某储气库注采气管道内腐蚀直接评估方法

An internal corrosion direct assessment method for the gas injection/withdrawal pipeline of one underground gas storage

为研究某储气库注采气管道的内腐蚀情况,运用干气管道内腐蚀直接评估方法和湿气管道内腐蚀直接评估方法对该其进行评估,包括预评估、间接检测、详细检查及后评估4个步骤。在预评估阶段,结合该管道不定期双向流动的特点,从里程和时间两个角度划分内腐蚀直接评价分区;在间接检测阶段,运用湿气管道内腐蚀直接评估方法对采气过程进行评估,运用干气管道内腐蚀直接评估方法对注气过程进行评估,其中既考虑正常采气或注气阶段,又考虑较长的停输时期;在详细检查阶段,利用超声波测厚仪对管道进行壁厚测量,确定管道是否存在内腐蚀;在后评估阶段,主要评价管道的再评估周期。评估结果表明:该管道存在内腐蚀,但缺陷处的剩余强度未受到显著影响。

In order to study the internal corrosion of gas injection/withdrawal pipeline in one underground gas storage, Dry Gas Internal Corrosion Direct Assessment(DG-ICDA) method and Wet Gas Internal Corrosion Direct Assessment(WGICDA) method were applied to assess this pipeline through four steps, i.e., pre-assessment, indirect inspection, detailed examination and post assessment. In the pre-assessment step, ICDA regions are divided from two aspects of mileage and time, based on the characteristics of bidirectional flow at irregular intervals. In the indirect inspection step, WG-ICDA method is used to assess gas withdrawal process and DG-ICDA method is used to assess gas injection process. In this step, not only normal gas injection or withdrawal periods, but also longer shutdown periods are taken into consideration. In the detailed examination step, wall thickness is measured by the ultrasonic thickness gauge to determine if the pipeline is suffered from internal corrosion. And in the post assessment step, the reassessment interval of this pipeline is evaluated. The assessment results indicate that there is internal corrosion in this pipeline, but the remaining strength at the defects is not affected significantly.