BP deployed microseismic monitoring arrays in two observation wells in a Rocky Mountain tight gas province for the purpose of mapping hydraulic fractures in a nearby lateral. Engineering Seismology Group (ESG) collaborated with BP to conduct an advanced re-analysis of the large data set obtained from the dual-well microseismic monitoring program.

The goals of the re-analysis included recalculating observed fracture azimuths and selecting a subset of events with good signal-to-noise ratios and key signal characteristics (e.g., distinct P- and S-wave first arrivals, amplitude data and first motion polarities) to conduct further, detailed analyses. Event locations were recalculated, combined with signal characteristics and inverted to solve for moment tensor solutions. The derived set of solutions provides a robust determination of fracture azimuth as well as offering additional, unique insights into the stress history in the vicinity of the project. As such, these more comprehensive, in-depth microseismic analytical techniques have proven themselves to be valuable tools that can increase understanding of local geology and stress histories, thus aiding design of effective, future fracture treatments.

Douglas C. Bleakly*; James E. Wolfe**;
Ian Leslie, Marc Prince, Vladimir Shumila and Ted Urbancic***
*ESG,Walnut Creek, California, USA; **BP, North America Gas; ***ESG, Kingston, Ontario, Canada