Lateral heterogeneity of basin-plain turbidites of the Cloridorme Formation, Quebec, Canada: Implications for horizontal well prediction

Abstract

Facies models for basin-plain turbidite systems often depict very simplistic event-bed geometries that are tabular at the kilometre scale. However, recent studies have demonstrated more complex facies architectures, including rapid changes in event-bed thickness and facies composition. This lateral event-bed heterogeneity can have a significant impact on reservoir heterogeneity prediction in basin-plain turbidite systems developed for hydrocarbon production, carbon sequestration or geothermal energy. Coastal outcrops on the Gaspé Peninsula in Quebec expose the Middle Ordovician Cloridorme Formation, a synorogenic ‘flysch’ turbidite system developed in the Taconic foreland basin. The formation is interpreted to occupy a basin-floor position due to long-distance (tens of kilometres) correlations of bedsets in the direction of palaeocurrent. This outcrop-based study of the Cloridorme Formation utilises drone photogrammetry, centimetre-scale graphic logs and handheld gamma ray scintillometry data to better understand the detailed turbidite and hybrid event-bed architecture in a basin-plain setting. While most beds in this outcrop study can be traced for 500 m or more in a downcurrent direction, these results indicate significant intra-bed and inter-bed lateral complexity, including changes in bed thickness, grain-size distribution and mud content. The quantification of these lateral changes and comparison with other well-constrained outcrop analogues refines the environment of the Cloridorme Formation and aids in the prediction of subsurface heterogeneity in conventional and unconventional hydrocarbon reservoir systems through reservoir model parameterisation, as well as the characterisation of lateral heterogeneity important for horizontal-well geosteering and completion strategies.