Permeability Characterization of Upper Miocene Reservoirs, Lower Congo Basin, Offshore Angola; An Integrated Approach

Abstract

Permeability log is the main input required to deliver 3D reservoir property which alongside other properties are used for reservoir simulation to estimate recovery factor, reservoir connectivity, flow units, barriers, baffles and production profiles. This underscores the importance of this parameter which can be obtained mainly from core analysis, nuclear magnetic resonance (NMR), stoneley (sonic), well testing (DST), wireline formation tester, petrophysical evaluation of rock properties and mineralogy. Amongst these approaches, log based permeability estimation has over the years received consistent embrace due to robust measurements that provide permeability information at relatively small sample rates, which account for minor heterogeneities unlike conventional approach of large scale core based approximations. However, the need to ensure accuracy of log based measurements have drawn wide attention and many analysts have taken steps to validate log based permeability results with core data, formation tester and well test analysis results. Permeability characterization for two reservoirs in the Lower Congo Basin offshore Angola was done using log based measurements from basic triple combo and LWD spectroscopy measurements, mobility estimation from sonic alongside formation tester samples, SCAL analysis and well testing results. This paper presents the workflow for evaluation, integration and comparison of permeability from various sources, highlighting challenges and sources of error in the approach.