Horizontal vs. Vertical Borehole-based Microseismic Monitoring: Which is Better?

Monitoring hydraulic fracture stimulations of horizontal well often results in potential monitoring scenarios of either the vertical section or horizontal section of neighbouring wells. Each configuration imposes different issues and challenges, and the relative pros and cons can be examined in a pre-acquisition design study. A specific geometry was examined for the potential quality of microseismic monitoring from a vertical well compared with a horizontal well. In scenarios where the horizontal well is relatively close to the horizontal treatment well, the horizontal array results in improved sensitivity to record more events and improved accuracy of in-zone microseismicity. Vertical arrays result in improved accuracy for both in-zone and out-of-zone microseismicity for regions of the treatment well close to the vertical well. The answer to which array is better depends on the specific geometry, the importance of monitoring the entire treatment well and the importance of accuracy for out-of-zone activity.