f Geologic Framework for Critical Risk Factors Analysis of a Tertiary Carbonate Play in Colombian-Venezuelan Sedimentary Basins Along the Caribbean Margin of South America

Hydrocarbon accumulations in a Tertiary carbonate play in sedimentary basins of northern South America range from small to medium to giant. The fields are located both onshore and in shallow waters of the southern Caribbean Sea. The play has proven to be commercial in both marine and terrestrial environments. Onshore, economic development is profitable with modest sizes of the accumulations. Recent drilling results along the margin call for a revision of our understanding of the development and geologic controls on this prolific play to better delineate critical risk segments. This collaborative study offers an updated framework for exploration plans in northwest South America. The play is mainly associated with isolated basement highs with reservoirs found in Late Oligocene to Early Miocene limestones and associated slope sands sourced and capped by massive Miocene shales. To date, eight commercial accumulations and three discoveries have been registered with approximately 21 TCF of gas in place distributed between 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 analogues have been documented in the exhumed Falcon basin of west Venezuela and in the Guajira peninsula in Colombia. The Neogene basins are genetically related and likely formed by transtensional collapse of Paleogene orogens. Basin subsidence was initiated by pervasive normal faulting of igneous-metamorphic 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 Middle Miocene.

The primary source for thermogenic hydrocarbons is marine Oligo-Miocene shales with important terrestrial influence, controlled by the proximity to the continent. In Lower Guajira and Lower Magdalena basins of Colombia, there are also proven effective petroleum systems that involve biogenic gas in commercial quantities.

Recent discoveries and wide variation in the play's field sizes generate renewed interest in the exploration in the region onshore and offshore. The exploratory risk could be reduced by a better understanding of controls on the field size distribution and reservoir presence and/or quality.

Published large-scale structural models do not explain details revealed by recent drilling of the carbonate play along the edge of northern South America. Our integrated analysis from onshore to deep-water settings honours drilling results and updates the framework for analysing critical risks of petroleum systems impacted by complex Caribbean plate geodynamics.