Thermal Wellbore Failure Detection Case Studies: A High Temperature Multi-Finger Caliper Surveillance Approach

Cooling of thermal wellbores such as steam assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) wells, is a common prerequistite to allow deployment of logging instruments due to the temperature limitation of imaging instruments’ electronics (<150°C). This paper presents a memory caliper technology housed in a thermoshield that can perform at up to 220°C, with the acquired data used to evaluate the integrity of tubulars and completion items (metal loss, deposition, deformation, and gap/hole damage), negating the need for cooling before deployment. Two cases are presented. One is a SAGD well with liner screens across the lateral section. The memory multi-finger caliper was deployed using coiled tubing and the data were successfully obtained across the lateral section with a maximum recorded temperature of 169°C. The second example is a vertical well in a steam flood field. Because of the uncertainty over the downhole temperature at the time of the well intervention, a temperature sensor was deployed in surface read-out mode above the caliper. This ensured the 220° temperature limit of the caliper would not be breached, and a maximum temperature of 208°C was recorded. The data confirm the feasibility of acquiring high accuracy/high resolution data from thermal wellbores without having to resort to manipulative cooling techniques to attain a temperature below 150°C. Enlargement of a limited entry perforation (LEP) was observed in the horizontal well and buckling was clearly detected in the vertical well. The broad measurement range of the caliper – 1.85" – 7.2" – enabled both the tubing and liner to be logged in a single well intervention, which facilitated a swift resumption of of steam injection activities. Ultimately, the high temperature MFC's ability to minimize deliberate cooling the thermal wellsbore before deployment, has time and cost saving implications throughout the life cycle of the well. Much of the existing literature examining downhole data acquistion in thermal wells, for the diagnosis of wellbore integrity issues, has relied on technologies that are unable to withstand temperatures much greater than 150°C. The ability to execute well interventions for data acquistion at higher temperatures offers the potential for empirical studies that compare the status and integrity of the wellbore completion in thermal and cooled conditions.