1.2.1.1.2 Toolachee Formation

Thick, laterally extensive coal seams are characteristic of the Toolachee Formation. The average coal seam thickness in the Toolachee Formation is 4.3 m, but individual seams may be up to 22 m. Forty-two percent of coal seams exceed 2 m thickness (Alexander et al., 1998). The Toolachee Formation coals are sufficiently mature for thermogenic gas generation in the Nappamerri and Arrabury troughs, and parts of the Patchawarra Trough. In addition, high mud gas readings (natural gas readings detected in returned drilling muds) have commonly been recorded during drilling through mature Toolachee Formation coals (Menpes et al., 2012). Coal in the Toolachee Formation intersected in drilling has been described as black to greyish black, dull to subvitreous, moderately hard to firm and variably silty (e.g. Beach Energy, 2012a, 2012b; Santos Limited, 1988, 1997).