Natural-gas prices edged higher Friday, as the October contract expired and traders bought futures to close out bets that the market would fall. Natural gas for October, the front-month contract, settled up 1.3 cents, or 0.3%, at $3.984 a million British thermal units on the New York Mercantile Exchange. The market was in the red for most of the day but rallied in the last half hour of trading. Analysts said the gains had all the markings of a market that had heavily been betting against price increases now trading out of those positions with the expiration of the contract–particularly in the absence of fundamental drivers that would be bullish for prices.