UPDATE 3-National Oilwell Q3 profit doubles but shares off

(Adds byline, analyst comment, comments from conference call; updates share price)

By Anna Driver

HOUSTON, Oct 24 (Reuters) - National Oilwell Varco Inc (NOV.N), which makes oil and gas drilling equipment, on Wednesday said its third-quarter profit doubled on strong demand from international customers and national oil companies, but its North American outlook weighed on its shares.

Profit in the third quarter was $366 million, or $1.02 per share, compared with $176.6 million, or 50 cents per share, a year earlier.

Analysts on average had expected a profit of 94 cents a share, according to Reuters Estimates.

Revenue jumped 45 percent to $2.58 billion.

"International demand for our equipment and services continues to build, particularly from national oil companies, while North American operators appear to be adopting a more cautious stance as we enter the fourth quarter," Pete Miller, the company's chief executive, said in a statement.

And on a conference call with analysts, National Oilwell's chief financial officer Clay Williams said equipment sales activity in North America "has continued to drift down" as spending on new rigs slows.

Shares of National Oilwell fell more than three percent, or $2.45, to $72.32 on the New York Stock Exchange.

Roger Read, analyst with Natixis Bleichroeder said two factors were weighing on the shares.

"Number one is the order trend in North America, and number two is some of their segments in the fourth quarter are expected to be relatively consistent with what they did in the third quarter."

The company's rig technology segment posted a 72 percent jump in revenue from a year ago to $1.52 billion.

Backlog for capital equipment orders for the company's rig technology unit increased to $8 billion from $7.2 billion in the prior quarter.

New orders during the quarter were a record $1.9 billion. The company's backlog for capital equipment continued to increase, fueled by strong demand for its drilling equipment, particularly for international offshore rigs.

Shares in National Oilwell Varco have rallied by more than 140 percent this year as the broader Philadelphia Oil Service sector index .OIX has risen 24 percent. (Additional reporting by Matt Daily)