Geological Setting and Hydrocarbon Occurrences, Guajira Basin, Offshore Northern Colombia

Victor O. Ramirez-C
University of Alabama and Ecopetrol, Tuscaloosa, AL

The Guajira Basin is located in a tectonic setting characterized by two right lateral strike faults of regional scale (Oca and Cuisa faults). The stratigraphic section includes Jurassic and Cretaceous units having petroleum source and reservoir rock potential. The Tertiary interval, Eocene to Upper Miocene, accounts for the majority of the stratigraphic section in the basin, and Oligocene, Lower Miocene and Upper Miocene rocks are recognized as the reservoirs for most of the hydrocarbons in the basin.

Hydrocarbon records in wells and gas production from Chuchupa-Ballena fields, have led, along with the interpretation of geophysical (mainly seismics), geological and geochemical information, to a good understanding of the hydrocarbon prospectivity of the basin. Recent efforts of information integration has allowed for the preliminary definition of petroleum systems in this basin: Macarao – Siamana P.S. (.) (northeast part of the basin), Tertiary – Jimol/Uitpa P.S. (.) (producing in the Chuchupa-Ballena fields), Castilletes-Castilletes P.S. (?) (reservoir potential in deep water clastic environments), and Mesozoic-Cretaceous P.S. (?) (reservoirs as fractured Cretaceous limestones, analogous with Mara-La Paz Venezuelan fields).

Traditionally, the Guajira Basin has been regarded as a biogenic gas province (more than 6 TCF of dry gas, 97% methane, low maturity levels). Recent geochemical and geological data support the evidence for several petroleum systems, involving thermogenic processes relevant to the evolution of the basin. These systems are an important factor in the appraisal of the gas and oil prospectivity of the basin and to tie the offshore exploration potential to the inland known geological features.