The Upper Magdalena Valley Basin has an extension of 21 513 km2. It is a complex tectonic depression filled with a thick cover of Paleozoic to Quaternary rocks. The basement is constituted by Precambrian and Jurassic rocks cropping out in the foothills of Eastern and Central Cordilleras. The Cretaceous sequence consists of terrestrial and marine deposits. Two levels of source rocks rich on organic matter of middle Albian- Turonian have generated the hydrocarbons in the basin. Significant levels of Campanian- Maastrichtian sandstones represent a major exploration target. The Cenozoic sequence is composed totally of terrestrial rocks in form of Paleogene and Neogene molassic deposits. The biggest oilfields are associated with structural closures generated by fault flexural folds, faultpropagation folds and anticlines related to strike slip faults.