The efficiency of a thermal enhanced oil recovery project with surface steam generation can be significantly increased by using insulated tubing in the injection wells. In order to evaluate the performance of various insulated tubulars it is necessary to obtain detailed temperature measurements and accurate heat loss data under actual in—field conditions. A system to provide this information has been developed and is in operation at the Aberfeldy steam pilot near Lloydminster, Saskatchewan, Canada.
Temperature measurements are made using thermocouples inside and on the outer wall of the injection string; on the outside of the casing, and in a set of three 25 mm (1 in) ID thermowells attached to the casing. In addition, thin film heat flux sensors are bonded directly to the wall of the injection string. A probe system was designed to measure circumferential temperature variations in the thermowells at depths down to 100 m. This makes it possible to obtain detailed axial temperature profiles. Anticipated hot spots on an insulated joint will be detected in this manner. All of the data is recorded on a datalogger and detailed analysis is performed on a computer system.
To date a short test has been carried out using bare 60 mm (2–3/8 in) injection string tubing. This bare string provides data for comparison with insulated strings. High resolution radial temperature profiles were obtained during this test. Variations in heat loss from the string as functions of time and operating conditions have also been successfully monitored. Heat losses from the string during initial start up on the order of 1.0 Kw/m (1050 Btu/hr-ft) were observed with the heat flux sensors. This is in good agreement with the expected heat loss. The heat flux sensors make it possible to both simplify and improve the determination of insulated tubular thermal performance.