings only delay corrosion in aggressive water.

Question 6Drilling general exam

A driller needs to grout the annular space of a well to seal off a shallow aquifer. Which property of the grout is most important for forming a reliable hydraulic seal?

  1. Rapid set within minutes
  2. Low permeability and minimal shrinkage Correct answer.
  3. Bright color for inspection
  4. High compressive strength after 28 days

Explanation

The seal depends on a continuous, low-permeability grout column that does not shrink away from the casing or borehole wall. Neat cement or bentonite-cement blends are common because they bond and stay tight. Compressive strength matters for structural casing support but is not the sealing mechanism.

Question 7Drilling general exam

During a pump test, drawdown is measured as the difference between which two values?

  1. Casing diameter and screen diameter
  2. Static water level and land surface
  3. Static water level and pumping water level Correct answer.
  4. Pumping water level and total depth

Explanation

Drawdown is the drop in water level caused by pumping, measured from the static (non-pumping) level to the pumping level. It reflects the combined effects of aquifer loss and well loss. Recording both levels is essential for calculating specific capacity.

Question 8Drilling general exam

A well is completed with a screen whose slot size is much larger than the formation sand. What is the most likely consequence?

  1. Reduced yield from the aquifer
  2. Improved well efficiency
  3. Excessive sand entry and possible pump damage Correct answer.
  4. Permanent lowering of static water level

Explanation

Screen openings must be sized to retain the formation material or a properly developed filter pack. Oversized slots allow sand to enter the well, which abrades pumps and fills the sump. A gravel pack can correct the mismatch when designed correctly.

Question 9Drilling general exam

Which term describes the pressure exerted by a column of drilling fluid that prevents formation fluids from entering the borehole?

  1. Annular velocity
  2. Circulation loss
  3. Hydrostatic pressure Correct answer.
  4. Pump pressure

Explanation

Hydrostatic pressure comes from the weight of the fluid column and is controlled by fluid density and depth. Keeping it slightly above formation pore pressure prevents inflow while avoiding unintended fracturing. Annular velocity and pump pressure describe flow, not the static pressure balance.

Question 10Drilling general exam

A driller observes that drilling fluid is disappearing into the formation and returns to the pit have dropped sharply. What is the most appropriate initial response?

  1. Reduce fluid loss and consider loss-circulation material Correct answer.
  2. Increase pump speed to restore returns
  3. Add more cuttings to the pit
  4. Raise the bit and stop circulating permanently

Explanation

Lost circulation occurs when fluid escapes into a permeable or fractured zone. The response is to reduce loss by treating the fluid and, if needed, adding loss-circulation material while monitoring pit level. Increasing pump rate usually worsens the loss.

Question 11Drilling general exam

What is the main function of a packer in a water well completion?

  1. To measure water level
  2. To screen out gravel
  3. To increase pump discharge head
  4. To isolate a section of the borehole or annulus Correct answer.

Explanation

A packer seals the annular space to isolate zones, allowing separate testing, treatment, or production of selected intervals. It prevents cross-connection between aquifers. Packers are not used to boost pump head or to filter sediment.

Question 12Drilling general exam

Which condition most directly increases the risk of the drill string parting at a tool joint?

  1. Running a slightly undersized bit
  2. Using new drill collars
  3. Circulating clean water
  4. Exceeding recommended make-up torque and cycling the joint in fatigue Correct answer.

Explanation

Over-torquing a tool joint stresses the threads, and repeated bending during rotation accumulates fatigue cracks that lead to failure. Proper make-up torque and inspection intervals reduce this risk. Clean fluid and bit size do not cause joint failure.

Question 13Drilling general exam

A well produces water with visible fine sand after development. Which step should be evaluated first before returning the well to service?

  1. Verifying screen slot size and the effectiveness of development Correct answer.
  2. Increasing the pump setting depth
  3. Adding chlorine to the well
  4. Reducing the casing diameter

Explanation

Sand production usually indicates a mismatch between screen openings and formation grain size, or incomplete development that left fines near the borehole. Confirming slot size and development status addresses the root cause. Simply moving the pump deeper exposes it to more sand.

