Department of Geology and Geological Engineering Van Tuyl Lecture Series- Spring 2016 4:00-5:00 p.m. in Berthoud Hall Room 241    Thursday, January 21, 2016 John Lorenz President FractureStudies LLC    “The Interaction of Hydraulic Stimulation Fractures with Natural Fractures”   Abstract: Four factors are required in order to plausibly predict the nature of the interactions between a hydraulic stimulation and a natural fracture system: detailed characteristics of the natural fractures both 1. individually and 2. as a network; and the 3. magnitudes and 4. orientations of the in situ stresses. Fracture systems may be mineralized, partially mineralized, or open, controlling rock strength and fracture permeability; fractures may consist of extension fractures or shear fractures, providing highly anisotropic and vertically limited, or more laterally and vertically interconnected permeability, respectively; fractures may also consist of superimposed fracture sets, complicating the evidence offered for interpreting the system. Stresses may be highly anisotropic or may be nearly equal, and the maximum stress may be vertical, inclined, or horizontal. Pore pressure is an integral part of the stress system and is not static, changing as a reservoir is stimulated or produced. Fracture permeability is equally dynamic, since fractures oriented parallel or oblique to the stress may close or shear, respectively, during reservoir stimulation and depletion. Such a system can be quantified with detailed measurements and a decent, carefully characterized fracture and stress data base. If a default fracture system exists, it does not consist of open, orthogonal slots.