Top North American energy executives made a plea for continued North American free trade at a high-profile conference where Prime Minister Justin Trudeau will deliver a keynote speech later this week.

In separate sessions, Enbridge Inc. chief executive Al Monaco and Exxon Mobil Corp.'s Darren Woods argued industry and consumers are best served by open markets and free trade.

Asked about the Trump administration's plan to reopen the North American free-trade agreement, Mr. Monaco said it is too early to know the impact on his Calgary-based company, which is now the continent's largest energy infrastructure operator.

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"One thing I do know, the value from the integrated energy market between the two countries is unquestionable," he said. "And at the end of the day, you go back to first principles and that should drive good outcomes for both countries."

Enbridge completed its $28-billion (U.S.) acquisition of Houston-based Spectra Energy Corp. this past month, giving it a continent-wide network of oil-and-gas pipelines, local distribution companies and processing plants. It is also awaiting regulatory approval from the state of Minnesota to dramatically expand its main crude-export line from Alberta to the U.S. Midwest, and from there connecting to the Gulf Coast.

Mr. Monaco said he is confident that project won't be affected by President Donald Trump's executive order to require U.S. steel to be used in U.S. pipelines. The White House said last week that it would exempt TransCanada Corp. and its Keystone XL project from that order.

In addition to Mr. Trudeau, Natural Resources Minister Jim Carr and Alberta Premier Rachel Notley will speak at the IHS Markit's CERAWeek conference this week. Mr. Carr was hoping to meet with newly confirmed Energy Secretary Rick Perry.

Mr. Monaco praised the effort of federal and provincial governments to ensure Canada's interests are protected as the Trump administration considers trade and taxation proposals that could hurt the Canadian economy. That includes a renegotiation of NAFTA and a potential border-adjustment tax that is being proposed by Republican leaders in the House of Representatives as part of an overall tax reform that would slash corporate rates.

However, the Enbridge CEO said governments in Canada need to ensure that the cumulative impact of their policies – including carbon pricing and other climate regulations – do not undermine the competitiveness of energy producers.

Exxon Mobil's Mr. Woods also endorsed free-trade policies that ensure an easy flow of energy commodities, investment and capital goods needed to develop projects.

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"It's hard to be in the oil business and not support open and free markets and free trade," Mr. Woods told the conference. "The world benefits with free and open trade." However, he supported Mr. Trump's demand that trade deals must also be "fair."

Exxon Mobil has refocused its business on the Gulf Coast, with an announcement Monday that it will invest $20-billion in petrochemical manufacturing over the next 10 years, after completing a $5.6-billion acquisition in the prolific shale oil Permian Basin in West Texas.

Mr. Woods said its acquisition yielded 3.5 billion barrels of reserves with a total of 60 billion barrels of oil in place that could be recovered with advancing technology and higher prices.

The company also wrote off 3.5 billion barrels of its oil sands reserves, saying they were uneconomic at prices that prevailed last year.

The Permian has become the top draw for capital and drilling among the U.S. shale oil fields. Half of the U.S. drilling rigs brought back into service since the industry hit bottom in May, 2016, have been targeted to the Permian, Genscape Inc. analyst Jodi Quinnell said in a blog post.

The International Energy Agency projected U.S. shale oil production will make a strong comeback and grow by 1.4 million barrels a day over the next five years, assuming a price average around $60 a barrel.

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But the Paris-based agency said global supply growth may not keep up with rising demand, unless major new projects are approved soon. Prices could spike higher after 2020 due to the lack of capital investment in key producing regions.

While capital spending on U.S. shale production is climbing, "early indications of global spending for 2017 are not encouraging," the IEA said.

"Unless investments globally rebound sharply, a new period of price volatility is on the horizon," IEA executive director Fatih Birol said Monday at the IHS Markit's CERAWeek conference.