Quantifying Heterogeneities and Their Impact from Fluid Flow in Fluvial-Deltaic Reservoirs: Lessons Learned from the Ferron Sandstone Outcrop Analogue

Peter E. Deveugle¹, Matthew D. Jackson¹, Gary J. Hampson¹, Craig S. Calvert², Anthony R. Sprague², Michael E. Farrell², and Jonathan Stewart^2
1Earth Science and Engineering, Imperial College London, London, United Kingdom
²ExxonMobil Upstream Research Company, Houston, TX

Fluvial-dominated deltaic oil and gas reservoirs are economically important, but are characterized by complex facies architectures and flow behaviours. We have used a high resolution, reservoir-scale (4000 x 7000 x 50 m) geologic model of part of the Ferron Sandstone, an outcrop analogue for such reservoirs, to quantify key aspects of deltaic facies architecture, and to examine the impact of heterogeneity on fluid flow during production using streamline simulations directly on the model.

The dimensions of delta lobes vary from 6 to 10 km in length, 2.5 to 9 km in width, and 4 to 30 m in thickness. A key control on recovery is the connectivity between delta lobes, which is affected by (i) the presence of distributary and/or fluvial channel sandstones, which can increase recovery by improving connectivity between delta lobes, but also decrease recovery if the permeability contrast between channel and delta lobe facies is large, and (ii) the continuity of distal delta front facies, which controls the sweep of lobes that are not penetrated by wells. Recovery is also affected by well spacing, because this dictates the degree of cross-flow between delta lobes, and by the orientation of channels with respect to injector-producer well pairs, because channel sandstones can act as thief zones.

Quantification of stratigraphic architecture and associated fluid flow has enabled the representation of various geologic heterogeneities and their relative impact on recovery to be evaluated. Guidelines for reservoir geologists and engineers seeking to build quantitative models in a similar geologic setting are presented.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas