Ambient seismic activity generated by producing wells can be used to map the volume of rock surrounding the wellbore. This acoustically active rock volume is termed the active production volume (APV). While monitoring microseismic activity during hydraulic fracturing has become a common practice, using the lower-amplitude ambient signal to monitor production is a new and promising technology. Small changes in local stresses can result in failure on small pre-existing fractures. This generates acoustic activity that, when imaged, reveals reservoir features including the volume of rock contributing to production. Fluid noise in the fracture system is also imaged. When a well is producing, the drainage network that is connected to the wellbore experiences enhanced activity because of the movement of fluid; the resultant changes in local stress cause failure events. Global Geophysical Services’ Ambient Seismic production monitoring is useful for observing changes in APVs over time. This 4D monitoring, when conducted at regular intervals over years of production, provides unprecedented views of reservoir production. These APVs can be used for making predrill predictions about production volumes, for understanding the interactions between producing wells, and for determining refracturing candidates and infill-drilling strategies.