An Application of Sedimentary Process Modeling to Reservoir Characterization

Daniel M. Tetzlaff

Basin-wide two-dimensional sequence stratigraphic models, now widespread in industry, help to explain the processes that filled a sedimentary basin, and have numerous exploration applications. More detailed three-dimensional models based on physical principles of sedimentation appear to be useful at the reservoir scale as well. They provide a geologically consistent scenario of the spatial distribution of petrophysical properties, in the form of three-dimensional grids that can be used directly by the reservoir engineer.

This paper shows an application of such model to an ancient fluvial sequence in the North Sea, penetrated by four wells and surveyed seismically. The modeling result has a resolution comparable to that of well logs throughout the entire simulated volume, showing channels, levies, and point bars. It incorporates all geologic knowledge of the area, and is constrained by physical principles of erosion, transport, deposition, and compaction of clastic sediments. The outcome is still uncertain, in that the location of individual channels that are thinner than seismic resolution cannot be established with complete accuracy; but the overall reservoir architecture can be used readily by a reservoir simulator to determine the fluid conduction properties of the sedimentary package between wells If individual channel location is important, the uncertainty can be quantified by Monte Carlo simulation.

When wells are sparse and seismic resolution is low, but the depositional environment is fairly well known, this approach appears to be more geologically rigorous than many geostatistical simulation methods, and more practically useable to the reservoir engineer than intuitive geologic interpretations.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995