DESIGN OF RESEARCH WELLFIELD FOR CALIBRATING GEOPHYSICAL METHODS AGAINST HYDROLOGIC PARAMETERS

A wellfield (Boise Hydrogeophysical Research Site or BHRS) is being developed in Boise, Idaho, for hydrologic and geophysical research in a shallow, coarse (cobble-and-sand), alluvial aquifer. Our goal is to develop cost-effective methods for quantitatively characterizing the distribution of permeability in heterogeneous alluvial aquifers using hydrologic and geophysical techniques. Responses to surface geophysical techniques (e.g., seismic, radar, and transient electromagnetics) will be calibrated against a highly characterized volume (the wellfield) with determined three-dimensional distributions of geologic, hydrologic, and geophysical properties. Well coring and construction methods, and the well arrangement in the field, are designed to provide detailed control on lithology (facies distribution and sediment properties), and to support a variety of single-well tests (e.g., borehole geophysical logging, permeability logging, and vertical seismic and radar profiling), crosshole tests (e.g., seismic, radar, and resistivity tomography), and multiwell tests (e.g., pumping and tracer tests). The wellfield has a central well surrounded by two rings of six wells each, and five outer iboundaryi wells. Wells are screened through the cobble-and-sand aquifer to a clay that underlies the BHRS at about 20 m depth. Permeability will be measured with the flowmeter and pumping method in each well, and with a series of tests where successive discrete intervals will be pumped in a given well while multiple zones will be monitored in surrounding wells. Wellfield dimensions (e.g., ~20 m diameter of central well cluster) and design specifics are based on experience at the nearby Capital Station remediation site in the same aquifer material, and are designed to provide detailed control on the variation of properties over a range of volume scales (<1 m 3 to ~6000 m 3 ). A Monte Carlo search was used to refine the wellfield design to optimize well-pair distances and azimuths for determination of geostatistical parameters and anisotropy.

[1]  Fred J. Molz,et al.  The Impeller Meter for measuring aquifer permeability variations: Evaluation and comparison with other tests , 1989 .

[2]  Peter Huggenberger,et al.  Pleistocene Rhine gravel: deposits of a braided river system with dominant pool preservation , 1993, Geological Society, London, Special Publications.

[3]  G. K. Boman,et al.  Three‐Dimensional Modeling of a Two‐Well Tracer Test , 1992 .

[4]  Denis R. LeBlanc,et al.  A Statistical Evaluation of Formation Disturbance Produced by Well‐Casing Installation Methods , 1988 .

[5]  Philip H. Nelson,et al.  Well logging for physical properties , 1985 .

[6]  E. Eric Adams,et al.  Field study of dispersion in a heterogeneous aquifer: 1. Overview and site description , 1992 .

[7]  Paul Michaels,et al.  The Anomalous Behavior Of Sh-Waves Across The Water Table , 1996 .

[8]  Peter Huggenberger,et al.  Radar facies: recognition of facies patterns and heterogeneities within Pleistocene Rhine gravels, NE Switzerland , 1993, Geological Society, London, Special Publications.

[9]  E. Eric Adams,et al.  Field study of dispersion in a heterogeneous aquifer , 1992 .

[10]  P. Jussel,et al.  Transport modeling in heterogeneous aquifers: 1. Statistical description and numerical generation of gravel deposits , 1994 .

[11]  John L. Wilson,et al.  An approach to estimating hydraulic conductivity spatial correlation scales using geological characteristics , 1989 .

[12]  P. H. Nelson,et al.  Permeability-porosity relationships in sedimentary rocks , 1994 .

[13]  R. Clarke.  Reservoir Properties of Conglomerates and Conglomeratic Sandstones: GEOLOGIC NOTES , 1979 .

[14]  Edwin P. Weeks,et al.  Determining the Ratio of Horizontal to Vertical Permeability by Aquifer‐Test Analysis , 1969 .

[15]  Yoram Rubin,et al.  Mapping permeability in heterogeneous aquifers using hydrologic and seismic data , 1992 .

[16]  E. Poeter,et al.  Field example of data fusion in site characterization , 1995 .

[17]  Reprint from the Proceedings of the 32nd Symposium on Engineering Geology and Geo- technical Engineering, March 26-28, 1997, Boise, ID. LITHOLOGIC, HYDROLOGIC AND PETROPHYSICAL CHARACTERIZATION OF AN UNCONSOLIDATED COBBLE-AND-SAND AQUIFER CAPITAL STATION SITE, BOISE, IDAHO , 1997 .

[18]  S. Gorelick,et al.  Estimating lithologic and transport properties in three dimensions using seismic and tracer data , 1996 .

[19]  S. Jackson,et al.  Geostatistical characterization and comparison of outcrop and subsurface facies; Shannon Shelf sand ridges , 1986 .