高温高压多元热流体环境CO2腐蚀与氧腐蚀交互作用机理

Injection of multiple thermal fluids huff-puff technology has increasingly become the main method to improve the oil production in offshore heavy oil fields. The resulting high temperature and high pressure CO2 and O2 coexisting corrosion environment can easily lead to short-term failure of oil well tubing. Therefore, the interaction mechanism between high temperature and high pressure CO2 corrosion and O2 corrosion has become a scientific problem to be solved urgently in the field of corrosion control. This project is based on commonly used oil well tubing as the object under high temperature and high pressure CO2-H2O-O2 environment. On the basis of the thermodynamic simulation of the interaction between CO2 and O2 on the water chemical properties, the high temperature and high pressure corrosion simulation test and in situ electrochemical measurement are used to investigate the corrosion product formation evolution pattern and electrochemical corrosion mechanism in CO2-H2O-O2 environment combining microstructure characterization of corrosion product, and then reveal the interaction mechanism of CO2 corrosion and O2 corrosion. Corrosion model of CO2-H2O-O2 system in oil and gas field is established based on the research results, which will provide theoretical basis and technical support for the corrosion control and protection of the metal in the coexistence environment of CO2 and O2 in the oil and gas fields.

注多元热流体吞吐技术日益成为海上稠油油田增产的主要手段，由此带来的高温高压CO2和O2共存的腐蚀环境极易导致油井管短期失效。因而高温高压CO2腐蚀与O2腐蚀的交互作用机理就成了腐蚀控制领域亟待解决的科学问题。本项目以高温高压CO2-H2O-O2环境下的常用油井管材为研究对象，在CO2与O2交互作用对水化学性质影响热力学模拟的基础上，开展高温高压腐蚀模拟实验和原位电化学测试，结合腐蚀产物膜的微观结构表征，从本质上探明油气田CO2-H2O-O2体系管材腐蚀产物的形成演化模式和腐蚀电化学机理，揭示CO2腐蚀与O2腐蚀的交互作用机理，并据此建立油气田CO2-H2O-O2体系管材腐蚀模型。为油气田CO2与O2共存环境下金属的腐蚀控制与防护提供理论基础和技术支撑。

注多元热流体吞吐技术日益成为海上稠油油田增产的主要手段，由此带来的高温高压CO2和O2共存的腐蚀环境极易导致油井管短期失效。因而高温高压CO2腐蚀与O2腐蚀的交互作用机理成为亟待解决的科学问题。本项目以高温高压CO2-H2O-O2环境下的常用油井管材为研究对象，开展高温高压腐蚀模拟实验、原位电化学测试以及运用SEM、EDS、XRD等现代表面分析技术，系统地研究了油井管钢在多元热流体环境中的腐蚀行为。具体结果如下：1）在CO2-O2共存环境中，P110的腐蚀速率随氧含量的降低逐渐减小。腐蚀产物膜为双层膜结构，外层为红褐色的铁氧化物，内层由FeCO3与少量FeOOH、Fe2O3构成。随着氧含量的降低，腐蚀产物膜电阻(Rf）与电荷传递电阻(Rt)逐渐增大，腐蚀产物膜电容(Cf)减小，腐蚀产物膜保护性显著提升。2）当Cr含量低于5%时，试样表面腐蚀产物主要由FeCO3、FeOOH、Fe2O3及Fe-Cr固溶体构成。随着Cr含量的增加，膜层电阻(Rf)、电荷传递电阻(Rt)、线性极化电阻(LPR)增大，膜层电容(Cf)减小，显著增强的材料的耐蚀性。3）在150℃~240℃的CO2-O2-H2O(g)环境中，N80钢的腐蚀产物均呈双层膜结构，腐蚀产物均为Fe3O4。在CO2-O2-H2O(l)环境中，N80钢的腐蚀速率随温度变化规律：60℃~150℃时，腐蚀速率逐渐降低；150℃~180℃时，腐蚀速率小幅升高；180℃~240℃时，腐蚀速率降低。60~120℃时，腐蚀产物为双层膜结构，外层腐蚀产物为疏松的铁氧化物，内层腐蚀膜为致密性较差的(FeCa)CO3，150℃~210℃时，腐蚀产物为三层膜结构，内层膜均为Fe3O4，240℃时，腐蚀产物为单层膜结构，为致密性较好的Fe3O4。4）随着流速的增大，N80腐蚀速率增大，腐蚀产物膜为双层膜结构，外层腐蚀产物主要为疏松多孔的Fe2O3和FeOOH，基本不具有保护性能，而内层腐蚀产物主要由FeCO3构成。流速增大，冲刷力增大，内外层膜均减薄，Rp变小，腐蚀电流(Icorr)增大，膜层电阻(Rf)和电荷传递电阻(Rt)减小，电荷越过基体与腐蚀介质界面双电层的阻力减小，0.5m/s流速条件下腐蚀产物膜的较为致密，对离子的扩散有很大阻力。本研究结果为油气田CO2与O2共存环境下金属的腐蚀控制与防护提供理论基础和技术支撑。