CWD Cheat Sheet 2026

The 30 highest-yield CWD facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Why is it important to use drilling mud during rotary drilling? → To cool the bit and stabilize the borehole
2. What is the PDCA cycle in CWD quality management? → Plan-Do-Check-Act: an iterative continuous improvement method
3. Which software feature in modern well-design programs helps drillers ensure casing strings do not exceed tensile yield limits? → Load case analysis and casing stress modeling
4. Fall protection is required at drilling sites when workers are exposed to a fall hazard of how many feet or more (per OSHA construction standards)? → 6 feet
5. What does an E-log (electric log) primarily measure in a borehole? → Electrical resistivity and spontaneous potential of formations
6. During a step-drawdown test, what is the primary data being collected? → Drawdown at successively increasing pumping rates
7. Under the NGWA Code of Ethics, a Certified Well Driller must represent their qualifications: → Accurately and honestly, without overstating expertise
8. Which type of risk assessment uses numerical probabilities and consequence values to calculate a quantitative risk score? → Quantitative risk assessment (QRA)
9. What is the primary purpose of conducting a bacteriological water quality test immediately after well development? → To confirm the well is free of coliform contamination before placing it in service
10. Which communication protocol is most commonly used to transfer data between downhole data loggers and surface computers in modern monitoring wells? → SDI-12, Modbus, or wireless telemetry (cellular/satellite)
11. During drilling in a known pesticide-contaminated area, workers should wear at minimum which respiratory protection? → Half-face air-purifying respirator with organic vapor cartridges
12. What should be done before starting drilling equipment? → Check equipment, surroundings, and perform safety checks
13. Why is ground stability important at a drilling site? → To prevent ground-related hazards and equipment instability
14. What is the purpose of running a borehole flowmeter (spinner log) in a completed well? → To identify which zones are contributing flow and their relative yields
15. Which scenario represents 'risk avoidance' on a well drilling project? → Selecting an alternate drill site to avoid drilling through a known contaminated zone
16. Which field measurement should be taken immediately upon collecting a groundwater sample to ensure data accuracy? → pH, temperature, specific conductance, and dissolved oxygen
17. In states using the 'riparian rights' doctrine, who has the right to use groundwater? → Landowners overlying the aquifer, who may use reasonable amounts
18. When a driller encounters a sudden increase in drilling rate (fast drilling) in otherwise tight formation, this MOST likely indicates: → A fault zone or fracture with open voids
19. Which document is typically required BEFORE a driller can legally pull a permit for a new water well in most US states? → Proof of the driller's state license or certification
20. When completing a well log for a domestic water well, what is the significance of recording the 'total depth drilled' versus 'finished well depth'? → Total drilled depth may exceed finished depth if the bottom was sealed or abandoned
21. Which communication practice is most effective when explaining technical drilling data to a non-technical client? → Use plain language, analogies, and visual aids where possible
22. When rehabilitating an old well, which test should be performed BEFORE chemical treatment to establish a baseline? → All of the above
23. What does confined aquifer mean? → An aquifer under pressure between impermeable layers
24. Which action should a driller take FIRST upon observing a rapid increase in the drilling fluid return flow rate (flowback) without increasing pump output? → Close the blowout preventer and assess for formation fluid influx
25. Which water quality parameter is used as a surrogate measure for overall mineral content dissolved in water? → Total dissolved solids (TDS)
26. When a well driller encounters unexpected contamination during drilling (e.g., petroleum odors), the first action should be to: → Stop drilling, secure the site, and notify the appropriate regulatory authority
27. The vadose zone is best defined as: → The unsaturated zone between the land surface and the water table
28. What is the primary safety hazard associated with compressed air used in air rotary drilling? → High-velocity air and cuttings discharge at the surface causing debris injuries
29. What is the function of a drilling rig’s mud pump? → To circulate drilling fluid through the system
30. A driller is working adjacent to an active agricultural field. Which risk is MOST specific to this setting? → Pesticide and fertilizer contamination of shallow groundwater