Lower Bab Member (A0): a study of sequence stratigraphy, porosity characterization and tight reservoir development, Abu Dhabi, UAE

Abstract

The Aptian-aged Shu'aiba Formation carbonate platform is one of the most hydrocarbon-productive formations in the Middle East. Equivalent to the Shu'aiba formation is the Lower Bab Member (A0) that comprises the basinal facies in the intra-shelf Bab basin. The Lower Bab Member (A0) has shown hydrocarbon potential in fields located in the southeastern part of the UAE. The A0 potential comes from its high storage capacity that comes from microporosity in the matrix reaching up to 25% but low permeability (up to 3mD). This study goals focus on (1) understanding of the relationship between the Shu'aiba Formation and the Lower Bab Member stratigraphically using the existing core descriptions, well logs, stable isotopes and seismic; (2) characterization of porosity and permeability to identify potential target production zones; and (3) suggest best practices for future development plans to produce the hydrocarbon from this tight carbonate reservoir. Results of this thesis include significant findings about the A0. Three lithofacies have been identified with carbonate texture of wackestone-mudstones. The carbon isotope record was a useful tool for interfield and global correlations, while the oxygen isotope record helped for intrafield correlations as well as providing information about diagenesis. Reservoir rock characterization of the A0 showed that the majority of the porosity comes from the interparticle porosity in the micrite. QEMSCAN and SEM have shown that there is significant isolated porosity in lithofacies 1 that is not contributing to the effective porosity. This isolated porosity comes from the coccoliths and foraminifera. These microfossils were not destroyed due to the early cementation that held their morphology intact. Clay-rich seams and stylolites formed vertical flow barriers by dissolving micrite and re-precipitation into diffused cement. The A0 contains light oil that makes it feasible to develop, hence, more dynamic data are required for full field development.