Ichnofabric and Enhanced Reservoir Quality in the Cretaceous Ben Nevis Formation, Jeanne D¢ Arc Basin, Newfoundland, Canada

Effective production of petroleum from bioturbated reservoirs requires reliable prediction of facies related reservoir properties and facies distribution between wells. In such settings facies are essentially ichnofabrics. Ichnofabric analysis is a method used to describe the sedimentology and ichnology of a horizon in terms of diversity, bioturbation intensity and colonization history. Our integrated approach to the prediction of reservoir quality in bioturbated reservoir intervals from Ben Nevis Formation involves study of ichnofabric in core and further laboratory based analyses of samples. Distribution of ichnofabrics within core is of relevance to understanding reservoir characterization, and can be used to improve recovery from both petroleum reservoirs and aquifers.

Ben Nevis L-55 core from the Hebron Field, Jeanne D'Arc Basin, Offshore Newfoundland is currently being studied from a sedimentological and ichnological perspective, with particular emphasis on the bioturbated net pay horizons. This research is aimed at generating a more complete understanding of the role that organisms have in controlling the porosity and permeability of sandstone reservoir intervals. In particular examining the effect bioturbation has on porosity and permeability. In order to determine the influence bioturbation has on petrophysical properties, 64 metres of core was logged and analyzed. Core logging from both a sedimentological and ichnological (ichnofabric assignment) perspective is complimented with laboratory analyses of samples, including petrographical analysis using thin sections and large thin slices. Permeability is measured using a probe-permeameter, while porosity is estimated using dye impregnated thin section analysis within selected ichnofabrics. Preliminary analysis reveals both reduction and enhancement in permeability across burrows. Enhanced resolution and understanding of these permeability variations are gained when fine-scale permeability measurements are coupled with large thin slice images. The resultant images when viewed in transmitted light, reveal sedimentary and biogenic features that are not otherwise visible in polished hand specimen or conventional core sample analysis.