CUEVAS GOZALO, MARGARITA C., and MARINUS E. DONSELAAR, Delft University of Technology, Delft, Netherlands

ABSTRACT: Reservoir Heterogeneities in Stacked Fluvial Point Bars, Loranca Basin, Spain

Internal facies heterogeneities in sandstone fluvial deposits may be the cause of oil entrapment. Heterogeneities occur at different scales: (1) within channel-belt sandstone bodies, heterogeneities are related to finer grained channel abandonment facies; (2) within a single meander-loop deposit, heterogeneities are related to facies changes as a consequence of major paleochannel discharge fluctuations; (3) within individual point bars, heterogeneities are related to the vertical facies distribution and the occurrence of lateral accretion surfaces; (4) heterogeneities at the scale of sedimentary structures.

A study of the relationship between facies heterogeneities and permeability contrasts, as well as gamma-ray response is done on outcrop examples. For this purpose, fluvial sandstone bodies are studied in three dimensions by means of architecture analysis, sedimentary logs, and in-situ permeability and gamma-ray logs.

In order to model and visualize the heterogeneities in three dimensions, a stratigraphic cellular modeling software package is used. Bounding surfaces between point bars and meander-loop units serve as framework for the model. Log data are converted to well information and introduced as attributes in the framework model. Interpolation between the wells results in 3-D models for the different attributes.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.