The Predictive Modelling of Lithotypes and Lithofacies Using Geochemical Data from Core and Cuttings: A Case Study on the Devonian to Carboniferous Sequences of 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

Devonian to Carboniferous sequences encountered in the RKF Field, from the Berkine Basin of eastern Algeria, consist of progradational cycles of shoreface to shallow marine sandstones and estuarine deposits capped by offshore marine mudstones. Some of the sandstones represent important oil reservoirs, though modelling reservoir distributions is difficult, partly due to the complex interplay of paralic facies, which hampers field development and well targeting. The differentiation and mapping of lithofacies is further complicated by a lack of extensive core coverage, thus it becomes essential to try to extract lithofacies information from cuttings whose lithological and mineralogical characteristics have been obliterated by turbo-drilling. This paper demonstrates how inorganic geochemical data (acquired as part of a larger chemostratigraphic correlation study) are used not only to model lithotypes and lithofacies, but also to construct a viable sequence stratigraphic model for the cored and uncored wells. By the statistical analysis of geochemical data for core samples categorised (using sedimentological log criteria) into lithofacies groups the geochemical signatures for each lithofacies have been defined and used to predict lithotypes and lithofacies in the other study wells, using both core sample data and cuttings data. These geochemically-predicted lithotypes and lithofacies are also used to establish a sequence stratigraphic scheme, which has been corroborated by biostratigraphic data. The ability to extract valuable facies information from cuttings whose primary lithological and textural characteristics have been obliterated by drilling has major implications with improved reservoir correlation in the RKF Field and potentially in many other fields worldwide.

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