Advanced Methods of Aquifer Analysis · Conceptual Hydrogeological Model (CHM) Well Completion...
Transcript of Advanced Methods of Aquifer Analysis · Conceptual Hydrogeological Model (CHM) Well Completion...
WaterTech 2017
Brent Morin, B.Sc., P.Geol.Waterline Resources Inc.
Conceptual Hydrogeological Model (CHM) Well Completion Aquifer Testing Data Collection and Preparation Aquifer Test Analysis and Interpretation
Step-Rate and Constant-Rate Test Derivative Plots Composite Plots Theis and Cooper Jacob Daugherty-Babu Van der Kamp Method Long-term Sustainable Yield (Q20)
Note:
Type of aquifer Confined vs. unconfined
Fractured vs. porous
Physical boundaries Faults
Facies changes
Surface water bodies
Hydraulic boundaries Constant-head
No flow
Leaky confined aquiferSource: http://www.maine.gov/dacf/mgs/explore/water/facts/aquifer.htm
Depositional environment
Continental
Transitional
Marine
Laterally extensive vs bounded
Heterogeneous vs homogeneous
Well sorted vs poorly sorted
Understand your systemSource: modified from https://www.slideshare.net/hzharraz/sedimentary-ore-deposit-environments
If little is known about the aquifer, at least the following well details should be known:
Well depth
Screened interval
Borehole diameter
Casing inner diameter
Aquifer thickness
Source and Observation Wells
Geology and static groundwater levels consistent?
Full vs partial penetration
Source: Aqtesolve
Source: Aqtesolve
Step-Rate Test (SRT):
Constant-rate steps over same time interval
Short-term test to help understand well performance
Well losses
Well efficiency
Determine rate for long-term test
Constant-Rate Test (CRT)
Long-term test to obtain estimates of aquifer properties
Design to meet both regulatory and operational requirements
s
Q
s
t
Step-Rate Test (SRT):
Constant-rate steps over same time interval
Short-term test to help understand well performance
Well losses
Well efficiency
Determine rate for long-term test
Constant-Rate Test (CRT)
Long-term test to obtain estimates of aquifer properties
Design to meet both regulatory and operational requirements
s
Q
s
t
Step-Rate Test (SRT):
Constant-rate steps over same time interval
Short-term test to help understand well performance
Well losses
Well efficiency
Determine rate for long-term test
Constant-Rate Test (CRT)
Long-term test to obtain estimates of aquifer properties
Design to meet both regulatory and operational requirements
Compensate pressure data for barometric variations
Define initial static level
Plot drawdown and flow rate vs. time
QA/QC:
Manual vs. automatic
Drawdown at observation wells consistent with distance to source well
Constant-rate (+/-5%)
Totalizer vs. physical volume
Split data in three files:
SRT, CRT and combined SRT-CRT
SRT CRT
t1=0 t2=0
Ability to analyze test is completely dependant on the quality of data collected
Primary objective is to estimate the aquifer: Tranmissivity (T)
Storativity (S)
Large number of unknown parameters – solution may be non-unique
Analysis has to be customized for the project
Refine CHM if necessary and select what data should be analyzed: Derivative Plot
Composite Plot
Use aquifer properties to calculate Q20
Helps identify: Periods of infinite acting
radial flow (IARF)
Double porosity or unconfined aquifer
No flow boundary
Wellbore storage and skin effects
Leaky aquifer
Constant head boundary
Reference: Renard P., Glenz D. and Mejias M. (2009). Understanding diagnostic plots for well-test interpretation. Hydrogeology Journal 17: 589-600.
Helps identify: Periods of infinite acting
radial flow (IARF)
Double porosity or unconfined aquifer
No flow boundary
Wellbore storage and skin effects
Leaky aquifer
Constant head boundary
Reference: Renard P., Glenz D. and Mejias M. (2009). Understanding diagnostic plots for well-test interpretation. Hydrogeology Journal 17: 589-600.
Helps identify: Periods of infinite acting
radial flow (IARF)
Double porosity or unconfined aquifer
No flow boundary
Wellbore storage and skin effects
Leaky aquifer
Constant head boundary
Reference: Renard P., Glenz D. and Mejias M. (2009). Understanding diagnostic plots for well-test interpretation. Hydrogeology Journal 17: 589-600.
Helps identify: Periods of infinite acting
radial flow (IARF)
Double porosity or unconfined aquifer
No flow boundary
Wellbore storage and skin effects
Leaky aquifer
Constant head boundary
Reference: Renard P., Glenz D. and Mejias M. (2009). Understanding diagnostic plots for well-test interpretation. Hydrogeology Journal 17: 589-600.
