Building a Discrete Fracture Network Based on the Deformation History: A Case Study from the Guaduas Field, Colombia

Armelle Kloppenburg¹, D. Richards¹, G. Rodriguez Charry², and J. C. Alzate^2
1 Midland Valley Exploration, Glasgow, United Kingdom
² Sipetrol S.A, Bogota, Colombia

Production from a limestone reservoir in the Guaduas Field west of Bogotá, Colombia is largely from fractures. It carries high risk as the fracture network, as observed from limited well data, is spatially erratic and not well understood.

To predict the fracture pattern, we focus on understanding the present day geometry of the reservoir as well as the change of shape (strain) throughout its geological history. We test and determine parameters for modeling based on the structural development through time, while also matching the fracture distributions in the wells. The parameters derived from these methods allow geologically reasonable prediction of fractures in the areas where there is no data.

Four main fracture sets with characteristic orientation are recognized in the wells and confirmed in outcrop studies. The density distributions of the fracture sets correspond with either strain or tectonic thickness maps, and these maps were used to govern the density when building the discrete fracture model. In addition, a late, strike-slip fault system has been identified on the satellite image, on time slices in the seismic survey and in the field. A fracture network was built with length distributions that follow the outcrop observations.

Relative connectivity of the fracture network, with the four fracture sets as well as the km-scale strike-slip faults, showed that the latter have an important role in drainage of the system. Fractures with a high risk of being closed due to present day stress were exempted from the network in this analysis.

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