The U.S. Energy Information Administration just released December 2011 data for U.S. petroleum trade. The EIA reports that net oil imports fell last year to 45.2% (lower even than previously reported based on data that didn't include year-end figures), which is the lowest level for net oil imports in 16 years, going back to a 44.5% share in 1995. Part of this 16-year low for net oil imports is because of the domestic shale oil revolution that allowed North Dakota to surpass the daily oil production of OPEC-member Ecuador last year.
At the current pace of monthly increases, North Dakota will be producing oil later this year at a level that could displace imports from Venezuela or Nigeria, and it will also likely surpass Alaska and California this year to become the No. 2 oil-producing state in the U.S. This year will also likely be the seventh consecutive year of falling U.S. net oil imports, and if net oil imports fall below 44% (which is likely), it will be the lowest level in 20 years.
Update: The new EIA data also show that U.S. petroleum production reached an 8-year high in 2011 (highest since 2003) and oil from the lower 48 states reached a 14-year high (highest since 1997), see chart below. Since the lows in 2008, total U.S. oil production has increased by 14.6% overall and by almost 20% in the lower 48 states.