Evaluation of Stratigraphic Elements on Fluid Flow – An Experiment Based on Deep-Water Slope Channels in the Capistrano Formation (Miocene), California

Stewart, Jonathan¹, Ben Fischer¹, Colin Lyttle¹, Kirt Campion¹, Anthony Sprague¹ (1) ExxonMobil Upstream Research Company, Houston, TX

Accurate predictions of flow rates, timing of water and gas breakthrough, and hydrocarbon recovery are necessary to assess the economic viability of deep-water reservoir developments. Typically, this is achieved by constructing a geologic model, up-scaling, and performing flow simulation. However, the replication of organized stratigraphic architectural elements in geological models and the preservation of these elements in up-scaled reservoir simulation models are difficult, often resulting in poor predictions of reservoir performance.

To examine the effects of stratigraphy on fluid flow, fine-scale 3D geologic models, based on descriptions and measurements of deep-water channel remnants in the Miocene Capistrano Formation, were constructed. This well-exposed formation contains a variety of deep-water architectural elements including storeys, channels and channel complexes. The lithofacies within the Capistrano Formation include gravel-rich turbidites, sandy turbidites, and thin-bedded muddy turbidites.

Without up-scaling the geologic model, a number of flow simulation experiments were carried out to test the impact of gravel beds and shale drapes at the margins of channels on reservoir performance. The presence of these heterogeneities had a significant negative impact on recovery efficiency and timing of water breakthrough. The results from these simple simulation experiments compared favorably with behavior observed in subsurface reservoirs based on production and 4D seismic data. A remaining challenge is to preserve the effect of these stratigraphic details in coarser-scale simulation models, and we suggest one such method.