Well Development and Rehabilitation
What the exam tests
Development and rehabilitation test whether you can remove drilling damage without damaging the formation, and whether you can diagnose a declining well before recommending treatment.
Development methods
- Surging and bailing pull fines into the well and remove them; effective in screened sand and gravel.
- Jetting uses directed water to wash the screen and gravel pack.
- Air-lift development uses an airline to lift water and surge the formation; common in bedrock.
- Overpumping draws fines at high rate, but excessive rates can pack gravel or pull sand.
- Hydrofracturing injects water at high pressure to open or reconnect fractures in bedrock; it is not a cure for a collapsed screen or a sand-filled well.
- Chemical dispersants help remove clay and drilling mud; they must be compatible with the formation and flushed.
Worked example
A 6-inch bedrock well produced 15 gpm at completion but 6 gpm two years later. A downhole camera shows iron-bacteria matting on the fracture face; the pump test shows drawdown increasing at the same rate. Brush the borehole, shock-chlorinate, and surge with air. If specific capacity does not recover, hydrofracture the producing interval. Do not acidize unless the formation is carbonate and the chemistry is understood - acid in a sulfide-bearing rock can release metals and damage the pump.
Traps
Overdeveloping a fine sand well can cause permanent sand entry. Do not judge development by clear water alone; require stable specific capacity and sand-free discharge. Do not chlorinate before collecting a bacteria sample. Do not hydrofracture a well with a failed casing or ungrouted annulus - pressure will follow the path of least resistance and may migrate contamination.