Abstracts

• 35037 Fracture Mechanics Interpreted from Stress Inversion Analysis on Microseismic Event Source Mechanisms in the Marcellus Shale Analysis of microseismicity induced by hydraulic fracture stimulation in the Marcellus Shale shows changes in stress state for different zones of failure. During the treatment, shear failure occurs on both the J1 and J2 fracture orientations in response to different maximum stress orientations, indicating localized changes in the orientation during the treatment. Reactivation of a fault near the wellbore is associated with failure mechanisms with a higher volumetric component, indicating possible inflation of faults and fractures by the introduction of the slurry. Quantification of the stress conditions that are associated with inflation could potentially be used to optimize the stimulation by identifying which fractures will preferentially take on slurry volume. Fracture Mechanics Interpreted from Stress Inversion Analysis on Microseismic Event Source Mechanisms in the Marcellus Shale
  Fracture Mechanics Interpreted from Stress Inversion Analysis on Microseismic Event Source Mechanisms in the Marcellus Shale
• 35038 Induced Hydraulic Fractures or Reactivated Natural Fractures? Microseismicity induced by hydraulic fracture stimulation of a horizontal well was mapped with a near-surface buried array. Distinct linear trends of events were not parallel to the direction of fast shear wave polarization measured in the reservoir with a crossed-dipole anisotropy tool. Analysis of core from a nearby well revealed numerous calcite-filled fractures that did not induce shear wave polarization, but did significantly impact the failure behavior of the reservoir rock during the stimulation treatment. Hydraulic fracture simulation with DFN modeling and source mechanism analysis supports the interpretation of reactivated existing fractures rather than the formation of hydraulically-induced tensile fractures. Induced Hydraulic Fractures or Reactivated Natural Fractures?
  Induced Hydraulic Fractures or Reactivated Natural Fractures?
• 35035 Possible Pitfalls for Interpreting b-values as a Stress Meter In seismology, the constant b in the Gutenberg-Richer law expresses the relationship between the magnitude and total number of earthquakes in any given region and time period of at least that magnitude. The value of b is typically equal to 1.0 in seismically active regions, and variations in that value have been attributed to different stress regimes. In recent years, workers applying this analysis to microseismicity have used it to interpret processes related to hydrofrac treatments and have also interpreted b values as a "stress meter" in the reservoir. This talk examines alternative, geologically-based explanations for b values. Possible Pitfalls for Interpreting b-values as a Stress Meter
  Possible Pitfalls for Interpreting b-values as a Stress Meter