Rural Water Resources Planner: Well Rehabilitation
PFRA Logo
PFRA Logo

Common menu bar links

Institutional links

Well Rehabilitation




What is Water Well Rehabilitation?

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.


Top of page



What is the Difference Between Preventative Maintenance and Well Rehabilitation?

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.


Top of page



What are Common Well Problems and the Basic Rehabilitation Approaches?

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:

  • Overpumping; with no evidence of well screen plugging
    • reduce pumping rate/extend pumping time; install cistern for peaking needs
  • Increased Microbiological Activity; with no decline in well yield
    • identify source of problem; pH-adjusted chlorination
  • Corrosion or Structural Failure
    • identify cause; repair or replacement of well
  • Sand Pumping
    • identify cause; redevelop well to remove sand, repair/replace well
  • Pump Failure
    • identify cause; clean pump assembly; replace faulty parts.
  • Plugging of Well Intake Area; decline in well yield
    • identify cause; select appropriate mechanical and chemical treatment methods.

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.

Rehabilitation objectives for well plugging problems

  • Must achieve effective deposit removal.
  • Must be custom-tailored to the specific problem, well construction details, and formation type.
  • Must have penetration into surrounding formation.
  • Must have good agitation.

Well rehabilitation considerations

  • Well will be off-line for 2-3 days to complete well treatment; pump must be removed.
  • Specialized equipment and trained personnel are needed to complete any rehabilitation work.
  • Both chemical and mechanical methods are generally required for an effective cleaning.
  • The type of deposit and physical condition of the well must be considered.
  • Well construction details and previous treatment/rehab work should be reviewed.

General steps for well rehabilitation

  1. Pre-Treatment Diagnostics
    • pump test, water sampling, pump removal/inspection, video inspection
  2. Mechanical Cleaning
    • dislodge and remove mineral and bacterial slime build-up
  3. Chemical Treatment
    • dissolve mineral incrustations and disrupt biological slimes for easier removal
  4. Redevelopment
    • dislodge and remove spent treatment chemicals and plugging material
  5. Post Treatment Diagnostics
    • compare to pre-treatment results to evaluate effectiveness of rehab work
  6. Chlorination
    • after rehabilitation has been completed, disinfect well and associated works

Top of page



Methods for Removal of Mineral Deposits and Biofouling Deposits

Common methods

Mechanical and chemical cleaning are the most common methods.

Mechanical methods

Mechanical methods include wire brushing, air-lift pumping, high-pressure jetting, and surge block/swabbing.

Wire Brushing
  • assists in the removal of mineral/biological buildup, increasing the effectiveness of any chemical treatments applied
wellrehab1.jpgwellrehab2.jpg

Surge Block/Swabbing
  • surging action of water loosens minerals and aquifer fines, drawing them into the well for removal
wellrehab4.jpg
wellrehab3.jpgwellrehab5.jpg

Chemical cleaning methods
  • Mineral Acids - dissolves mineral precipitates (i.e. CaCO3, Fe, Mn)
  • Organic Acids - dissolves organic compounds (i.e. biofilms)
  • Surfactants - improves penetration of treatment chemicals (i.e. biofilms)
  • Dispersants - prevents the reformation of minerals/biofilms and keeps materials in suspension for easier removal
  • Proprietary products - formulated product that contains a combination of treatment chemicals designed for specific applications
Common well cleaning acids
  Carbonate
Scale
Sulfate
Scale
Iron/Mn
Scale
Biofilm
Sulfamic
Acid
Very Good Good Fair Poor
Hydrochloric
Acid
Very Good Good-Poor Very Good Poor
Phosphoric
Acid
Very Good Good-Poor Good Poor
Hydroxyacetic
Acid
Poor-Fair Very Poor Good Moderately
Good
Citric Acid Poor Very Poor Chelates Poor
Oxalic Acid Very Good Good Good Moderately
Good
Acid concentration based on degree and type of mineral scale
  • High Carbonate/Sulfate deposition potential................... 10 - 12%
  • Some Carbonate/Sulfate or High Fe/Mn ........................ 8 - 10%
  • Moderate mineral deposition potential .......................... 6 - 8%
  • Very low or no mineral deposition; water pH below 7.0 .... 3 - 5%
  • No alkalinity; water pH below 6.0 ................................ 3%
  • Recently cleaned well; re-cleaning for biofilm removal ..... 1%
Considerations for applying chemical treatments
  • Well construction details
  • Aquifer type
  • Concentrations of various chemicals
  • Sequencing of chemicals
  • Residence time
  • Temperatures (i.e. groundwater vs treatment chemical)
Applying chemical treatments
wellrehab6.jpg
Inflatable packers used to isolate injection zone.
   wellrehab7.jpg




wellrehab8.jpg
Pouring Chemicals into Well Screen
wellrehab9.jpg
  Injection of Treatment Chemicals

Alternate Treatment Methods

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.

Utra Acid Base (UAB) treatment


wellrehab10.jpgwellrehab11.jpg

Heat and combination of chemicals used to "shock", disrupt and remove mineral/biofilm deposits

Sonar-JetTM treatment


wellrehab12.jpg wellrehab13.jpgwellrehab14.jpg

Shock waves generated by high pressure gas pulses

AQUA FREED

wellrehab15.jpg


STEP 1: Packer installed
to create a seal to allow
for injection of CO2 .




STEP 2: Carbon dioxide
injected into the well and
surrounding aquifer.




STEP 3:
Carbon dioxide causes
expansion, carbonic acid
formation and freezing of water.




STEP 4: After treatment,
well is redeveloped and
tested; then returned to
service.



AIR BURST TECHNOLOGY
swwcontent/img/wellrehab16.jpg

IMPULSE GENERATION TECHNOLOGY
wellrehab17.jpg


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.







Top of page



Well Redevelopment

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

wellrehab18.jpg
wellrehab19.jpg

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.

Observations on well rehabilitation

  • Once the cause of the problem has been identified, appropriate well rehabilitation measures can be applied.
  • Rehabilitation work will generally improve the well performance and help to extend well life.
  • Severely plugged wells are difficult to restore to their original state.
  • No treatment produces permanent results; expect deposition of minerals/biofilm to reoccur.
  • Preventative maintenance and monitoring must follow to extend time between rehabilitation work