Question 14Drilling general exam

Which unit is conventionally used to express specific capacity of a water well?

  1. Feet per second
  2. Percent by volume
  3. Gallons per minute per foot of drawdown Correct answer.
  4. Pounds per square inch

Explanation

Specific capacity is discharge divided by drawdown, commonly reported as gallons per minute per foot of drawdown. It indicates how efficiently the well yields water for each unit of head loss. Higher values generally indicate a more productive or better-developed well.

Question 15Drilling general exam

A driller is setting casing in a deep hole and wants to reduce the chance of the casing collapsing under external pressure. Which factor should be checked against the manufacturer's rating?

  1. The thread lubricant brand
  2. The collapse strength for the planned installation depth and fluid conditions Correct answer.
  3. The color of the casing
  4. The length of the discharge pipe

Explanation

External hydrostatic and formation pressures can collapse casing, so the selected wall thickness and material must meet the manufacturer's collapse rating for the installation depth. Collapse resistance decreases with larger diameter and thinner wall. Thread lubricant and pipe length do not govern collapse.

Question 16Drilling general exam

What is the purpose of developing a newly drilled well?

  1. To sterilize the aquifer
  2. To remove drilling fines and improve communication between the aquifer and the well Correct answer.
  3. To lower the static water level
  4. To increase the casing diameter

Explanation

Development removes drilling mud, cuttings, and fine formation material from the screen and near-well zone so water can flow freely into the well. It typically improves yield and reduces sand entry. Disinfection is a separate final step.

Question 17Drilling general exam

A driller plans to use a bentonite-based drilling fluid. Which property should be monitored to ensure the fluid can lift cuttings without becoming too thick?

  1. Hoist line speed
  2. Marsh funnel viscosity Correct answer.
  3. Bit weight
  4. Casing torque

Explanation

Marsh funnel viscosity gives a quick field measure of how thick the fluid is and whether it can carry cuttings. Fluid that is too viscous raises pump pressure and can cause formation damage. Bit weight, casing torque, and line speed are rig operating parameters.

Question 18Drilling general exam

Which practice best protects a well from surface contamination after completion?

  1. A gravel pack extending to land surface
  2. A properly grouted annulus and a sealed, sanitary well cap Correct answer.
  3. An open casing top for ventilation
  4. A pit lined with drilling cuttings

Explanation

A continuous grout seal and a sanitary cap prevent surface water and debris from entering the annulus or casing. These are standard sanitary completion requirements. Open casing tops and unsealed gravel packs create pathways for contamination.

Question 19Drilling general exam

A pump is installed in a well and the driller must set it above the top of the screen. Why is this placement preferred?

  1. To reduce the casing diameter
  2. To increase the static water level
  3. To eliminate the need for a check valve
  4. To avoid drawing sand and to keep the motor in cooler, flowing water Correct answer.

Explanation

Setting the pump above the screen reduces the chance of pulling sand and keeps the motor in flowing water for cooling. Placing the intake in the screen section can agitate and draw fines. Check valves and casing size are separate design matters.

Question 20Drilling general exam

What does a falling-head test in a completed well primarily estimate?

  1. The rate at which water flows back into the formation from a slug of added water Correct answer.
  2. The grout compressive strength
  3. The casing wall thickness
  4. The pump motor horsepower

Explanation

A falling-head (slug) test measures how quickly an introduced column of water drains into the formation, giving an estimate of hydraulic conductivity near the well. It is quick and requires no pumping. Motor horsepower and casing thickness are unrelated design values.

Question 21Drilling general exam

Which safety hazard is most associated with hydrogen sulfide gas encountered during drilling?

