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Use of vertical-radar profiling to estimate porosity at two New England sites and comparison with neutron log porosity

Marc L. Buursink, CGISS, Boise State University, Boise, ID
John W. Lane Jr., OGW-BG, U.S. Geological Survey, Storrs, CT
William P. Clement, CGISS, Boise State University, Boise, ID
Michael D. Knoll, CGISS, Boise State University, Boise, ID

Abstract

Vertical-radar profiles (VRPs) and neutron porosity logs were acquired at two sites in New England – Haddam Meadows State Park in Connecticut and Massachusetts Military Reservation on Cape Cod. Both sites include boreholes drilled to depths from 30 to 50 meters into unconsolidated fluvial or glacial sediments. The VRP data are inverted using Tikhanov regularization to obtain interval radar propagation velocities. Of the two sites, the radar velocities at Haddam Meadows State Park show more variability with depth because this site consists of poorly sorted fluvial sediments, whereas the radar velocities at Cape Cod show much less variability because this site consists of well-sorted glacial sediments.

The interval radar propagation velocities from the VRPs are converted to estimates of saturated sediment porosity using the Topp and time-propagation petrophysical models. VRP-derived porosities are compared to neutron log-derived porosities and yielded a correlation between values derived from the two methods. Lack of correlation between the VRP-derived porosities and the neutron log-derived porosities at some depths may be explained by discrepancy in the sample volume of each method, by problems in the petrophysical models, or by differences in borehole construction methods used at each site. Overall correlation between the VRP-derived porosities and the neutron log-derived porosities supports the advantage of deriving porosities from VRP data due to the decreased cost and ease of data acquisition, and simple processing and inversion routines.

Final copy as submitted to Symposium on the Application of Geophysics to Engineering and Environmental Problems for publication as: Buursink, M.L., Lane, J.W., Jr., Clement, W.P., and Knoll, M.D., 2002, Use of vertical-radar profiling to estimate porosity at two New England sites and comparison with neutron log porosity, in Symposium on the Application of Geophysics to Engineering and Environmental Problems, Las Vegas, Nevada, February 10-14, 2002, Proceedings: Denver, Colorado., Environmental and Engineering Geophysical Society, CD-ROM, 12 p.

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