Integrated Structural and Fracture Modeling of a Structurally Complex Reservoir, Llanos Foothills, Colombia

David R. Richards¹, German Meza C², Alberto Ortiz F³ (1) Midland Valley, Golden, CO (2) TSP, Bucaramanga, Colombia (3) Instituto Colombiano del Petroleo, Bucaramanga, Colombia

Production in the structurally complex Cupiagua field is at high rates from generally low porosity sandstone units, suggesting that fractures make a major contribution to the production. Maximizing the production through the life of the field depends on an understanding of the fracture network and its connectivity. The primary objective of this study was to integrate all significant data and apply it to create fracture models, which aid in optimizing production.

A well-defined structural model is critical as a first step to understanding fracture sets, sub-seismic scale faults and the sequence of fracturing. 2D and full 3D balancing was performed on a 3D interpretation to test and insure a valid model. Once the validity of the model was established, detailed analysis of the geometric and strain attributes of the key mapped horizons provided the base for fracture modeling. The second key component of the modeling was analysis of fracture populations interpreted from 22 image logs, followed by integration of these data and core data with the deformation history. Key fracture characteristics that define the model include: intensity distribution, orientation and deviation of orientation, stratigraphic and spatial distribution.

Fracture sets and a proposed fracture history were determined from the combined image log, 3D structural analysis and deformation history. The modeled 3D fracture networks take into account the observed fracture characteristics in wells, the deformation history, and geometric and strain characteristics of the unit. This integrative approach to structural and fracture modeling provided geologically reasonable fracture models and yielded insights for development.