Giant Chicontepec Field of East-Central Mexico
Daniel A. Busch
Although the Chicontepec formation occurs in close proximity to the world-famous Golden Lane reef, its significance as a major source of hydrocarbons was not recognized until Busch and Govela (1978) completed the first of three studies of this turbidite canyon fill. Well to well correlations within the canyon sediments are extremely difficult to impossible, due to the absence of conventional marker beds, i.e., limestone, bentonite, coal, evaporite, etc. Microfauna, although abundant, are predominantly Cretaceous in age and occur in intimate association with Late Jurassic, Paleocene, and early Eocene microfauna. In other words, the entire canyon fill consists of recycled sediments and their contained fauna. The sandstone beds are extremely lenticular, occur abundantly thro ghout the canyon fill, and generally exhibit shows of hydrocarbons.
The key to evaluating the Chicontepec is to gain an early understanding of its environment of deposition. This was accomplished by the construction of a series of stratigraphic cross sections of not just the Chicontepec but the enclosing sediments as well. In so doing the abrupt truncation of the Cretaceous formations, on opposite sides of the canyon, could be readily recognized and their respective subcrops mapped. In the eastern part of the study area it could be seen that the Chicontepec rests directly on the subcrop of the oil-bearing Upper Jurassic. The striking chemical similarity of the Jurassic and Chicontepec (Paleocene and early Eocene) oils is, thus, readily explained by leakage of Jurassic oil into the Chicontepec lenticular sandstones. Migration of the oil has been updip o the west-northwest within the lenticular sandstones of the Chicontepec. The trapping mechanism for the oil accumulations is the updip shale out of all sandstone lenses along the axial trend of the Chicontepec canyon fill. Thus, these multiple reservoirs constitute a gigantic stratigraphic trap along the west-southwest side of the Golden Lane reef trend.
AAPG Search and Discovery Article #91028©1989 AAPG History of Petroleum Industry Symposium, September 17-20, 1989, Titusville, Pennsylvania.