Structure and Tectonic Evolution of the Provincia Field, Middle Magdalena Valley, Colombia

Martin Morales and Shankar Mitra
University of Oklahoma, Norman, OK

The Provincia field is located on a tight asymmetric fault-related fold in the Middle Magdalena Valley, in front of the eastern Cordilleran Foothills in Colombia. Oil production from the structure is primarily from fluvial sandstones of Eocene age. The structure has formed above a detachment within the upper Cretaceous Umir Formation, and dissipates slip associated with the formation of the ramp-related Los Cobardes structure to the east. The Provincia structure has been interpreted by constructing a series of balanced cross sections, using data from more than 20 wells and two-dimensional seismic data. The structural interpretations have been integrated into a 3-D model. Because of its tight geometry and the presence of faults on the front-limb, previous studies have mostly interpreted the structure as a fault-propagation fold. Detailed analysis suggests that the structure is a tight detachment fold involving Cretaceous to Miocene beds, and cored by interlayered shales and coals of the Umir Formation. The structure is cut by low displacement faults on the front and back limb. The structure also changes from a west-vergent structure in the south to an east-vergent structure in the north, a feature typical of detachment folds. The maximum shortening associated with the formation of the structure is approximately 4000 meters. Progressive restoration of the structure reveals that it is a growth structure, with the growth occurring as early as the middle Eocene, but with most of the growth occurring during the lower to middle Miocene.