According to DIBP, new visa arrangements came into effect on 31 March 2015. These affects non-citizens other than permanent residents intending to work in Australia's offshore oil and gas industry.
People intending to work on resources installations should hold either a Subclass 457 Temporary Work (Skilled) visa or a Subclass 400 Temporary Work (Short Stay Activity) visa.
People who are participating in, or supporting, an offshore resources activity from a vessel will be granted the Special Purpose Visa by operation of law.
For more information, click: Working in Australia's offshore oil and gas industry