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GA Well Driller practice questions

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Question 1Well Siting, Geology, and Hydrogeology

A landowner's proposed well site sits on a floodplain terrace beside a river. Which siting consideration most directly protects the well from surface contamination during high-water events?

  1. Placing the casing top above the expected flood level and sealing the annulus Correct answer.
  2. Installing a larger pressure tank to buffer flood surges
  3. Choosing a site downwind of the septic drainfield
  4. Drilling to a depth greater than 30 meters regardless of geology

Explanation

Floodwaters can overtop an unsealed wellhead and carry contaminants directly down the annulus into the aquifer. Raising the casing termination above the flood level and grouting the annular space creates a physical barrier. Depth alone does not protect a well if the head is submerged and unsealed.

Question 2Well Siting, Geology, and Hydrogeology

In an unconfined aquifer, the water level in a well that is not pumping represents which of the following?

  1. The water table at that location Correct answer.
  2. The potentiometric surface of the confined unit below
  3. The capillary fringe upper limit
  4. The land surface elevation

Explanation

In an unconfined aquifer the water table is the upper surface of the saturated zone, and a non-pumping well open to that zone will equilibrate at that level. The potentiometric surface applies to confined aquifers, where pressure head rises above the top of the unit. Capillary fringe and land surface are different references.

Question 3Well Siting, Geology, and Hydrogeology

A driller encounters a thick, laterally continuous layer of dense clay above a sand aquifer. What is the primary hydrogeologic significance of this layer for well design?

  1. It eliminates the need for grouting the annulus
  2. It guarantees high yield because clay transmits water readily
  3. It acts as a confining unit that limits vertical recharge to the sand Correct answer.
  4. It indicates the sand below is unconfined

Explanation

Dense clay has very low permeability and functions as a confining layer, restricting vertical leakage between units. Recognizing it helps the driller anticipate confined conditions and design casing and screen intervals accordingly. Clay does not transmit water readily and does not remove the need for annular seals.

Question 4Well Siting, Geology, and Hydrogeology

Which rock type is most likely to yield usable quantities of groundwater through fractures rather than primary pore space?

  1. Clean beach sand
  2. Well-sorted river gravel
  3. Pumice fall deposit
  4. Crystalline granite Correct answer.

Explanation

Crystalline igneous and metamorphic rocks such as granite have minimal primary porosity, so groundwater is stored and transmitted mainly in fractures and joints. Successful wells depend on intersecting fracture networks. The other options are granular materials with intergranular porosity.

Question 5Well Siting, Geology, and Hydrogeology

A driller needs to estimate the static water level before pump installation. Which method provides a direct measurement in an open borehole?

  1. Estimating from the topographic map contour
  2. Calculating from the driller's log of cuttings
  3. Reading the pressure gauge on the pump
  4. Lowering a calibrated electric water-level tape Correct answer.

Explanation

An electric water-level tape with a conductivity probe gives a direct, accurate depth-to-water measurement in an open or cased borehole. Cuttings logs, topographic contours, and pump gauges are indirect or unrelated to static level. Direct measurement is the standard for setting pump depth and baseline monitoring.

Question 6Well Siting, Geology, and Hydrogeology

What does a specific capacity value express for a pumping well?

  1. Depth of the well below land surface
  2. Total volume of water stored in the aquifer
  3. Rate of recharge from precipitation
  4. Yield per unit of drawdown, such as liters per minute per meter Correct answer.

Explanation

Specific capacity is the pumping rate divided by the resulting drawdown, typically reported as flow per unit drawdown. It is a practical index of well efficiency and aquifer transmissivity. It is not a storage volume, recharge rate, or depth.

Question 7Well Siting, Geology, and Hydrogeology

Why is a sanitary seal required at the top of a drilled well?

  1. To increase the pumping rate of the well
  2. To prevent surface water and shallow contamination from entering the annulus Correct answer.
  3. To anchor the drop pipe to the casing
  4. To reduce the electrical load on the pump motor

Explanation

The sanitary seal closes the space between the casing and the wellhead so that surface runoff, insects, and shallow contaminated water cannot enter the well. It is a public-health and water-quality requirement. It does not affect pump performance or pipe support.

