Hydrocarbon Potential of La Luna Formation in the Cesar Valley Basin, Colombia

The La Luna Formation, a Cretaceous sequence, is one of the most important source rocks in Colombia and its hydrocarbon potential is not completely known. The importance of this study is to define the potential of La Luna Formation as a source rock for conventional hydrocarbon accumulation in Tertiary strata and as a reservoir for conventional and unconventional systems in the Cesar Valley Basin, Colombia. The study area has been tectonically affected by compressive regimes, the Bucaramanga-Santa Marta Fault system, the Cesar Thrust system, the Perija Uplift Fault System. These tectonics created anticline structures for the Jurassic and Cretaceous sequences and Syncline structures for the Tertiary sequences. Regional representative 2D seismic lines were interpreted for the Cesar Valley Basin, for defining the structural style. The proposed Tectonics were created by a compressive regime formed initially by a basement detachment. These tectonics are: 1) Anticline Folding, an Imbricate Fault Bend Fold with Forward Breaking that involves the Jurassic and Cretaceous Sequences. This Structure has been named Anticline HT-1; 2) Syncline Folding, the Syncline Fault Propagation Fold HT-1 that deforms the Late Cretaceous and Tertiary formations and is formed for reactivation of the HT-1 faulting. This study showed that the beginning of the deformation of La Luna Formation was in the Late Cretaceous, which generates the Cesar thrust system. The Perija uplift in the Miocene-Pliocene generated the reactivation of the Cesar thrust system, forming an emergent fault that crates the Syncline HT-1. The Geochemical modeling 1D and 2D indicates that La Luna Formation reached the oil window since 45.5 Ma ago, and also that the Tertiary Coal Sequence of the Cesar basin reached the gas generation since 20 Ma ago. The area of the Cesar Valley Sub Basin where the modeling was made doesn`t show hydrocarbon accumulation because there are not efficient seals. However in other areas with structural traps and efficient seals, is very possible to find conventional hydrocarbon accumulation. For shale gas asses, there is a remaining potential that can be storaged in the La Luna carbonate and shale matrix, but the compressive tectonics affect the fracture behavior, thus considering this formation as a naturally fractured reservoir in the study area.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California