Petroleum reservoir characterization using downhole microseismic monitoring
S. C. Maxwell1, J. Rutledge2, R. Jones3, and M. Fehler4
Imaging of microseismic data is the process by which we use information about the source locations, timing, and mechanisms of the induced seismic events to make inferences about the structure of a petroleum reservoir or the changes that accompany injections into or production from the reservoir. A few key projects were instrumental in the development of downhole microseismic imaging. Most recent microseismic projects involve imaging hydraulic-fracture stimulations, which has grown into a widespread fracture diagnostic technology. This growth in the application of the technology is attributed to the success of imaging the fracture complexity of the Barnett Shale in the Fort Worth basin, Texas, and the commercial value of the information obtained to improve
completions and ultimately production in the ﬁeld. The use of commercial imaging in the Barnett is traced back to earlier investigations to prove the technology with the Cotton Valley imaging project and earlier experiments at the M-Site in the Piceance basin, Colorado. Perhaps the earliest example of microseismic imaging using data from downhole recording was a hydraulic fracture monitored in 1974, also in the Piceance basin. However, early work is also documented where investigators focused on identifying microseismic trace characteristics without attempting to locate the microseismic sources. Applications of microseismic reservoir monitoring can be tracked from current steam-injection imaging, deformation associated with reservoir compaction in the Yibal ﬁeld in Oman and the Ekoﬁsk and Valhall ﬁelds in the North Sea, and production-induced activity in Kentucky, U.S.A.
Microseismic imaging has developed into a common technique to image fracture-network deformation that accompanies oil and gas operations. The most extensive application of microseismic monitoring is to image hydraulic-fracture operations, although the technique is also used to monitor microseismic events induced by inelastic deformation associated with injection of steam/water/gas for secondary recovery and production e.g., Maxwell and Urbancic, 2001 . Associated with the growth of the technology have been several workshops and forums focused on the technology as well as dedicated sessions at AAPG, SPE, SEG, and EAGE conferences. The technology is somewhat unique in that although it is a geophysical method, its users and main drivers tend to be reservoir engineers. In fact, based on a keyword search on the respective Web sites, there is more discussion of the technology through SPE than with SEG and EAGE combined.
Although the routine application of microseismic monitoring is relatively new to the oil and gas industry, it has been used in geothermal ﬁelds since the 1970s and 1980s as a routine method to image fracture networks activated during production and injection Majer and McEvilly, 1979; Denlinger and Bufe, 1982; Eberhart-Phillips and Oppenheimer, 1984 and during hydraulic-fracture stimulation Albright and Hanold, 1976; Pearson, 1981; Pine and Batchelor, 1984; Fehler, 1989 . Prior to observations of microseismicity associated with reservoir stimulation and monitoring, passive monitoring of microseismicity was used extensively in the mining industry to monitor stress changes around mine openings, primarily from the workplace hazard associated with induced seismicity e.g., Gibowicz and Kijko, 1994 . Microseismic monitoring has also been extensively studied as a technique to monitor crack development around underground excavations intended as sites for waste disposal e.g., Collins and Young, 2000 .
Manuscript received by the Editor 8 December 2009; revised manuscript received 3 April 2010; published online 14 September 2010. 1...