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Abstract: A New Methodology for Fractured Reservoir Analysis and Modelling

Marie-Christine Cacas, Jean Letouzey

Dynamic modelling of fractured reservoirs involves a conceptual double-porosity medium equivalent to the real medium. Geometric modelling of the discrete fracture network has become a classical approach for deriving the parameters which characterize this equivalent double porosity medium. These models are often based on the statistical description of the fracture geometry, deduced from observations along wells and cores. Unfortunately, it is now obvious that fracturing is a highly non-stationary process. Paleo-stresses, paleo-strains and lithology variations at the scale of the reservoir govern the spatial distribution of the fracture network characteristics.

We are developing a new methodology for studying fractured reservoirs, which is based on a deterministic prediction of these non-stationarities, constrained by subsurface and outcrop data. It is supported by a new software in which:

-- geostatistical stratigraphic modelling is used to predict possible locations of jointed units,

-- horizon topography maps from 3D seismic data are used for curved space analysis, which gives information on the location and orientation of fold-related joints,

-- fractal analysis is used to generate sub-seismic faults extrapolated from the network of major faults,

-- geomechanical modelling and analogue modelling yield stress and strain history, which are interpreted in terms of fracture attributes.

These approaches yield 3D maps of fracture attributes at the scale of the reservoir. They are used for zoning the reservoir, in terms of "fracture facies."

This methodology is being carried out on the Garreth El Gueffoul structure, in the Ahnet desert, Algeria.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France