Petrophysical Analysis of Hydrocarbon Reservoirs in the Calabar Flank for Reserves Estimation

Abstract

Despite the favourable geological settings of the Calabar Flank for hydrocarbon generation and accumulation, the lack of quantitative reservoir evaluation remains a limitation in the South-eastern part of Nigeria. This study applies petrophysical analysis to characterize reservoir quality and estimate hydrocarbon reserves in this region using well data (gamma ray, resistivity, density and sonic log) from selected wells, which were interpreted to derive key parameters such as gross sand, net sand, gross pay, net pay, porosity, water saturation (Sw), hydrocarbon saturation (Sh), net-to-gross ratio (NTG) and bulk volume of water (BVW). The results of this study reveal continuous reservoirs with gross sand and pay thicknesses of up to 879 ft and NTG values between 0.81 and 0.95, indicating high reservoir continuity and minimal shale intercalation. Porosity values of 0.37 reflect excellent pore space development, while water saturation remains a relatively low value of 0.09 and hydrocarbon saturation values as high as 0.91, highlighting significant hydrocarbon presence. Low BVW values further demonstrate effective hydrocarbon displacement. All analysed intervals were classified as oil-down-to (ODT) systems that indicate laterally continuous oil-bearing zones. These findings highlight Calabar Flank’s high-quality reservoir properties and its potential for substantial commercial hydrocarbon reserves. This study provides quantitative insights into reservoir behaviour, strengthens the understanding of hydrocarbon prospectivity within the region, and offers practical guidance for exploration and development strategies.