f Integrated geophysics in challenging areas: from joint planning to joint interpretation

In 2007 Eni acquired a multidisciplinary geophysical survey in a desert area located in southwestern<br>Libya, combining seismic and non-seismic geophysical methods.<br>The investigated area is located in SW Libya and represents the erosion remnant of a<br>Palaeozoic intra-cratonic basin located on the Saharan Platform of North Africa. The<br>sedimentary fill is mainly Paleozoic to Mesozoic in age and reaches a thickness of about 4000<br>m in the basin centre.<br>The project was aimed at reducing the exploration risk using different geophysical disciplines.<br>Acquisition of non-seismic data was performed in correspondence of 2D seismic lines<br>previously shot.<br>Densely spaced gravity stations were located along these seismic lines (called “central lines”).<br>The acquisition grid was progressively coarsened along lines parallel to the central lines, in<br>order to be integrated with the regional gravity data already available in the area.<br>Densely spaced magnetotelluric data were acquired along the same seismic/gravity lines for a<br>total of 50km.<br>Distance between successive MT stations was set at 100-200m, depending on operational<br>difficulties.<br>High ground resistance was the biggest factor which affected the data quality in the<br>investigated area. It was reduced injecting salty water in deep holes were the electrodes were<br>positioned. 254 MT stations were acquired with satisfactory Signal/Noise ratio. Reliable<br>inversion results (Figures 1 and 2) were obtained and checked with the resistivity logs<br>available in the area.