A sedimentological approach to refining reservoir architecture using the well log data and core analysis in the saharan platform of algeria

Abstract

Improved reservoir characterisation in the mature oil applied to Gourara Field of Sahara in Algeria, aimed at maximising both in-field and near-field hydrocarbon potential, requires a clearer understanding of sub-seismic stratigraphy and facies distributions. In this context, we present a regional, high-resolution sequence stratigraphic framework for the Oued Namouss Field based on extensive sedimentological re-interpretation of core and wireline log data, combined with core analysis and published literature. This framework is used to place individual reservoirs in an appropriate regional context, thus resulting in the identification of subtle sedimentological and tectono-stratigraphic features of reservoir architecture that have been previously overlooked. We emphasise the following insights gained from our regional, high-resolution sequence stratigraphic synthesis: (1) improved definition of temporal and spatial trends in deposition both within and between individual reservoirs, (2) development of regionally consistent, predictive sedimentological models for two enigmatic reservoir intervals (the Formations I and II), and (3) recognition of subtle local tectono-stratigraphic controls on reservoir architecture, and their links to the regional structural evolution of the Province. We discuss the potential applications of these insights to the identification of additional exploration potential and to improved ultimate recovery.In this research a procedure was developed to assess and quantify uncertainties in hydrocarbon estimates related to depositional facies, petrophysical data and gross reservoir volumes. This procedure was applied to the Gourara Field, which is a mature gas field in the Oued Namous Basin, Algeria. The aim was to investigate the reasons for an unexpectedly high hydrocarbon recovery factor