Controlled Source Electromagnetics (CSEM) is used to monitor and image a three well zipper frac operation. We examine the interaction between the completions operation and a fault zone at reservoir depth.

Using two grounded dipole transmitter lines and 350 receiver locations, 27 frac stages were monitored in the Anadarko basin for three horizontal wells. Our broadband signal is transmitted before the start of the frac stage, during the frac stage, and after the frac stage is completed. This allows us to establish a baseline image prior to the start of the frac stage and to generate a response throughout the frac. The electromagnetic data collected provides a direct measurement of the conductivity change in the subsurface caused by the hydraulic fracturing process and from this we infer fluid movement.

This case study presents the effects of a fault at reservoir depths that is intersected by the three wells and examines the possible effects of formation heterogeneities on frac fluid migration. Images produced by our CSEM method illustrate the lateral extent of the fluid, fracture azimuth, and identify reservoir heterogeneities. In addition, unlike microseismic, the CSEM method records signal generated from fluid flow in natural fractures as well as those fractures created by hydraulic pressure. As a result, CSEM allows us to infer fluid propagation and location to gauge frac behavior near and away from the fault where the fault zone is seen possibly acting as a sink and barrier. CSEM monitoring of a frac operation not only serves as a tool for monitoring and fracture diagnostic, it can also be used to identify geologic controls that can affect reservoir stimulation.

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