Two-Dimensional Simulation of the Controls of Fracture Parameters on Fracture Connectivity

Fracture permeability is strongly controlled by the connectivity of fractures. The connectivity of a fracture network depends on the geometry and characteristics of individual fractures and also on how the fracture sets are distributed in space. Increasing fracture propagation leads to the formation of clusters or connected fractures. The cluster may increase in size as (1) an increasing number of fractures are added to the system, (2) the length of the fractures increases to connect individual fractures, (3) the orientation of fractures in a set exhibits a higher degree of dispersion, or (4) fractures of multiple sets are added to the system.

A series of fracture simulations are modeled to investigate the influence of all the four characteristics on the fracture network, and to identify the relative contribution of each factor towards network connectivity. Preliminary studies show that increase of fracture density, length and dispersion within a fracture set increase the connectivity of a network. There is a threshold of fracture length and density for a constant area of rock above which the connectivity increases dramatically. The most dramatic increase in connectivity is exhibited by introducing a second set of fractures within the fracture network. Also, the higher the difference in orientation of the second set to the first set, the higher is the connectivity of the fracture network. The simulations are compared to examples of natural fractures seen in outcrops to understand the effects of different fracture parameters on connectivity in natural fractures systems.