Reducing velocity model uncertainty and improving microseismic event location accuracy: Crosswell seismic tomography using a repeatable downhole sparker source

Velocity model errors are a major source of uncertainty in microseismic event location - A source of uncertainty that often goes unaddressed. This paper demonstrates how a commercial downhole sparker source can be used to produce crosswell tomography surveys that result in much improved velocity profiles. The combination of improved velocity model and more accurate event time picking deliver a much more constrained error distribution of micro seismic event location. This paper will outline a description of a repeatable and broadband downhole source, and the expected improvement to event location accuracy which is likely to be achieved, along with suggestions on how this may be applied to future monitoring surveys.