Question 8Well Siting, Geology, and Hydrogeology

A well is screened across the water table in a sandy unconfined aquifer. During pumping, the water level near the well falls below the top of the screen. What condition does this create?

  1. Reversal of regional groundwater flow
  2. A rise in the potentiometric surface
  3. Artesian flow into the casing
  4. Cascading water and possible air entrainment in the pump intake Correct answer.

Explanation

When drawdown drops the water level below the screen top, water falls through the unsaturated screen and can entrain air, causing cascading and pump cavitation or loss of efficiency. The driller should set the pump and screen so the intake stays submerged. Artesian flow and regional flow reversal are unrelated to this local effect.

Question 9Well Siting, Geology, and Hydrogeology

A driller logs a borehole and finds 40 meters of sand and gravel overlying fractured shale. The static water level rises 6 meters above the top of the sand when the borehole is cased through the sand. What does this indicate?

  1. The sand is unconfined and receiving direct recharge
  2. The shale is the producing zone
  3. The water level measurement is erroneous
  4. The sand is confined and its head is above the top of the unit Correct answer.

Explanation

A water level that rises above the top of a permeable unit indicates confined conditions, with the measured level representing the potentiometric surface. The sand is the aquifer and its head exceeds the top of the unit. This is a normal confined response, not an error.

Question 10Well Siting, Geology, and Hydrogeology

Two wells are 100 meters apart in a homogeneous sand aquifer with a hydraulic gradient of 0.005. Using Darcy's law with a hydraulic conductivity of 10 m/day, what is the approximate specific discharge between them?

  1. 0.05 m/day Correct answer.
  2. 50 m/day
  3. 0.5 m/day
  4. 5 m/day

Explanation

Darcy's law gives specific discharge as conductivity times gradient: 10 m/day times 0.005 equals 0.05 m/day. Distance between wells does not enter this calculation for specific discharge. The result is a velocity-like flux, not a total volume.

Question 11Well Siting, Geology, and Hydrogeology

A well produces cloudy water containing fine sand shortly after pumping begins, and the problem clears after several minutes. Which condition best explains this behavior?

  1. The aquifer is confined and the head is dropping
  2. Fine particles accumulated in the casing and screen during non-pumping periods are being flushed Correct answer.
  3. The pump intake is set above the static water level
  4. The well is overpumped beyond its safe yield

Explanation

Fine material that settles in the casing, screen, or gravel pack during idle periods is often expelled when pumping resumes, causing temporary turbidity that clears. Persistent turbidity would suggest formation damage, poor development, or excessive velocity. Overpumping and intake placement cause different symptoms such as sustained drawdown.

Question 12Well Siting, Geology, and Hydrogeology

A driller is siting a well on a hillside underlain by limestone. Which feature most warrants investigation before drilling?

  1. Thickness of the soil A horizon
  2. Presence of solution channels or sinkholes that could route surface contamination rapidly Correct answer.
  3. Slope aspect relative to prevailing wind
  4. Depth of frost penetration

Explanation

Karst limestone can contain solution channels and sinkholes that transmit surface water and contaminants rapidly with little filtration. Siting must avoid direct connections to such features. Soil horizon thickness, wind aspect, and frost depth are not primary contamination-pathway concerns.

Question 13Well Siting, Geology, and Hydrogeology

What is the purpose of a pump test conducted at a constant discharge rate?

  1. To measure the casing diameter needed
  2. To measure the aquifer's response and estimate transmissivity and storativity Correct answer.
  3. To determine the mineral content of the water
  4. To establish the depth of the water table before drilling

Explanation

A constant-rate pump test measures drawdown over time, and the resulting curve is analyzed to estimate aquifer properties such as transmissivity and storativity. It also informs safe yield and well efficiency. It does not measure water chemistry or determine casing size.

Question 14Well Siting, Geology, and Hydrogeology

A driller observes that the water level in a new well continues to rise slowly for several hours after drilling stops. What is the most likely explanation?

