| Abstract: | Conventional electrical prospecting can be extended to the search for deep-seated hydrocarbon deposits, by using the steel casings of drill-holes as vertical line sources. These sources produce at depth a density of current higher than the density created by point sources located at the ground surface. Several tests have shown that the contrast of conductivity between resistive hydrocarbon deposits and the surrounding salt water produces relevant anomalies on a resistivity map obtained with vertical line sources, especially where there exists a superficial masking effect caused by a highly resistive layer. In a survey carried out in the USSR, combined measurements were performed, both with line source and with surface point sources. The detected residual resistivity anomaly roughly delineates the contours of the known hydrocarbon deposit. |
