The upgrade was made following a review by Mincom on completed drilling.
The new modelling increases the inferred resource by 50Mt from the last project update of 104.74Mt three weeks ago that took in results from the Krueger deposit.
Cockatoo said the new additional resource had a stripping ratio of 9:1 when using a density of 1.45 grams per cubic centimetre; however, the majority of 48Mt occurred at a stripping ratio of 8:1.
Two rigs are currently drilling at the project in the Surat Basin.
The company’s wholly owned Surat project stretches over seven exploration permits for coal (EPCs) and two exploration permits for coal applications (EPCAs) covering around 3800 square kilometres.
Shares in the junior have remained flat at 28.5c.
