BUENOS AIRES—Pan American Energy, one of Argentina’s leading oil and gas companies, plans to invest $1.4 billion in the country, people familiar with the plans said this week.

Pan American runs the largest oil field in Argentina, Cerro Dragon, and has so-called tight gas projects in the province of Neuquén, home to Vaca Muerta, one of the world’s leading resources of unconventional oil and gas. The company is expected to announce that it will invest around about $900 million in production at its oil field in Chubut province. Most of the rest of the investment likely will go to Neuquén, people familiar with the plans said.

A spokesman for Pan American, which is expected to announce details of its plans late Thursday afternoon alongside Argentine President Mauricio Macri, didn’t respond to repeated requests for comment. It was unclear how long ago the company made its investment decision.

It also was unclear if the investment would occur in 2016 or over a longer period.

“This is remarkable under current events. This is quite a substantial investment,” said Daniel Gerold, director at G&G Energy Consultants, who noted that low global oil prices have caused other companies here and abroad to slash capital expenditures.