A New Approach to Thermal Profiling in High Temperature Reservoirs Based on Advanced, Polymeric Insulated Thermocouples to Increase Measurement Point Density
Authors: Penny Scott , Bui Cao Tri , Hutter Naima , Braungart Heinz , Thompson Scott , Molzan Kyle , Desmarais Adrien , Bockrath Brian , Geywitz Eva , Schreiner Juergen 
Published: November 2015

Thermal recovery schemes are becoming increasingly common as many processes transition from trials and piloting to fully commercialized technologies. These processes often rely on high quality temperature and pressure data that are accurate and reliable over an extended period of time and at reservoir temperatures in excess of 180°C, potentially up to 300°C. Ideally, the number of discrete temperature measurement points in a well is maximized to decrease the possibility that temperature related events go undetected. This new approach is based on a thin, advanced, high temperature index polymeric insulation material which enables reliable Type-K thermocouples to be used.

The development of the thermocouple pairs was based on fundamental material characterization, followed by lab and simulated-use testing. A customized two dimensional stationary thermal simulation tool was utilized to optimize efficiency in temperature response behavior of the cable design. It allowed for the modeling of a multipoint thermocouple bundle temperature profile under the influence of longitudinal and axial heat conduction. The combination of experimental testing and theoretical simulation created an architecture which offers the highest density of thermocouple points possible in standard stainless steel tubing sizes.

Mechanical testing in combination with temperature exposure shows high temperature performance within cut-through and thermoplastic flow tests. The most critical potential failure modes relate back to these properties and could yield false temperature measurements at wrong locations. In addition, accelerated aging testing demonstrates insulation integrity with a temperature index of 300°C. Comparison measurement with standard available polymeric insulation shows a significant increase in reliability, achievable number of measurement points, and higher operating temperatures. Temperature simulation data show a high level of agreement to measured laboratory testing.

A prototype cable has been installed in an observation well at Statoil's SAGD Leismer Demonstration Project by suspending the cable inside of the casing. This observation well intersects the active steam chamber; thus, the cable is exposed to high and ambient temperatures with an abrupt transition between the two zones. Standard mineral insulated (MI) Type-K thermocouples were previously clamped to the exterior of the casing and cemented in place. Field trial data will be presented demonstrating a high degree of correlation between the prototype cable thermocouples and the standard thermocouples over a significant period of time.

Novel/Additive Information: The innovative, durable, thin, polymeric insulation material capable of operating up to 300°C, enables the use of thermocouples. A cable design utilizing this material is presented, which allows for a high density of temperature points. Well-operators can now rely on established Type-K thermocouples to provide high resolution data over the length of the well. For instance, over 60 points encapsulated in ½″ tubing can be used to monitor the subcool of a SAGD well.