Well Development, Testing, and Disinfection
Well Development, Testing, and Disinfection
This domain tests what happens after drilling: removing drilling fines, proving yield, and sanitizing the well. Development methods include surging, bailing, airlifting, jetting, and overpumping. The goal is to stabilize the formation around the screen and improve specific capacity without pulling in formation sand. Testing usually includes a yield or pump test with drawdown and recovery measurements, plus water-quality sampling after disinfection.
Core rules
- Development: remove fines until the water clears; avoid overdevelopment that destabilizes the gravel pack.
- Testing: measure static level, pumping level at stabilized rate, drawdown, and recovery; record time and rate.
- Disinfection: shock chlorinate to roughly 50–100 mg/L free chlorine, hold 12–24 hours, then flush; do not mix chlorine with acids or other chemicals.
- Sampling: sample for bacteria after chlorine has been flushed and the well has returned to normal operation.
Worked example
A 6-in casing holds water to 100 ft. Volume = π/4 × (0.5 ft)² × 100 = 19.6 ft³ = 147 gal. Using 5.25% household bleach (about 52,500 mg/L chlorine), to reach 100 mg/L: 147 gal × 100 ÷ 52,500 ≈ 0.28 gal. Add the bleach below the water surface, circulate, hold, and flush. The reasoning is a mass balance: target concentration times water volume divided by bleach concentration.
Traps
- Disinfecting before development is complete, so fines and bacteria are reintroduced.
- Sampling too soon after chlorination; residual chlorine masks or alters results.
- Reporting a yield from a short test as a long-term sustainable yield.
- Using scented bleach or mixing chemicals, which adds contaminants or creates hazardous gas.