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Petroleum Geology and Resources of Southeastern Mexico, Northern Guatemala, and Belize

James A. Peterson

Petroleum deposits in southeastern Mexico and Guatemala occur in two main basinal provinces: the Gulf Coast Tertiary basin area, which includes the Reforma and offshore Campeche Mesozoic fields, and the Peten basin of eastern Chiapas State (Mexico) and Guatemala. Major oil production, in order of importance, is from Cretaceous, Paleocene, and Jurassic carbonate reservoirs in the Reforma and offshore Campeche areas. Several small oil fields have been discovered in Cretaceous carbonate reservoirs in west-central Guatemala. Almost all important production is in salt structure traps or on domes and anticlines that may be related to deep-seated salt movement. Some minor oil production has occurred in Cretaceous carbonate reservoirs in a buried overthrust belt along the west fl nk of the Veracruz basin. Gas production is mainly from Tertiary sandstone reservoirs.

The sedimentary cover of Paleozoic through Tertiary rocks ranges in thickness from about 6,000 m (20,000 ft) to as much as 12,000 m (40,000 ft) or more in most of the region. During the past 12 years, about 50 large oil fields were discovered in the Reforma and offshore Campeche areas of Mexico. Oil is produced from intensely microfractured Cretaceous, Paleocene, and Jurassic dolomite reservoirs on block-faulted salt swells or domes. Oil source rocks are believed to be organic-rich shales and shaly carbonate rocks of latest Jurassic and possibly Early Cretaceous age. At least six of the Mesozoic discoveries are giant or supergiant fields. Oil columns are unusually large (from 50 to 1,000 m, or 160 to 3,300 ft). Production rates are extremely high, averaging at least 3,000-5,000 BOPD; ome wells produce more than 20,000 BOPD, particularly in the offshore Campeche area, where wells producing 30,000-60,000 BOPD are reported. Many offshore and onshore structures have not yet been tested.

Tertiary basin fields produce primarily from Miocene sandstone reservoirs. About 50 of these are oil fields, ranging in size from 1 million to 200 million bbl, located on faulted salt structures in the Isthmus Saline basin. Another 30 are gas fields located on salt structures or probable salt structures.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.