Pitfalls locating microseismic events from borehole measurements - Practical observations from field applications

Borehole microseismic monitoring of hydraulic fracturing is among the best tools for reservoir stimulation evaluation. After decades of research and execution, the technique has gained a well-deserved place within the engineering toolbox. Moreover, in recent years, its popularity has increased exponentially, together with the development of unconventional resources. However, while involved with a significant number of borehole microseismic monitoring campaigns, I noticed that it is a common practice to overlook fundamental principles during the location of microseismic events. This may lead to potentially erroneous hydraulic fracturing assessments. Examples of microseismic results qualitatively illustrate this assertion showing poor recording, velocity models, processing constraints, and display. They also underscore the interpreter's role in ensuring the most reasonable outcome from a microseismic hydraulic fracture evaluation. In this respect, any conclusion derived from a microseismic experiment should be fully supported by a thorough understanding of the impact that multiple acquisition and processing assumptions have on the interpretation, as is the case for all other geophysical techniques. Ultimately, my intent is to raise awareness of some common pitfalls while also providing recommendations to increase the value of a microseismic monitoring exercise.