井喷火灾下油气井口材料高温力学性能实验研究

Experimental study on the high-temperature mechanical properties of oil and gas wellhead materials under a blowout fire scenario

为了精确评估井喷火灾情况下井口装置的剩余力学强度,该文针对井口常用材料35CrMo开展了高温拉伸实验,旨在分析不同温度条件下该材料的拉伸断裂形态及其力学性能的变化规律。在相同应变条件下,随着温度升高,35CrMo的应力、弹性模量、屈服强度和抗拉强度均呈下降趋势。这些高温拉伸实验所获得的力学性能数据,为工程师更准确地评估在极端温度条件下井口装置的安全性和可靠性提供了重要支持,有助于制定有效的井喷火灾处置和预防策略。基于该实验,不仅能够深化学生对专业知识的理解,还能显著提升学生解决实际工程问题的能力,同时培养学生创新思维和科学研究的兴趣。

[Objective]Blowouts and fires are extreme accidents in oil and gas field development.During such accidents,the wellhead is exposed to extreme heat from uncontrolled flames,leading to a progressive degradation of its mechanical strength.Therefore,assessing its residual strength in the aftermath of a blowout fire is essential for ensuring the safety and effectiveness of disaster response measures.To accurately evaluate the mechanical resistance of wellhead materials at high temperatures,35CrMo,a steel commonly used in wellhead construction,is selected as the research object due to a notable gap in experimental research regarding its behavior under thermal stress.[Methods]Herein,twelve high-temperature tensile tests were conducted across four temperature levels(400,500℃,600℃,and℃700),with three replications for each temperature,and three ambient temperature tests for comparison.The test specimens were℃fabricated using the Vturn S26/110 precision CNC lathe.Based on the High Temperature Tensile Test Methods for Metal Materials(GB/T4338-2006)standards,experimental tests were conducted using the microcomputer-controlled electronic universal testing machine UTM5105HB.[Results]The experimental results reveal that at temperatures≤500,a larger fracture d℃iameter of the specimen is observed,indicating that the material keeps its high plasticity and toughness within this temperature range.Meanwhile,at temperatures>500,the specimen exhibits a smaller fracture diameter and obvious necking phenomenon,ind℃icating a decrease in plasticity and toughness of the material under a high-temperature environment.Moreover,the material tends to undergo concentrated deformation and rapid fracture in local areas,indicating a shift in its fracture mode toward brittle behavior.With the increase in temperature,the stress value of the material at the same strain level shows a gradually decreasing trend.Especially in temperature ranges of room temperature to 400℃and 500 to 600,the decrease in stress is particularly significant,indicating a significant decrease in the mechanical properties of the℃℃material within these temperature ranges.Furthermore,with the increase in temperature,the elastic modulus,yield strength,and tensile strength gradually decrease.Compared with room temperature,the elastic modulus,yield strength,and tensile strength are decreased by 89.5%,92.2%,and 92.0%,respectively.This significant decrease in performance leads to a significant reduction in the structural integrity and load-bearing capacity of the material in high-temperature environments.[Conclusions]The obtained experimental data offer valuable insights for engineering evaluations of the safety and reliability of the wellheads in extreme temperature conditions,providing a reference for the development of blowout fire disposal and prevention strategies.Moreover,this work covers relevant fundamental knowledge and incorporates practical engineering application scenarios,in line with the principle of advancement,innovation,and challenge proposed by the Ministry of Education for practical courses.Such experiments can deepen students’understanding of fundamental knowledge,enhance their ability to solve practical engineering problems,and cultivate innovative thinking skills and scientific research interests.