Monitoring Well
Post-Installation Consideration
By:
Pierre-Orly Dupont
Introduction
► Post-Installation
for:
Considerations is important
 Well’s and system’s integrity.
 Well’s Identity.
 Long-term operation.
Well Post-Installation considerations
include:
► Monitoring
well development.
► Reporting of construction details.
► Maintenance and rehabilitation.
► Abandonment (decommission).
Well Development
General
Considerations
Methods
AirLift Surging and
Pumping with
Compressed Air
Mechanical Surging
Work for most
monitoring well
Variety of depth-towater conditions
Surface Centrifugal
Pump
Submersible Pump
Surge Block
Bailer
High-Pressure Water
Jetting
Decontamination
Surveying
General Considerations
► During
installation:
 There can be a loss of drilling fluids when encountering
high permeable materials.
This loss must be recovered.
 Fine materials from adjacent formation must be removed
as they can alter the permeability of filter-packed
monitoring wells.
 Extraneous materials may be dropped into the well.
 Cuttings may stick to the borehole wall above water table
(air-rotary drilling).
 Cuttings from silt or clay can smear the borehole wall
(hollow stem auger).
General Considerations
► Goals





of monitoring well development:
Remove fine materials (silt, clay, fine sand).
Remove water lost during drilling.
Correct damage to the borehole wall.
Stabilize the filter pack and formation
Maximize the hydraulic communication between
the well and the adjacent formation material.
Installation of a monitoring well
should not be considered
complete until it has been
properly developed.
In other words, developing a well involves
procedures used to maximize its yield by
attempting to restore the geologic formation
to a predrilling state.
Well development activity
► The
application of sufficient energy to
create ground-water flow reversals
(surging).
► Pumping to draw water lost to the formation
during drilling out of the borehole and
adjacent formation, along with the fines
that have been brought into the well during
surging.
Monitoring well development should
continue until:
► Visibly
clear water is discharged during the active
(surging) portion of the development process.
► Field-measured quality (e.g., pH, Eh, conductivity)
of the discharged water stabilizes and the turbidity
is reduced to less than 10 Nephelometric Turbidity
Units (NTU).
► The total volume of water discharged from the
well is at least equal to the estimated volume of
fluid lost to the formation during drilling and well
installation.
► Therefore,
there are methods to accomplish this
development.
Well Development
General
Considerations
Methods
AirLift Surging and
Pumping with
Compressed Air
Mechanical Surging
Work for most
monitoring well
Variety of depth-towater conditions
Surface Centrifugal
Pump
Submersible Pump
Surge Block
Bailer
High-Pressure Water
Jetting
Decontamination
Surveying
Airlift Surging and Pumping with
Compressed Air
► Work
for most monitoring wells.
► Should use a dual-line airlift system instead of
conventional single-line airlift.




Introduction of oil.
Change in water chemistry.
May reduce hydraulic conductivity of formation.
Difficult to control
Airlift Surging and Pumping with
Compressed Air
► Work
for most monitoring wells.
► Should use a dual-line airlift system instead of
conventional single-line airlift.




