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50 Years State of the Art in IP and Complex Resistivity

It is worth looking back to see how far the field of geophysics exploration has come. Presented in 2003, this paper was a combination of retrospective and forecast in which Ken Zonge outlined industry progress after a renewed interest in the IP method in the early 1950s. He then summarized Zonge company progress over the thirty years since his own development of the complex resistivity method and instruments in 1973.

Zonge called for three improvements yet to be made in the instruments of that day: higher resolution, faster processing, and smaller, lighter tools. In the subsequent decade, Zonge International has helped achieve radical improvements in all three of these areas.

Multi-dimensional inversion, which he predicted, is now the standard, and the research community is examining how to turn the EM response — once considered noise — into a useful tool for understanding deeper resistivity structure.

Scott Urquhart, president and managing geophysicist, Zonge International

Publisher — Zonge, 2003. Presented at KEGS (Canadian Exploration Geophysical Society) 50th Anniversary Symposium, Mining and Environmental Geophysics – Past, Present and Future. March 8, 2003, Toronto, Ontario.

Authors — Kenneth L. Zonge and Phil Matthews, Zonge Engineering and Research Organization

Paper — [pdf]  SofA_IPCR

The use of resistivity and spontaneous potential by the Schlumberger brothers is documented at least as early as 1900 – over 100 years ago! Conrad Schlumberger received a patent on the IP technique in 1912. However, it was almost forty years before Newmont renewed interest in its use and application. From that time (the late 1940’s) activity flourished for roughly forty years in both theory and practice, mainly in the search for disseminated sulfides, or more specifically, porphyries.

Then with the crash of copper prices in 1983, interest in disseminated sulfide (porphyry copper) deposits declined dramatically with a concurrent drop in research concerning the source and nature of the induced polarization (IP) response. The precipitous decline in oil prices in 1985 further reduced interest in IP, which was being used as one of the non-seismic alternatives in hydrocarbon exploration. Only in the last few years has interest been renewed.

Despite this general lack of interest, development of instrumentation applicable to resistivity and IP surveys has continued at a fast pace, capitalizing on the availability of high-speed, low-cost microprocessors. New microprocessors also fueled the development of robust data processing routines and 2- and 3-D inversion programs.

Today research continues on the effects of hydrocarbons and other groundwater contaminants on the IP response. IP is used extensively in the search for precious metals by mapping areas hosting disseminated sulfides that may occur in conjunction with precious metals. Interest has been renewed in porphyry deposits in third-world countries, and complex resistivity (CR) or spectral IP is being used in attempts to discern the source of IP responses and to discriminate between valid metallic IP responses and electromagnetic (EM) coupling effects. Most recent is the use of IP as a cost-effective method in environmental surveys.