Abstract
Microseismic monitoring is becoming an integral part of hydraulic fracturing. The observed microseismic events reflect the rock failure that occurs during or after the stimulation, and so the events’ spatial distribution is often used to determine the stimulated rock volume (SRV) and the event frequency is used to derive stimulation effectiveness. However, discrepancies are often observed between the production rate (or the flow rate) and the stimulation effectiveness computed using the observed microseismic event locations and frequency. This study presents a multi-step workflow for calculating stimulation effectiveness. The workflow is developed based on two observations. The first is the recognition that the attributes used for calculating stimulation effectiveness must be related to deformation. The second is that it is possible by using a method based on the parameters of the Gutenberg-Richter to correct for spatial detection bias. We first describe the workflow and then apply it to calculate stimulation effectiveness using a microseismic event data set obtained during multistage fracturing stimulation of an upper Devonian shale gas reservoir in southern West Virginia. The workflow provides an improved estimate of stimulated reservoir volume. The approach has been tested here using only the magnitudes and locations of the events. Further improvement is possible using moment tensor / focal plane solutions.
