CALGARY -- The CEO of Talisman Energy Inc. (TSX:TLM) says a multibillion-dollar takeover by Spanish energy giant Repsol is the best case scenario for shareholders in a gloomy oil price environment.

The total purchase price is US$13 billion -- US$8.3 billion for Talisman stock plus the assumption of its debt.

The Repsol deal is a "terrific outcome" for a company facing a litany of challenges as crude prices plummet, from its large debt load to its sizable spending commitments in the U.K. North Sea, CEO Hal Kvisle told reporters Tuesday.

The takeover has the unanimous support of both companies' boards of directors, said Kvisle, the oilpatch veteran who came out of retirement more than two years ago to help turn the Calgary-based company around. He said he intends to stick around until the deal closes.

"The board considered in detail other alternative options and this transaction was viewed as superior to all other options available to the company," Kvisle told analysts earlier in the day.

The US$8 per share (C$9.33) offer marks a 75 per cent premium to Talisman's seven-day average share price.

Repsol started kicking Talisman's tires back in the summer but at that point Repsol "couldn't get to the bottom of certain complex issues," like Talisman's underperforming North Sea operations, which are prone to unplanned outages and production misses.

But with further analysis, Repsol eventually figured out how to make those assets work, Kvisle said.

Talisman's share price was as high as $12 during its first round of talks with Repsol.

In that context, Tuesday's deal is not necessarily a "good trade" for Talisman, said Himalaya Jain, portfolio manager at ScotiaMcLeod

But with oil prices dropping by nearly half over the past six months -- and Talisman's share price dipping to the $4 range before the takeover talk re-emerged last week -- it's a different story.

"From Talisman's perspective, their time was really running out," said Jain.

"Talisman did not have a conservative balance sheet so their ability to ride out these very low oil prices was very short. So I think they were quite keen on doing something very quickly."

Talisman's shares closed up about 48 per cent Tuesday at C$8.84 on the Toronto Stock Exchange.

Shareholders are to vote on the deal at a special meeting in mid-February and the transaction is expected to close during the second quarter of 2015.

Among other conditions, Repsol will need to apply for approval under the Investment Canada Act -- the same legislation under which oilpatch takeovers by Malaysian and Chinese state interests were reviewed in 2012.

Unlike those firms, however, Repsol is a fully privatized with no Spanish state control.

In 2012, Ottawa approved the takeovers of Nexen by China's CNOOC, and Progress Energy Resources Corp. by Malaysia's Petronas but tightened rules governing big takeovers by state-owned firms.

Kvisle said he's expecting the process for getting Ottawa's approval to be "fairly straightforward" and that he'd be "very surprised" if the review dragged on. Also working in favour of a speedy approval is the fact that Repsol plans to establish a major corporate presence in Calgary.

The deal will also need approval in various other countries in which Talisman operates, said Kvisle.

Repsol welcomes the scrutiny from Ottawa, spokesman Kristian Rix said in an interview from Madrid.

"I think we're expecting to be carefully examined like any other foreigner entering your market and that's fine with us. We are very conscious that we're guests in the countries where we operate," he said.

"We will do out best to pass that test and to show that we can build benefit for Canada, for Alberta, for the employees and for the company as a whole."

In a research note, CIBC World Markets analyst Arthur Grayfer said he doesn't see why Ottawa would block the deal, noting Talisman has no presence in the oilsands -- one of the concerns raised with CNOOC's takeover of Nexen.

Plus, Grayfer notes, Talisman's Canadian production is only 15 per cent of its total corporate output, with the rest mainly coming from the United States, Southeast Asia, Colombia and the North Sea.

Repsol has been on the hunt for investment opportunities since its holdings in Argentina were expropriated by the government of the South American country in 2012. The Talisman acquisition will roughly double Repsol's upstream presence, said Kvisle.

Often, workforce cuts are an outcome of such deals, as roles overlap. But Rix said Talisman's employees were a big draw for Repsol as it looks to grow.

"A strong part of that rationale for us is that you have people whose talents are very complementary to what we do already," he said.

"And those people are also in places where we really want to grow significantly, specifically Canada and the U.S."

The combined company will be among the 15 largest privately-owned oil and gas companies with activity in more than 50 countries and more than 27,000 employees.

Repsol has the expertise and financial wherewithal to deal with Talisman's challenges, said Rix.

"It's a great machine and it has great technicians," he said. "It probably needs a little bit of oil. Hopefully that's where we come in."