R$ 800 billion. That is the market value Petrobras reached for the first time at the close of trading on October 14, according to G1. Market value is the combined price of all of a company's shares on the stock exchange, as if someone were buying the entire company at once.

For small investors, the math is simple: preferred shares (PETR4), the most common among retail savers, are up about 100% in 2026, while common shares (PETR3) have gained nearly 110%. In practice, anyone who put R$ 10,000 into the stock in January would now hold something around R$ 20,000 to R$ 21,000, before fees and taxes. The result also matters to people who have never bought a share, because the federal government is Petrobras's largest shareholder and bigger profits tend to mean bigger dividends flowing into public coffers.

The company attributes the performance to a favorable international oil scenario, its financial results and rising production, which reached 2.7 million barrels per day in the second quarter, up 15% from the same period in 2025, according to G1. The latest driver of optimism, however, sits on the map: expectations over oil in the Equatorial Margin.

Understand

The Equatorial Margin is the offshore strip along Brazil's northern coast, between the states of Amapá and Rio Grande do Norte. The region has been nicknamed the "new pre-salt", a reference to Brazil's giant deepwater fields in the Southeast, because its geology resembles that of neighboring Guyana and Suriname, where major oil discoveries were made in recent years.

It was there that Petrobras announced, on October 2, its second oil discovery at the Morpho well, 175 kilometers off the Amapá coast, according to Agência Brasil. The oil was found in ultra-deep waters, at a water depth of 2,886 meters, in the Foz do Amazonas Basin. "The discovery expands knowledge about the area's exploratory potential and will provide additional information for assessing the petroleum systems and resource potential of the Foz do Amazonas Sedimentary Basin," the company said in a statement, as reported by Agência Brasil.

The size of the bet helps explain the stock market record. A study by the Energy Research Company (EPE), linked to the Ministry of Mines and Energy, estimates the basin could hold up to 10 billion recoverable barrels, compared with about 70 billion barrels in reserves for all of Brazil at the end of 2025, according to data from the National Petroleum Agency (ANP) cited by Agência Brasil. Before any commercial production, the material will undergo laboratory analysis and drilling will continue to measure the reservoir's extent.

The project also faces resistance. The drilling license, granted in October 2025 by Ibama, Brazil's federal environmental agency, pitted parts of the government and the oil industry against environmentalists worried about the impacts of exploration on the Amazon coast. Petrobras says its drilling is done safely and with respect for the environment.