The geologically ancient land mass of Australia has approximately the same size as the United States and has a large continental shelf area. It encompasses all known geological conditions; thus a survey of interpretation in Australia covers a wide range of problems. Typical cases of sedimentary basins have been selected and examples developed to demonstrate interpretation problems met and methods of interpretation used. In the Surat Basin (sub basin of the Great Artesian Basin) the problems are fresh formation waters and the difficulty of establishing formation-water resistivity and hence of evaluating water saturation. In the Cooper's Creek Basin the problem is tight shaly sands with difficulty in establishing formation water resistivity and porosity. In the Otway and Gippsland Shelf Basins the problems are:
Massive quartzose sandstones with clay minerals and coals, and variable or unknown formation water resistivity.
Variable invasion diameter. 3. Gas-oil contact determination.
