10 -6

1. PT2 PT1 Skin K = Base K /10 Thickness 0.02 m Kr : Kz = 100:1 Legend 10-2 10-2 10-6 10-4 10-6 10-4 1 1 Injection Screen Pressure Port 10-2 10-6 10-4 1 Δh1 5 tests, K structure assumed known 5 tests, K structure assumed unknown Δh1-Δh2 Pressure Port 15 tests, K structure unknown 15 tests, Inverse Zonation Adjusted The Direct-Push Permeameter for High-Resolution Characterization of Spatial Variations in Hydraulic Conductivity: Tool Design Gaisheng Liu, Geoff Bohling, James J. Butler, Jr., Kansas Geological Survey, The University of Kansas; Peter Dietrich, Centre for Environmental Research, Germany IV> DPP Injection-Induced Head Distribution I> Introduction The direct-push permeameter (DPP) is a tool for the in-situ characterization of hydraulic conductivity (K) in shallow, unconsolidated formations. Our previous studies, including field work (Butler et al., 2007) and a systematic simulation assessment (Liu et al., 2008), have demonstrated that the DPP offers a promising means of obtaining K information at an unprecedented level of detail, accuracy and speed. In this study, we conduct a series of numerical simulation analyses to further explore different configurations of the DPP tool, such that the most information can be obtained from this technique in an efficient manner. Butler, J. J., Jr., P. Dietrich, V. Wittig, and T. Christy (2007), Characterizing hydraulic conductivity with the direct-push permeameter, Ground Water, 45(4), 409– 419. Liu, G., G. C. Bohling, and J. J. Butler Jr. (2008), Simulation assessment of the direct-push permeameter for characterizing vertical variations in hydraulic conductivity, Water Resour. Res., 44, W02432, doi:10.1029/2007WR006078. • Small impact by the low-K • skin on DPP accuracy • Estimate the horizontal • component of anisotropic K • More influence by low-K than high-K layers II> The Direct-Push Permeameter (DPP) • The prototype configuration consists of an injection screen and two pressure transducers. • The tool is advanced into the subsurface by direct-push technology. • At desired depth, several hydraulic injection tests are conducted at different rates. • Head changes are monitored at transducers. • K estimate is obtained analytically or numerically. • The steady-shape flow conditions allows for a dramatic reduction in the time needed in field application. V> Tool Design Results (b) DPP Configurations Investigated (a) K Profile Under Steady-Shape Conditions, 10-2 10-6 10-4 1 Under Steady-State Conditions, (d) Three-PT Configurations (A) r1=0.15m, r2=0.25m, r3=0.40m, (B) r1=0.10m, r2=0.20m, r3=0.30m, (C) r1=0.15m, r2=0.30m, r2=0.50m (c) Two-PT Configurations (A) Prototype - r1=0.15m, r2=0.40m, (B) r1=0.15m, r2=0.50m, (C) r1=0.10m, r2=0.20m 10-2 10-6 10-4 1 K=1.5e-3 m/s Ss=5e-6 /m. Δh2 5 tests, K structure assumed known 5 tests, K structure assumed unknown III> Sensitivity Analysis 0 2-D Radial 1-D Layered • is the small perturbation around the base value at location i; and is the change in the difference ( ). • Positive: the DPP K estimate increases with the medium K. • Negative: the DPP estimate decreases when the medium K increases. • Zero: the DPP estimate does not change with the medium K. 15 tests, K structure unknown 15 tests, Inverse Zonation Adjusted VI> Concluding Remarks:  The DPP is able to provide an accurate, high-resolution K profile in a time-effective manner.A single test is most sensitive to the area immediately surrounding the interval between the injection screen and the pressure transducers.Thin layers can be characterized by adding transducers or refining the intervals for tool advancement. Information on the K structure is important for the inverse estimation process. Such information may be obtained through continuously monitoring the back-injection pressure while the tool is advanced.  Based on the results from this work as well as additional practical constraints, the three-PT configuration (A) is recommend as the optimal design. 0