Erosion-corrosion and its mitigation on the internal surface of the expansion segment of N80 steel tube
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Erosion-corrosion and its mitigation on the internal surface of the expansion segment of N80 steel tube Tan Shang 1), Xian-kang Zhong 1), Chen-feng Zhang 1), Jun-ying Hu 1), and Bálint Medgyes 2) 1) State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China 2) Department of Electronics Technology, Budapest University of Technology and Economics, Budapest H-1111, Hungary (Received: 25 February 2020; revised: 6 May 2020; accepted: 7 May 2020)
Abstract: We investigated erosion-corrosion (E-C) and its mitigation on the internal surface of the expansion segment of N80 steel tube in a loop system using array electrode technique, weight-loss measurement, computational-fluid-dynamics simulation, and surface characterization techniques. The results show that high E-C rates can occur at locations where there is a high flow velocity and/or a strong impact from sand particles, which results in different E-C rates at various locations. Consequently, it can be expected that localized corrosion often occurs in such segments. The E-C rate at each location in the expansion segment can be significantly mitigated with an imidazoline derivative inhibitor, as the resulting inhibitor layer significantly impedes the electrochemical reaction rate. However, we found that this inhibitor layer could not effectively reduce the difference in the erosion rates at different locations on the internal surface of the expansion segment. This means that localized corrosion can still occur at the expansion segment despite the presence of the inhibitor. Keywords: erosion-corrosion; expansion segment; array electrode technique; inhibitor; localized corrosion
1. Introduction Erosion-corrosion (E-C), considered to be one of the greatest safety threats in the petroleum and natural gas industry, causes pipeline thinning, leakage, and even perforation, which result in serious economic losses and can even have catastrophic consequences. The expansion of the internal diameter of a tube is often designed for a certain number of wells for which some production parameters must be adjusted. For example, tubing with various internal diameters may be used in one well due to the need to adjust the flow and production rates. Additionally, a threaded connection can cause changes in the internal diameters of the tube. For example, the internal structure of the America Petroleum Institute thread connection is usually characterized by different internal diameters [1]. When fluid flows through a tubing segment with variable diameters, the hydrodynamic parameters, such as the flow velocity or shear stress on the internal surface, obviously change [2‒4], especially when solid particles are carried in the transmission medium, which results in serious E-C damage in these segments. As such, changes in the hydrodynamics parameters can cause further mass loss, which poses a huge safety risk. Therefore, it is im
portant to understand
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