钛合金油套管抗挤毁性能计算与实验

钛合金材料由于具有高的比强度，低弹性模量，优异的韧性、疲劳性能和耐蚀性，已经成为严酷工况环境下油井管和海洋油气开发工具的热门候选材料，但采用API、ISO的标准体系中的油套管挤毁计算方法得出的钛合金油套管抗挤毁强度缺乏验证。为此，在考虑制造缺陷的条件下，通过比较ISO/TR 10400标准中计算方法、外压强度挤毁准则计算方法、有限元模拟等3种不同方法计算出的钛合金油套管的抗挤毁强度，并与同等条件下钢制油套管的抗挤毁强度进行对比，得出了钛合金油套管的抗挤毁强度变化规律，最后选取了4种规格的钛合金油套管进行了实物外挤毁试验验证。研究结果表明：①钛合金油套管抗挤毁强度均随着径厚比的升高而下降，在径厚比值较低时，钛合金油套管和钢制油套管的抗挤毁强度相差不大，而当径厚比值较高时，钛合金油套管抗挤毁强度则显著低于钢制油套管；②强度挤毁准则方法计算出来的钛合金油井管抗挤毁强度和实际试验值较为接近，同时在径厚比大于15时，计算结果乘以0.9的系数，具有较好的安全性。结论认为，该项研究成果可以为钛合金油套管的设计、使用和管理提供参考。

Calculation and experimental studies on the collapse strength of titanium alloy tubing and casing

Titanium alloy has become a promising candidate material for oil country tubular goods (OCTG) in rigorous service environment and for offshore oil and gas development tools, owing to its high specific strength, low elastic modulus and excellent toughness, fatigue and corrosion resistance. However, the collapse strength of titanium alloy tubing and casing which is calculated by means of the tubing and casing collapse calculation method stipulated in API and ISO standard systems lacks verification. Taking the manufacturing defects into consideration, this paper clarified the change laws of the collapse strength of titanium alloy tubing and casing by comparing such collapse strength calculated by three calculation methods (i.e. the calculation method in ISO 10400 standard, the calculation in the Strength Collapse Rule and the finite element simulation) and the calculation results with the collapse strength of steel tubing and casing under the same condition. Finally, the change laws were verified by selecting four types of titanium alloy tubing and casing for full-scale collapse test. And the following research results were obtained. First, the collapse strength of titanium alloy tubing and casing decreases with the increase of the diameter-to-thickness ratio (D/t). When the D/t value is low, there is little difference between the collapse strength of titanium alloy tubing and casing and that of steel tubing and casing. When the D/t value is high, the collapse strength of titanium alloy tubing and casing is significantly lower than that of steel tubing and casing. Second, the collapse strength of titanium alloy tubing and casing calculated by the method in the Strength Collapse Rule is closer to the actual test value. And the calculation result at D/t ＞15 shall be multiplied by the coefficient of 0.9, so as to ensure better safety. In conclusion, the research results can provide technical reference for the design, utilization and management of titanium alloy tubing and casing.