Acquisition Instrumentation Limitations of Recording Passive Seismicity

To properly characterize and interpret microseismic events appropriate instrumentation and digitization needs to be utilized to maximize the usable bandwidth of the signals. We discuss various influences on data quality of the recording system, consisting of geophone elements, the sensor pod, a cable, a mechanism to couple the pods to the wellbore, the coupling of the wellbore to the earth, and the digitizing/recording units. Each of these components introduces noise into the observed signal that can erode signal quality and thereby result in limiting the usable bandwidth. To enhance the magnitude range to be covered properly, we propose the use of a system with mixed frequency response sensors to be used. We furthermore discuss how coupling affects signal quality, noise characteristics and temporal variation of vector fidelity.