页岩气集输系统的腐蚀评价与控制——以长宁—威远国家级页岩气示范区为例

四川盆地南部长宁—威远国家级页岩气示范区页岩气开采普遍采用了体积压裂技术，单井水平井压裂液用量介于4×104～5×104 m3、支撑剂（石英砂和陶粒）用量介于2.5×103～3.0×103 t，在压裂施工结束后的页岩气排采和生产过程中，压裂返排液对地面排采流程和地面集输系统带来了不同程度的腐蚀，有可能致使设备和管线穿孔失效，进而影响生产系统的安全运行。为了提高页岩气集输系统的安全运行水平，基于中国石油西南油气田公司天然气腐蚀控制技术支撑平台，借助于腐蚀环境和生产工况分析、材料失效评价及优选、杀菌缓蚀剂应用和生产工艺参数控制优化等方法和手段，开展了川南页岩气集输系统腐蚀行为和控制措施研究。研究结果表明：①川南页岩气集输系统主要表现为冲刷腐蚀和电化学腐蚀；②冲刷腐蚀主要集中在页岩气站内工艺流程，体现在砂粒对弯头、三通、阀门等部位持续的机械磨损；③电化学腐蚀主要集中在页岩气站外集气管线，体现在积液环境中二氧化碳与硫酸盐还原菌的共同腐蚀作用；④采用提高除砂效率、优化流程设计等手段，可以有效控制冲刷腐蚀；⑤加注杀菌缓蚀剂并配套生产管理措施，可以有效控制电化学腐蚀；⑥页岩气集输系统腐蚀评价与控制工作应从设计阶段就开始考虑。结论认为，所形成的集材料优选、设备结构优化、腐蚀介质处理和运行工艺参数优化控制等为一体的页岩气集输系统整体腐蚀控制技术，有效地减缓了川南页岩气集输系统的腐蚀失效、提升了安全运行水平。

Corrosion evaluation and control of a shale gas gathering and transportation system: a case study of the Changning-Weiyuan National Shale Gas Demonstration Area

In the Changning–Weiyuan National Shale Gas Demonstration Area of southern Sichuan Basin, volumetric fracturing technology is commonly used in shale gas production, and the fracturing fluid consumption and proppant (quartz sand ceramsite) consumption per horizontal well are in the range of 4×104–5×104 m3 and 2.5×103–3.0×103 t, respectively. In the process of shale gas drainage and production after fracturing is completed, fracturing flowback fluid causes different degrees of corrosion to surface drainage process and surface gathering and transportation system and may result in equipment and pipeline failures, which may impact safe operation of the production system. In order to improve the safe operation level of the shale gas gathering and transportation system, this paper studies the corrosion behaviors and control measures of the shale gas gathering and transportation system in the southern Sichuan Basin by means of corrosion environment and production performance analysis, material failure evaluation and optimization, bactericide/corrosion inhibitor application and production technological parameter control & optimization, based on PetroChina Southwest Oil & Gasfield Company's natural gas corrosion control technology supporting platform. And the following research results were obtained. First, shale gas gathering and transportation system corrosion in the southern Sichuan Basin mainly includes erosion corrosion and electrochemical corrosion. Second, erosion corrosion mainly happens at the technological process inside the shale gas station, which appears as continuous mechanical wear by sand grains at bends, tee joints, valves and other parts. Third, electrochemical corrosion mainly happens at the gas gathering pipeline outside the shale gas station, which is embodied as the joint corrosion of CO2 and sulfate reducing bacteria in the environment of liquid loading. Fourth, erosion corrosion can be controlled effectively by increasing the desanding efficiency and optimizing the process design. Fifth, electrochemical corrosion can be controlled effectively by injecting bactericide/corrosion inhibitor and taking supporting production management measures. Sixth, corrosion evaluation and control of shale gas gathering and transportation system shall be initially considered in the design stage. In conclusion, by virtue of the developed comprehensive corrosion control technology of shale gas gathering and transportation system which integrates material selection, equipment structure optimization, corrosion medium treatment and operation technological parameter optimization & control, the corrosion failure of the shale gas gathering and transportation system in the southern Sichuan Basin is alleviated effectively and the safe operation level is improved.