Microseismic feasibility studies - identifying the challenges in assessing Probability of Success of monitoring projects
W. Berlang, S.J. Oates and Y. Freudenreich
Event name: First EAGE Workshop on Borehole Geophysics
Session: Other Borehole Seismic (1)
Publication date: 16 January 2011
Info: Extended abstract, PDF ( 1.56Mb )
Price: € 20
We present our approach to microseismic feasibility studies with the aim of promoting discussion of the methods used and assumptions made in assessing the Probability of Success (PoS) of a monitoring project. A feasibility study includes the following elements: assessment of the Value of Information (VoI); identification of hardware options; survey of analogue cases; modelling of event location errors and detectability (magnitude of the smallest detectable event) for candidate array geometries; generation of full waveform synthetics. A study comprising these elements provides the reference frame for discussions with the service companies, limiting misunderstandings and missed opportunities. To calculate event detectability the source corner frequency and medium Q factors are required: these are parameters with large associated uncertainties and the modelling results can be strongly dependent on the values chosen. Global earthquake compilations show a clear trend for corner frequency as a function of magnitude but it is unclear how this should be extrapolated to microearthquake magnitudes. It must also be decided whether the level of seismicity will be sufficient for imaging. We begin to consider whether expected levels of seismic activity can be estimated from easily available rock mechanical data to allow more confident assessments of the PoS of monitoring.