  1. Rapid oxygen displacement and toxicity at low concentrations Correct answer.
  2. Corrosion protection of steel casing
  3. Improved fluid viscosity
  4. Spontaneous combustion on contact with water

Explanation

Hydrogen sulfide is toxic at low concentrations and can displace oxygen in confined spaces, so gas monitoring and ventilation are required. It also corrodes steel, but that is a materials concern rather than a safety benefit. Drillers must follow confined-space and gas-detection procedures.

Question 22Drilling general exam

A driller notices the drill string is suddenly dropping and torque has fallen off during rotary drilling. Which condition is most consistent with these observations?

  1. A blocked screen slot
  2. A plugged bit with high pump pressure
  3. A worn hoist brake
  4. A broken drill string or bit Correct answer.

Explanation

A sudden loss of torque combined with the string dropping suggests a parted string or a lost bit. The driller should stop rotation, note the depth, and plan recovery. A plugged bit would typically raise pump pressure rather than drop torque.

Question 23Drilling general exam

Which type of pump is best suited to a deep, small-diameter well with a low static water level?

  1. A hand pitcher pump
  2. A shallow-well jet pump
  3. A trash pump
  4. A submersible pump sized to the well diameter and total head Correct answer.

Explanation

A submersible pump fits inside the casing and is rated for the total dynamic head and well diameter. Shallow-well jet pumps lose effectiveness as lift increases. Pitcher and trash pumps are not intended for deep small-diameter wells.

Question 24Drilling general exam

What is the primary reason for recording a driller's log during well construction?

  1. To satisfy the pump manufacturer
  2. To document formation changes, depths, and construction details for the completed well Correct answer.
  3. To replace the state well report
  4. To calculate the driller's hourly wage

Explanation

A driller's log records the geology, water strikes, casing and screen settings, and grouting details that describe how the well was built. It supports later maintenance decisions and regulatory reporting. It does not substitute for required state records.

Question 25Drilling general exam

A well yields 150 gallons per minute with a drawdown of 25 feet. What is the specific capacity?

  1. 150 gallons per minute per foot
  2. 6 gallons per minute per foot Correct answer.
  3. 25 gallons per minute per foot
  4. 3,750 gallons per minute per foot

Explanation

Specific capacity equals discharge divided by drawdown: 150 divided by 25 equals 6 gallons per minute per foot. This value indicates the yield obtained per foot of water-level decline. It is a common measure for comparing well performance.

Question 26Drilling general exam

Which drilling method removes cuttings from the borehole mainly by continuously circulating drilling fluid down the drill pipe and up the annular space?

  1. Hand augering
  2. Cable tool drilling
  3. Jet percussion drilling
  4. Rotary drilling Correct answer.

Explanation

Rotary drilling uses a rotating bit and a circulating fluid that carries cuttings up the annulus to the surface, where they settle in the pit. Cable tool and auger methods remove material with a bailer or bucket rather than continuous fluid circulation.

Question 27Drilling general exam

In a cable tool rig, what is the function of the drilling line and walking beam assembly?

  1. To rotate the drill pipe at high speed
  2. To set the well screen after completion
  3. To lift and drop the heavy string so the bit fractures the formation Correct answer.
  4. To circulate mud through the annulus

Explanation

Cable tool rigs fracture rock by repeatedly lifting and dropping a heavy string with a chisel bit; the walking beam converts engine power into this reciprocating motion. There is no rotary table or mud pump circulation loop in this method.

Question 28Drilling general exam

A driller is preparing a bentonite slurry for a rotary hole and wants to check that the mix will carry cuttings efficiently. Which measurement is most directly used for this purpose?

  1. Chloride concentration
  2. Specific gravity of the cuttings
  3. Sand content of the cement
  4. Marsh funnel viscosity Correct answer.

Explanation

Marsh funnel viscosity measures how readily the fluid flows and is the standard field check on a mud's ability to suspend and transport cuttings. Chloride and sand tests assess contamination or solids, not the carrying capacity of the slurry.

Question 29Drilling general exam

What is the primary purpose of a surface seal around the casing of a water well?

