Abstract

With the increase in environmental awareness, and particularly with the increase in environmental litigation, the oil industry finds itself needing to increase its ability to accurately, and cost effectively, locate and define areas where various environmental problems may have resulted from past and present drilling and production activities.

Traditionally an area of suspected environmental damage was visually inspected and then sampled by soil borings and/or monitor wells. These sampling programs, although necessary, are expensive, generally limited because of expense, and many times poorly located due to an incomplete understanding of the total problem.

Electomagnetic surveying uses highly portable, non-intrusive instruments to measure interval ground conductivity from the surface to various depths beneath the surface. The technology is essentially the same used in induction electric logging in well bores. Since it is an induction method, it does not require ground contact nor is it plagued by the other problems associated with resistivity surveys. Since most environmental problems in the oilfield have associated saltwater or salty mud, this is a reliable and cost effective method to collect large quantities of closely spaced data points to very accurately define not only the visible problem, but the entire problem. By using multiple pass surveys with tools having different depths of investigation, the problem can not only be defined laterally, but vertical analysis can also performed by a competent, experienced interpreter.

Electomagnetic surveying does not replace traditional sampling programs but is most effective as a first-pass investigation to accurately define the parameters of the problem. The resulting benefit will be a need for fewer soil borings and monitor wells which will be more effectively located.