![]()
Abstract Using an innovative workflow incorporating microseismic attributes and geomechanical well logs, we have defined major geomechanical drivers of microseismic expression to understand reservoir stimulation response in engineering and geological contexts. We sampled microseismic data from two hydraulically fractured Marcellus wells in the Appalachian Basin, northern West Virginia, vertically through the event cloud, crossing shale, limestone, sandstone, and chert. We focused our analysis on the Devonian organic shale and created pseudo-logs of moment magnitude (Mw), b-value, and event count. The vertical moving-average sampling of microseismic data was completed such that the sample interval matched that of the geophysical well log. This technique creates robust, high-resolution microseismic logs that show subtle changes in microseismic properties and allows direct cross-plotting of microseismic versus geophysical logs. We chose five geomechanical properties to form the framework against which to interrogate the microseismic data: Young's modulus (YM), Poisson's ratio (PR), brittleness, lambda·rho (λρ), and mu·rho (µρ). Additionally, we included natural gamma as a useful measure of organic content. Having defined this microseismic-geomechanical cross-plot space, we derived insights into the response of these units during hydraulic fracturing. Observations include:larger magnitude microseismicity occurs in high PR, high YM rocks; high event counts are found in low PR rocks;
low b-value (high in-situ stress) is consistent with the occurrence of larger magnitude events and low event counts; and
YM and PR act as bounding conditions, creating "sweet spots" for high and low Mw, event count, and stress. In our cross-plot space, there is a meaningful link between microseismicity and the elastic properties of the host rock. In light of this dependence of stimulation potential on elastic properties, the calculation of microseismic pseudo-logs at stimulation sites and application of our cross-plot framework for microseismic-geomechanical analysis in unconventional shale will inform operators in planning and forecasting stimulation and production, respectively.
Site News