Three-dimensional fracture continuum characterization aided by surface time-domain electromagnetics and hydrogeophysical
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ORIGINAL PAPER
Three-dimensional fracture continuum characterization aided by surface time-domain electromagnetics and hydrogeophysical joint inversion—proof-of-concept Michael Commer1
· Stefan Finsterle2 · G. Michael Hoversten3
Received: 8 July 2019 / Accepted: 6 February 2020 © This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2020
Abstract Efficient and safe production of hydraulically fractured reservoirs benefits from the prediction of their geometrical attributes. Geophysical methods have the potential to provide data that are sensitive to fracture geometries, alleviating the typically sparse nature of in situ reservoir observations. Moreover, surface-based methods can be logistically and economically attractive since they avoid operational interference with the injection well infrastructure. This contribution investigates the potential of the surface-based time-domain electromagnetic (EM) method. EM methods can play an important role owing to their sensitivity to injection-induced fluid property changes. Two other advantageous factors are the EM signal-enhancing effect of vertical steel-cased wells and the fact that injected proppants can be enhanced to produce a stronger electrical conductivity contrast with the reservoir’s connate fluid. Nevertheless, an optimal fracture characterization will no doubt require the integration of EM and reservoir injection and production data. We hence carry out our investigations within a hydrogeophysical parameter estimation framework where EM data and injection flow rates are combined in a fully coupled way. Given the interdisciplinary nature of coupled hydrogeophysical inverse modeling, we dedicate one section to laying out key aspects in a didactic manner. Keywords Fracture parameter estimation · Coupled hydrogeophysical inverse modeling · Time-domain electromagnetics · Petrophysical transformation · Parameter correlation
1 Introduction With the onset of high production from land-based unconventional hydrocarbon reservoirs, the characterization of hydraulically fractured zones has become an important factor for production optimization. Efficient production requires prediction of the extent, orientation, and active surface area of fractures or fracture networks that are created and/or activated. Remotely sensing geophysical methods promise to provide a relatively inexpensive set of tools for deriving fracture attributes [16, 29], given
Michael Commer
[email protected] 1
Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
2
Finsterle GeoConsulting, Kensington, CA, USA
3
Chevron Energy Technology Company, Houston, TX, USA
their generally larger spatial coverage compared with well data. Two classes of geophysical methods, seismic and electromagnetic, are sensitive to the hydromechanical property changes accompanying fracture evolution as well as hydraulic state changes in existing fractures. Using active (artificially sourced) seismic methods, one can u
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