Temperature fall-off logs are routinely performed on a number of operating wells at Statoil's Leismer field to monitor well integrity. So far, all wells have demonstrated normal temperatures in formations overlying the steam chamber, less than steam temperatures, and with fall-offs according to typical heat conduction. However, one injector well did not fall-off as expected after a 24 hour shut-in; instead showed temperatures exceeding 200°C in formations above the steam chamber. An investigation was launched and a multidisciplinary team evaluated possible causes for the high temperatures.
A review of 4D seismic data showed that a neighbouring steam chamber was intersecting the wellbore. This led to the hypothesis that the high temperatures were the result of wellbore heating from the neighbouring steam chamber, and a follow-up, extended temperature fall-off log confirmed the hypothesis. The extended logging period confirmed that temperatures outside casing did fall-off, albeit at a slower rate than other wells, due to the heating effect of the neighbouring steam chamber. The temperature log measurements indicate that heat from an intersecting steam chamber can cause a counter-intuitive segregation of steam and water in the wellbore, with condensed liquid water held above steam in the upper section of the well. This case study highlights strategies for interpreting downhole temperature anomalies using temperature logs and 4D seismic, and also the benefits of a well integrity investigation with strong cross-discipline collaboration.