Presented by Lauren Cameron What is a Single Well Test A singlewell test is a test in which no piezometers are used Waterlevel changes are measured in the well Influenced by well losses and borestorage ID: 442133
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Slide1
Chapter 15: Single Well tests
Presented by:
Lauren
CameronSlide2
What is a Single Well Test?
A single-well test is a test in which no piezometers are used
Water-level changes are measured in the well
Influenced by well losses and bore-storage
Must be considered
Decreases with time and is negligible at
t >
25r,2/KD
To determine if early-time drawdown data are dominated by well-bore storage:
Plot log-log of drawdown s vs. pumping time
Early time drawdown = unit–slope straight line = SIGNIFICANT bore storage effect
Recovery test is important to do!Slide3
Methods to analyze Single-well tests
Constant Discharge
Confined aquifers
Papadopulous
-Cooper Method
Rushton-Singh’s ratio method
Confined and Leaky aquifersJacob’s Straight-Line methodHurr-Worthington’s method
Variable-Discharge
Confined Aquifers
Birsoy
-Summers’s method
Jacob-
Lohman’s
free-flowing-well method
Leaky aquifers
Hantush’s
free flowing-well methodSlide4
Important note
Slide5
Recovery Tests
Theis’s
Recovery Method
Birsoy
-Summer’s’ recovery method
Eden-Hazel’s recovery MethodSlide6
Constant Discharge Methods
Confined aquifers
Papadopulous
-Cooper Method
Rushton-Singh’s ratio method
Confined and Leaky aquifers
Jacob’s Straight-Line methodHurr-Worthington’s methodSlide7
Papadopulos-Cooper’s Method 1: assumptions
Curve Fitting Method
Constant Discharge
Fully Penetrating Well
Confined Aquifer
Takes Storage capacity of well into account
Assumptions:Chapter 3 assumptions, Except that storage cannot be neglectedAdded: Flow to the well is in UNSTEADY stateSkin effects are negligibleSlide8
Papadopulos-Cooper’s Method
2: The Equation
This method uses the following equation to generate a family of type curves:Slide9
Papadopulos-Cooper’s Method
3: remarks
Remarks:
The early-time = water comes from inside well
Points on data curve that coincide with early time part of type curve, do not adequately represent aquifer
If the skin factor or linear well loss coefficient is known
S CAN be calculated via equations 15.2 or 15.3 S is questionable Slide10
Rushton-Singh’s ratio Method 1: Assumpions
/uses
Confined aquifers
Papadopulos
-Cooper type curves = similar
Difficult to match data to (enter Rushton-Sing’s Ratio method)
More sensitive curve-fitting methodChanges in well drawdown with time are examined (ratio)AssumptionsPapadopulos-Cooper’s Method Slide11
Rushton-Singh’s ratio Method 2: Equation
The following ratio is used:Slide12
Rushton-Singh’s ratio Method 3: Remarks
Values of ratio are between 2.5 and 1.0
Upper value = beginning of (constant discharge) test
Type curves are derived from numerical model
Annex 15.2Slide13
Jacob’s Straight Line Method 1:
Uses/Assumptions
Confined AND Leaky aquifers
Can also be used to estimate aquifer
transmissivity
.
Single well testsNot all assumptions are met so additional assumptions are addedSlide14
Jacob’s Straight Line Method 2:
Remarks
Drawdown in well reacts strongly to even minor variations in discharge rate
CONSTANT DISCHARGE
No need to correct observed drawdowns for well losses
In theory:
Works for partially penetrating well (LATE TIME DATA ONLY!)Use the “1 ½ log cycle rule of thumb” to determine is well-bore storage can be neglectedSlide15
Hurr-Worthington’s Method 1: assumptions/Uses
Confined and Leaky Aquifers
Unsteady-State
flow
Small-Diameter well
Chapter 3 assumptions Except
Aquifer is confined or leakeyStorage in the well cannot be neglectedAdded conditions
Flow the well is UNSTEADY STATESkin effect is neglegable
Storativity
is known or can be estimatedSlide16
Hurr-Worthington’s Method 1: assumptions/Uses continuedSlide17
Hurr-Worthington’s Method
2: The EquationSlide18
Hurr-Worthington’s Method
3: Remarks
Procedure permits the calculation of (pseudo)
t
ransmissivity
from a single drawdown observation in the pumped well. The accuracy decreases as
Uw decreasesIf skin effect losses are not negligible, the observed unsteady-state drawdowns should be corrected before this method is appliedSlide19
Variable Discharge Methods
Confined Aquifers
Birsoy
-Summers’s method
Jacob-
Lohman’s
free-flowing-well methodLeaky aquifersHantush’s free flowing-well methodSlide20
Birsory-Summers’s Method :
The
Birsory
-Summers’s method from 12.1.1can be used for variable discharges
Parameters s and r should be replaced by
Sw
and rewSame assumptions as Birsory-Summers’s method in 12.1.1Slide21
Jacob-Lohman’s
free flowing-well method
1: Assumptions
Confined Aquifers
Chapte
3 assumptions
Except: At the begging of the test, the water level in the free-flowing well is lowered instantaneously. At t>0, the drawdown in the well is constant and its discharge is variable.Additionally: Flow in the well is an unsteady stateUw
is < 0.01Remark: if t value of rew is not known, S cannot be determined by this methodSlide22
Jacob-Lohman’s
free flowing-well method 2: EquationSlide23
Leaky aquifters
,
Hantush’s
free-flowing well method
1
:
AssumptionsVariable dischargeFree-flowingLeaky aquiferAssumptions in Chapter 4ExceptAt the begging of the test, the water level in the free-flowing well is lowered instantaneously. At t>0, the drawdown in the well is constant and its discharge is variable
.Additionally:Flow is in unsteady state
Aquitard
is incompressible, changes in
aquitard
storage are
neglegable
Remark: if effective well radius is not known, values of S and c cannot be obtainedSlide24
Leaky
aquifters
,
Hantush’s
free-flowing well method 2 : EquationSlide25
Recovery Tests
Theis’s
Recovery Method
Birsoy
-Summer’s’ recovery method
Eden-Hazel’s recovery MethodSlide26
Theis’s Recovery Method 1: Assumptions
Theis
recovery method, 13.1.1, is also applicable to data from single-well
For
Confined, leaky, or unconfined aquifersSlide27
Theis’s
Recovery
Method
2: RemarksSlide28
Birsoy-Summers’s Recovery Method
Data type
R
esidual
drawdown data from the recovery phase of single-well variable-discharge tests conducted in confined aquifers
Birsoy
-Summers’s Recovery Method in 13.3.1 can be used Provided that s’ is replaced by s’wSlide29
Eden-Hazel Method : uses/Assumptions
For Step-drawdown tests (14.1.2) is applicable to data from the recovery phase of such a test
Assumptions in Chapter 3 (adjusted for recovery
test:s
)
Except:
Prior the recovery test, the aquifer is pumped stepwiseAdditionallyFlow in the well is in unsteady stateu < 0.01u’ < 0.01