Calculation of collapse strength and full-scale testing of titanium alloy casing and tubing under high temperatures

With the exploration and development of deep and ultra-deep wells, downhole temperatures are increasing, posing a significant challenge to the collapse strength of titanium alloy oil pipes and casing pipes at high temperatures. To investigate this impact, this paper employs a combination of full-scale physical testing and finite element simulation. The study focuses on the collapse resistance of these pipes at both room and high temperatures. The finite element simulation results are in good agreement with the experimental values, with an error of only 2.86%. At the same temperature, as the diameter-to-thickness ratio (D/t) increases, the collapse strength of titanium alloy oil pipes and casing pipes gradually decreases. When the diameter-to-thickness ratio is within the range of 0-16, the collapse strength decreases with increasing temperature; the smaller the diameter-to-thickness ratio is, the greater the impact of temperature will be. However, when the diameter-to-thickness ratio exceeds 22, the collapse strength of the pipes is almost unaffected by temperature changes. Finally, based on the calculation results, a relationship for calculating the collapse strength of titanium alloy oil pipes and casing pipes at high temperatures is established. The error between the calculated values using the formula and the experimental values is approximately 2%.