Mapping of Low Temperature Prospects by Combined IP/Resistivity Soundings (Electrical Factor Method)

Abstract

Low temperature prospects standing in clay-rich country rocks or rocks saturated with saline pore fluids produce, in general, rather indistinct resistivity anomalies. Laboratory tests have shown that the ratio of apparent polarizability (rja) and apparent resistivity (pa), here defined as combined electrical factor F = (Ha/Pa)' *s n o t much affected by the concentration of the electrolyte but increases almost linearly with temperature. Field surveys using combined DC and IP soundings have shown that distinct high F-anomalies can be obtained over a low temperature prospect (Xiamen City in Fujian Province) where the country rocks are saturated with diluted sea water causing a rather indistinct low apparent resistivity pattern. The method has also been tested over a few other low temperature prospects, namely Xiaotangshan near Beijing and at Zhangzhou City in Fujian Province, in both areas rather high F-anomalies were found to be associated with shallow thermal waters.