With the widespread application of CO 2 -Enhanced Oilfield Recovery (CO 2 -EOR) technology, CO 2 in large quantities enters oil and gas gathering pipelines and causes severe corrosion. As a result, this paper investigates the corrosion behaviour of 20# steel in produced water and 40% water content emulsion with different CO 2 contents by combining Wire Beam Electrode (WBE) technology and the corrosion weight loss method, and establishes a corrosion mechanism model for analysis and explanation. The results demonstrate that variations in CO 2 concentration have a greater impact on the corrosion process in the produced water simulated fluid, and there is considerable corrosion non-uniformity in the CO 2 saturated state, as well as polarity reversal throughout the whole corrosion process. On the contrary, corrosion in the emulsion is more stable and uniform because the crude oil in the emulsion obstructs the mass transfer process of the depolariser agent and forms a 'surface wetting' effect on the metal surface, which seriously hinders the corrosion process.

Galvanic corrosion is a type of localized corrosion that widely exists in all kinds of metal structures and causes severe damage, jeopardising the safety and dependability of equipment. This paper reviews the mechanism of galvanic corrosion and related influencing factors, including the material characteristics and geometric factors of the metal pair and environmental factors. As a unique surface testing technique, wire beam electrode (WBE) is widely used in various corrosion research fields represented by galvanic corrosion. On this basis, the research progress of the WBE technique in the field of galvanic corrosion is mainly reviewed from three perspectives. The experiments also proved that the WBE technique can well characterize the corrosion evolution progression and investigate the polarity reversal mechanisms. Finally, it is pointed out that the urgent scientific problems to be solved in the research of galvanic corrosion include: galvanic corrosion research in a variety of special environments; the mechanism of the galvanic couple reversal caused by the change of corrosion factors; the corrosion behavior of a complex coupling system composed of multiple metal connections; the development of corrosion prediction models.

Purpose Oil-water two-phase flow is the most prevalent medium in oil field gathering pipelines, and the corrosion of pipelines is often highly localized. Therefore, the purpose of this paper is to investigate the corrosion behavior of 20# pipeline steel in the oil-water stratified liquids, vary the water content of the upper emulsion and study the difference of the corrosion process. Design/methodology/approach Combine the wire beam electrodes (WBE) technique and the corrosion weight loss method to investigate the corrosion behavior of 20# steel in produced water simulation fluid and oil-water stratified liquids, and a corrosion mechanism model was established for analysis and explanation. Findings The results of mass loss experiments showed that the average corrosion rate increased with the increase in the water content of the upper emulsion. The corrosion current distribution maps indicated that the most serious corrosion occurred in the produced water simulation liquid, and the corrosion process showed the law of waterline corrosion. In addition, it was also found that the corrosion of the WBE in the stratified liquids had obvious non-uniformities. The electrode wires at the oil-water interface suffered from severe corrosion, caused by the dissolution of crude oil acids in water and the uneven distribution of oxygen in the corrosive medium. Originality/value The WBE technique provides a deep insight into the corrosion phenomena at the oil-water interface, which is helpful for characterization of the non-uniformity of corrosion parameters and evaluating the risks of multiphase corrosive media.