Controlled-source electromagnetics (CSEM) has been commercially applied for hydrocarbon exploration for more than 10 years. The normalized amplitude response (NAR), a common measure for CSEM anomaly strength, is the ratio of the CSEM response at the target to the background response. Use of this measure allows anomaly strength to be quantified but leaves open the question of how strong the NAR level needs to be before it can be considered significant for hydrocarbon exploration. We apply three statistical approaches to determine the appropriate NAR threshold for defining a CSEM anomaly and for estimating the overall significance of the CSEM method in hydrocarbon exploration. The analysis is based on the published data in Hesthammer et al. (2010a, 2010b), referred to here as “the Hesthammer database.” This database reports NAR levels and hydrocarbon exploration outcomes versus the depth to the target for a set of drilled prospects. The database authors used an NAR level of 1.15 (or 15%) for their anomaly threshold, while all three of our analyses indicate that this threshold should be higher.

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