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.

bmorin@waterlineresources.com

http://www.waterlineresources.com