南海高温高压含CO2气井管柱腐蚀适用性评价

目的明确南海高温高压含CO2气井管柱材料腐蚀适用性,指导现场管柱材料选择。方法采用高温高压釜腐蚀实验仪器对井筒高温高压环境条件下不同材料腐蚀速率进行实验分析,并采用扫描电镜及能谱分析仪对腐蚀实验后试样腐蚀形貌进行分析,评价不同井筒环境下管柱材料腐蚀适用性。结果150℃条件下,材料腐蚀速率随分压的增加而增大,同时随着材料Cr含量的增加,材料腐蚀速率降低,其中P110钢材料腐蚀速率到达0.3511mm/a,属于严重腐蚀;180℃条件下,三种材料试样表面均存在不同程度的局部腐蚀,其中13CrS-110试样表面出现点蚀的程度较其他两种材料更严重,其点蚀坑存在向内发展的趋势。结论南海高温高压含CO2环境下,Cr含量的增加提高了材料抗腐蚀性能,且随着CO2分压的提高,溶液中CO2溶解度不断增大,增加了材料腐蚀。在180℃高温条件下,13CrS-110钢、15Cr-110钢、15Cr-125钢均存在不同程度点蚀,但13CrS-110钢存在开裂风险,在现场应用前应进行开裂风险评估。针对高温高压含CO2气井管柱选材,可根据井筒温度、压力、CO2分压分布情况进行分段设计,在保障井筒完整性的基础上,降低开发成本。

Applicability Evaluation of String Corrosion in High Temperature and High Pressure Gas Wells Containing CO2 in South China Sea

This paper aims to clarify the corrosion applicability of string materials for high-temperature and high-pressure gas wells in South China Sea and guide the selection of field string materials.The corrosion rate of different materials in wellbore under high temperature and high pressure environment is analyzed by using high temperature and high pressure kettle corrosion test instrument,and the corrosion morphology of samples after corrosion test is analyzed by using scanning electron microscope and energy spectrum analyzer to evaluate the corrosion applicability of pipe string materials in different wellbore environments.The results show that:at 150℃,the corrosion rate increases with the increase of partial pressure,and decreases with the increase of Cr content.The corrosion rate of P110 steel reaches 0.3511 mm/a,which belongs to serious corrosion;at 180℃,there are different degrees of local corrosion on the surface of three kinds of materials,and the pitting corrosion degree of 13CrS-110 sample is higher than that of other materials.The pitting pits tend to extend inward.Therefore,in the high temperature and high pressure CO2 environment in the South China Sea,the increase of Cr content improves the corrosion resistance of the materials,and with the increase of the partial pressure of CO2,the solubility of CO2 in the solution increases,which increases the material corrosion;under the high temperature of 180℃,the pitting corrosion exists in 13CrS-110 steel,15Cr-110 steel and 15Cr-125 steel,but 13CrS-110 steel has the risk of cracking.Cracking risk assessment should be carried out before field application.In view of the string material selection for high temperature and high pressure gas well containing CO2,according to the wellbore temperature,pressure and CO2 partial pressure distribution,the design can be carried out in sections so that the development cost can be reduced on the basis of ensuring the integrity of the wellbore.