Assessment of hydrate blockage risk in long-distance natural gas transmission pipelines

Hydrate generation and pipe blockage in long-distance natural gas transmission pipelines has always been a major issue affecting the transmission safety. Although considerable progress have been made in recent years, there is still a long way to go in the study of the hydrates generation and plugging prediction in the gas pipelines. Hydrate plugging and accumulation is a gradual process. However, the previous studies have focused only on the prediction of whether hydrates are formed. Actually, the research on hydrate formation rate and pipelines blockage degree at different times is also important for the hydrate prevention and control. In this work, the authors proposed a novel risk assessment method for hydrate blockage in long-distance natural gas transmission pipelines. Firstly, considering the hydrate formation process, a new model consist of mass, momentum and energy balance equations was established. Secondly, the model results are solved by the iterative method and finite difference method. After comparison, the calculation results and the field data are in good agreement. Finally, the sensitivity analysis were performed on the important parameters of our model. According to the sensitivity analysis, transmission rate, inlet temperature, and natural gas dew point temperature have different effects on the hydrate generation, the location of the largest plugging point, and the degree of blockage. Meanwhile, considering the actual gas transmission process and the hydrate plugging characteristics, the proposed hydrate prevention and control measures can be taken to achieve safe and efficient natural gas transmission.