Helps identify: Periods of infinite acting
radial flow (IARF)
Double porosity or unconfined aquifer
No flow boundary
Wellbore storage and skin effects
Leaky aquifer
Constant head boundary
Helps identify: Periods of infinite acting
radial flow (IARF)
Double porosity or unconfined aquifer
No flow boundary
Wellbore storage and skin effects
Leaky aquifer
Constant head boundary
Reference: Renard P., Glenz D. and Mejias M. (2009). Understanding diagnostic plots for well-test interpretation. Hydrogeology Journal 17: 589-600.
Helps identify: Periods of infinite acting
radial flow (IARF)
Double porosity or unconfined aquifer
No flow boundary
Wellbore storage and skin effects
Leaky aquifer
Constant head boundary
Reference: Renard P., Glenz D. and Mejias M. (2009). Understanding diagnostic plots for well-test interpretation. Hydrogeology Journal 17: 589-600.
Analyze drawdown data for one or more observation wells
Determine if observation well completed in same aquifer as the pumping well
Ensure one consistent value for complete dataset
Source: Aqtesolve
Theis (1935) Solution Assumptions
Cooper-Jacob (1946) Solution Assumptions
Source: Aqtesolve
Source: Aqtesolve
Dougherty-Babu (1984) Solution for accounts for:
Full or partial penetration
Wellbore storage effect
Skin effect
Unsteady flow
Non-linear well losses
Better suited for the production well
Source: Aqtesolve
Partial penetration: well not screened across the full aquifer thickness
Wellbore storage effect: delayed aquifer response
Skin effect:
Positive skin – interface between aquifer and wellbore damaged
Negative skin – enhanced permeability near wellbore
-5 < Sw < 5
Non-Linear well losses: General form of well losses
(Rorabaugh, 1953):
B is linear well losses (laminar)
C is non-linear well losses (due to turbulent flow)
P is the order of nonlinear well losses (1.5 < P < 3.5) Source: Aqtesolve
Source: Aqtesolve
Challenge of the Dougherty-Babu solution: too many parameters! (risk for non-uniqueness of solution): T (transmissivity) [m2/d] - Unknown S (storativity) [-] - Unknown Kz/Kr (hydraulic conductivity anisotropy ratio) [-] - Unknown Sw (dimensionless wellbore skin factor) [-] - Unknown r(w) (well radius) [m] - Known r(c) (nominal casing radius) [m] - Known r(eq) (equipment radius) [m] - Known C (nonlinear well loss coefficient) [min2/m5] - Unknown P (nonlinear well loss exponent) [-] - Unknown
Propose step-wise approach to adjust each parameterGoal: obtain one set of parameters that matches drawdown, recovery and
step-rate test data.
1. Set-up file for CRT, SRT and SRT/CRT combined:
• Well construction parameters.
• Aquifer geometry parameter.
2. Recovery (CRT):
• Estimate T
3. Derivative Analysis (CRT):
•WSW (drawdown)
•Identify boundaries
•Identify IARF window
4. Composite Plot (CRT)
•With the OBS wells
•Estimate T and S
5. Step-Rate Test [Excel]
•Estimate of C
6. Step-Rate Test [Aquifer Test Software]
•Enter T, S and C
•Adjust Sw to match data
•Adjust C again
7. Full test [Aquifer Test Software]:
•Small adjustments of input parameters
•Check input parameters match full test
Analysis Requires:- Step-rate test- Separate constant-rate test- Observation and source well water
level data
AKA deconvolution method
Uses superposition theory to extend drawdown curve with measured recovery data
Useful to see hydraulic boundaries since they are time dependent
Requires good drawdown data Source: Neville C. (2014). The significance and interpretation of recovery data.(Professional training course)
Choosing a solution
Use the “Solution Expert”
Forward solution Q20 calculations
In the field analyze early data to try and estimate expected total drawdown
Ability to set boundary conditions in aquifer properties
Well interference option
If several sets of pumping rates are entered, you can activate cumulative effects
Use the aquifer parameter estimates to calculate Q20
Source: http://aep.alberta.ca/water/education-guidelines/documents/GroundwaterAuthorization-Guide-2011.pdf
Use your CHM to select appropriate aquifer test analytical solution
Hydraulic boundaries are time dependent and not rate dependent
Aquifer parameter estimates are only as good as the data collected
Hold as many variables constant (i.e., minimize variables) during the aquifer test to avoid having to deal with non-unique solution
Thank you!
Brent Morin
Waterline Resources Inc.
http://www.waterlineresources.com