Microseismic Monitoring of Petroleum Reservoirs and Mines

Category Tectonic & Seismotectonic
Group GSI.IR
Location 4th internetional Conference on Seismology
Holding Date 11 March 2008
     We have developed a software system for automatic monitoring of microseismic data, designed to allow for the use of 3C seismic sensors deployed in 3D configurations, including observation wells. The system contains modules for the interactive input of geophone positions, data formats, seismic velocities and technical parameters for the individual processing steps. Additionally it provides a module to determine the orientation of the geophones. Usually borehole geophones are gimbal-mounted so that one component is oriented into the vertical direction, while the orientation of the horizontal components is random and has to be determined by use of calibration shots. The key elements of the automatic data processing are detection, phase picking, polarization analysis and finally the localization.
We will present the application of the software system to a hydro-fracturing data set. The data were recorded continuously with 12 3C geophones deployed in a vertical observation well about 100 m away from the injection well. The sampling rate was 0.5 ms resulting in a data flow of about 1 Gbyte per hour. During the 1hour recording period about 1000 microseismic events occurred which exhibit temporal and spatial clustering. The processing and localization could be performed in real time.
The system is presently being used and tested also against other data sets, such as the San Andreas Fault Observatory at Depth (SAFOD) at Parkfield, where data have been obtained from a 32 level 3 component geophone string deployed in a 2 km deep pilot well. Later, a 4 km deep main borehole will be drilled and instrumented, penetrating the fault zone.

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