Monitoring Well Post-Installation Consideration By: Pierre-Orly Dupont

Monitoring Well Monitoring Well Post-Installation Post-Installation ConsiderationConsideration

By:By:

Pierre-Orly DupontPierre-Orly Dupont

IntroductionIntroduction

►Post-Installation Considerations is Post-Installation Considerations is important for:important for: Well’s and system’s integrity.Well’s and system’s integrity. Well’s Identity.Well’s Identity. Long-term operation. Long-term operation.

Well Post-Installation Well Post-Installation considerations include:considerations include:

►Monitoring well development.Monitoring well development.►Reporting of construction details.Reporting of construction details.►Maintenance and rehabilitation.Maintenance and rehabilitation.►Abandonment (decommission).Abandonment (decommission).

Well DevelopmentWell DevelopmentGeneral

Considerations

Methods Decontamination Surveying

AirLift Surging and Pumping with

Compressed Air

Mechanical Surging

High-Pressure Water Jetting

Surface Centrifugal Pump

Submersible Pump

Surge Block Bailer

Work for most monitoring well

Variety of depth-to-water conditions

General ConsiderationsGeneral Considerations

► During installation:During installation: There can be a loss of drilling fluids when There can be a loss of drilling fluids when

encountering high permeable materials. encountering high permeable materials.

This loss This loss must be recoveredmust be recovered.. Fine materials from adjacent formation Fine materials from adjacent formation must be must be

removedremoved as they can alter the permeability of filter- as they can alter the permeability of filter-packed monitoring wells.packed monitoring wells.

Extraneous materials may be dropped into the well.Extraneous materials may be dropped into the well. Cuttings may stick to the borehole wall above water Cuttings may stick to the borehole wall above water

table (air-rotary drilling).table (air-rotary drilling). Cuttings from silt or clay can smear the borehole Cuttings from silt or clay can smear the borehole

wall (hollow stem auger).wall (hollow stem auger).

General ConsiderationsGeneral Considerations

►Goals of monitoring well development:Goals of monitoring well development: Remove fine materials (silt, clay, fine Remove fine materials (silt, clay, fine

sand).sand). Remove water lost during drilling.Remove water lost during drilling. Correct damage to the borehole wall.Correct damage to the borehole wall. Stabilize the filter pack and formationStabilize the filter pack and formation Maximize the hydraulic communication Maximize the hydraulic communication

between the well and the adjacent between the well and the adjacent formation material.formation material.

Installation of a monitoring Installation of a monitoring well should not be well should not be

considered complete until it considered complete until it has been properly has been properly

developed.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 activityWell development activity

►The application of sufficient energy to The application of sufficient energy to create ground-water flow reversals create ground-water flow reversals (surging).(surging).

►Pumping to draw water lost to the Pumping to draw water lost to the formation during drilling out of the formation during drilling out of the borehole and adjacent formation, borehole and adjacent formation, along with the fines that have been along with the fines that have been brought into the well during surging.brought into the well during surging.

Monitoring well development Monitoring well development should continue until:should continue until:

► Visibly clear water is discharged during the Visibly clear water is discharged during the active (surging) portion of the development active (surging) portion of the development process.process.

► Field-measured quality (e.g., pH, Eh, Field-measured quality (e.g., pH, Eh, conductivity) of the discharged water stabilizes conductivity) of the discharged water stabilizes and the turbidity is reduced to less than 10 and the turbidity is reduced to less than 10 Nephelometric Turbidity Units (NTU).Nephelometric Turbidity Units (NTU).

► The total volume of water discharged from the The total volume of water discharged from the well is at least equal to the estimated volume of well is at least equal to the estimated volume of fluid lost to the formation during drilling and fluid lost to the formation during drilling and well installation.well installation.

► Therefore, there are methods to accomplish Therefore, there are methods to accomplish this development.this development.


Considerations



Compressed Air

Mechanical Surging



Submersible Pump

Surge Block Bailer



Airlift Surging and Pumping with Airlift Surging and Pumping with Compressed AirCompressed Air

►Work for most monitoring wells.Work for most monitoring wells.►Should use a dual-line airlift system Should use a dual-line airlift system

instead of conventional single-line airlift.instead of conventional single-line airlift. Introduction of oil.Introduction of oil. Change in water chemistry.Change in water chemistry. May reduce hydraulic conductivity of May reduce hydraulic conductivity of

formation.formation. Difficult to controlDifficult to control

Airlift Surging and Pumping with Airlift Surging and Pumping with Compressed AirCompressed Air

►Work for most monitoring wells.Work for most monitoring wells.►Should use a dual-line airlift system Should use a dual-line airlift system

instead of conventional single-line airlift.instead of conventional single-line airlift. Introduction of oil.Introduction of oil. Change in water chemistry.Change in water chemistry. May reduce hydraulic conductivity of May reduce hydraulic conductivity of

formation.formation. Difficult to control.Difficult to control.

►Must be at least 20%-40% of Must be at least 20%-40% of submergence of the air discharge line.submergence of the air discharge line.

Determine submergenceDetermine submergence

% pumping submergence =% pumping submergence =

Length of air line below pumping water Length of air line below pumping water levellevel

Total length of air lineTotal length of air line

XX

100100

= (195/395) X 100= 50%


Considerations



Compressed Air

Mechanical Surging



Submersible Pump

Surge Block Bailer



Mechanical SurgingMechanical Surging► To force water to flow into and out of a screen by To force water to flow into and out of a screen by

operating a plunger up and down in the casing.operating a plunger up and down in the casing.


