3-D Modeling of Discrete Fracture Networks in a Complex Fold and Thrust Belt in the Northern Portion of the Eastern Cordillera Foothills, Colombia: Implications for Petroleum Exploration and Production

Javier Andres Acevedo¹, Freddy Corredor², David Richards³, and John Jairo Aristizabal^4
1 Universidad Nacional de Colombia, Bogotá D. C, Colombia
² Harvard University, Cambridge, MA
³ Midland Valley Exploration Inc, Golden, CO
⁴ Ecopetrol S. A, Bogotá D. C, Colombia

A recent discovery in the northern culmination of the Eastern Cordillera foothills, Colombia tested hydrocarbons from highly fractured Cretaceous-Tertiary reservoirs on eastward-verging, imbricated thrust sheets, above ramps which cut through the Cretaceous La Luna Formation. From a relatively closely spaced grid of 2D seismic lines, surface geologic information, and well image data, we constructed a 3D model of this fold belt that was sequentially restored and forward modeled using different directions of shortening based on two models of regional basin development. Model 1 proposes a single episode of NW-SE directed shortening, and Model 2 proposes two different events of deformation with an initial episode of SW-NE oriented shortening, followed by an episode of NW-SE oriented shortening. For each restoration we model the 3D discrete fracture network, including joints parallel to fold axis and conjugate sets of fractures, based on the dilatation of surfaces between the unfold and fold stages, and maximum stress direction respectively, which is key for new exploration and production efforts in this region. In order to test the two kinematic hypotheses and implicitly the most appropriate simulated fracture network, we compare observed fracture data from a satellite image, surface geologic mapping and two borehole image logs with the modeled fractures. The two episodes model yielded three main fracture patterns in common with observed data (N5W, N29E and N81E). These results suggest that the northern part of Eastern Cordillera may have formed by two shortening episodes of different orientation during the uplift of this thrust belt.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005