  1. To prevent surface water and shallow contamination from moving down the annulus Correct answer.
  2. To reduce the weight of the casing string
  3. To increase the well yield
  4. To improve the efficiency of the pump motor

Explanation

A properly constructed surface seal, typically of grout or bentonite, blocks the annular pathway that would otherwise let surface water and shallow contaminants travel down along the casing. It does not add yield or affect pump efficiency.

Question 30Drilling general exam

Which term describes the vertical distance the water level in a well drops when pumping begins?

  1. Specific yield
  2. Gradient
  3. Static head
  4. Drawdown Correct answer.

Explanation

Drawdown is the difference between the static (non-pumping) water level and the pumping water level. Static head is the non-pumping level itself, while gradient and specific yield describe aquifer behavior rather than the drop in the well.

Question 31Drilling general exam

A driller must choose a drilling fluid additive to increase the density of the mud column. Which material is most commonly used for this purpose?

  1. Barite Correct answer.
  2. Soda ash
  3. Calcium hypochlorite
  4. Diesel fuel

Explanation

Barite is a dense mineral powder added to drilling fluid specifically to raise its density and thereby increase hydrostatic pressure. Soda ash treats hardness, hypochlorite disinfects, and diesel is not a weighting agent.

Question 32Drilling general exam

Which device is installed on the discharge line of a well to prevent water from flowing backward into the well when the pump stops?

  1. Torque arrestor
  2. Check valve Correct answer.
  3. Pressure relief valve
  4. Air volume control

Explanation

A check valve allows flow in one direction only, so it holds the column of water and prevents backflow into the well when the pump shuts off. Relief valves, air controls, and torque arrestors serve different functions in the system.

Question 33Drilling general exam

A driller is bailing a cable tool hole and notices the bailer is bringing up mostly fine sand that settles slowly. What does this most likely indicate?

  1. The drilling line is too tight
  2. The hole is producing formation sand that may need a mud or casing strategy Correct answer.
  3. The bit has lost its cutting edge
  4. The walking beam is out of adjustment

Explanation

Fine sand that continues to enter the hole suggests an unstable or unconsolidated formation that may require a heavier mud, casing, or a different completion approach. Bit wear, line tension, and beam adjustment affect drilling action rather than the type of material entering the hole.

Question 34Drilling general exam

A driller is running a submersible pump and wants to avoid drawing the water level down to the pump intake. Which installation practice best addresses this concern?

  1. Setting the pump near the top of the casing
  2. Increasing the pump discharge pressure setting
  3. Reducing the size of the drop pipe
  4. Installing a low-water-level cutoff control Correct answer.

Explanation

A low-water cutoff control shuts the pump off when the water level drops to a set point, protecting the pump from running dry. Pump depth, pressure settings, and pipe size do not by themselves prevent the water level from reaching the intake.

Question 35Drilling general exam

During rotary drilling, a driller observes that the pump pressure has risen sharply while the penetration rate has dropped. Which condition is most consistent with these observations?

  1. The rotary speed is too high
  2. The formation has become softer
  3. The mud weight is too low
  4. A bit nozzle is plugged or the bit is balled up Correct answer.

Explanation

A plugged nozzle or a bit balled with clay restricts flow and reduces cutting efficiency, raising standpipe pressure while slowing penetration. Softer formation would speed penetration, and low mud weight or high rotary speed do not produce this pressure rise.

Question 36Drilling general exam

A driller is cementing casing and wants to ensure the cement slurry will displace the drilling fluid effectively in the annulus. Which practice is most important?

  1. Pumping the slurry as fast as possible without regard to volume
  2. Leaving the casing stationary during the job
  3. Using a spacer fluid and sufficient displacement volume behind the slurry Correct answer.
  4. Adding sand to the slurry to increase weight

Explanation

A spacer separates the cement from the drilling fluid and helps prevent channeling, and adequate displacement volume ensures the slurry reaches the desired height in the annulus. Speed alone, sand addition, or keeping the casing still do not guarantee good displacement.

