MIMO - Microseismic Monitoring software

NORSAR has developed software to automatically detect and locate microseismic events (Oye and Roth, 2003). The MIMO-software is designed for real-time data processing of microseismic data as recorded in local seismic networks possibly in combination with deep borehole data. All processing can be conducted automatically, in a user-controlled step-by-step mode or completely manually.

The automatic processing consists of several steps:

1. Event detection, based on STA/LTA ratio for each receiver
2. Event association, assigning all relevant detections to a single event using the principle of the Generalized Beam Forming (GBF) algorithm
3. P-wave onset time picking, designing an auto-regressive noise model and applying the Akaike Information Criteria
4. P-wave polarization analysis, based on an eigenvalue decomposition to determine the direction of the incoming wave field and to rotate the waveforms into the ray-coordinate system
5. S-wave onset time picking on the two channels perpendicular to the incoming wave field, also based on an auto-regressive AIC method
6. Directed grid search localization, using pre-calculated lookup tables for onset times and polarization angles (e.g. using NORSAR-3D ray-tracing)
7. Estimation of basic source parameters (comprising seismic moment, moment magnitude, corner frequency, Brune stress drop and radiated seismic energy), using integrals of S-wave spectra.

From the result files, basic statistics as well as event bulletins can be created. All characteristics of the events can be displayed in color coding or scaling and the occurrence of events can be animated in movies. 

MIMO processing workflow.

The MIMO software can handle different sampling rates within the network, which may further consist of both single- and three-component stations. All technical parameters for the above mentioned processing steps can be adjusted individually for each geophone, thereby allowing the user to optimize the localization performance for a target volume. For localization, homogeneous as well as complex 3D velocity models can be implemented using state of the art wave propagation software to prepare travel time tables. 

 

MIMO panels for step-by-step processing; visible are panels for file selection,
a display of waveforms, the parameter selection panel for the P-onset picker,
the results of the polarization analysis and the results of the localization.

Additionally, NORSAR can offer software solutions (mainly using NORSAR-3D ray-modelling software and illumination maps) to determine optimum receiver configurations for either hydraulic fracture experiments, long term microseismic monitoring within oil and gas reservoirs, for geothermal fields and for C02 storage applications.