  1. The water level is equilibrating toward the static level after disturbance by drilling Correct answer.
  2. The pump is running at too high a rate
  3. The well screen is clogged
  4. The aquifer is being recharged by the drilling fluid

Explanation

Drilling disturbs the water level, and after drilling stops the level recovers toward the true static level as the aquifer equilibrates. Slow recovery can also indicate low-permeability material. The driller should wait for stabilization before measuring static level.

Question 15Well Siting, Geology, and Hydrogeology

Which factor most strongly controls the sustainable yield of a well completed in a confined sandstone aquifer?

  1. The depth of the casing shoe
  2. Transmissivity and the available drawdown to the top of the aquifer Correct answer.
  3. The diameter of the drill bit used
  4. The color of the sandstone

Explanation

Sustainable yield depends on the aquifer's ability to transmit water (transmissivity) and on how much drawdown is available before the head falls below the top of the confined unit or the pump intake. Rock color, bit diameter, and casing shoe depth do not govern yield.

Question 16Well Siting, Geology, and Hydrogeology

A driller plans a well near a stream in a valley fill of sand and gravel. Which siting approach best uses the stream as a recharge source while protecting water quality?

  1. Set the well back from the bank and screen the gravel adjacent to the stream Correct answer.
  2. Site the well immediately downgradient of a barnyard
  3. Drill through the gravel into the underlying bedrock only
  4. Place the well in the streambed itself

Explanation

A well set back from the bank and screened in stream-adjacent gravel can induce infiltration of stream water, providing reliable yield while allowing some bank filtration. Placing the well in the streambed or near a contamination source compromises water quality. Drilling only into bedrock may miss the productive gravel aquifer.

Question 17Well Siting, Geology, and Hydrogeology

What does a low specific yield value indicate for an unconfined aquifer?

  1. A large volume of water is released per unit decline in the water table
  2. The aquifer is confined
  3. The aquifer has no transmissivity
  4. A small volume of water drains from storage per unit decline in the water table Correct answer.

Explanation

Specific yield is the drainable porosity of an unconfined aquifer, representing the volume of water released per unit area per unit decline in the water table. A low value means little water drains from storage for a given decline. It does not imply confinement or zero transmissivity.

Question 18Well Siting, Geology, and Hydrogeology

A driller encounters a layer of gravel containing iron staining and a sulfurous odor. What does this most likely suggest about the groundwater chemistry?

  1. The water is likely oxygenated and free of dissolved metals
  2. The water may be anoxic and contain dissolved iron and sulfide Correct answer.
  3. The gravel is impermeable
  4. The water is suitable for immediate potable use without testing

Explanation

Iron staining and a sulfurous odor indicate reducing, anoxic conditions where dissolved iron and sulfide are present. Such water typically requires treatment and testing before use. The presence of staining does not indicate high permeability or suitability without testing.

Question 19Well Siting, Geology, and Hydrogeology

A well is sited in a fractured basalt terrain. Which exploration method is most appropriate for locating a productive fracture zone before drilling?

  1. Measuring soil pH at the surface
  2. Measuring wind speed across the site
  3. Counting the number of surface boulders
  4. Electrical resistivity or electromagnetic surveys to detect fracture-related conductivity contrasts Correct answer.

Explanation

Geophysical methods such as electrical resistivity or electromagnetics can detect contrasts related to fractures, moisture, and clay-filled zones in basalt. These surveys help target drilling locations. Surface pH, boulder counts, and wind measurements do not locate subsurface fractures.

Question 20Well Siting, Geology, and Hydrogeology

A well in a confined aquifer shows a static water level 15 meters above the top of the aquifer but 3 meters below land surface. What type of well is this?

  1. A non-flowing artesian well Correct answer.
  2. A dug well
  3. A flowing artesian well
  4. An unconfined water-table well

Explanation

The well is artesian because the head rises above the top of the confined aquifer, but it does not flow at the surface because the head is below land surface. A flowing artesian well would have a head above land surface. Unconfined and dug wells do not match the described head conditions.

