PROBE PERMEABILITY STUDIES FOR BETTER RESERVOIR UNIT EVALUATION WITH EXAMPLES FROM THE TIRRAWARRA SANDSTONE, COOPER BASIN AND THE MURTA AND MCKINLAY MEMBERS, EROMANGA BASIN

Abstract

Probe permeametry studies have enabled a better understanding of permeability characteristics of three clastic reservoirs: The Tirrawarra Sandstone in the Tirrawarra and Gidgealpa fields of the Cooper Basin and the Murta and McKinlay Members in the Jena and Biala fields of the Eromanga Basin.

An empirical relationship between Hassler-sleeve core plug measurements and probe permeametry is used for calibration. The probe permeameter takes sufficient non-destructive readings to define permeability better within an individual facies or reservoir flow unit.

Frequency versus log (permeability) plots and semi-variograms allow visual comparison of individual reservoirs and facies. Histograms of plug and probe data show similar distributions, but the plug data generally have a lower variance than the probe data.

For the Tirrawarra Sandstone there is a better match between probe permeability data and wireline predicted permeability than between the latter and core plug permeability.

Azimuth directional permeability is evident for the braided fluvial sands of the Tirrawarra Sandstone. Permeability within the measured formations is primarily related to depositional facies. Secondary reduction in permeability within the Tirrawarra Sandstone is mainly due to ductile rock fragment compaction and authigenic clay precipitation with possible groundwater flow control in the Gidgealpa field.