New Mexico Geological Society Annual Spring Meeting — Abstracts

Suites of borehole geophysical logs are available for more than 80 water-production wells in the City of Albuquerque. Such log suites represent a significant resource of subsurface hydrogeologic information for Albuquerque's principal aquifer, the Santa Fe Group. This paper presents preliminary results from the study and analysis of the log suites and associated well cuttings and side-wall cores.

Specific geophysical logs available for a particular well varies, but conductivity, deep induction and shallow resistivity, and spontaneous potential logs are typically available at a minimum. Comprehensive suites of electric, sonic, and nuclear logs are available for 12 wells. Much of study focused on these wells to (1) determine the geophysical-log response characteristics of the various Santa Fe Group lithofacies, and (2) identify and map the subsurface distribution of Santa Fe Group lithofacies.

Geophysical-log responses vary among the 10 lithofacies previously defined for the Santa Fe Group. Typically, the response of any single geophysical log is not characteristic of particular lithofacies. Response behavior of suites of logs, however, proved diagnostic of lithofacies type. In particular, preliminary analysis suggests that combinations of electrical-conductivity, gamma-ray, density, and acoustic-velocity logs can be used for lithofacies interpretation. Such a log suite is widely available for wells in the Albuquerque area, and preliminary results suggest that it can be used to map lithofacies distribution within the Santa Fe Group aquifer.

Geophysical log analysis identified a potential drilling target for water-resource evaluation west of the Rio Grande. At depths below approximately 1500 ft in the College 1, College 2, and Ladera wells, located on the west side of Albuquerque, a thick sand-rich interval occurs. Preliminary analysis of geophysical logs north and south of the College and Ladera wells suggests that the sand-rich interval extends at least several miles in each direction.