Special Considerations for Well Tubular Design at Elevated Temperatures

Abstract

Summary Understanding of material properties for tubular design under high-pressure/high-temperature (HP/HT) conditions goes well beyond the basics of the classic methods routinely used in the industry. Coupon test results of high-strength tubulars commonly used in HP/HT wells are presented to demonstrate the temperature and strain-rate dependencies of the stress-strain response. Based on the coupon test results, analytical equations and advanced nonlinear Finite Element Analysis (FEA) are used to illustrate the substantial impact that the temperature and rate-dependent material properties have on pipe body and connection performance in HP/HT applications. This paper raises an awareness of the importance of strain-rate effects, and recommendations are made on a few special considerations to account for these effects in well tubular design for elevated temperature applications. In addition, the findings also provide the basis for a critical discussion of the applicable American Society for Testing and Materials (ASTM)/American Petroleum Institute (API) test standards and the need to understand the effect of different strain/loading rates that may be used in material characterization and full-scale testing of tubular products at elevated temperatures. Collectively the information and results presented in the paper are expected to be very useful to the new generation of engineers charged with the tubular design for challenging well applications involving elevated temperature and severe load conditions.