Nov. 1 (Bloomberg) -- Denbury Resources Inc., a U.S. oil and natural-gas producer, said it will buy Encore Acquisition Co. for about $4.5 billion to add fields in the Rocky Mountains and Gulf of Mexico.

Encore stockholders will get $50 per share, comprised of $15 in cash and $35 in Denbury common stock, the companies said in a joint press release distributed via Business Wire. Encore closed at $37.07 a share on Oct. 31, and the stock is up 45 percent this year. The purchase includes assuming Encore’s debt.

The acquisition will double oil reserves for Plano, Texas- based Denbury, a specialist in extracting crude from mature fields. Denbury said it would postpone its third-quarter earnings release and conference call because of the transaction, which will allow Denbury to undertake larger projects using carbon dioxide to get oil in a process known as enhanced oil recovery.

“With the addition of the Encore properties, we more than double our current inventory of oil reserves recoverable with carbon dioxide, and greatly expand our future growth potential with a second new core EOR area in the Rockies,” Phil Rykhoek, Denbury’s chief executive officer, said in the statement. The combined companies will have total reserves of more than 500 million barrels of oil equivalent, he said.

Denbury’s results will occur on Nov. 5, not Nov. 3 as originally planned, according to a separate press release distributed via Business Wire. Denbury’s shares closed at $14.60 on Oct. 31 and have gained 34 percent this year.

Bullish Options

J.P. Morgan Securities Inc., a division of JPMorgan Chase & Co., advised Denbury. Barclay’s Capital Inc., part of Barclays Plc, worked with Encore, according to the release.

Trading in bullish options on Encore jumped to a 17-month high last week, before Denbury announced that it would purchase the company. Call trading rose to 3,338 contracts on Oct. 27, the most since May 2008. After U.S. markets closed that day, Encore reported less profit than analysts estimated on average, and the shares plunged 7.1 percent the next day.

Denbury is the biggest oil and natural gas operator in Mississippi and has Barnett shale natural-gas assets in Texas, according to the company’s Web site. Encore has operates oil and natural gas projects in the Rockies, Mid-Continent and Permian basins.

The combined company will be known as Denbury Resources Inc.

To contact the reporters responsible for this story: Lester Pimentel at lpimentel1@bloomberg.net; Mark Shenk in New York at mshenk1@bloomberg.net

Last Updated: November 1, 2009 20:52 EST