Evaluation of permeability from geophysical logs in the Barrow field, Western Australia

The Mardie Greensand is one of several producing reservoirs in the Barrow Island field, Carnarvon Basin, Western Australia. It is a glauconite-rich and multi mineral lithologically complex sandstone sedimentary unit. It is important for geologists, geophysicists and reservoir engineers to estimate accurately permeability from geophysical logs and improve reservoir description techniques. This paper presents a study of permeability evaluation using core and log data. Core porosity and permeability data were used to analyze the formation heterogeneity and to establish porosity±permeability transforms as well as to subdivide the Mardie Greensand into various hydraulic units. Electrofacies patterns and decision functions were determined to establish a link to permeability transforms in order to identify electrofacies and to obtain permeability values from well logs where cores were not available. Estimates of permeability through the techniques described in this paper were found to be more accurate than using other published methodologies. Some field examples of the application of this improved estimate of permeability values have shown sufficient promise to extend the methodology to the identification and characterization of potential reservoirs in other areas of the Mardie Greensand.