Geological Modelling and Flow Simulation of a Base-of-Slope and Ponded Basin-Plain Turbidite Sequence (Peira Cava Outcrop, France)

Lawrence Amy, Simon A. Peachey, and Andy R. Gardiner
Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, United Kingdom

Basins in which turbidity currents are completely or partially trapped are known from many tectonically active, deep-water settings and to form productive hydrocarbon reservoirs. Previously, outcrop work on an Eocene-Oligocene turbiditic system in the Peïra Cava area, a sub-basin of the Alpine foreland in southeastern France, has allowed spatial characterization of a ponded basin fill on the basis of a correlation framework derived from measured outcrop sections and photomosaics. The basin-fill architecture comprises a sand-rich, proximal scour-and-fill facies with a downstream progression to mud-rich, basin-plain turbidite sheet facies. The field data have been used to construct a three-dimensional, ‘deterministic’, geological model of the Peïra Cava stratigraphy and reservoir flow simulations have been run in order to: i) evaluate the reservoir behaviour of realistic turbidite geology using finer detail static models than normally used in a commercial setting; ii) test which sediment heterogeneities are the most important controls on flow behaviour; iii) quantify how predictions based on coarser or upscaled models deviate from the ‘truth’ case. Initial results show that sweep efficiency is particularly sensitive to the permeability of laterally extensive gravel and conglomerate units. If these units have relatively high values, as noted from some subsurface reservoirs, some parts of the reservoir can remain unswept due to the rapid advance of the flood front through the coarser-grained intervals, leading to relatively early-water breakthough. The absence of extensive high-permeability beds allows greater sweep efficiency.

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