-- CANCELLED -- Fault and Fracture Identification and Characterization in 3D Seismic Data from Unconventional Reservoirs

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Noha Farghal, USGS

Wednesday, March 20, 2019 at 10:30 AM

Building 3, Rambo Auditorium

Unconventional reservoirs are becoming increasingly important on the world energy stage. Such reservoirs need stimulation of some kind in order to be produced in an economically viable way, unlike conventional sources, where oil or gas readily flows into producing wells through more permeable strata. Nevertheless, unconventional recovery factors are still considerably low, and further research contributions are needed to better understand how these reservoirs work and interact with stimulation. In this talk, I present work done at Stanford University under the supervision of Prof. Mark D. Zoback as part of my doctoral degree research. I focus on the role that faults and fractures play in low permeability reservoirs' response to stimulation, particularly hydraulic fracturing. We analyzed three data sets acquired from and around injection and monitoring wells in the Barnett Shale in Texas. In two of these data sets, I identified small-scale faults and integrated faulting information with other data from wells (e.g. microseismic recordings) to understand how the presence of faults affects injected fluid flow. Results showed that even small-scale faults can have significant effects on hydraulic fracturing progress by providing corridors for fluid flow along them (a high permeability path due to fractures surrounding faults) or by dissipating fluid pressure across them, preventing fluids from effectively crossing to the other side of the fault. For one data set with different seismic surveys acquired before and after stimulation and gas production, we used 3D seismic attribute analysis to identify fractures in and around injection wells to evaluate the methods used, namely azimuth-dependent Amplitude Vs. Offset (AzAVO) and Velocity Vs. Azimuth (VVAz), and to understand how stimulation and production affected fractures in this area of the Barnett. Results showed that fracture density, rather than orientation, is more affected by the pressure introduced during stimulation and by pressure reduction with injected fluid removal and production.

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