Reducing Structural Uncertainty in the Recetor-Piedemonte-Niscota Area of the Eastern Cordillera Fold and Thrust Belt, Colombia
Richards, David1 and Ceballos, Claudia Patricia
Uncertainty in modeling the extent of productive and prospective thrust sheets in the Piedemonte area of the Eastern Cordillera is high, owing to the difficult environment for seismic imaging. The thrust-bounded packages each contain Paleogene Mirador, and sometimes Barco and Upper Cretaceous Guadalupe Formations, and production is from these naturally fractured, low porosity sandstone reservoirs. The productive and prospective thrust sheets underlie shallow to surface structures, notably the Nunchia syncline and the El Morro anticline. Production rates are typically high from the thrust sheets and any reduction in uncertainty will prove valuable in further drilling in the area. Detailed structural modeling is key to reducing the uncertainty in mapping and 3D modeling in this area.
Reprocessed 3D seismic, along with new information from several recently drilled wells, provide the base for a refined 3D model of the area. The antiformal stack of thrust sheets extends for tens of kilometers along-strike, from the Recetor area, through Piedemonte and into the Niscota area. Individual thrust sheets also extend for tens of kilometers along strike, as supported by production history, pressure interactions and occasional tracer data. Wells aligned in the dip direction provide the best base for interpreting sections and understanding dip extent of the thrust sheets. Iterative balancing of sections using all wells yields sections where the cutoffs are best constrained. The shortening and stacking of the prospective thrust sheets must explain the translation and uplift of the Nunchia syncline and other shallow to surface structural features. Changes in style and number of thrust sheets along strike are reflected in changes in the Nunchia syncline and other shallower features. Interpretation and balancing of sections that are constrained by the wells yield a fault network that accounts for all the structures. Carrying the interpretation through a network of sections provides an interpretation template for the the 3D seismic volume. This approach maximizes the well constraints and allows effective interpretation in 3D where the image is poor. Further testing for balance in 3D yields a model with significantly reduced uncertainty. The refined model aids in evaluating potential reserves, extent and connections between the various thrust sheets and in defining targets for drilling, including possible untested thrust sheets.
AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013