Microseismic Maps Production Volume New microseismic monitoring techniques capture lower-amplitude signals and continuous background seismicity to image the pretreatment natural-fracture network, as well as the amount of reservoir rock stimulated during pressure pumping and the active portions of the stimulated volume during the production phase. By Jan Vermilye and Charles Sicking HOUSTON-Ambient monitoring of microseismic activity before, during and after hydraulic fracture treatments can provide valuable information on the size and geometry of the rock volumes and fractures that contribute to production. A major goal of microseismic monitoring of hydraulic fracture treatments is to determine the size of the stimulated reservoir volume (SRV), which is the volume of rock containing the connected fracture network generated by the stimulation. The size of the SRV is most commonly estimated from the volume of the microseismic event (sometimes referred to as hypocenter) cloud. The events that define this cloud are observed during the well stimulation. SRV has been of great interest because it was at first thought to be positively correlated to well performance. However, this relationship is being challenged. The size of the SRV is measured while the well is being actively stimulated, but not all of these active fractures will contribute to production. Changes in stress and fluid pressure that take place after stimulation is complete and during flowback result in some fractures closing. This is especially true for those fractures that did not receive proppant. Tech Trends 2016 JANUARY 2016 81