渤海油田油管腐蚀规律及剩余强度研究

Corrosion Law and Residual Strength of Tubing in Bohai Oilfield

近年来,部分老油田地层能量衰减,产量持续降低,需要通过注水进行二次开采,导致油田进入高含水开采期。高含水率的产出流体加速了CO2对油管柱的腐蚀,使油管柱壁厚减薄,强度降低,甚至引起油管柱穿孔、断裂,严重威胁了安全生产。为此,考虑含水率、CO2含量、温度、产量、压力等影响因素,基于ECE腐蚀预测模型,计算了不同条件下油管的腐蚀速率,建立了腐蚀后剩余强度及服役寿命计算方法。最后,运用此模型方法对实例井不同的生产阶段腐蚀规律进行了研究,并利用剩余强度理论对该井油管服役寿命进行预测。同时,分析了主控因素对油管柱腐蚀速率的变化规律。结果表明,CO2含量较低时,含水率成为油管腐蚀的主控因素。通过该模型计算得到的腐蚀速率与现场实测油管柱的腐蚀速率较符合,能有效指导安全生产。

In recent years,the formation energy of some old oilfields has been attenuated and the production has been decreasing continuously.It is necessary to carry out secondary exploitation through water injection,which leads to the oilfield entering the high water cut production period.The produced fluid with high water content accelerates the corrosion of CO2 to the tubing string,reduces the wall thickness and strength,and even causes perforation and fracture,which seriously threatens the safety of production.For this reason,considering water content,CO2 content,temperature,output,pressure and other factors,based on ECE corrosion prediction model,the corrosion rate of tubing under different conditions was calculated,and the calculation method of residual strength and service life after corrosion was established.Finally,this model was used to study the corrosion law in different production stages of an example well,and residual strength theory was used to predict the service life of the tubing.In addition,the variation rule of the main control factors on the corrosion rate of tubing string was analyzed.The results show that water content is the main controlling factor for tubing corrosion when CO2 content is low.The corrosion rate calculated by the model is in good agreement with the corrosion rate measured in situ,which can effectively guide production.