Question 37Drilling general exam

A well is screened in a confined aquifer and the driller observes that the pumping water level stabilizes quickly at a modest drawdown. What does this most likely suggest about the aquifer?

  1. The well screen is plugged
  2. The aquifer can readily transmit water to the well Correct answer.
  3. The aquifer has very low transmissivity
  4. The static water level is falling rapidly

Explanation

A modest, stable drawdown at a given pumping rate indicates that the aquifer can supply water readily, which reflects relatively high transmissivity. Low transmissivity or a plugged screen would cause a large or steadily falling drawdown.

Question 38Drilling general exam

Which factor most directly determines the collapse strength of steel well casing?

  1. The wall thickness and diameter of the casing Correct answer.
  2. The color of the casing coating
  3. The type of pump installed
  4. The length of the casing string

Explanation

Collapse resistance depends on the geometry of the casing, chiefly wall thickness and diameter, along with the steel grade. Coating color, string length, and pump type do not determine collapse strength.

Question 39Drilling general exam

A driller is developing a new gravel-packed well and wants to remove drilling fluid and fines from the formation near the screen. Which method is most appropriate?

  1. Surge blocking and jetting with clean water Correct answer.
  2. Adding more bentonite to the annulus
  3. Increasing the mud weight and shutting in the well
  4. Backfilling the screen with drill cuttings

Explanation

Development with surge blocks or jetting uses alternating flow and clean water to loosen and flush fines and drilling fluid from the gravel pack and formation. Adding bentonite or weighting the mud would worsen blockage rather than remove it.

Question 40Drilling general exam

A driller is installing a pitless adapter on a well and must consider the frost line. What is the main reason for placing the adapter below the frost line?

  1. To increase the pumping rate of the well
  2. To allow the well to be drilled deeper
  3. To keep the discharge line from freezing where it exits the casing Correct answer.
  4. To reduce the cost of the pump

Explanation

The pitless adapter carries water through the casing wall below ground, so placing it below the frost line keeps the lateral line from freezing in cold climates. It does not affect pumping rate, pump cost, or drilling depth.

Question 41Drilling general exam

A driller is logging a borehole and notes a sudden decrease in penetration rate with a change in cuttings from sand to angular gravel. What is the most reasonable interpretation?

  1. The pump has lost its prime
  2. The bit has entered a harder or coarser formation Correct answer.
  3. The drilling fluid has become too light
  4. The rotary table speed is too low

Explanation

A drop in penetration rate accompanied by a change in cuttings is a classic indication that the bit has entered a harder or coarser unit. Fluid weight, pump prime, and rotary speed would not by themselves explain the change in cuttings type.

Question 42Drilling general exam

Which practice best reduces the risk of the drill string parting at a tool joint during deep rotary drilling?

  1. Increasing the rotary speed to the maximum
  2. Using a lighter drilling fluid
  3. Inspecting and torquing tool joints to specification Correct answer.
  4. Shortening the drill string during drilling

Explanation

Most string failures occur at tool joints, so proper inspection and torquing to the recommended makeup value reduce fatigue and connection failures. Higher rotary speed increases stress, and fluid weight or string length are not the direct controls.

Question 43Drilling general exam

A driller is testing a well with a falling-head test. Which quantity is being estimated from the rate at which the water level recovers?

  1. The casing's collapse pressure
  2. The aquifer's permeability or hydraulic conductivity near the well Correct answer.
  3. The cement's compressive strength
  4. The pump's motor horsepower

Explanation

In a falling-head test the water level is allowed to rise back toward static, and the recovery rate is used to estimate the permeability or hydraulic conductivity of the material around the well. Motor horsepower, casing strength, and cement strength are unrelated to this test.

Question 44Drilling general exam

A driller must abandon a well that is no longer in use. Which action is most consistent with proper abandonment?

