PETROLEUM GEOLOGY OF NORTHERN CENTRAL AMERICA

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Abstract
Major reserves of oil exist in the Reforma area of Tabasco and Chiapas states and the Campeche Shelf of SE Mexico in high‐energy, bank‐edge, reef‐derived or reef‐associated carbonate rocks, ranging in age from Late Jurassic to earliest Late Cretaceous. It is the conclusion of this study that the Reforma reservoir facies does not extend into W Guatemala. However, there the potential for major reserves in bank and lagoonal carbonates of similar age is considered excellent. A variety of structures, mostly resulting from salt tectonics, is present. Known reservoir rocks include fractured carbonates with secondary porosity resulting from solution and dolomitization, and limestones with primary intergranular porosity. An indigenous source is likely for the large quantitis of oil which have been tested at Rubelsanto. Seals, in the form of thick intervals of Cretaceous anhydrite and, in places, of Tertiary fine‐grained clastics, are abundant.The area E of Rubelsanto may have considerable merit, particularly if detailed structural analysis indicates that similar salt‐tectonic features are present. The less deeply buried areas of Cretaceous carbonates are not highly regarded because: (1) salt is absent: (2) temperatures sufficient for maturation of hydrocarbons may be lacking: and (3) a considerable number of dry holes with no significant shows has been drilled. N Guatemala is somewhat attractive, because the proper combination of unmetamorphosed Paleozoic organic shale on basement highs, well‐developed Todos Santos sandstone reservoirs, and the overlying thick evaporite seal could trap sizable hydrocarbon accumulations. However, as degree of metamorphism decreases, presumably basinward, distance from source terrain for detritus increases and reservoirs may be inadequate.