Net income at Baker Hughes rose 5.4 percent to $395 million, or $1.27 a share, according to a statement Tuesday by the Houston-based company. Smith, also based in Houston, reported a 9.4 percent gain, to $175 million, or 87 cents a share.

Baker Hughes, Smith and larger rivals are expanding overseas, where crude prices above $100 a barrel drove a 6.5 percent increase in first-quarter drilling activity.

The North American market, driven more by natural gas drilling, had a 1.4 percent increase. 

BJ Services Co., an oil field contractor that is more reliant on North America, on Tuesday reported a 33 percent drop in profit, falling short of analyst estimates.

"Wall Street is anticipating and waiting for the next leg up in the entire sector," said analyst Dan Pickering of Tudor, Pickering, Holt & Co. Securities in Houston. "Navigating the short term ¡ª

Baker Hughes fell 70 cents to $81.12 in New York Stock Exchange composite trading, and Smith dropped $1.32 to $76.69. Houston-based BJ plunged $4.82, or 15 percent, to $27.98, its biggest drop since selling shares to the public in 1990.

Oil field contractors such as Baker Hughes and Smith provide equipment and services to oil and gas producers. Gas accounts for 81 percent of U.S. drilling.

U.S. inventories of the heating and power-plant fuel climbed to as high as 21 percent above their five-year average last May, causing Chesapeake Energy Corp. and other producers to pull back on drilling plans.

Baker Hughes Chief Executive Officer Chad Deaton has invested in infrastructure and staff to refocus overseas.

With operations in 90 countries, Baker Hughes relied on North America for 44 percent of first-quarter revenue, up from 43 percent a year earlier. The biggest revenue gain was in Latin America, at 9.2 percent.

Total first-quarter revenue at Baker Hughes rose 8 percent to $2.67 billion. Smith had a 13 percent gain, to $2.37 billion.

BJ was hurt by increased competition in its chief business, a service known as pressure pumping, Chief Executive Officer Bill Stewart said in a statement. Pricing fell the most in January and appeared to stabilize some in February and March, he said.

Pressure pumping injects water or sand into rock formations, creating fissures that help the gas move more easily.

Low profit margins may increase the likelihood of consolidation in the oil field services industry, Stewart said during BJ's earnings conference call.