Grupo Carso Acquires Additional 5% Stake in Zama

The binding agreement disclosed to the BMV deepens Carlos Slim's position in Mexico's most important offshore discovery, a field with up to 800MMb of recoverable reserves and a projected peak output of 180Mb/d by 2029, representing roughly 10% of Mexico's total national production target.

Grupo Carso disclosed that it had reached a binding agreement with Harbour Energy to acquire an additional 5% stake in the Zama offshore oil field for US$75.25 million, in a transaction that will be executed through a subsidiary of Zamajal, Carso's dedicated upstream investment vehicle. The announcement, filed as a material event with the Mexican Stock Exchange, confirms a continuing consolidation of private Mexican capital in one of the country's most strategically significant hydrocarbon assets.

Once the transaction closes, subject to regulatory approvals from the government and relevant authorities, Zamajal will hold approximately 17.84% of the Zama field. The resulting ownership structure will see PEMEX retain the majority with 50.43%, followed by Harbour Energy with 27.26%, Zamajal with 17.84%, and Talos Energy with 4.47%. The US$75.25 million, approximately MX$1.3 billion, will be directed primarily toward the development of the field.

The Field and Its Strategic Weight

Zama holds estimated recoverable reserves of between 600MMboe and 800MMboe, making it one of the most significant offshore discoveries in Mexico in recent decades. According to Marcos y Asociados, the field has a projected peak production of 180Mb/d in 2029, representing close to 10% of Mexico's total national production target at that date. The total planned investment over the life of the contract is estimated at more than US$9 billion through 2045.

The field is located in the Sureste Basin off the coast of Tabasco state in shallow water, a depth profile that makes it more economically feasible than deepwater developments and gives it a realistic development timeline. Harbour Energy was formally appointed as operator of Zama in early 2026, following an agreement among the field's partners, PEMEX, Grupo Carso, and Talos Energy Mexico, that was subsequently approved by SENER. The appointment ended years of operational disputes and positional negotiations that had delayed the field's development timeline.

Carso's Step-by-Step Accumulation

Wednesday's transaction is the latest in a sequence of moves by Slim to increase his direct and indirect stake in Zama specifically, and in Mexico's upstream sector more broadly. In September 2023, Zamajal completed the acquisition of 49.9% of Talos Mexico, the US company's Mexican subsidiary, for US$124.7 million, giving Slim indirect exposure to Talos's then-17.4% stake in Zama.

In a prior transaction that closed in early 2026, Grupo Carso had already acquired an additional direct Zama stake through a separate deal, also structured through Zamajal. That transaction involved a partial cash payment at closing and a deferred payment contingent on the field entering commercial production, a structure that aligns Carso's cost with the asset's performance.

The agreement adds another 5% of direct ownership on top of that accumulated position, making Zamajal the second-largest non-state shareholder in Mexico's most watched upstream development project. Slim's upstream exposure has expanded further in recent months: Grupo Carso announced the acquisition of Lukoil's Mexican subsidiary, Fieldwood México, earlier in 2026, giving Carso full control of the Ichalkil and Pokoch fields offshore Campeche, assets that complement the Zama position with existing infrastructure and near-term cash flow.

A Vote of Private Confidence in Mexico's Upstream

The transaction's timing carries a signal beyond Carso's own portfolio strategy. It arrives as PEMEX’s own 1Q26 capital investment fell to its lowest first-quarter level in eight years, as the government's mixed contract program has attracted primarily domestic construction firms rather than experienced upstream operators, and as the USMCA review has placed Mexico's energy sector under bilateral scrutiny. In that context, Slim's continued accumulation of Zama equity, at a disclosed price that implies a field valuation in line with international offshore comparables, represents a direct vote of private sector confidence in the project's commercial viability under the current regulatory framework.

Harbour Energy CEO Linda Cook had previously noted that Mexico's administration was showing a more open stance toward strategic projects, providing a context for both the operatorship transfer and the ongoing equity transactions in the consortium. With Harbour now as operator, Carso as the second-largest private partner, and PEMEX retaining majority control, Zama's governance structure reflects the hybrid public-private model that the Sheinbaum administration has been promoting through its mixed contract and Plan México frameworks.