Displacement – Length Linkage Model Applied to Footwalls Traps: Examples from the Eastern Llanos Basin of Colombia
Lopez-Gamundi, Oscar1; Carrascal, Diana P.; and Pablos, Andrea
Low-relief footwall traps on east dipping normal faults constitute a significant number of oil accumulations in the Llanos basin of Colombia. Normal fault systems in this basin are generally formed by discrete fault segments arranged in echelon and separated by relay ramps. The associated footwall traps are in many cases defined in map view as three ways against a normal fault. The structural relief of these traps is related principally to the magnitude of fault displacement. Thus these individual closures associated with discrete fault segments exhibit a simple geometry with the highest structural point (and crest) generally coincident with the maximum fault throw and trap relief tapering toward the fault tips. These fault segments, in some cases, propagate laterally and link forming rather continuous fault systems. This lateral linkage of the discrete fault segments can be inferred by fault throw versus distance diagrams. Results from the application of this methodology validate the displacement-length linkage model (Watterson, 1986) for these footwall traps. This analysis is critical to prevent misinterpretations that might lead to "oversized" footwall traps formed by discrete normal faults separated by saddles (locations of the ancestral relay ramps) and also to infer, via progressive decrease of fault offset toward the fault tips, the presence and dimensions of footwall traps where seismic is absent or of poor quality, due to common problems such as local velocity changes related commonly to fault shadows, associated with the Miocene, mud-prone León Formation, or acquisition problems. Examples of this type of analysis are provided from the central Llanos where these footwall traps have been successfully explored.
AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013