Based on this map (which, by the way, is two years old), does it look to you like the oil and gas industry has not been aggressively exploring the deepwater Gulf of Mexico? That's where a big chunk of the 68 million acres of non-producing Federal oil and gas leases are located.
Even the Washington Post recognizes the fallacy of counting non-producing leases: deepwater tracts take a long time to bring on production due to the large-scale specialized and exotic hardware required to produce them. See Streiff's excellent front page diary on the topic.
I have assembled a layman's guide to offshore oil and gas leasing and development called Offshore GOM 101. It is written in the form of a blog, so it is in reverse chronological order. It will make more sense to you if you read it as it was written, starting at the bottom of the archive.
The base document for much of this is the MMS pdf Active Leases and Infrastructure, a planning document for the August 20, 2008 lease sale, covering leases in the Western GOM Planning Area. It's a huge display, with more detail than most people will be interested in, but it's a start in getting one's mind around the leasing policy issues that are at the heart of today's debate.