Chapter 15: Single Well tests

1 / 29

# Chapter 15: Single Well tests - PowerPoint PPT Presentation

Chapter 15: Single Well tests. Presented by: Lauren Cameron. 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

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Chapter 15: Single Well tests' - charis

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Chapter 15: Single Well tests

Presented by: Lauren Cameron

• 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!
What is a Single Well Test?
Constant Discharge

Variable-Discharge

Confined Aquifers

Birsoy-Summers’s method

Jacob-Lohman’s free-flowing-well method

Leaky aquifers

Hantush’s free flowing-well method

• Confined aquifers
• Rushton-Singh’s ratio method
• Confined and Leaky aquifers
• Jacob’s Straight-Line method
• Hurr-Worthington’s method
Methods to analyze Single-well tests

Theis’s Recovery Method

• Birsoy-Summer’s’ recovery method
• Eden-Hazel’s recovery Method
Recovery Tests

Confined aquifers

• Rushton-Singh’s ratio method
• Confined and Leaky aquifers
• Jacob’s Straight-Line method
• Hurr-Worthington’s method
Constant Discharge Methods

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 neglected
• Skin effects are negligible

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

Confined aquifers

• Papadopulos-Cooper type curves = similar
• Difficult to match data to (enter Rushton-Sing’s Ratio method)
• More sensitive curve-fitting method
• Changes in well drawdown with time are examined (ratio)
• Assumptions
Rushton-Singh’s ratio Method 1: Assumpions/uses

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 15.2
Rushton-Singh’s ratio Method 3: Remarks

Confined AND Leaky aquifers

• Can also be used to estimate aquifer transmissivity.
• Single well tests
Jacob’s Straight Line Method 1:Uses/Assumptions
• 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 neglected
Jacob’s Straight Line Method 2:Remarks

Confined and Leaky Aquifers

• Small-Diameter well
• Chapter 3 assumptions Except
• Aquifer is confined or leakey
• Storage in the well cannot be neglected
• Flow the well is UNSTEADY STATE
• Skin effect is neglegable
• Storativity is known or can be estimated
Hurr-Worthington’s Method 1: assumptions/Uses

Procedure permits the calculation of (pseudo) transmissivity from a single drawdown observation in the pumped well. The accuracy decreases as Uwdecreases

• If skin effect losses are not negligible, the observed unsteady-state drawdowns should be corrected before this method is applied
Hurr-Worthington’s Method 3: Remarks

Confined Aquifers

• Birsoy-Summers’s method
• Jacob-Lohman’s free-flowing-well method
• Leaky aquifers
• Hantush’s free flowing-well method
Variable Discharge Methods

The Birsory-Summers’s method from 12.1.1can be used for variable discharges

• Parameters s and r should be replaced by Sw and rew
• Same assumptions as Birsory-Summers’s method in 12.1.1
Birsory-Summers’s Method :

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.
• Flow in the well is an unsteady state
• Uw is < 0.01
• Remark: if t value of rew is not known, S cannot be determined by this method
Jacob-Lohman’s free flowing-well method 1: Assumptions

Variable discharge

• Free-flowing
• Leaky aquifer
• Assumptions in Chapter 4
• 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.
• 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 obtained

Theis’s Recovery Method

• Birsoy-Summer’s’ recovery method
• Eden-Hazel’s recovery Method
Recovery Tests

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’w
Birsoy-Summers’s Recovery Method

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 stepwise