Question 21Well Siting, Geology, and Hydrogeology

A driller is asked to evaluate whether a proposed well could cause interference with a neighboring well 50 meters away. Which approach is most technically sound?

  1. Compare the proposed pumping rate against the neighbor's casing diameter
  2. Estimate the drawdown cone using aquifer properties and distance, considering pumping rates and durations Correct answer.
  3. Measure the color of the water in both wells
  4. Assume interference is negligible because the wells are more than 10 meters apart

Explanation

Interference depends on aquifer transmissivity and storativity, pumping rates, durations, and distance between wells. Estimating the drawdown cone with these parameters allows a defensible assessment. Casing diameter, arbitrary separation distances, and water color do not quantify interference.

Question 22Well Siting, Geology, and Hydrogeology

A well completed in a sand aquifer shows a step-drawdown response in which drawdown increases sharply at higher pumping rates. What does this most likely indicate?

  1. A decrease in aquifer transmissivity with depth
  2. A rise in the regional water table
  3. An increase in specific yield at high rates
  4. Well losses from turbulent flow near the screen or gravel pack Correct answer.

Explanation

Nonlinear increases in drawdown at higher rates indicate well losses, often from turbulent flow near the screen, gravel pack, or pump intake. A step-drawdown test separates these well losses from aquifer losses. Transmissivity and specific yield are aquifer properties that do not change in this manner with rate.

Question 23Well Siting, Geology, and Hydrogeology

A driller observes that a proposed well location lies on a topographic divide between two drainage basins. What is the primary hydrogeologic implication for groundwater flow direction?

  1. Groundwater will flow only vertically upward
  2. Groundwater will flow inward toward the divide from both sides
  3. Groundwater will not move at all beneath the divide
  4. Groundwater will generally flow outward from the divide toward each basin Correct answer.

Explanation

Topographic divides commonly coincide with groundwater divides, so shallow groundwater flows outward from the high ground toward the adjacent drainage basins. This affects recharge capture and potential contamination pathways. Groundwater still moves under the divide; it does not stagnate or flow only upward.

Question 24Well Siting, Geology, and Hydrogeology

A well is to be sited in an area where a previous well encountered a thick sequence of swelling clay. Which construction concern is most relevant?

  1. The clay will increase the transmissivity of the aquifer
  2. The clay eliminates the need for a sanitary seal
  3. The clay may swell and damage casing or reduce the annulus, requiring careful casing and grouting design Correct answer.
  4. The clay indicates the aquifer is unconfined

Explanation

Expansive clays can swell against casing, deform the borehole, and complicate grouting, so casing and annulus design must account for these movements. The clay does not enhance transmissivity or indicate unconfined conditions, and the sanitary seal remains required.

Question 25Well Design and Construction

Under typical state well construction rules, what is the primary purpose of the annular seal (grout) placed between the borehole wall and the casing?

  1. To protect the casing from corrosion by formation fluids
  2. To hold the casing centered during gravel packing
  3. To increase the pumping rate of the finished well
  4. To prevent surface and shallow groundwater from migrating down the annulus Correct answer.

Explanation

The annular seal is a barrier that stops contaminated water and surface runoff from moving vertically down the space outside the casing into the producing zone. Centering is done by centralizers, and corrosion protection or yield improvement are not the purpose of the seal.

Question 26Well Design and Construction

A driller is setting a well screen in a clean sand aquifer. Which screen opening size is generally selected?

  1. Sized to match the inside diameter of the riser pipe
  2. Sized as small as manufacturing allows to block all particles
  3. Sized larger than the median grain size so sand freely enters the well
  4. Sized to retain a large percentage of the formation sand while allowing fines to be developed out Correct answer.

Explanation

Screen openings are chosen so the formation is partly retained while fine material can be removed during development, leaving a stable filter pack around the screen. Oversizing admits sand, and making openings as small as possible plugs the screen and reduces yield.

Question 27Well Design and Construction

What is the standard reason for installing a gravel pack around a well screen in a fine-grained sand formation?

