The Burke - Dullingari structure involves the Permian Toolachee and Patchawarra Formations, both of which contain multiple sandstone reservoirs. Of the three culminations mapped in the Toolachee Formation, two have been drilled, as have two of the four culminations mapped at the Patchawarra level. Considerations of structure, and of the geology which is known only from four wells, have led to gas-in-place estimates of 328.1 billion standard cubic feet (SCF) Proven and Probable reserves in the Toolachee Formation, plus 45.9 billion SCF of Possible reserves. Gas reserve estimates at the Patchawarra Formation level are based on two criteria: if the Dullingari structure is filled only down to the level of the lowest gas-bearing sand encountered in the Dullingari 2 well, then the total reserves in the Proven and Probable category are 474.6 billion SCF, and in the Possible category 203.9 billion SCF; but if the Dullingari structure is filled down to the gas/water contact, the field Proven and Probable reserves are at least 474.6 billion SCF, plus 681.7 billion SCF of Possible gas-in-place.