Mechanical Properties Test and Strength Design of Drill String Materials in Low-Temperature Environments

Strength checking and design of drill strings at low temperature are crucial to solving the technical problems of drill string in low-temperature environments such as the Arctic region. In this paper, tests were carried out at both low and normal temperatures on drill string materials G105 and S135, and their temperature-dependent parameters including tensile strength, yield strength, and impact performance,etc. were obtained. On the basis of these results, the strength design method of drill strings in low-temperature environments was proposed. The results show that both tensile and yield strength of G105 and S135 increase as the temperature decreases while the cross section reduction rate remains unchanged. In low-temperature environments, it is important to note that to ensure the safety of the drill strings, their strength design should be controlled by both stress and strain, instead of only by stress in normal temperature environments. Yield strength of drill string materials should be determined according to the strength characteristics of the materials in the wide-temperature range. The results show that this study has directive significance to guarantee the engineering design of drill strings and their safety in low-temperature environments.