Cojan, Isabelle¹, Olivier Fouche¹, Simon Lopez¹, Jacques Rivoirard¹
(1) Ecole des Mines de Paris, Fontainebleau, France

ABSTRACT: Representation of Geological Heterogeneities by a Forward and Stochastic Modelling of Meandering Fluvial System

Fluvial systems are characterized by sedimentary bodies of varied sizes, the distribution of which is linked to the stream evolution. The combined approach of process-based and stochastic modelling of fluvial meandering systems at the scale of oil reservoir allows to reproduce realistically geological heterogeneities at different time and spatial scales. The model is controlled by a few parameters which reflect the channel morphology and the flow characteristics. It allows the accumulation of sediments in the channel and in the floodplain by the interaction of lateral accretion and aggradation of the channel as well as by aggradation of the floodplain via overbank floods, crevasse splays and avulsions. Rules of deposition and evolution are based on hydraulics and experimental observations.
The heterogeneities observed in geological setting are represented through the facies distribution, which is both controlled by autocyclic evolution and external forcing. Forward process-based modelling produces very realistic realizations of the autocyclic evolution. Point bar facies, ox-bow lake and crevasse-splay lobe deposits are located in relation to channel migration, overbank alluvium are distributed on the floodplain with respect to channel location and floodplain topography. Heterogeneities linked to external forcing are taken care of via the stochastic component. Facies distribution is honoured by the use of vertical proportion curves, while some stochastic parameters allow deposition of specific facies where expected from data or observations. Several realizations of distinct fluvial architectures are produced quickly using a limited number of parameters.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.