Turbidite Channel Architecture: Recognizing and Quantifying the Distribution of Channel Base Drapes Using Core and Dipmeter Data

Mark Barton, Ciaran Obyrne, Carlos Pirmez, Bradford Prather, and Frans Van der Vlugt
Shell International Exploration and Production Company, Houston, TX

Field and simulation studies indicate that channel architecture and presence of channel base drapes can have a significant impact on oil recovery since they represent one of the main uncertainties in the development of a turbidite channel reservoir. In various oil field developments of channelized turbidite reservoirs such as the Schiehallion and the Ram Powell (N/M sand) fields, where oil recovery factors fall well below 40%, channel base drapes are thought to have an important impact on recovery efficiency. Simulation studies suggest that channel base drapes can decrease oil recovery by 3-4 percent for every 10 percent increase in shale drape coverage below 50 percent and by 6-8 percent for every 10 percent increase in coverage above 50 percent. Accordingly, understanding the frequency and distribution of channel base drapes provides valuable insights into reservoir performance and reduces uncertainty related to turbidite channel architecture. Criteria for the recognition of disconformities and channel base drapes using core and dipmeter data provide a basis for statistical assessment of their frequency and distribution, by comparing the observed number of channel base disconformities to the observed number of disconformities overlain by mudstone. Analog outcrop data provides information on how the drapes are positioned relative to the channel morphology. Or current practice is to apply the frequency of shale drape percentage observed in wells to the spatial coverage of individual channels elements in the reservoir model.