Petrophysical analysis of the unconventional reservoirs of the Lennard Shelf and Fitzroy Trough in Canning Basin, Australia

Abstract

A US operator with a commitment to future drilling, stimulation and testing of unconventional wells has initiated a new evaluation to better define and understand the hydrocarbon plays along the northern margin of the Canning Basin’s Lennard Shelf and Fitzroy Trough. The goal of the evaluation is to determine the commercial viability of the region. In this paper, an integrated petrophysical hybrid model that has been calibrated to core data is highlighted. From this model, multiple play types were identified, including an unconventional siltstone-shale play, a conventional basin-centred tight gas play and a fractured tight gas play with potential analogs to North American unconventional plays. Six primary lithofacies were identified through the integration of thin section analyses, core descriptions, logs and petrophysical models. The results were calibrated to high-resolution formation image data to better understand the thin-bedded nature of these plays. The lithofacies were also utilised for defining core poro/perm transforms. Furthermore, an integrated descriptive mud log algorithm was utilised to define the types of hydrocarbons, including wetness, balance and ratios as the hydrocarbons’ fingerprints. Significant gas influxes were noted at the intervals with highly permeable beds, at swarms of fractures and faults, as well as within the organic rich layers. In this study, a pressure top seal for the Laurel Formation was defined as well as the highlights of one well, which includes 11 zones and over 389m of net pay behind pipe. The significance of this work is that it highlights a path forward for unconventional development that, if economically viable, would provide increased energy independence for Australia.