  1. Sealing the well with grout or bentonite to prevent cross-contamination Correct answer.
  2. Leaving the casing open at the surface to allow drainage
  3. Removing the casing and leaving an open borehole
  4. Filling the well with sand and leaving the casing uncapped

Explanation

Proper abandonment seals the well so that surface water and water from one aquifer cannot move through the borehole to another. Leaving the well open, filling with loose sand, or pulling casing and leaving an open hole all create pathways for contamination.

Question 45Drilling general exam

A driller is setting a screen in a sand-and-gravel aquifer and must select the slot size. Which approach is most appropriate?

  1. Match the slot size to the gradation of the formation or the gravel pack Correct answer.
  2. Choose the smallest slot size available regardless of formation
  3. Choose a slot size much larger than the formation grains to maximize open area
  4. Select slot size based only on the casing diameter

Explanation

Screen slot size should be matched to the formation grain size or to the surrounding gravel pack so the pack retains the formation sand while allowing water to enter. Oversized slots pass sand, and slot size is not determined by casing diameter or by choosing the smallest opening.

Question 46Drilling general exam

A driller is calculating the volume of grout needed to seal the annular space between a 10-inch borehole and 6-inch casing to a depth of 100 feet. Which formula gives the required volume?

  1. Volume = borehole diameter × casing diameter × height
  2. Volume = π × (borehole radius² − casing radius²) × height Correct answer.
  3. Volume = π × borehole radius² × height
  4. Volume = π × casing radius² × height

Explanation

The annular volume is the difference between the borehole cross-sectional area and the casing cross-sectional area multiplied by the sealed height. Using the borehole area alone or the casing area alone gives the wrong volume, and the diameter product is dimensionally incorrect.

Question 47Drilling general exam

A driller observes that the pump in a well is cycling on and off rapidly. Which condition is the most likely cause?

  1. A screen with too much open area
  2. An oversized pressure tank or a failed check valve
  3. A pump set too deep in the well
  4. A waterlogged pressure tank or a failed check valve Correct answer.

Explanation

Rapid cycling usually means the pressure tank has lost its air charge or the check valve is leaking, so the system reaches the cut-out pressure almost immediately. A properly sized tank and a holding check valve prevent short cycling.

Question 48Drilling general exam

A driller is drilling through a cavernous limestone and the mud returns are lost completely. Which response is most appropriate to maintain hole stability and continue drilling?

  1. Continue at the same rate and wait for returns to resume
  2. Reduce pump rate and use lost-circulation materials or drill blind with water Correct answer.
  3. Add barite to the mud to seal the cavern
  4. Increase the mud weight to overcome the loss zone

Explanation

Total loss of returns in a cavernous zone calls for reducing pump output and using lost-circulation material, or drilling ahead blind with water while monitoring the hole. Increasing mud weight would worsen losses, and barite does not seal voids.

Question 49Drilling general exam

A driller is evaluating specific capacity data for two wells completed in the same aquifer. Well A yields 200 gpm at 40 feet of drawdown, and Well B yields 120 gpm at 20 feet of drawdown. Which well has the higher specific capacity?

  1. Well B, at 6 gpm per foot Correct answer.
  2. Both wells have equal specific capacity
  3. Well A, at 8 gpm per foot
  4. Well A, at 5 gpm per foot

Explanation

Specific capacity is yield divided by drawdown. Well A gives 200 ÷ 40 = 5 gpm per foot, while Well B gives 120 ÷ 20 = 6 gpm per foot, so Well B has the higher specific capacity.

Question 50Drilling general exam

A driller is planning a well in an area where nearby wells show high iron and manganese. Which completion consideration is most relevant?

  1. Setting the pump above the static water level
  2. Increasing the casing diameter to dilute the minerals
  3. Selecting materials and treatment options that resist fouling from mineral precipitation Correct answer.
  4. Using a larger slot size to flush the minerals out

Explanation

High iron and manganese can precipitate and foul screens, gravel packs, and pumps, so material selection and provision for treatment are the key planning considerations. Dilution by casing size, pump elevation, or slot size does not address mineral fouling.