The Predictive Modeling of Authigenic Mineralogy and Reservoir Quality Using Geochemical Data from Core and Cuttings: A Case Study on Devonian to Carboniferous Sequences from the RKF Field (Berkine Basin, Eastern Algeria)

Tim J. Pearce¹, Teresa Batrina², and Antonio Alaminos Martinez^2
1Chemostrat Ltd, Powys, United Kingdom
²CEPSA, Madrid, Spain

The paralic Devonian to Carboniferous sequences from the RKF Field of the Berkine Basin (eastern Algeria) represent locally important oil reservoirs, whose reservoir quality is strongly influenced by the distribution of authigenic clay minerals, carbonate minerals and quartz overgrowths. Establishing the distribution of the authigenic minerals is hampered by lack of extensive core coverage, so it becomes vital to try to extract mineralogical information from cuttings whose lithological and mineralogical characteristics have been obliterated by turbo-drilling. This paper demonstrates how inorganic geochemical data (acquired from core and cuttings as part of a larger chemostratigraphic correlation study) are used to determine the authigenic mineralogy of the reservoirs and the impact such mineralogy has on reservoir quality. Mineralogical data (petrographic and XRD) have been acquired from fifty core samples, with the aim of demonstrating how geochemical data can be used to model the distribution and abundance of authigenic clay minerals and carbonate minerals. Variations in the concentrations of Si, Al, Fe, Ca, Mg, Mn, K, Sr, Cs, Ga, Rb and La are used to model the abundance and distribution of siderite, chlorite, kaolinite, smectite and quartz (as authigenic overgrowths), with the mineralogical data being used to corroborate the geochemically-based findings. Such geochemical mineral modelling is extended to uncored sections, providing a means of establishing the mineralogical factors controlling the NPHI log response over an entire reservoir interval.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece