Oil and natural gas are only found in certain places on earth because a number of rare events all must happen in the same place. ... The oil/gas must be trapped in the reservoir: sufficiently impermeable shale or salt layers must be oriented so that the oil/gas which is more buoyant than water does not escape.
Since the country has a smaller area and a large amount of people (although smaller than Australia) the ratio of land to people in New Zealand is much larger than the ration of land to people in Australia.
