Transcripción del resumen del autor: Microseismic measurements provide qualitative information about the location of a fracture stimulation. However, there is also quantitative information to consider, a fact that has largely been neglected. We have developed a geomechanical model to predict the extent of shear failure during fracture stimulation of a well. The model identifies different types of failures, tensile and shear, which will occur on natural fractures or vertical planes of weakness. It is a "screening model," meaning it takes a global perspective where point-by-point details of natural fracture distribution, fluid leakoff, and failure prediction are not emphasized. By matching the model to the extent of the microseismic cloud of shear failure, we obtain an injection permeability and porosity which characterize the volume of the microseismic cloud, which we assume to be a quasi-uniform fracture network with a system permeability enhancement. The model can be applied to any formation in which the microseismic distribution in each fracture stage is widespread, as happens in many tight shales (i.e., not elongated, as in a dominant vertical fracture). From our modeling studies, a high injection permeability (> 100 md) is required to pressure the formation and achieve failure out as far as the microseismic events extend. Low injection porosity ( < 0.1%) is required for the fracture fluid to leak off that far (this is typically much less than formation porosity of 3-5%). These numbers are symptomatic of fracture-controlled flow. Reports on interference with offset wells support this interpretation. As a case history, the method and results for sequential stimulation of two sister horizontal wells in the Barnett shale are described. The geomechanical model is matched to the composite cloud of all microseismic events measured in that well. Not all wells in a field have microseismic data, but the first few wells usually do, and modeling of these cases can provide useful directives for future wells. For example, the injection permeability can provide information on average fracture spacing and aperture width during injection, and these can be important for tailoring proppant size to acess the fracture network in gas and oil plays in tight shales.

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