Methods of monitoring for influx and/or loss events using a plurality of measurements compared with expected values. One method 100 includes: receiving a measurement 120 of flow out rate or active volume, and comparing the measurement with an expected value to provide a deviated measurement value. A pump pressure value of a pump associated with the wellbore is also measured and compared with an expected pump pressure value to provide a deviated pump pressure value. It is then established whether an influx or a loss event may have occurred 160 based on at least the deviated measurement value and deviated pump pressure value. Also claimed is a method wherein three separate measurement values are received and at least two are compared with an expected value to provide deviated measurement values, which are used to establish whether an influx or loss event may have occurred. Systems configured to monitor for influx and/or loss events in a wellbore are also disclosed, said systems utilizing sensors 115 and processor 116 to compare sensed measurement values with expected values to provide deviated values.
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