Research Progress in Synergetic Corrosion and Protection of Pipelines in Oil and Gas Production Environment

Pipeline corrosion in CO2 / H2S environments at high temperatures and pressures is a critical problem in oil and gas fields that must be solved urgently CO2, H2S, and Cl(- )are common corrosion media in oil and gas pipelines. CO2 changes the chemical properties of water in a solution and decreases the pH value of the solution, which promotes cathodic hydrogen evolution reaction. Corrosive ions dissociated from H2S exhibit strong penetrability, which accelerates pitting and sulfide stress cracking. The barrier function and catalytic effects of Cl- reduce the adhesion of corrosion products, which accelerates metal corrosion. The synergistic corrosion between CO2, H2S, Cl-, and external factors, such as temperature, pressure, pH value, water content, and flow rate, leads to the severe corrosion of pipelines. These external factors impact the corrosion process by influencing the morphology of the corrosion products. A harsh corrosion environment loosens the corrosion products and weakens the barrier effect of the corrosion products on the corrosive medium, thereby accelerating the corrosion of the substrate. Thus, it is necessary to investigate the synergistic corrosion mechanisms of corrosive media and external factors and to propose measures to mitigate pipeline corrosion. In view of the corrosion problem of metal pipelines encountered during oil and gas exploitation, the roles of CO2, H2S, and Cl- in the synergistic corrosion process are summarized in this paper. In addition, the effects of external factors, such as temperature, pressure, pH value, water content, and flow rate, on the morphology and composition of corrosion products under actual working conditions are discussed. The characteristics of existing pipeline corrosion protection technology and processes are discussed. Doping with alloy elements can modify the composition of the corrosion products and improve the corrosion morphology and compactness of the corrosion product layer. Doping with elements, such as Ni, Cr, Mo, and Ti, can effectively slow the pitting and stress corrosion cracking of metals. Plasma diffusion and coating technology can be applied to prepare a dense protective layer to absorb a part of the corrosion medium and decrease the corrosion rate. The corrosion resistance of a metal is effectively improved by infiltrating interstitial atoms into the metal surface using chemical heat treatment techniques, such as nitriding, carburizing, and carbonitriding. The addition of a corrosion inhibitor can slow the cathodic or anodic reaction of the pipeline, or form an adsorption layer to decrease the corrosion rate. However, traditional measures for protecting oil and gas pipelines, such as the use of corrosion-resistant alloys and corrosion inhibitors, are limited owing to their high operating costs and environmental pollution. The preparation of advanced coatings on the inner surfaces of pipelines is expected to achieve a compromise between corrosion protection and cost, and is one of the most effective methods for protecting metal pipelines. Ni-P coatings effectively decreases the corrosion rate by absorbing the corrosive medium to generate corrosion products. Diamond-like carbon films prepared via hollow cathode plasma-enhanced chemical vapor deposition on the inner surfaces of pipelines are also considered one of the most effective methods for future oil and gas field pipeline protection because of their excellent chemical inertness and minimal chemical reactions with acids, alkalis, and salts. Finally, future directions for the advancement of pipeline protection technology in oil and gas fields are proposed. It is necessary to further investigate the synergistic corrosion effect between corrosive media and external factors, and simulate the corrosion environment under actual conditions to effectively protect pipelines in oil and gas production environments. This can be achieved by conducting systematic experimental tests on existing protection technologies, such as plasma diffusion and coating technology, and using corrosion inhibitors.