ABSTRACT
Wellbore heat loss and steam quality downhole, at the sandface, are primary factors affecting the performance of steam injection wells used in enhanced oil recovery. Secondary factors critical to steam injection operations are casing thermal stress and packer seal integrity. A practical, durable, and economical insulated downhole steam tubular system has been developed by the General Electric Company, Advanced Energy Department, Thermal Systems, in Tacoma, Washington. This insulated tubular is the latest product in the General Electric patented "ThermoCase" line of insulated downhole oilfield products and is designated "ThermoCase III".
The new insulated tubing allows deeper wells, protects old wells, improves steam quality, oil production, and simplifies completion design. A.P.I. standard tubulars, installation procedures, and rig equipment are used. Evolved from successful deployment at Prudhoe Bay, the welded double tube construction with expansion bellows, hermetically sealed, provides high performance insulation, protects tubular threads, and maintains low casing temperature when flowing 635°F (335°C), 2000 psi (141 kg/cm2), steam. Initial applications of ThermoCase III in Canadian heavy oil, and tar sands in California and Venezuela are now underway.
A thermal description of the product along with a discussion of a number of verification test results will be given. In addition, thermal/structural and financial/economic computerized analysis results will be given for a typical steam injection field application with 635°F (335°C) saturated steam at 2000 psia (141 kg/cm2) flowing down a 2300 ft. (701 m) well. In summary, "ThermoCase III" has been designed to give outstanding thermal performance with a nominal overall K-factor of 0.20 Btu-in/ft2-hr-°F (0.028 W/m°K). Typical significant reductions in casing temperature with ThermoCase III versus standard uninsulated steam tubing were determined to be approximately 431 percent. A similar reduction in relative packer axial movement of approximately 734 percent was also realized in the above mentioned example.
