Gravity and Magnetic Profile along Seismic Intersect Ku – 89 – 04, Southern Kufra Basin - Libya

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Gravity and Magnetic Profile along Seismic Intersect Ku – 89 – 04, Southern Kufra Basin - Libya

Abstract
The present work is designed to study the sedimentary cover of part of the Kufra Basin by means of potential field analyses and modeling. The basin has been poorly explored (geologically) mainly due to its remoteness, being at least 450 km from the nearest existing oil infrastructure (Sarir Oilfield), and because of the existence of two discouraging dry exploration wells drilled in the northern part of the basin.
In this study, approximately 350 km length of gravity and magnetic profile along seismic intersect Ku–89–04 has been constructed from an existing gravity and magnetic data set. The profile trends NNW from Jabel Nuqay in the west and terminates towards the Jebal Aweinat Massif located at the eastern part of the basin. The observed Bouguer gravity and magnetic anomalies from the produced maps and the constructed profile are composites of several anomalies with varying wavelengths. First, a regional trend in the
Bouguer gravity is present, with generally more negative values to the northwest. This regional trend is likely a reflection of gradually thickening crust from southeast to northwest, or a gradual reduction in average subsurface densities, or a combination of both. High density light basement blocks are interpreted to be the source of the magnetic anomalies, these reflect the effects of variable magnetized igneous bodies. The depths to the top of the igneous bodies range from 3 km to 4 km. The profile shows that the sedimentary cover at this part of the basin causes a large negative anomaly in the Bouguer anomaly map. It reflects the distribution of thick sequences of Paleozoic rocks,
and moderately thick Mesozoic rocks. The gravity and magnetic data in this case provides some insights into the early history of the basin, while the seismic data shows that the geometries in this part of the Basin are much larger and thicker. The model has shown flat, gentle strata thickening at the middle and it coincides with the interpreted seismic section. The modeling results also show a high correlation between the residual gravity, (reduced to pole residual magnetic) and the basement geometry, which suggests that the density and the magnetic content of the basement rocks are homogeneous.
Locally, gravity and magnetic observations help constrain the interpretations of low density anomalies located at the western and the eastern ends of the profile. They may be associated with sedimentary bodies composed of clastic sediments ranging in age from Infracambrian to Cambro – Ordovician. The Modeling interpretations of the magnetic field constrain the depths and geometry of heterogeneous basement structures, including Precambrian and Paleozoic formations of variable density. Locally, the interpreted low density bodies and these basement structures may control the locations of prospective hydrocarbon traps in the southern flank of the Kufra Basin.