Well Tests to Characterize Idealized Lateral Heterogeneities by Vasi Passinos and Larry Murdoch Clemson University K 1,S 1 K 2,S 2

Faults Steeply Dipping Beds

Igneous Rocks Facies Change Reef Marine Clay Batholith Country rock Dike Channel sand Floodplain deposits

Conceptual Models LocalNeighboring T1 S1T1 S1 T 2 S 2 =S 1 LL 2-Domain Model3-Domain Model Region 1Region 3 Strip T 1 S 1 T 3 = T 1 S 3 = S 1 LLw T 2 S 2 =S 1

Methods 2-Domain Model –Transient analytical solution using Method of Images (Fenske, 1984) 3-Domain Model –Transient numerical model using MODFLOW –T r and w of the strip were varied. –Grid optimized for small mass balance errors

2-Domain Model T Contrast T r =10 T r = 1 T r =0.1

3-Domain Model T Contrast T r = 10 T r = 1 T r = 0.1

2-Domain T Contrast – 0.125L

2-Domain T Contrast – 0.5L

3-Domain T Contrast L

3-Domain T Contrast - 0.5L

Strip Transmissivness & Conductance Hydraulic properties of the strip depend on strip conductivity and width Strip is a higher K than matrix Strip is a lower K than matrix

Strip Transmissivness & Conductance

Graphical Evaluation Boundary Type and Location Well High T to Low T Low T to High T

Graphical Evaluation Estimate Aquifer Properties t o =0.029 S=0.017  s=2.3 T=1 t o =0.42 S=0.35  s=4.1 T = 0.55

Graphical Evaluation Estimate Aquifer Properties t o = 2.7 S=0.136  s = 4.1 T=0.55

T E =1 S E = T L =0.55 S L =0.25 T E =1 S E = T L =0.55 S L =0.136 T L =0.55 S L =0.06 T L =0.55 S L =0.27 T L =0.55 S L =0.021 T L =0.55 S L =0.068 T L =0.55 S L =0.029 T L =0.55 S L =0.021 L LL

Graphical Evaluation Estimate Aquifer Properties t o =0.09 S =  s = 2.3 T = 1 t o =0.028 S =  s = 2.3 T = 1

Determine Properties of Strip SSL analysis on the first line will give T and S of the area near the well. Take the derivative of time and determine the maximum or minimum slope. Using equations from curve fitting determine T sd or C d of the layer. Solve for T s or C

Field Case K.G. Fault

Field Case - Site Map BW-109 BW2 L

Drawdown from Piezometers

Drawdown from Pumping Well

Using Semi-Log Straight-Line Analysis : Minimum slope using the derivative curve is 0.5 T sd =33.99=K s w/K a L Determining Hydraulic Properties L = 280 ft Distance to fault b = 21.5 ft screened thickness T = ft 2 /min S = 2x10 -4 ??? T s = ft 2 /min T s /T a = 450

Conclusions 2-Domain Model Semi-Log Straight-line Method Piezometers r<0.3L gives T, S of local region. Piezometers r>0.3L gives average T of both regions. Piezometers r>0.3L unable to predict S Piezometers in neighboring region also give average T of both regions. Analyzing piezometers individually poor approach to characterizing heterogeneities.

Conclusions 3-Domain Model Drawdown for low conductivity vertical layer controlled by conductance. C=K s /w Drawdown for high conductivity vertical layer controlled by strip transmissivness. T s =K s *w Feasible to determine properties of a vertical layer from drawdown curves. Drawdown curves non-unique. Require geological assessment.