AN EVALUATION OF BASEMENT DEPTH DETERMINATIONS FROM AIRBORNE MAGNETOMETER DATA

Abstract

Four years ago Creole Petroleum Corporation submitted identical airborne magnetometer data for a portion of the Eastern Venezuela basin to two different geophysical contractors for independent, detailed analysis. These contractors offer the customary generalized basement depth maps; but they specialize in delineating areas of relatively local relief on the basement surface. Both kinds of interpretation were requested by Creole. The main purpose of the study was to evaluate the reliability of interpretations of local basement relief from magnetic data. Accordingly, the region for study was deliberately chosen to include, in part, areas for which Creole had considerable knowledge of basement depths and local basement configuration from other sources. Local basement relief shown by the two magnetic interpretations is in poor agreement with basement depth information from seismograph and well data. Moreover, the two magnetic pictures bear little resemblance one to the other. With respect to regional basement depth contours, one of the magnetic interpretations compares statisfactorily with the picture based on seismograph and well control. A tentative conclusion is that local basement relief cannot be reliably interpreted from magnetometer data alone.