Electromagnetic methods for development and production: State of the art

lectrical and electromagnetic methods are a natural addition to the toolbox of a development and production geophysicist because formation resistivity is a strong function of the reservoir fluid saturation and temperature. Unfortunately, the high degree of cultural noise in developed oil fields has limited the use of surface electrical techniques, and the preponderance of steel well casings has limited the deployment of borehole tools in completed wells. The result is that, with the exception of open-hole logging, electrical methods are not routinely used in oil fields after the exploration phase is complete. Recently, however, several experimental applications of electromagnetic techniques for water and steam flood monitoring have yielded impressive results (see TLE, March 1995). Crosshole EM measurements, made in fiberglass-cased observation holes, have yielded images of interwell resistivity structure and bed continuity in several California oil fields. Repeated application of EM tomography was used to obtain images of resistivity variations during steam-flooding operations. These data were in turn used to track the flow of injected steam. In this short article we discuss the relative merits of electrical methods as applied to oil-field development and production. We then briefly describe several new technologies that apply EM methods in innovative ways to the hostile oil-field environment.