An Integrated Geomechanical and Microseismic Study of Multi-Well Hydraulic Fracture Stimulation in the Bakken Formation

Yang, Yi; Zoback, Mark; Simon, Michele; Dohmen, Ted

We present an integrated study of multi-stage hydraulic fracture stimulation of two parallel horizontal wells in the Bakken formation in the Williston Basin, North Dakota. There are two distinct parts of this study: Development of a geomechanical model for the study area, and analysis of the microseismic and hydraulic fracturing data. Despite the limited amount of well log data available, we estimate the current stress state to be characterized by a NF/SS regime, with Pp= 0.66 psi/ft, Sv=1.05 psi/ft, Shmin=0.79-0.85 psi/ft and SHmax= 0.85-1.22 psi/ft. Published data just south of the study area indicate that SHmax is orientated ~N40-50°E on the basis of drilling-induced tensile fractures observed in FMI image logs. The microseismic events were recorded in six observation wells during hydraulic fracturing of parallel wells A and C. There are three unusual aspects of the microseismic events. First, many occur along the length of the well B (a parallel well located between A and C that has been in production for about 2 years) rather than in proximity of the stages being pressurized in A or B. Second, relatively few fracturing stages are associated with an elongate cloud of events trending in the direction of SHmax. Rather, the microseismic events from many stages appear to trend about 300 from the direction of SHmax. Finally, the microseismic events are observed at two distinct depths, one close to the depth of the well being pressurized in the Bakken formation and the other ~800 ft above in another formation. We believe all three of these patterns result from the hydraulic stimulation being dominated by flow channeling along pre-existing fractures and faults.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013