Bullish natural gas futures extend gains as a smaller-than-expected increase in inventories last week reduced the storage surplus, the EIA reports. Natural gas in underground storage increased by 70 billion cubic feet to 2,633 Bcf as of May 10, which was 620 Bcf or 31% above the five-year average for the week, according to the data. The week before the surplus was 33% above average. Analysts in a Wall Street Journal survey had predicted an increase of 79 Bcf. Natural gas is up 3.6% at $2.503/mmBtu.