US oil and gas company Noble Energy announced that its fourth-quarter profit tumbled sharply as it wrote down the value of some of its natural gas operations in the US, the Gulf of Mexico and Ecuador.

Noble said it made $8m, or 5¢ per share, for the quarter ending in December 2009, compared with profit of $305m, or $1.72 per share, in the same period a year earlier.

Discounting charges, Noble said it made $178m, or $1.01 per share, for the quarter.

Revenue totalled $760m compared with $573m in the year-ago quarter even as production fell slightly to 206,000 barrels of oil equivalent per day from 208,000 barrels in Q4 2008.