Abstract: Electromagnetic Surveying: a Basic Tool for Defining Environmental Problems in the Oilfield
Gary J. Newman
With the increase in environmental awareness and environmental litigation, the oil industry must improve its ability to accurately, and cost-effectively, locate and define areas where environmental problems may have resulted from drilling and production activities.
Traditionally, areas of environmental damage were visually inspected and sampled by soil borings and/or monitor wells. Although necessary, these sampling programs are generally limited because of expense and may be poorly located due to incomplete understanding of the total problem.
Electromagnetic surveying uses highly portable, non-intrusive instruments to measure interval ground conductivity to various depths beneath the surface. The technology is essentially the same used in induction well bore logging. Since it is an induction method, ground contact is not required, nor is it plagued by the other problems associated with resistivity surveys. Because environmental problems in the oilfield usually involve saltwater or salty mud, conductivity is a reliable and cost-effective method to collect large quantities of data. Increased data allows accurate definition of not only the visible problem, but the entire problem. Using multiple surveys with different depths of investigation, a competent, experienced interpretor can perform vertical analysis as well as definin the lateral extent of the problem.
Electromagnetic surveying does not replace traditional sampling programs but is most effective as first-pass investigations to accurately define the problem parameters. The benefits are fewer soil borings and monitor wells that will be more effectively located.
AAPG Search and Discovery Article #90957©1995 AAPG Mid-Continent Section Meeting, Tulsa, Oklahoma