The lnterpretation of geophysical well logs in water bores in unconsolidated sediments

Abstract

A significant proportion of Australia's groundwater is derived from aquifers in unconsolidated sediments. Because of the cost and inherent difficulties of direct sampling and testing procedures, geophysical well-logging plays an important role in the location, definition and evaluation of these unconsolidated aquifers. lnterpretation at present is semi-quantatitive at best, and generally qualitative. Nevertheless, with modern drilling methods, a well-logging programme and interpretation are prerequisites for aquifer evaluation and correct bore completion. The research work described herein arose from requests by State and Federal hydrogeological authorities for an investigation into the utility and efficacy of geophysical logging in unconsolidated sedimentary environments. The project was undertaken in the Department of Geology and Geophysics at the University of Sydney during the period 1969 to 1971. Some additional work was carried out from the nominal completion date to the time of writing. Funds were provided by the Australian Water Resources Council as part of its water research programme. The investigation was called the A.W.R.C. Project 68/7. We acknowledge with thanks the support given by the A.W.R.C. in their funding of the project, and also the services provided by the University of Sydney. In addition we thank those geophysicists and geologists working on hydrogeological problems in State and Federal bodies throughout Australia for their assistance and support. In particular we express gratitude to the staff of the New South Wales Water Conservation and Irrigation Commission for their considerable help throughout the project.