  1. To allow the use of a smaller diameter borehole
  2. To increase the effective open area and stabilize the formation near the screen Correct answer.
  3. To raise the static water level in the well
  4. To eliminate the need for an annular seal

Explanation

A properly graded gravel envelope keeps formation sand from moving into the well while providing high permeability close to the screen. It does not change static water level and does not replace the annular seal.

Question 28Well Design and Construction

Which casing material is most commonly specified for a municipal well where the water is aggressive (low pH, elevated chloride) and long service life is required?

  1. Corrosion-resistant alloy or coated steel casing Correct answer.
  2. Thermoplastic (PVC) casing
  3. Galvanized sheet-metal casing
  4. Asbestos-cement casing

Explanation

Aggressive water attacks mild and galvanized steel, so corrosion-resistant alloys or properly coated steel are specified for long-life municipal wells. PVC has strength limits at larger diameters and depths, and asbestos-cement is largely obsolete.

Question 29Well Design and Construction

During grouting of a well annulus, what is the purpose of pumping grout from the bottom up (tremie method) rather than pouring from the top?

  1. To reduce the volume of grout needed
  2. To displace drilling fluid upward and avoid voids or bridging in the seal Correct answer.
  3. To keep the casing from floating
  4. To speed up the set time of the cement

Explanation

Bottom-up placement pushes drilling mud and cuttings ahead of the grout so the annulus fills continuously without voids or bridging. Top-down pouring can channel through the fluid and leave gaps in the seal.

Question 30Well Design and Construction

A well is completed with the screen set opposite a confined sand aquifer. What is the main function of the filter pack in this setting?

  1. To support the weight of the pump column
  2. To seal off the aquifer from the surface
  3. To provide a reservoir of water for peak demand
  4. To prevent formation sand from entering the screen while allowing water to flow Correct answer.

Explanation

The filter pack acts as a graded transition that holds back formation particles while transmitting water to the screen. Sealing from surface water is the job of the annular seal, and the pack is not a structural support or storage reservoir.

Question 31Well Design and Construction

A driller is designing a well in a fractured bedrock aquifer. Which completion approach is most appropriate?

  1. Open-hole completion through the producing fracture zones Correct answer.
  2. Casing and gravel pack through every fracture
  3. Slotted casing set only in the overburden
  4. Full-length screen from surface to total depth

Explanation

In stable fractured rock, an open-hole interval lets water from fractures enter directly without a screen, which would otherwise block or clog. Screens and gravel packs are used in unconsolidated formations, not competent bedrock.

Question 32Well Design and Construction

What does the term "well development" refer to in well construction?

  1. The legal process of obtaining a water right for the well
  2. The process of removing drilling fluids and fines from the formation near the screen to improve yield Correct answer.
  3. The survey work that sets the well location
  4. The step of installing the pump and pressure tank

Explanation

Development clears mud, cuttings, and fine particles from the gravel pack and formation so the well produces clear water at its potential rate. It is a physical cleaning process, not a legal, mechanical, or surveying step.

Question 33Well Design and Construction

Which development method is best suited to a well completed in a clay-rich, low-permeability formation where gentle cleaning is needed?

  1. Surge blocking with a plunger Correct answer.
  2. Overpumping at several times design yield
  3. High-pressure jetting at maximum pressure
  4. Air-lift development at high rate

Explanation

Surge blocking with a plunger works the water back and forth gently through the screen, loosening fines without damaging the formation. High-energy jetting, air lifting, or overpumping can mobilize clay and collapse the pack in soft formations.

Question 34Well Design and Construction

A well is to be constructed so that the casing extends a minimum distance above the ground surface. What is the main reason for this requirement?

  1. To provide space for the pressure gauge
  2. To keep surface water and debris from entering the well Correct answer.
  3. To allow the casing to expand with temperature
  4. To raise the pump above the water table

Explanation

Extending casing above grade, often with a seal or cap, prevents runoff, insects, and debris from entering the well. It has nothing to do with pump elevation, thermal expansion, or gauge mounting.

