Sierra Madre de Chiapas-Peten Foldbelt

Commentary

Mexico's country view is Neutral: the 2025 reforms restored Pemex's primacy, and mixed contracts, all ten of which had been signed by September 2026, are now the main entry route, but awards have so far gone to fields in Tabasco, Veracruz and north-east Mexico rather than Chiapas, and judicial reform and the 2026 USMCA review add risk. On the Guatemalan side, the Xan field has been shut since August 2025 and the state is funding the closure of its wells, removing the basin's main producing operation. No sanctioned neighbour bears on the basin. The USGS's 2024 assessment confirms material undiscovered oil and gas, but with access constrained on both sides of the border, the resource does not lift the basin above the country view. Outlook: Neutral.

Updated

October 11, 2026

Location

Description

The Sierra Madre de Chiapas–Petén Foldbelt (USGS Province 5310) extends from Chiapas in south-east Mexico into the Petén of northern Guatemala and, in the USGS's 2024 assessment of Mexico, Belize and Guatemala, comprises the NW–SE-trending Sierra Madre de Chiapas Fold Belt and its foreland, the Petén Basin. It lies north of the crystalline Chiapas Massif (Province 5311), and the Southern Petén Basin lies south of the Yucatán Platform. Deformation began with subduction of the Farallon plate in the Late Cretaceous–Eocene, and Miocene subduction of the Cocos plate formed the present fold belt and foreland basin. The fill is dominated by Mesozoic platform carbonates and evaporites, with up to 5,000 m of Cretaceous shallow-marine carbonates and evaporites and thin organic-rich pelagic limestones in the Southern Petén Basin, overlain by Eocene foredeep deposits of the Petén Group. Producing reservoirs are the Albian Cobán C and Cenomanian Cobán B carbonates at fields such as Rubelsanto and Chinajá, while fractured carbonates in structural traps and Miocene–Pliocene sandstones provide further targets.

Summary

The USGS's 2024 assessment gives the Sierra Madre de Chiapas–Petén Fold Belt and Basin Reservoirs AU mean undiscovered resources of 494 MMBO and 5,134 bcf of non-associated gas, plus 395 bcf of associated gas and about 115 MMBNGL. On the Guatemalan side, the Xan field in Petén, whose contract covered around 80% of national crude output, stopped producing on 13 August 2025 when Perenco's contract 2-85 expired and its 59 wells and facilities returned to the state. The state is expected to bear a closure cost of about US$50 million, and the 2026 budget allocates Q148.4 million for the technical closure, which the Ministry of Energy and Mines will put out to tender. In Mexico, Pemex's mixed contracts have so far gone to fields in Tabasco, Veracruz and north-east Mexico rather than Chiapas.