酸性环境中油井管钢裂纹扩展特性研究

发布时间：2018-01-09 11:12

本文关键词：酸性环境中油井管钢裂纹扩展特性研究　出处：《西安石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：在油气井的开采过程中,一般会利用酸化等工艺对油气井进行酸化处理以此来提高产量,使得原本偏酸性的油气田酸性增强。这些酸性介质对油井管钢带来严重的腐蚀损伤,同时服役的油井管钢还承受着环空外压、内压、弯曲、载荷以及扭矩等作用,酸性腐蚀介质与外加载荷(交变载荷和静载荷)的协同作用,产生腐蚀疲劳与应力腐蚀损伤,导致油井管钢裂纹的萌生、扩展甚至断裂。因此,研究酸性环境中油井管钢的裂纹扩展速率,可有助于预测油井管钢的剩余寿命。本文主要研究在不同酸性环境中油井管钢分别发生腐蚀疲劳与应力腐蚀时的裂纹扩展速率。首先,在腐蚀疲劳研究中,探索酸性溶液中H+浓度(PH=3、4、5)、加载频率(5Hz与1Hz)、不同材质(P110、13Cr)对油井管钢腐蚀疲劳裂纹扩展速率da/dN的影响,根据实验结果建立腐蚀疲劳剩余寿命速率模型。其次,在应力腐蚀研究中,采用慢应变速率法,研究酸性溶液中H+浓度(PH=3、4、5)对应力腐蚀裂纹扩展特性的影响,以及不同PH值下对应力强度因子门槛值KIscc的影响,分析应力腐蚀裂纹扩展速率da/dt和应力强度因子幅△K两者之间的函数关系。得出以下结论:(1)在腐蚀疲劳研究中,当频率为5Hz时,相比较于大气环境与3.5wt%NaCl的腐蚀环境,偏酸性的3.5wt%NaCl明显促进了P110油井管钢腐蚀疲劳裂纹的扩展,同时随着酸性溶液中H+浓度的提高,由PH=5降为PH=3,裂纹扩展速率有所提高。将频率降为1Hz时,由于频率的降低,加大了H+对P110的腐蚀损伤时间,促进了油井管腐蚀疲劳裂纹的扩展。改变材质,对于13Cr材质油井管钢,频率均为1Hz时,相比较于大气环境与3.5wt%NaCl的腐蚀环境,在含H+离子的3.5wt%NaCl环境中裂纹扩展速率有所提高,随着H+浓度的增加,裂纹扩展速率有稍微降低,与P110油井管钢相反。(2)在应力腐蚀研究中,将交变载荷设定为静载荷进行应力腐蚀实验,设定恒定的位移速率为5×10-5mm/s,P110油井管钢在偏酸性的3.5wt%NaCl溶液中的应力强度因子门槛值随着H+浓度的增加而降低,整个过程中所吸收的总能量也有所降低,说明酸性介质H+能够促进应力腐蚀的发生,且裂纹扩展速率也随着H+浓度的增加而增大。
[Abstract]:In the process of exploitation of oil and gas wells, usually on the oil well acidizing treatment in order to improve the yield of the acidification process, making the original acidic oil field. These acidic acidic medium steel brings severe corrosion damage to the oil pipe, and service oil pipe steel also bear the annulus pressure, internal pressure and bending load and torque effect, acid corrosion medium and the external load (alternating load and static load) the synergistic effect of corrosion fatigue and stress corrosion damage, resulting in crack initiation of steel tube wells, expansion and fracture. Therefore, the rate of crack extension of oil pipe steel in acidic environment, can have contribute to the residual life prediction of steel tube wells. This paper mainly studies in different acidic environment of oil pipe steel were corrosion fatigue and SCC crack propagation rate at first, in the study of corrosion fatigue, explore acid The concentration of H+ solution (PH=3,4,5), frequency (5Hz and 1Hz), different materials (P110,13Cr) effect on the growth rate of da/dN oil pipe steel corrosion fatigue crack, according to the experimental results establish the model of corrosion fatigue residual life rate. Secondly, the research on stress corrosion, using slow strain rate method of acid the concentration of H+ solution (PH=3,4,5) stress corrosion crack propagation effect, and the stress intensity factor under different pH value threshold effects of KIscc function to analyze the relationship between the stress corrosion crack growth rate of da/dt and the stress intensity factors K two. Draw the following conclusions: (1) in the study of corrosion fatigue and when the frequency is 5Hz, compared with the atmospheric environment and corrosive environment 3.5wt%NaCl, acidic 3.5wt%NaCl significantly promoted the expansion of steel corrosion fatigue crack of P110 oil well pipe, at the same time as the concentration of H+ acid in the solution increased by P H=5 reduced to PH=3, the crack propagation rate increased. The frequency is reduced to 1Hz, due to the decrease of the frequency, increase the corrosion damage time of H+ to P110, to promote the expansion of corrosion fatigue crack of tube wells. To change the material, 13Cr material for oil pipe steel, the frequency was 1Hz, compared to the corrosive environment the atmospheric environment and 3.5wt%NaCl, in the 3.5wt%NaCl environment with H+ ion in the crack growth rate increased with the increase of H+ concentration, the crack growth rate was slightly decreased, and the P110 oil pipe steel instead. (2) in the study of stress corrosion, the alternating load setting for static load stress corrosion test. Set the displacement rate constant is 5 * 10-5mm/s, 3.5wt%NaCl steel in the acidic solution of the stress intensity factor decreases with the increase of H+ concentration and the P110 tube wells, total energy absorbed in the whole process can be reduced, the acidic medium The quality of H+ can promote the occurrence of stress corrosion, and the rate of crack growth increases with the increase of H+ concentration.

【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE983

【相似文献】