Design of High Capacity Design of High Capacity Energy Efficient Wells Energy Efficient Wells Jay Lazarus, Jim Riesterer, P.G. Jay Lazarus, Jim Riesterer, P.G. Glorieta Geoscience, Inc. Glorieta Geoscience, Inc. PO Box 5727 PO Box 5727 Santa Fe NM 87502 Santa Fe NM 87502 www.glorietageo.com www.glorietageo.com Waste to Worth Conference April 2-4, 2013 Waste to Worth Conference April 2-4, 2013 GLORIETA GEOSCIENCE, INC.
Design of High Capacity Energy Efficient Wells
May 25, 2015
For more: http://www.extension.org/63747 Agriculture is the largest user of ground water in the United States. Ground water at dairies is used for cow drinking, milking parlor clean-up and crop irrigation. Ground water is produced from wells that often are improperly designed and completed. Inefficient well design, including improperly sized pumps, results in increased pumping costs and increases the frequency that wells and/or pumps have to be replaced. Inefficient wells require significantly more energy to pump lesser amounts of water than properly designed wells. Sand production from unconsolidated or poorly-consolidated aquifers reduces the effective life of the well and pump. Sand production is significantly reduced by properly sizing the well screen and filter pack. Pilot holes are drilled so grain size analyses can be conducted and well screen and filter pack can be properly sized. Geophysical logs may be utilized to identify zones of maximum potential production. The pilot holes are reamed out to the design diameter and the well is constructed with an optimal screen and filter pack combination. Efficient wells are designed with maximum open-area and proper filter packs, so well screens are not dewatered and the well does not pump sand or air. Production tests on the completed well allow the pump motor and bowls to be sized and set to a depth that will maximize pump efficiency and water production while minimizing power costs. An efficient, sand-free well will save a farmer significant money on energy costs to produce water, and the well and pump lifetime will be extended significantly. Water wells should be designed carefully to maximize well and pump efficiency in order to conserve energy and not produce sand.
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Design of High Capacity Energy Design of High Capacity Energy Efficient WellsEfficient Wells
Jay Lazarus, Jim Riesterer, P.G.Jay Lazarus, Jim Riesterer, P.G.Glorieta Geoscience, Inc.Glorieta Geoscience, Inc.
PO Box 5727PO Box 5727
Santa Fe NM 87502Santa Fe NM 87502
www.glorietageo.com www.glorietageo.com
Waste to Worth Conference April 2-4, 2013Waste to Worth Conference April 2-4, 2013
GLORIETA GEOSCIENCE, INC.
Efficient Water Use At DairiesEfficient Water Use At Dairies Agriculture is the largest user of groundwater in the Agriculture is the largest user of groundwater in the
United StatesUnited States Ground water at dairies used for cow drinking, milking Ground water at dairies used for cow drinking, milking
parlor clean-up and crop irrigation is produced from wells parlor clean-up and crop irrigation is produced from wells that often are often improperly designed and completed.that often are often improperly designed and completed.
Inefficient well design results in increased pumping costs Inefficient well design results in increased pumping costs and increases the frequency that wells and/or pumps and increases the frequency that wells and/or pumps have to be replaced. have to be replaced.
Inefficient wells require significantly more energy to Inefficient wells require significantly more energy to pump lesser amounts of water than properly designed pump lesser amounts of water than properly designed wells.wells.
GLORIETA GEOSCIENCE, INC.
GLORIETA GEOSCIENCE, INC.
Well DrillingWell Drilling
Types of WellsTypes of Wells
GLORIETA GEOSCIENCE, INC.
DomesticDomestic MunicipalMunicipal CommercialCommercial IrrigationIrrigation
Types of screenTypes of screen
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Torch cutTorch cut Plasma cutPlasma cut Saw cut (PVC)Saw cut (PVC) Mill slotMill slot Wire wrappedWire wrapped LouveredLouvered
Photo from johnsonscreens.com
Well EfficiencyWell EfficiencyInefficient well:Inefficient well:•Limited open areaLimited open area•Incorrect/no filter packIncorrect/no filter pack•Screens get dewateredScreens get dewatered•Pumps sand and/or airPumps sand and/or air•Oversized pump motorOversized pump motor•Artificially high total dynamic headArtificially high total dynamic head
Efficient well:Efficient well:•Maximize open areaMaximize open area•Proper filter packProper filter pack•Screens are not dewateredScreens are not dewatered•Does not pump sand and/or airDoes not pump sand and/or air•Properly sized pump motorProperly sized pump motor•Minimizes total dynamic headMinimizes total dynamic head
Why is Well Efficiency Important?Why is Well Efficiency Important?
GLORIETA GEOSCIENCE, INC.
Energy cost savingsEnergy cost savings An efficient, sand-free well will save a An efficient, sand-free well will save a
farmer significant money on energy costs farmer significant money on energy costs to produce the water and the well and to produce the water and the well and pump lifetime will be extended pump lifetime will be extended significantly.significantly.
When Does a Pump Fail?When Does a Pump Fail?
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When you need it the most…..When you need it the most…..
During the hottest time of the irrigation During the hottest time of the irrigation season…..season…..
When the pump contractor is servicing a When the pump contractor is servicing a municipal well for a bigger client…..municipal well for a bigger client…..
Why Does a Pump Fail?Why Does a Pump Fail?
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Old AgeOld Age Excessive sand productionExcessive sand production Excessive drawdown Excessive drawdown
Water not cooling the pump effectivelyWater not cooling the pump effectively Air entrainment Air entrainment Cavitation Cavitation
Other…Other…
What Causes Sand Production?What Causes Sand Production?
