A Model to Describe the Behavior of Opening / Closing of Naturally Fractured Systems

Abstract

Abstract

An extension to the geomechanical behavior of Parson's model is proposed, using a combination of both Parson's and Pedrosa's models. The new Parsons model is expressed in terms of normal effective stress acting on the natural fracture system. Results show a decreasing of aperture of fracture system, when it is compared with classical Parson's model.

There are models for studying the opening / closing of a fracture system; they take into account characteristics of the system like fracture indices and the inclination angle respect to the horizontal plane, among others, but they do not consider the state of stress acting on the system and the azimuth angle; so, from geomechanical viewpoint, they describe partially the behavior of fracture system reactivation. The proposed model is an extension of Parson's model, which is expressed in terms of normal effective stress acting on the system of natural fractures. The resultant expression describes the opening / closing of a natural fracture system as a function of the parameters mentioned.

The model has been applied to wells in the Colombian Foothills field, which have presence of natural fracture systems and show sensitivity to stresses. The results show opening / closing behavior of the natural fracture system as a function of pore pressure. Some applications are: i) in a stimulation process is possible to identify the viability of packaging of fracture system; ii) in the production process, optimal production pressure for stabilizing the shutdown of natural fractures and maximizing well production can be determined. In addition, results are compared to those obtained with Parson's model, finding that for same pressure change, opening/closing of new model is minor than Parson's model.

The outstanding difference of the modified Parson's model is the consideration of geomechanical aspects such as the stress state and the stress alignments respect to orientation of the natural fracture system.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016