Sweet-spot mapping of the Goldwyer Formation through formation evaluation and property modelling in the Canning Basin, Barbwire Terrace case study

Abstract

The Goldwyer Formation of the Canning Basin has been regarded as a highly prospective shale petroleum play. This study assesses the potential prospectivity of this source rock as an unconventional hydrocarbon resource via property modelling. Considering the sparsity of wells penetrating the Middle Ordovician Goldwyer across the vast under-explored area of the Canning Basin, a basin-wide study of the source rock is not justified. Due to a higher well density, assessment of the Goldwyer Formation within the Barbwire Terrace, a sub-division of the Canning Basin, is carried out instead. This assessment includes the estimation of key shale play properties, such as, total organic carbon, total porosity, water saturation, and brittleness. Each property was estimated from available well wireline log data by testing multiple estimation methods. Total organic carbon values were derived from multiple regressions of different well data. A simplified Archie’s equation was used to estimate water saturation. Density porosity method was used for total porosity estimations. Sonic data along with density were utilised to estimate the brittleness index. Each property was then modelled across the Barbwire Terrace, which provided geostatistical estimates on the propagation of each parameter. In order to generate sweet spot maps, averaged maps of the properties were combined in a weighted manner. In the model, the Goldwyer Formation was divided into three layers based on dominant lithology. The uppermost shale dominated layer was predicted by the model to be the most prospective stratigraphic zone. The sweet spot maps highlight the southern flanks of the northern and western part of the Barbwire Terrace as the highest prospective geographic locations. This approach attempts to simplify the complexity of unconventional resource assessment, and has provided a single product evaluating the prospectivity of the Goldwyer as a hydrocarbon resource.