This paper presents a study about corrosion-erosion phenomenon in natural gas production pipeline when FeS scale is formed on the inner surface of the pipeline. FeS scale is chosen here because its reaction is faster and more reactive than the other scale such as FeCO3.

A literature study was firstly conducted to develop the idea of corrosion-erosion model. Several phenomena were considered to be the best to describe corrosion-erosion process. Then, the mathematical model to calculate corrosion-erosion rate was derived. The corrosion-erosion process was divided into two steps: fluid flow and heat transfer phenomena to establish corrosion-erosion environment and diffusion phenomena to make the corrosion-erosion happened. The first phenomena were modeled using Thermodynamics equation with considering Joule Thomson effect and gas flow equation (Katz for vertical-inclined tubing and Panhandle-B for horizontal pipeline). The second phenomena consisted of mass transfer equations including erosion process to evaluate scale growth. Finally, the model was applied to calculate an example case of gas well. The result was then compared with several simulators' result.

Pressure profile, temperature profile, liquid distribution, scale formation rate and erosion rate are generated as the first phenomena simulation and become the basis to evaluate the corrosion-erosion rate value. The simulation of second phenomena will provide the value of corrosion-erosion rate for each segment in production pipeline. Corrosion is mainly caused by the reaction of iron in pipe and corrosive agents in produced fluid such as CO2 and H2S. Supporting by erosion process, corrosion will badly damage the pipeline. Moreover, the simulation's result shows that at early time, corrosion and erosion simultaneously occurs because of the absence of FeS scale. However, at time t, when the FeS scale has been formed, the corrosion rate is reduced. If the erosion rate is larger than the scale formation rate, corrosion and erosion will conjunctly occur as at the early time. In addition, the difference in model and simulators' result is primarily caused by the effect of considering the scale growth process.

Corrosion and erosion are critical problems which need to be early prevented. An accurate prediction determines the effective prevention action. This paper gives a more accurate prediction by considering Joule Thompson effect and scale formation process. A segmented corrosion-erosion rate as the result of this paper can be considered to choose an effective action.

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