--> --> Tectonothermal Modeling of Hydrocarbon Maturation, Central Maracaibo, Venezuela, by M. C. Manske; #90986 (1994).
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Abstract: Tectonothermal Modeling of Hydrocarbon Previous HitMaturationNext Hit, Central Maracaibo, Venezuela

M. Charles Manske

The petroliferous Maracaibo basin of northwestern Venezuela and extreme eastern Colombia has evolved through a complex geolofic history. Deciphering the tectonic and thermal evolution is essential in prediction of hydrocarbon Previous HitmaturationNext Hit within the basin. Individual wells in two areas of the central basin, Blocks III and V, have been modeled to predict timing of hydrocarbon generation within the source Upper Cretaceous La Luna Formation as well as within interbedded shales of Lower-Middle Eocene Misoa Formation reservoir sandstones.

Tectonic evolution, including burial and uplift (erosional) history, has been constrained with available well data. The initial extensional thermal regime of the basin has been approximated with a MacKenzie-type thermal model, and the following compressional stage of basin development using a foreland basin model. Corrected Bottom Hole Temperature (BHT) measurements from wells in the central basin along with thermal conductivity measurements of rock samples from the entire sedimentary sequence allowed a present day heat flow to be estimated. An understanding of the basin's heat flow, then, allowed extrapolation of geothermal gradients through time. The effects of geothermal gradients on overpressure within the Upper Cretaceous hydrocarbon-generating La Luna Formation and thick Colon F rmation shales was also taken into account.

Previous HitMaturationNext Hit modeling by both the conventional Time-Temperature Index (TTI) and kinetic Transformation Ratio (TR) methods predicts the timing of hydrocarbon Previous HitmaturationTop in the source units of these two wells. These modeling results are constrained by vitrinite reflectance and illite/smectite clay dehydration data, and show general agreement. These results also have implications toward the timing of structural formation and hydrocarbon migration into Misoa reservoirs as documented by previous workers. A final prediction of the modeling is that the porosity and permeability of Misoa reservoir sandstone's may have been diagenetically enhanced by organic acids expulsed form adjacent shales just prior to hydrocarbon generation.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994