Schlumberger blames lower pricing in U.S. land operations and seasonal weather factors for its lower fourth quarter margins. Pressure on the onshore U.S. market came also from lower marine utilization as several of the company's vessels were placed in dry dock. The company had to pay higher that expected start-up costs in South America, which also cut into margins.

Looking ahead, Schlumberger said the shorter-term growth outlook presents "a more complex picture than the immediate past." The company shows optimism over its land activity outside North America which is expected to remain strong.

Higher oil prices that reached $100 a barrel lifted the company demand over the past few quarters. Thus Schlumberger saw its stock price climbing more than 50% over the past year. In all, the oilfield services company posted a profit of $5.18 billion for the full year 2007, on revenue of $23.3 billion.

The oil sector has been under pressure recently on increased concerns over an economic slowdown. However, I expect to see further gains for the company as crude oil prices show no significant signs of easing too much more.

Eliza Popescu is a financial writer for the online investment advisory service Investor's Observer.