Energytsars,an interesting read,these rigs are designed...

Energytsars,
an interesting read,
these rigs are designed primarily for mineral exploration.
Drilling in the Cooper Basin, primarily sediments overlying the granite is a bit different from drilling the granites of WA.
The GDY holes are large diameter, so the drill pipe is 3-4 times heavier. Casing is required to be set at great depth, so the drilling rig needs to be able to suspend heavy lengths of drill pipe or casing, hence the size of the Lightning rig.
Secondly there are pressures involved, potentially from hydrocarbons in the sediments, and from the water in the granite. This requires a space for the pressure containment devices, ie BOP's that stand below the drilling platform, some 9m is required for this. So the design, and capacity is a bit different to handle the different requirements.