Look back studies help review exploratory concepts in light of recent advances.  With a regional look focused on critical elements of the petroleum system, we present here a review of  the Oligo –Neogene play of carbonates and related clastics present both offshore and onshore in the South Caribbean and hosts gas accumulations that range from small to medium and giant in five basins of Colombia and Venezuela.

The play forms in isolated basement highs with reservoirs found in Late Oligocene to Early Miocene carbonates and associated slope sands, sourced and capped by massive Miocene shales. Eight commercial accumulations and three discoveries had been registered, with approximately 21 TCF of gas in place distributed in five clustered Neogene basins: Lower Magdalena, Lower Guajira, and Upper Guajira in Colombia and Golfo de Venezuela, Urumaco, and La Vela in western Venezuela.  

Play analogs were found in the exhumed Falcon basin of western Venezuela and the Guajira peninsula in Colombia. These Neogene basins are genetically related and likely formed by the tectonic collapse of Paleogene orogens. Basin subsidence initiated with pervasive normal faulting of the accreted substrate and continued in the Miocene when subsiding basins were filled with marine shales. 

Renewed compression in Miocene–Pliocene caused tectonic inversion throughout the region. We estimate that an East-West right-lateral active strike-slip Oca fault is responsible for 30 to 40 km of total offset since the Middle Miocene. Primary sources for thermogenic hydrocarbons are marine Oligo – Miocene shales with significant terrestrialinfluence. Biogenic gas is also present in commercial volumes in some basins and light oil-proven source rock.

These Oligo – Neogene carbonates had been explored since the 1940s, with giant gas discoveries in the 1970s and more recently in 2009. When viewed in a multi–basin perspective, field size distribution and creaming curves suggest that important yet – to find volumes might be present in the region. This collaborative study from onshore to deep-water settings offers an updated framework for exploration plans for the play, honoring drilling results and highlighting critical risks of petroleum systems impacted by complex Caribbean plate geodynamics. In that sense, we think that exploratory risk could be reduced by a better understanding of controls on hydrocarbon migration and reservoir presence and/or quality.

This paper will be presented in ICE AAPG Cartagena 2022, Colombia.