Considerations



Compressed Air

Mechanical Surging



Submersible Pump

Surge Block Bailer



Mechanical SurgingMechanical Surging

For shallow well.For shallow well.

Surface Centrifugal Surface Centrifugal PumpPump

► Can be performed only if the Can be performed only if the depth to water is within the depth to water is within the practical limit of suction lift.practical limit of suction lift. Less than 20 feet below ground Less than 20 feet below ground

surface.surface.

For wide variety of depth.For wide variety of depth.

Submersible PumpSubmersible Pump

► Pump must be Pump must be decontaminated.decontaminated.

► New, unused discharge line New, unused discharge line from the pump should be used.from the pump should be used.

► No touching ground to avoid No touching ground to avoid contamination.contamination.

► Not limited by suction lift.Not limited by suction lift.

using

Mechanical SurgingMechanical Surging

Surge BlockSurge Block► Swab.Swab.► Raising and lowering a surge Raising and lowering a surge

block heavy enough to free-fall block heavy enough to free-fall through the water.through the water.

► Dependent on the length and Dependent on the length and force of the surging strokes.force of the surging strokes.

► For deeper well, should use For deeper well, should use mechanical assistance.mechanical assistance.

► Involves only surging.Involves only surging.

BailerBailer► Useful for wells in low-yield Useful for wells in low-yield

formations.formations.► Bailer needs to clean.Bailer needs to clean.► Labor-intensive.Labor-intensive.► Require more time than other Require more time than other

methods.methods.

with


Considerations



Compressed Air

Mechanical Surging



Submersible Pump

Surge Block Bailer



High-Pressure Water JettingHigh-Pressure Water Jetting

► Required equipment is large.Required equipment is large.► Not man-portable.Not man-portable.► May be done by water or air.May be done by water or air.► Use centrifugal pumps or submersible pumps.Use centrifugal pumps or submersible pumps.► Help correct damage to the formation’s porosity Help correct damage to the formation’s porosity

and permeability.and permeability.


Considerations



Compressed Air

Mechanical Surging



Submersible Pump

Surge Block Bailer




Considerations



Compressed Air

Mechanical Surging



Submersible Pump

Surge Block Bailer



SurveyingSurveying

►Locations of monitoring wells may be Locations of monitoring wells may be plotted onto maps for developing and plotted onto maps for developing and interpreting hydrologic data.interpreting hydrologic data.

►Water-level measurements.Water-level measurements.►Ground water contour map.Ground water contour map.►Elevations (National Geodetic Vertical Elevations (National Geodetic Vertical

Datum)Datum)►GPS.GPS.►Well Identification:Well Identification:

Placing a number on protective case.Placing a number on protective case.



Reporting of construction Reporting of construction details.details.

►Results of monitoring can be affected Results of monitoring can be affected by the details of the well’s construction.by the details of the well’s construction.

►Presented in full detail as an appendix Presented in full detail as an appendix to a report.to a report.

►Report include: (page 866-817)Report include: (page 866-817) Borehole diameter.Borehole diameter. Length of screen.Length of screen. Ground surface elevation….Ground surface elevation….



Monitoring Well Maintenance Monitoring Well Maintenance and Rehabilitationand Rehabilitation

►Maintenance program: (page 870)Maintenance program: (page 870) Surface ObservationsSurface Observations Subsurface ObservationsSubsurface Observations Ground-water sample quality (wait for lab Ground-water sample quality (wait for lab

result)result)

►Rehabilitation program:Rehabilitation program: Well performance has been reduced.Well performance has been reduced. Ground-water sample quality has changed.Ground-water sample quality has changed.



Monitoring Well and Borehole Monitoring Well and Borehole Decommissioning. Decommissioning. (abandonment)(abandonment)

►One of most important post-construction One of most important post-construction of a ground-water monitoring program.of a ground-water monitoring program.

►2 main objectives to decommissioning:2 main objectives to decommissioning: Restore the borehole to its original condition.Restore the borehole to its original condition. Prevent cross-contamination between Prevent cross-contamination between

formation.formation.

►Should be planned and well document Should be planned and well document just like original well.just like original well.

Planning for Planning for DecommissioningDecommissioning

►6 key element:6 key element: State, federal or local regulations (Table State, federal or local regulations (Table

12.3)12.3)

Planning for Planning for DecommissioningDecommissioning

►6 key element:6 key element: State, federal or local regulations (Table 12.3)State, federal or local regulations (Table 12.3) Type of well or borehole to be Type of well or borehole to be

decommissioning.decommissioning. Hydrogeologic environment.Hydrogeologic environment. Chemical environment.Chemical environment. Disposal of potential contamination.Disposal of potential contamination. Type of equipment and quantity of grouting Type of equipment and quantity of grouting

needed.needed.

Decommissioning MaterialDecommissioning Material

► TYPE I Portland Cement.TYPE I Portland Cement.► Sodium bentonite.Sodium bentonite.► Use of granular, chip, or pellet forms of bentonite (when little Use of granular, chip, or pellet forms of bentonite (when little

water is present)water is present)

► Use a tremie pipe to place those materialsUse a tremie pipe to place those materials

Procedures for Procedures for DecommissioningDecommissioning

►Recheck planning of decommissioning.Recheck planning of decommissioning.►Be sure well is free of debris.Be sure well is free of debris.►Determine depth of well.Determine depth of well.►Fill the length of the screen with fine Fill the length of the screen with fine

sand.sand.►Place decommissioning material.Place decommissioning material.►Make records and reports.Make records and reports.

FINFINAny questions?Any questions?

Documents

Monitoring Well Post-Installation Consideration By: Pierre-Orly Dupont