Ionic Diffusion From Salt Domes

Analyses of salinity gradients around a salt dome show that spontaneous potential (SP) data yield false salinity calculations whenever a hydrocarbon environment is penetrated. This result is probably due to a back emf of oxidation-reduction reactions (redox potential). Location of this low potential difference between sands and shales gives useful information about hydrocarbon location. The reduction potential may be measured directly from cuttings, wireline devices, and indirectly from suppressed SP measurements. However, the SP is also decreased due to high pressure gradients and an increased clay content in sands. Hence, a direct measure of redox potential must be made. Calculations of salinity gradients about a dome and measurement of the water salinity allows determination of time transients so that salt dome movement rates may be calculated.