Question 35Well Design and Construction

What is the purpose of a well cap or sanitary seal at the top of a completed well?

  1. To increase the well's static water level
  2. To provide a watertight barrier against contamination while allowing access for service Correct answer.
  3. To anchor the drop pipe to the casing
  4. To filter sediment from the pumped water

Explanation

A sanitary seal closes the top of the casing against surface contamination and vermin while permitting venting and access. It does not alter water level, filter water, or support the drop pipe.

Question 36Well Design and Construction

A driller must choose a casing diameter for a well that will house a submersible pump. Which factor most directly sets the minimum inside diameter?

  1. The depth of the static water level
  2. The outside diameter of the pump and motor plus clearance for the drop pipe and cable Correct answer.
  3. The diameter of the drill bit used to drill the borehole
  4. The height of the casing above ground

Explanation

The casing must be large enough for the pump, motor, drop pipe, and cable to pass and operate with clearance. Bit size, casing height, and water level do not set the minimum inside diameter.

Question 37Well Design and Construction

Why is a pilot hole sometimes drilled before reaming a large-diameter well?

  1. To establish stratigraphy and verify depth before enlarging the borehole Correct answer.
  2. To reduce the total amount of drilling required
  3. To install the final casing in one pass
  4. To avoid the need for an annular seal

Explanation

A pilot hole reveals the formations, water-bearing zones, and total depth so the driller can plan the reamed diameter and completion. It does not reduce drilling, install final casing, or eliminate sealing.

Question 38Well Design and Construction

Which statement best describes the purpose of centralizers on a well casing?

  1. They filter sand from the formation
  2. They keep the casing centered in the borehole so the annular seal has uniform thickness Correct answer.
  3. They increase the collapse strength of the casing
  4. They measure the depth of the borehole

Explanation

Centralizers hold the casing away from the borehole wall so grout forms a continuous, even seal around the casing. They do not add strength, filter sand, or measure depth.

Question 39Well Design and Construction

A well penetrates two aquifers, one shallow and contaminated, and one deep and clean. What construction feature is essential to protect the deep aquifer?

  1. A larger screen in the shallow aquifer
  2. A gravel pack that extends through both aquifers
  3. A shorter casing string that stops above the shallow aquifer
  4. A continuous annular seal from the surface past the shallow aquifer Correct answer.

Explanation

A continuous seal across the contaminated zone prevents it from migrating down the annulus into the clean aquifer. Screens, short casing, or a continuous gravel pack would create a pathway for contamination.

Question 40Well Design and Construction

What is the primary function of a well screen in an unconsolidated sand aquifer?

  1. To measure the flow rate of the well
  2. To hold back the gravel pack and formation while allowing water to enter Correct answer.
  3. To prevent corrosion of the riser pipe
  4. To increase the strength of the casing string

Explanation

The screen is a permeable barrier that supports the filter pack and formation while letting water pass into the well. It is not a strength member, a corrosion control, or a flow meter.

Question 41Well Design and Construction

Which condition most strongly favors using a naturally developed well rather than a gravel-packed well?

  1. A uniform fine sand that produces sand with any screen
  2. A formation with a wide, well-graded grain-size distribution that can stabilize itself Correct answer.
  3. A fractured granite aquifer
  4. A formation with high clay content

Explanation

A well-graded formation can be developed so the coarse grains form a natural filter around the screen, avoiding the cost of a gravel pack. Uniform fine sands, clay-rich zones, and fractured rock are handled differently.

Question 42Well Design and Construction

What does a driller check by measuring the static water level in a newly completed well?

  1. The non-pumping water level that indicates the aquifer's natural head Correct answer.
  2. The depth of the screen
  3. The pumping rate of the well
  4. The thickness of the gravel pack

Explanation

Static water level is the water level when the well is not being pumped and reflects the natural head of the aquifer. It does not measure yield, screen depth, or pack thickness.

Question 43Well Design and Construction

A well is completed with the screen set too high relative to the producing zone. What is the most likely result?