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Improper Improper screen/filter screen/filter pack sand pack sand sizessizes
Casing failure Casing failure (bad welds, (bad welds, corrosion)corrosion)
Screen PlacementScreen Placement
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Best production intervalsBest production intervals Allow sufficient water column above Allow sufficient water column above
screen to prevent dewatering screensscreen to prevent dewatering screens Include margin for long-term drawdownInclude margin for long-term drawdown
Well Screen DesignWell Screen Design
GLORIETA GEOSCIENCE, INC.
Slot sizeSlot size Slot geometrySlot geometry Filter packFilter pack
Sized in conjunction with sieve analysis of Sized in conjunction with sieve analysis of formation material and screen slot sizeformation material and screen slot size
Increases hydraulic conductivity, reduces Increases hydraulic conductivity, reduces (eliminates) sand production(eliminates) sand production
Total open areaTotal open area
Well DevelopmentWell Development
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Removes drilling fluid from filter pack and Removes drilling fluid from filter pack and formation (increases production)formation (increases production)
Removes fines from filter pack, properly Removes fines from filter pack, properly grades filter pack and formation for long grades filter pack and formation for long term sand-free productionterm sand-free production
Photo from Driscoll, 1986
GLORIETA GEOSCIENCE, INC.
Defined as production rate per unit of Defined as production rate per unit of drawdown (Q/s) drawdown (Q/s) Typically expressed as gpm/ftTypically expressed as gpm/ft The bigger the number the better the wellThe bigger the number the better the well
Allows well to be designed in a manner Allows well to be designed in a manner that will avoid dewatering screensthat will avoid dewatering screens Often must estimate Q/s in design phase Often must estimate Q/s in design phase
based on nearby wells or lithologic based on nearby wells or lithologic analoguesanalogues
Confirm actual Q/s with test pumpConfirm actual Q/s with test pumpprior to selecting permanent pumpprior to selecting permanent pump
Specific CapacitySpecific Capacity
Directly impacts pumping costsDirectly impacts pumping costs
Specific CapacitySpecific Capacity
Proper screen and filter pack selectionProper screen and filter pack selection Proper screen locationsProper screen locations Proper well developmentProper well development Up front costs associated with these items Up front costs associated with these items
can easily be recouped in power savings can easily be recouped in power savings and pump longevityand pump longevity
Maximizing Specific CapacityMaximizing Specific Capacity
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Must have good specific capacity (step Must have good specific capacity (step drawdown) test at a minimum to select drawdown) test at a minimum to select best pump for the jobbest pump for the job
Select permanent pump AFTER step test Select permanent pump AFTER step test is conductedis conducted
Oversizing the pump requires choking Oversizing the pump requires choking back flow, creating artificial and back flow, creating artificial and unnecessary head (and increased unnecessary head (and increased pumping costs) pumping costs)
Maximizing Pump EfficiencyMaximizing Pump Efficiency
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Step Drawdown TestStep Drawdown Test
Using the Step Test ResultsUsing the Step Test Results
7 Day Drawdown Test7 Day Drawdown Test
Maximizing Pump EfficiencyMaximizing Pump Efficiency800
700
600
500
400
300
200
100
0
Tota
l Dyn
amic
Hea
d (f
t)
0 100 200 300 400 500 600Capacity (gpm)
80
70
60
50
40
30
20
10
0
Effi
cien
cy (
%)
50 hp
40 hp
30 hp
20 hp
10 hp
Assumed
Step testResult
~71 % eff.
~62 % eff.
If pump is selected based on the assumed flow and head, the pump will beoversized and actual operation will be ~9% less efficient and discharge willhave to be choked back creating an additional ~80 ft of artificial head.
Maximizing Pump EfficiencyMaximizing Pump Efficiency In our example*, a 9% reduction in pump In our example*, a 9% reduction in pump
efficiency and an extra 80 ft of head efficiency and an extra 80 ft of head translates to a cost increase of translates to a cost increase of approximately approximately $9200/year $9200/year for one pivot.for one pivot.
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*Q = 500 gpm, Q/s = 15 gpm/ft, Pipe diameter = 6”, pipe length = 1000 ft, power cost = $0.10/KWH
Well locationWell location GeohydrologyGeohydrology Distance from pivot (pipeline friction loss)Distance from pivot (pipeline friction loss) Elevation change to pivotElevation change to pivot
Other ConsiderationsOther Considerations
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Note: All other factors held Constant: Q = 500 gpm, Q/s= 15 gpm/ft, pipe diameter = 6”, elevation change = 0, energyCost = $0.10/KWH
Pipeline sizesPipeline sizes Properly sized pipes can significantly reduce Properly sized pipes can significantly reduce
friction loss/pumping costsfriction loss/pumping costs
Other ConsiderationsOther Considerations
GLORIETA GEOSCIENCE, INC.
Note: All other factors held Constant: Q = 500 gpm, Q/s= 15 gpm/ft, pipe length = 1000’, elevation change = 0, Energy cost = $0.10/KWH
Summary and ConclusionsSummary and Conclusions
GLORIETA GEOSCIENCE, INC.
Significant operational cost savings (power, pump Significant operational cost savings (power, pump replacement) can be realized through properly:replacement) can be realized through properly: Selecting screen size/geometry Selecting screen size/geometry Locating screened intervalsLocating screened intervals Selecting filter pack sizeSelecting filter pack size Developing the wellDeveloping the well Testing the wellTesting the well Maximizing pump efficiencyMaximizing pump efficiency Sizing pipelinesSizing pipelines Minimizing pipe runs where possibleMinimizing pipe runs where possible
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