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Electromagnetics Identify Effects of Geologic Controls During Zipper Frac Operations

ESG provided controlled-source electromagnetics (CSEM) to assist in monitoring and fracture diagnostics for a zipper frac operation in the Anadarko Basin, as well as identified how a local fault would affect operations.

Controlled-Source Electromagnetics (CSEM) is a common tool used to explore for mineral deposits but is less often used in onshore operations. Using CSEM to monitor a hydraulic fracturing operation allows operators to record signals generated from fluid flow in both natural and created fractures. This imaging shows not just where fracture networks are being created, but also where the fluid is flowing.


A three-well horizontal zipper frac operation in the Anadarko Basin required monitoring to understand the interaction between the frac operations and a local fault zone at reservoir depth.

ESG Solution

We deployed CSEM to monitor and image 27 frac stages over the three horizontal wells. This included two grounded transmitter lines and 700 sensors distributed among 350 receiver locations. Each stage was recorded for 2 hours, with the wells being labeled as X, Y, and Z.

We used ESG Solutions’ in-house software to process data and provide imagery showing the lateral extent of the fluid, fracture azimuth, and reservoir heterogeneities. The electromagnetic data showed a direct measurement of subsurface changes in conductivity caused by the hydraulic fracturing process. As a result, we were able to infer fluid propagation and location to gauge frac behavior around the fault.

We also found that frac signals for all three stages exhibited similar frac half-lengths, and frac azimuths for the first three stages trended north toward the fault zone while stage locations continued south. Further south in later-stage locations along well X, fault zone influence was no longer observed; the frac corrected in azimuth and the lateral extent increased in the expected direction of regional stress. From this, we concluded that the fault zone acted as a sink and barrier, which interfered with the client’s operations.

Our findings enabled the client’s engineers to develop procedures to avoid the fault and optimize stage spacing, well spacing, and well production.

Figure 1: (A) Side view of wine rack well array and (B) map view of one type of example zipper frac operation with diamonds representing frac stages.
Figure 2: Result of the fifth stage recorded of Well X, highlighting the end of frac azimuth and half-length of the fifth stage overlaid on the end of frac of the previous stage.
Figure 3: Resulting EM signal of the fifth stage recorded from Well Z, highlighting the end of frac azimuth and half-length overlaid on the max extent of that frac stage.
Figure 4: Result of the fourth stage recorded of Well Y, highlighting the end of frac azimuth and half-length overlaying the end of frac signal from an adjacent frac stage of Well Z.