  1. Increased yield because the pump is set shallower
  2. Improved sand control because the screen is above the fines
  3. No effect on yield because water rises to the screen
  4. Reduced yield because the screen does not intersect the most permeable water-bearing material Correct answer.

Explanation

The screen must be positioned opposite the most productive water-bearing material to capture flow. Setting it too high misses that zone and reduces yield, regardless of pump depth or sand control.

Question 44Well Design and Construction

Which practice helps ensure a proper annular seal when the borehole is larger than the casing?

  1. Using a grout volume calculated to fill the measured annular space plus an allowance for loss Correct answer.
  2. Using only the cuttings that fall back around the casing
  3. Pouring dry cement from the surface until it stops
  4. Filling the annulus with water before grouting

Explanation

Grout volume should be computed from the measured borehole and casing diameters with an allowance for loss to voids, so the seal is complete. Dry pouring, relying on cuttings, or pre-filling with water does not produce a reliable seal.

Question 45Well Design and Construction

What is the purpose of a drive shoe on the bottom of a casing string?

  1. To measure the depth of the borehole
  2. To provide a hardened cutting edge that protects the casing as it is driven Correct answer.
  3. To filter sand from entering the well
  4. To connect the screen to the riser

Explanation

A drive shoe is a hardened ring on the casing bottom that takes the driving impact and cuts through the formation. It does not filter, connect the screen, or measure depth.

Question 46Well Design and Construction

In a well completed with a gravel pack, what does the term "pack thickness" refer to?

  1. The depth of the casing below the surface
  2. The wall thickness of the casing
  3. The length of the screen interval
  4. The radial distance between the borehole wall and the screen Correct answer.

Explanation

Pack thickness is the annular width of gravel around the screen, measured radially from the borehole wall to the screen. It is not a length, a casing depth, or a casing wall dimension.

Question 47Well Design and Construction

Which construction choice most directly reduces the risk of the casing collapsing in a deep well?

  1. Increasing the diameter of the screen
  2. Selecting casing with adequate wall thickness and collapse rating for the expected external pressure Correct answer.
  3. Shortening the annular seal
  4. Using a larger gravel pack

Explanation

Collapse resistance depends on casing wall thickness and material grade matched to the external pressure at depth. Screen diameter, seal length, and pack size do not determine collapse strength.

Question 48Well Design and Construction

What does a driller do during well development if the water being pumped remains turbid after extended effort?

  1. Add more grout to the annulus
  2. Increase the pumping rate until the sand clears
  3. Stop development and accept the turbidity
  4. Assess whether the screen or pack design is admitting formation fines and adjust the development method Correct answer.

Explanation

Persistent turbidity usually signals that fines are passing the screen or pack, so the driller evaluates the design and changes the development approach. Simply pumping harder, giving up, or adding grout does not solve the cause.

Question 49Well Design and Construction

Which factor is most important when deciding the depth to set the pump intake in a new well?

  1. The diameter of the gravel pack
  2. The expected pumping water level plus a margin so the pump does not break suction Correct answer.
  3. The color of the formation cuttings
  4. The height of the casing above ground

Explanation

The pump intake must stay submerged below the pumping water level, with a safety margin for drawdown and seasonal changes. Casing height, pack diameter, and cuttings color do not govern pump setting depth.

Question 50Well Design and Construction

A driller is selecting screen slot size for a naturally developed well in a uniform fine sand aquifer. Which criterion best guides the slot opening?

  1. Slot opening sized to retain about 90 percent of the formation sand so the aquifer is not disturbed
  2. Slot opening sized to retain roughly 40 percent of the formation sand by weight, allowing the finer fraction to be developed out Correct answer.
  3. Slot opening sized equal to the largest grain diameter present in the aquifer sample
  4. Slot opening sized larger than the median grain diameter so the formation can flow freely into the well

Explanation

For natural development, the slot is chosen so that a controlled portion of the fine material can be drawn out and the coarser framework grains remain to form a stable filter. Retaining roughly 40 percent of the formation sample by weight is the standard design target. Slot openings much tighter than this prevent development, while oversized slots allow the whole formation to move.