A preliminary assessment of the hydrocarbon potential of Kerio valley basin: gravity and magnetic interpretation

Abstract

The aim of the study was to assess the hydrocarbon prospectivity of the Kerio Basin in the Kenya Rift. An Isostatically corrected anomaly map produced from a Bouguer anomaly grid was filtered using a Hanning low pass filter of order 2 to remove low wavelengths. Four profiles were extracted from the grid to give 1D interpretation along straight lines. Magnetic grid was corrected for IGRF, diurnal, filtered using a 1 Hz low pass 10km Hanning filter to reduce noise, later, reduced to equator to place all anomalies directly over underlying sources and make anomalies less complicated. Tilt derivative of the magnetic grid was used to estimate depth to basement. The residual analytic signal anomaly map derived from the magnetic grid was used to capture the response of existing near surface magnetic signatures even the reversely magnetized ones.

Kerio basin is characterised by low gravity anomalies ranging between 35mGals to -100mGals related to variations in quantities of sediments deposited. Gravity profiles show that sediment thickness gradually increases to the south where we expect hydrocarbon accumulation. The magnetic anomaly map reveals low susceptibility rocks of between -20nT to -200nT to the south of the basin. Magnetic tilt depth indicates sediment thickness of 2.0 -3.5Km above the basement. This corresponds to both gravity and magnetic interpretation of the same area. Integration of these data with seismic and other constraints may help gauge the hydrocarbon potential and reduce exploration uncertainty in the southern area of the Kerio Basin.