Next steps to crack the code on tight Permian Toolachee and Patchawarra sandstones of the Cooper Basin, southwest Queensland

Abstract

Historic wells drilled by Real Energy Corporation Limited (Real Energy) in the Windorah Trough (Cooper Basin, southwest Queensland) characterised the Toolachee and Patchawarra formations as being gas-charged, tight-gas, sandstone/lacustrine shale sequences having layers of coaly source rock with high total organic content and moderate hydrocarbon indices. Consistent with being tight-gas reservoirs, drill stem tests have mostly either failed to produce gas or resulted in non-commercial flow rates. To date, North American methodologies for tight and shale gas extraction have not been consistently successful when applied in non-normal stress regimes outside of North America (i.e. Cooper Basin, China, Poland, Middle East, etc). Real Energy anticipated that North American technologies and practices were not likely to be directly applicable, as noted by published case studies for Australian shale gas wells (Johnson and Greenstreet, 2003; Pitkin et al, 2012; Scott et al, 2013; Johnson et al, 2015). Thus, it became an imperative to evaluate any methodologies or technologies more applicable for the Australian strike-slip to transpressional stress regimes to prevent fracture misalignment or disorientation, effects that result in ineffective fracture stimulation. Overall, a more scientific approach must be applied to developing and understanding the most efficient reservoir stimulation processes (e.g. drilling techniques, rock mechanical properties determination, well azimuth, perforating schema, and well interval selection) to optimise the stimulated reservoir volume (SRV). In this extended abstract the authors take the first steps at defining the stimulation strategies required for these tight sandstones using data and results from two case study wells. The authors outline the well observations and report key lessons in a cooperative spirit to solicit industry feedback and further technologies that can aid development of fit-for-purpose technologies to facilitate extraction of these largely untapped resources across the undeveloped troughs and flanks of the Cooper Basin.