Well log correlation and petrophysical interpretation of “OS”-field, Niger Delta

Abstract

This study presents correlation analysis of four wells in ‘OS’-field in the Niger Delta. The sand and shale were first differentiated by the GR based on the relative occurrence of radioactivity in sand and shale. SP log differentiates permeable and impermeable beds based on differences in mud filtrate in the borehole and formation water. Three major sands (A, B and C) were correlated at the depth intervals (1736.95 - 1809.06 m), (1931.79 - 2052.82 m) and (2180 - 2285.89 m) respectively across the wells. In Well 2, radioactive sand was identified at 2013.83 m measured depth. It has a low GR curve but positive SP deflection. It is suspected that sand B in this well is radioactive (red) and therefore fake sand. It is treated as shale and it is part of shale resistivity marker. The shale correlation was done using Deep Induction Log (ILD). Three Shale Resistivity markers (SRM), SRM1, SRM 2 and SRM 3 were identified. Petrophysical analysis of the three mapped reservoir was also carried out. It revealed average porosity of 1.55, water saturation of 9.0%, hydrocarbon saturation of 91.0% and hydrocarbon pore volume of 91.16%. The porosity and hydrocarbon pore volume values of the reservoir within the field proved them to be quite prolific.

Keywords: Petrophysics, Radioactive sands, Reservoir, Spontaneous potential, Deep Induction