rio tinto in gove running out of gas, page-6

The gas supply wanted by Rio Tinto is 10 years in length, as for gas amount all I could find is this article

http://www.theaustralian.com.au/news/breaking-news/review-to-recommend-gove-closure-reports/story-fn3dxiwe-1226569917762

"But the plant would use about as much gas as currently is needed to power the NT, and allocating the refinery enough gas could lead to gas shortages elsewhere."

So it's safe to say it's a pretty big amount of gas.