Extra-Deep Azimuthal Resistivity in Deep Offshore Niger Delta

The benefits of drilling high-angle and horizontal wells include having increased exposure to the reservoir and the ability to connect laterally discontinuous features. Using geosteering to achieve these benefits becomes challenging if the reservoir has other complexities – variable reservoir thickness, multiple beds, formation heterogeneity, and presence of structural discontinuities. To mitigate these challenges, geosteering with fit-for-purpose tools and robust software is required. This is a case study of the application of the VisiTrak™ tool, Multi-Component While Drilling (MCWD) inversion software and borehole image data in the geosteering of Well-C.The oil field lies within the Oil Mining Lease OML 130 (formerly OPL246) located in water depths ranging from 1400–1750m and approximately 200 km from Port Harcourt. The field comprises several distinct accumulations deposited during the Middle to Late Miocene. The reservoir consists of several individual turbidite fans including stacked channels and extensive lobate sheet sands. The target reservoir is interpreted mainly as a channelized depositional system consisting of erosive-constructive meandering channels, in an interval of up to 230m gross thickness with two channel accumulations ( Fig. 1 ). The older sequence is called ‘Eastern Complex’, while the younger is termed ‘Western Complex’. Both East and West turbidite complexes have the same characteristic sedimentary evolution, i.e. initial deposition of an erosive base fairway followed by deposition of erosive-constructive channels. The West Complex overlies the East Complex and develops from it through a major erosive avulsion. Its initial deposits are a debris flow facies with thickness of up to 29m and these impermeable non-reservoir facies are likely to form a barrier between the East and West complexes.