Normal Fault Development in a Contractional Fold: Geomechanical Approach and Application to Fracture Prediction in the Tropical Anticline, Venezuela

Maerten, Laurent¹, Rene Manceda² (1) IGEOSS, Montpellier Cedex, France (2) RepsolYPF, Madrid, Spain

The relative westward motion between South American, North American and Caribbean plates is the main cause of active deformation in the Serrania del Interior, Venezuela. Tropical Anticline, located in the Furrial trend and oriented NE-SW, was formed as a result of a tec­tonic inversion of Jurassic rift, where thrusts and normal faults, affecting Cretaceous-Eocene passive margin sediments, co-exist in the same structure. It is believed that the undetected structural heterogeneities such as faults and joints are capable of significantly altering the flow of hydrocarbons in the area. Therefore, understanding the characteristics of these features will have a great economical impact on the recovery of natural reserves.

A first set of geomechanical models, using 3D elastic dislocation theory, were performed in order to understand the development of the subsidiary N170 striking normal faults and their relationship with the N60 striking thrust faults. It is found that the development of the normal faults may have been influenced by the larger thrust faults under the following con­ditions: (i) the thrust faults must have a left-stepping overlapping geometry and (ii) the development of the normal faults must have taken place close to the Earth surface. Based on these first results, a second set of models were conducted in order to predict the sec­ondary deformations characteristics (i.e. density and orientation of joints) that might have an impact in the flow properties of hydrocarbon, hence the quality of the wells during pro­duction. These results have been used to constraint deterministic simulation of joints in the reservoir.