桥式同心分注技术在超深双台阶水平井中的应用

塔里木油田埋地集输管道的阴极保护系统中, 电绝缘装置多次发生内腐蚀穿孔, 由于电绝缘装置在油气田集输管道中应用数量众多, 关系到站场、管道的完整性, 阴极保护中电绝缘装置的内腐蚀穿孔问题越来越引起人们的重视。通过研究阴极保护中电绝缘装置内腐蚀穿孔的诸多现象, 发现电绝缘装置所在管道输送的物料中都含有高矿化度的水, 且在绝缘接头(法兰) 的底部都有沉积水相存在；内腐蚀穿孔的位置都集中在非保护侧, 且都集中在底部, 越靠近绝缘环板处腐蚀越严重；腐蚀穿孔的速率明显高于CO2或H2S或二者共存时的自然腐蚀速率；腐蚀形貌特殊, 蚀坑呈圆形, 边缘清晰, 蚀坑内表面光洁, 无腐蚀产物沉积、附着, 具有典型的直流杂散电流腐蚀形貌特征。用等效电路法分析了发生腐蚀穿孔的原因, 并提出了相应的防止内腐蚀穿孔技术措施。

Application of Bridge Concentric Separated-layer Water-flooding to Ultra-deep and Double-step Horizontal Wells

In the cathodic (sacrificial) protection system for buried oil gathering pipeline in the T Oilfield, multiple internal corrosion perforations occurred in the electrical insulation device. Because of the large number of applications of electrical insulation devices to oil and gas gathering and transportation pipelines, this problem is related to the integrity of station fields and pipelines, thus it has been paid more and more attentions. Through studying many phenomena of corrosion perforations of electrical insulation devices in the cathodic protection, it has been found that the materials transported in the pipelines with electrical insulation devices have the water with high degree of mineralization or salinity, and there is deposit water facies on the bottom of the insulating joint (flange); the locations of the internal corrosion perforations are concentrated in the non-protected side and on the bottom. Where the closer to the annular insulcrete, the more serious the corrosion is; the velocity of the corrosion perforation is obviously higher than the rates of natural corrosion of CO2 or H2S or coexistence of the two. The patterns of the corrosion are special, with round corrosion pits, clear edges, smooth inner surfaces of the pits, without deposition or/ and attachment of the corrosion products. Thus it has the features of typical corrosion patterns of DC stray current. The causes of the internal corrosion perforations were analyzed with the equivalent circuit method, and corresponding technical measures to prevent internal corrosion perforations were put forward.