Shares of Weatherford International Ltd. fell 4 percent on Tuesday as Citi lowered its forecast of the oilfield-services company’s profits for the rest of 2012 citing less activity in North America.

THE SPARK: Citi lowered its earnings estimates for the third and fourth quarters to 25 cents per share in both, below the company’s forecast of earnings between 30 cents and 32 cents per share.

Analysts surveyed by FactSet were expecting the company to earn 27 cents per share in the third quarter and 32 cents per share in the fourth.

THE ANALYSIS: Citi analyst Robin Shoemaker said, however, that Weatherford is fighting “stalled momentum” in oil drilling in U.S. shale formations and less drilling in Canada, where the company is active.

Shoemaker said the U.S. rig count has fallen by 7 percent since December, and while it’s at or near the bottom it won’t rise significantly until next year’s first quarter. The analyst also expects margins to be thinner and corporate expenses for fixing income tax accounting to rise.

Shoemaker kept a “Buy” rating and $18 price target on the shares on the expectation of strong improvement in profits in 2013 and 2014.

SHARE ACTION: The shares fell 52 cents to close at $12.57. In the past year, they have ranged from $10.85 in October 2011 to $18.33 in February and have traded in a narrow band since they fell 8.8 percent on July 25, after the company reported second-quarter earnings that were less than analysts expected.