Water well rehabilitation comprises all measures that are undertaken to restore the functionality of a well, and generally consists of various treatments or reconstruction methods. The treatment method selected must be custom-tailored, depending on the problem, well construction details and type of aquifer formation. The pump discharge pipe and distribution lines must also be cleaned when biological, chemical or physical plugging is occurring. Follow-up preventative maintenance must continue after the well rehabilitation work has been completed.
Well rehabilitation is performed when the well has deteriorated to the point where preventative maintenance procedures no longer resolve well performance issues. Rehabilitation procedures are generally initiated when the well performance has decline by about 25 per cent, and are always performed by a licensed well driller or well rehabilitation specialist.
No one treatment process or rehabilitation strategy will effectively solve every well problem. However, an experienced local well driller can be an excellent source of knowledge on common well problems in a specific geographical area. He should also be able to recommend appropriate treatment options and assist the well owner in selecting the best method of treatment and to determine if the treatment has been effective by performing a specific capacity test and comparing the results to pre-treatment conditions.
Common well problems include:
Without an understanding of the problem, there is no guarantee that the treatment method applied will be effective. The main causes of well problems are usually physical, chemical and/or biological plugging.
Mechanical and chemical cleaning are the most common methods.
Mechanical methods include wire brushing, air-lift pumping, high-pressure jetting, and surge block/swabbing.Wire Brushing
|Very Good||Good-Poor||Very Good||Poor|
|Poor-Fair||Very Poor||Good|| Moderately
|Citric Acid||Poor||Very Poor||Chelates||Poor|
|Oxalic Acid||Very Good||Good||Good|| Moderately
There are less common but often effective technologies for treating and rehabilitating a plugged well. Most of these methods require specialized equipment that is not typically used by a well drilling contractor or is not widely available in Canada.
STEP 1: Packer installed
to create a seal to allow
for injection of CO2 .
STEP 2: Carbon dioxide
injected into the well and
Carbon dioxide causes
expansion, carbonic acid
formation and freezing of water.
STEP 4: After treatment,
well is redeveloped and
tested; then returned to
Impulse generation technology involves releasing impulses of high-pressure nitrogen in short, repetitive bursts. Through controlled release of compressed nitrogen, the generator produces an impulse with a secondary expansion of gas bubbles, which causes a pressure wave to move laterally through the well screen into the surrounding aquifer formation. The expansion of the compressed gas creates an air lift effect that vibrates and loosens mechanically plugged sediment and biological deposits from the screens and surrounding aquifer. Typically, the impulse generator is used in tandem with other mechanical methods (surging and isolation pumping) operated by a drilling contractor or well treatment specialist to remove loosened sediment and biological deposits.
After a treatment process has been completed, the well must be redeveloped to remove the plugging material that has been disrupted, loosened or broken-up, and any remaining treatment chemicals. Redevelopment methods include overpumping the well, mechanical bailing, surge blocking/swabbing and air-lift pumping to restore the well capacity
Well redevelopment procedures will generally produce very turbid discharge water that contains the plugging material (i.e. mineral incrustations, biological material), sediment and residual treatment chemicals. The redevelopment process should continue until the discharge water clears.