Juan Carlos Ramon, Stefan Bachu
The Llanos basin is a predominantly siliciclastic foreland sub-Andean basin situated in Colombia. Geothermal and geochemical data from several hundred wells in the basin have been used to study the source-rock maturation and thermal history of the basin. The present geothermal regime in the Llanos Basin is controlled by basement heat flow, depositional and compaction factors and probably hydrodynamic effects. The heat flow and geothermal gradients are moderate. The depth of the oil window isotherm indicates that only lower Cretaceous strata close to the thrust fold belt are in the stage of oil generation. TOC distributions show that the same strata have also good potential for hydrocarbon generation. Vitrinite reflectance distributions with depth show a major break at the sub-Cretaceo s unconformity. The areal distributions of vitrinite reflectance in Paleozoic and post-Paleozoic strata indicate different heat sources during these periods. Because the post-Paleozoic sediments are presently at their maximum burial depth, the paleo heat flow must have been higher in the past in order to produce the higher temperatures required for the generation of the hydrocarbons found in the Llanos basin. Three thermal events and three hydrocarbon-generation pulses are inferred from the geothermal and vitrinite reflectance data.
AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994