CWD Quality Assurance & Improvement 3 — Questions and Answers
Question 1: Which well development method is most effective for removing drilling fluid invasion from a fine-grained sand aquifer?
- Air surge and bail
- Overpumping only
- Jetting with high-velocity water
- Chemical polyphosphate treatment followed by surging (Correct answer)
Correct answer: Chemical polyphosphate treatment followed by surging
Polyphosphate dispersants break down drilling mud filter cake in fine sands, and subsequent surging removes the loosened material from the formation.
Question 2: What is the minimum annular space required between the drill hole and casing for proper grouting under most state regulations?
- 0.5 inch
- 1 inch
- 1.5 inches
- 2 inches (Correct answer)
Correct answer: 2 inches
Most state codes require a minimum 2-inch annular space to allow complete grout emplacement without bridging or voids.
Question 3: During well construction QA, a borehole caliper log shows the drilled diameter is 2 inches smaller than specified at 80 feet depth. What is the correct response?
- Proceed with casing installation and note the discrepancy
- Ream the borehole to the required diameter before casing (Correct answer)
- Use a smaller casing to fit the undersized hole
- Grout the undersized section and drill a new hole beside it
Correct answer: Ream the borehole to the required diameter before casing
The borehole must be reamed to the specified diameter to ensure proper annular space for grouting and casing installation.
Question 4: A well's specific capacity drops 40% six months after installation. Which cause should be investigated first?
- Pump wear
- Aquifer depletion
- Biofouling or incrustation of the screen (Correct answer)
- Power supply voltage fluctuation
Correct answer: Biofouling or incrustation of the screen
A significant specific capacity decline in a relatively new well most commonly results from iron bacteria or mineral incrustation blocking the screen openings.
Question 5: What does a sand content test using a Rossum sand tester measure in a water well?
- Grain size distribution of the aquifer
- Parts per million of sand in the pumped water by volume (Correct answer)
- Hydraulic conductivity of the formation
- Turbidity in nephelometric units
Correct answer: Parts per million of sand in the pumped water by volume
The Rossum sand tester captures sand settling in a graduated tube over a timed flow to determine sand concentration in ppm by volume.
Question 6: Which grouting material provides the best resistance to aggressive (low pH) groundwater conditions?
- Neat cement grout (Correct answer)
- Bentonite pellets
- Bentonite-cement blend
- Sand-cement grout
Correct answer: Neat cement grout
Neat cement grout (without bentonite additions) has higher chemical resistance to acidic groundwater than bentonite-containing mixes.
Question 7: In quality management, what does 'root cause analysis' seek to identify?
- The employee responsible for an error
- The fundamental reason a defect or problem occurred (Correct answer)
- The cost of fixing a quality problem
- The customer's original requirements
Correct answer: The fundamental reason a defect or problem occurred
Root cause analysis identifies the underlying systemic reason a problem occurred so corrective actions prevent recurrence rather than just treating symptoms.
CWD Quality Assurance & Improvement 3
Which well development method is most effective for removing drilling fluid invasion from a fine-grained sand aquifer?