Introduction of oil.
Change in water chemistry.
May reduce hydraulic conductivity of formation.
Difficult to control.
► Must
be at least 20%-40% of submergence of
the air discharge line.
Determine submergence
% pumping submergence =
Length of air line below pumping water level
Total length of air line
X
100
= (195/395) X 100
= 50%
Well Development
General
Considerations
Methods
AirLift Surging and
Pumping with
Compressed Air
Mechanical Surging
Work for most
monitoring well
Variety of depth-towater conditions
Surface Centrifugal
Pump
Submersible Pump
Surge Block
Bailer
High-Pressure Water
Jetting
Decontamination
Surveying
Mechanical Surging
► To
force water to flow into and out of a screen by
operating a plunger up and down in the casing.
Well Development
General
Considerations
Methods
AirLift Surging and
Pumping with
Compressed Air
Mechanical Surging
Work for most
monitoring well
Variety of depth-towater conditions
Surface Centrifugal
Pump
Submersible Pump
Surge Block
Bailer
High-Pressure Water
Jetting
Decontamination
Surveying
Mechanical Surging
using
For shallow well.
For wide variety of depth.
Surface Centrifugal Pump
Submersible Pump
►
Can be performed only if the depth
to water is within the practical limit
of suction lift.
 Less than 20 feet below ground
surface.
Pump must be decontaminated.
► New, unused discharge line from
the pump should be used.
► No touching ground to avoid
contamination.
► Not limited by suction lift.
►
Mechanical Surging
with
Surge Block
►
►
►
►
►
Swab.
Raising and lowering a surge block
heavy enough to free-fall through
the water.
Dependent on the length and force
of the surging strokes.
For deeper well, should use
mechanical assistance.
Involves only surging.
Bailer
Useful for wells in low-yield
formations.
► Bailer needs to clean.
► Labor-intensive.
► Require more time than other
methods.
►
Well Development
General
Considerations
Methods
AirLift Surging and
Pumping with
Compressed Air
Mechanical Surging
Work for most
monitoring well
Variety of depth-towater conditions
Surface Centrifugal
Pump
Submersible Pump
Surge Block
Bailer
High-Pressure Water
Jetting
Decontamination
Surveying
High-Pressure Water Jetting
►
►
►
►
►
Required equipment is large.
Not man-portable.
May be done by water or air.
Use centrifugal pumps or submersible pumps.
Help correct damage to the formation’s porosity and
permeability.
Well Development
General
Considerations
Methods
AirLift Surging and
Pumping with
Compressed Air
Mechanical Surging
Work for most
monitoring well
Variety of depth-towater conditions
Surface Centrifugal
Pump
Submersible Pump
Surge Block
Bailer
High-Pressure Water
Jetting
Decontamination
Surveying
Well Development
General
Considerations
Methods
AirLift Surging and
Pumping with
Compressed Air
Mechanical Surging
Work for most
monitoring well
Variety of depth-towater conditions
Surface Centrifugal
Pump
Submersible Pump
Surge Block
Bailer
High-Pressure Water
Jetting
Decontamination
Surveying
Surveying
► Locations
of monitoring wells may be plotted
onto maps for developing and interpreting
hydrologic data.
► Water-level measurements.
► Ground water contour map.
► Elevations (National Geodetic Vertical Datum)
► GPS.
► Well Identification:
 Placing a number on protective case.
Well Post-Installation considerations
include:
► Monitoring
well development.
► Reporting of construction details.
► Maintenance and rehabilitation.
► Abandonment (decommission).
Reporting of construction details.
► Results
of monitoring can be affected by the
details of the well’s construction.
► Presented in full detail as an appendix to a
report.
► Report include: (page 866-817)
 Borehole diameter.
 Length of screen.
 Ground surface elevation….
Well Post-Installation considerations
include:
► Monitoring
well development.
► Reporting of construction details.
► Maintenance and rehabilitation.
► Abandonment (decommission).
Monitoring Well Maintenance and
Rehabilitation
► Maintenance
program: (page 870)
 Surface Observations
 Subsurface Observations
 Ground-water sample quality (wait for lab result)
► Rehabilitation
program:
 Well performance has been reduced.
 Ground-water sample quality has changed.
Well Post-Installation considerations
include:
► Monitoring
well development.
► Reporting of construction details.
► Maintenance and rehabilitation.
► Abandonment (decommission).
Monitoring Well and Borehole
Decommissioning. (abandonment)
► One
of most important post-construction of
a ground-water monitoring program.
► 2 main objectives to decommissioning:
 Restore the borehole to its original condition.
 Prevent cross-contamination between formation.
► Should
be planned and well document just
like original well.
Planning for Decommissioning
►6
key element:
 State, federal or local regulations (Table 12.3)
Planning for Decommissioning
►6
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key element:
State, federal or local regulations (Table 12.3)
Type of well or borehole to be decommissioning.
Hydrogeologic environment.
Chemical environment.
Disposal of potential contamination.
Type of equipment and quantity of grouting needed.
Decommissioning Material
►
►
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TYPE I Portland Cement.
Sodium bentonite.
Use of granular, chip, or pellet forms of bentonite (when little water is
present)
Use a tremie pipe to place those materials
Procedures for Decommissioning
► Recheck
planning of decommissioning.
► Be sure well is free of debris.
► Determine depth of well.
► Fill the length of the screen with fine sand.
► Place decommissioning material.
► Make records and reports.
FIN
Any questions?