| Abstrakt: |
The lower Benue trough has been investigated for indications of hydrocarbon prospect using high resolution aeromagnetic data. Objectively, the study was meant to evaluate susceptibility contrasts related to structure and sedimentary units that could have direct bearing to hydrocarbon formation. Maps of magnetic parameters were generated using Oasis montaj, Surfer 13 and Arc GIS softwares for qualitative and quantitative interpretations. Results of the study reveal that the residual magnetic intensity (RMI) map exhibits distinct elliptical to isolated hemispherical magnetic lows bounded by ridge-like magnetic highs and both trending mostly in the NE-SW with minor E-W trend. These Low magnetic anomalies were delineated in Adani, Enugu-Ezike, Nsukka, Awka, Awgu, Enugu and Nkalagu areas while magnetic highs were delineated in Eha Amufu, Okposi, Igumale, Udi and Ukehe. Magnetic lineaments were mapped and occur predominantly in the NE-SW and NNE-SSW lineament orientations, with minor occurrences in the NW-SE, E-W and N-S lineament orientations. High lineament densities were delineated around Enugu, Udi, Ukehe, Eha-Emufu and Igumale, which suggest that these areas are more deformed than the low lineament density areas in Adani, Enugu-Ezike, Awka, Agwu, Nkalagu and Okposi. Areas of shallow basements depths (< 2000 m), with high magnetic intensities and high lineament densities were mapped in Enugu, Udi, Ukehe, Eha-Emufu and Igumale, suggesting structurally deformed areas with thin sediment cover unfavourable for hydrocarbon formation but with good prospect for mineral deposits and groundwater resource. comparison of SPI map, lineament map, residual magnetic map and the geologic map revealed that large basement depths (> 2000 m) with low magnetic intensities and low lineament densities were mapped in Adani, Enugu-Ezike, Awka Awgu, Okposi and Nkalagu (suggesting structurally less deformed areas with thick sedimentary cover favourable for hydrocarbon formation and accumulation in the lower trough) correlate to parts of the Mamu and Nkporo shale formations and Ajali Sandstones, reported to exhibit characteristics of potential hydrocarbon source rocks for a series of oil/gas and condensate shows found within the Ajali reservoir sandstones and were thus recommended for detailed seismic surveys. [ABSTRACT FROM AUTHOR] |
