Speaker: Jim Rutledge, Schlumberger  
Co-Authors:  Scott Leaney, Schlumberger, John Best, Michael Craven, and Laura Swafford, Chevron

A detailed microseismic survey was carried out in the Spraberry Field of Midland County, Texas. A vertical pilot well was completed in eight separate stages and was monitored from four surrounding wells within 300 m of the completion well. Each monitor well was equipped with a 20-level 3C geophone array spanning the completion zones, thus providing symmetric and full receiver coverage. A velocity model was built from dipole sonic and calibrated for vertical transverse isotropy (VTI) parameters using perforation shots, sonic-derived anisotropy, and crosswell seismic time picks. The microseismic locations reveal simple vertical planar clouds only a few meters wide and oriented along maximum horizontal stress direction. Moment tensor solutions show a mix of strike-slip and dip-slip shear mechanisms along failure planes aligned with the hydraulic fracture orientation. The common interpretation of stimulation microseismicity representing a discrete fracture network via connection and activation of natural fractures is not generally applicable in this case. Formation microimager (FMI) data indicate that natural fractures play little role in generating the microseismicity or steering fracture growth. Instead, the observations indicate that the microseismic shearing is directly associated with the development of vertical hydraulic fractures. The dip-slip events are mostly associated with upward growth in the Spraberry formation and are most abundant over depths where potential weak beds or weak interfaces occur, as identified on the FMI data.

Speaker Biography: Jim Rutledge, Schlumberger
Jim Rutledge has been employed with Schlumberger’s Microseismic Services since October, 2012. He spent most of his career, from 1984 to 2012, as a staff seismologist at Los Alamos National Lab. From 2004 to 2012 he also worked as a consultant for Schlumberger Cambridge Research and MEQ Geo, Inc. He received a BS in Geology from Pennsylvania State University and an MS in Geophysics from the University of Arizona. Starting in 1989, Jim has led and participated in several studies that demonstrated the uses of microseismic monitoring in oil, gas and geothermal fields for various applications including: hydraulic fracture monitoring, EOR monitoring, production-induced seismicity, subsidence and well-failure problems, gas storage, as well as subsurface CO2 sequestration.


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