Regional fractures commonly occur as bed-normal, vertical features, and most wellbores are also vertical. This figure plots the probability of fracture intersection against the diameter of the wellbore or core that is being used to interrogate the formation in order to characterize fractures. As shown, in order to have at least a 50% chance of intersecting a fracture with a 4-inch core or 8-inch wellbore, the fractures would have to be spaced a minimum of 8 or 16 inches, respectively. Few fractured reservoirs are this intensely fractured, thus it is difficult to recognize the importance of fractures or to characterize them