New Petroleum Generation Model of the Middle Magdalena Basin, Colombia: Is The Luna Formation the Most Prolific Source Rock?

Bernardo, Luis Miguel¹, Jorge Luis Rubiano¹, Myriam Caro¹, Carlos Arturo Alfonso² (1) Ecopetrol ICP, Bucaramanga, Colombia (2) Ecopetrol, Bogota, Colombia

Because of the presence of prolific Luna Formation in northern South America, other marine sequences are frequently ignored in generation models. In this study, multiple 1-D geochemical models were built on the basis of a chronostratigraphic and structural framework, to assess the importance of alternate source rocks in Colombia's Middle Magdalena Basin (MMB).

Three major structural domains were identified in the MMB. The eastern domain corresponds to the Magdalena Fold-and-Thrust Belt, comprising inverted and imbricate structures. The central domain is identified as a pre-Eocene zone of contraction, represented by an inverted fold-and-thrust belt and flower structures. The western domain is the slightly deformed monocline named Simiti Platform.

The most relevant stratigraphic events occurred during the Eocene, when deformation and erosion of the Cretaceous section took place. Minor tectonic events occurred during the Oligocene, Miocene, and Quaternary, causing faulting, tilting and erosion.

Our petroleum generation model shows that five Cretaceous source rock units have generated oil, but the time and amount of hydrocarbons generated vary for each structural domain. These variations result in various degrees of prospectivity for each domain. In the eastern domain, although all five units generated hydrocarbons, timing is the main geologic risk. The central domain contains the most efficient petroleum system and the largest known accumulation in the MMB, but contrary to conventional views, the Luna Formation may not be the most productive source rock. Within the Simiti Platform, only a small kitchen area was available, but oil charge was favored by proximity to the central domain.