The U.S. Energy Information Administration (EIA) on Thursday reported an injection of 15 Bcf natural gas into storage for the week ended July 22. The result fell below already modest expectations, leaving Nymex natural gas futures to whipsaw in and out of positive territory as market participants tried to assess its implications.

Ahead of the EIA report, the September futures contract, in its first day as the prompt month, was trading in a narrow range of gains and losses and hovered around $8.569/MMBtu.

After the print crossed the wires at 10:30 ET, the front month popped up more than 10 cents but then proceeded to see-saw again. Following another 30 minutes of erratic post-report trading, the September contract was ahead 1.6 cents to $8.570, as traders digested a weak...