Mechanical Properties and Strength Design of Typical Drill String at Low Temperature

With the extension of oil and gas exploration to high-latitude and high-cold regions, the mechanical properties and safety design of drill strings inlow-temperature environments have become key issues. Low-temperature conditions significantly affect the mechanical behavior of drill string materials. Metal components designed according to the normal temperature design method cannot ensure safety in low-temperature environments. This study systematically analyzed the mechanical properties of G105 and S135 drill pipes in the range of −60 °C to 20 °C.The results show that as the temperature decreases, both the tensile strength and yield strength of the materials increase. Based on this, a strength design method for drill strings suitable for low-temperature environments was proposed. The strength design method of the drill string is transformed from stress control at normal temperature to the joint control of stress and strain. When designing the strength of the drill string in a low-temperature service environment, the yield strength of the drill string material should be determined based on the material strength characteristics in a wide temperature range. The research results provide theoretical support for safe and efficient drilling in extremely cold regions.