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 aquifer Source: 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 system Source: 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 s Q 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 s Q 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 t1=0 t2=0 CRT 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
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. 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
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 Source: Aqtesolve Cooper-Jacob (1946) Solution Assumptions Source: Aqtesolve
Dougherty-Babu (1984) Solution for accounts for: Full or partial penetration Wellbore storage effect Skin effect Unsteady flow Non-linear well losses Source: Aqtesolve Better suited for the production well
Partial penetration: well not screened across the full aquifer thickness Wellbore storage effect: delayed aquifer response Skin effect: -5 < Sw < 5 Positive skin interface between aquifer and wellbore damaged Negative skin enhanced permeability near wellbore
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 nonuniqueness of solution): T (transmissivity) [m 2 /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) [min 2 /m 5 ] - Unknown P (nonlinear well loss exponent) [-] - Unknown Propose step-wise approach to adjust each parameter Goal: 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 6. Step-Rate Test [Aquifer Test Software] Enter T, S and C Adjust Sw to match data Adjust C again 5. Step-Rate Test [Excel] Estimate of C 4. Composite Plot (CRT) With the OBS wells Estimate T and S 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. bmorin@waterlineresources.com http://www.waterlineresources.com