ABSTRACT: The Application of High-resolution Aeromagnetics for Igneous Risk-assessment, Offshore West Africa

Abstract

As global hydrocarbon exploration progresses into frontier areas, the presence of recent igneous activity is one of the risk factors that must be considered. This is especially true along the margin of West Africa where Tertiary igneous activity is evident by the preponderance of volcanic island complexes and other near shore volcanic rocks. As a result of the inherent magnetic susceptibility present in volcanic and igneous rocks, highresolution aeromagnetic data can be successfully utilized to detect their presence. In the fall of 2000, Vanco Energy Company contracted AOA Geophysics to acquire and interpret approximately 6,000 line kilometers of airborne magnetic data over a small portion of the Vanco Dakar Offshore Profond license area, offshore Senegal. Survey specifications were optimized for the detection of shallow igneous rocks. The results of the survey indicated that such rocks were most-likely present. High-frequency magnetic anomaly patterns visible along individual profiles and in gridded magnetic data were consistent with the presence of shallow igneous sources. The anomalies displayed an excellent correlation with suspect seismic amplitude anomalies and with unusual seafloor features visible in previously collected 2-D seismic data.