This discussion responds to the recent paper by Karolyté et al. (2020), in which strategies for the application of the shale gouge ratio (SGR) algorithm to fault seals in CO₂ sequestration are discussed and outlined.

The authors propose that the observed hydrocarbon columns in the Katnook field in South Australia and the Boggy Creek field in Victoria are supported by fault rock seal. Fault rock seal (membrane seal) is thought to arise from a contiguous, fine-grained fault core, forming a capillary barrier for two non-miscible fluids (Yielding et al. 1997). The authors use the inferred hydrocarbon columns and pressures to calibrate and constrain the use of interfacial tension (IFT) and contact angle (CA) data for use in capillary seal calculations to forecast CO₂ accumulations.

The authors have not supplied the basic geologic data to support their work, and we question the author's conclusion that fault-rock seal is active in these two fields.

Using the data provided in the paper, we were unable to create Allan maps. The maps provided in figure 2 do not show contours thus we were unable to:

• tie the maps to the wells

• use the maps to assess fault geometry and displacement consistency

• check the Allan Maps that are presented.

Whilst well data …