Experimental Study and Prediction Model for Hydrate Plugging Formation in Single-Pass Gas-Dominated Pipes with Diameter Reduction

Gas hydrate plugging in flowlines acts as a major blockage risk in oil, gas, and natural gas hydrate production. Current studies on hydrate plugging is mainly conducted in pipes with a constant diameter, whereas the effects of varying diameters have been less explored. Pipes with diameter reductions are very common in the oil and gas production process. Herein, by performing experiments with pipes of four different sizes, including one with a constant diameter and three with diameter reductions, the hydrate plugging in single-pass gas-dominated pipes with diameter reduction is investigated systematically, the results of which show that the existence of diameter reduction can facilitate the deposition of hydrate particles on pipe walls and the formation of a hydrate deposition layer. Meanwhile, hydrate sloughing occurs during the growth of the hydrate deposition layer under fluid shear force. With the increase in the diameter reduction ratio or subcooling for hydrate formation, the hydrate deposition is observed to increase significantly, thus resulting in the reduction of time for hydrate plugging. According to these results, the hydrate plugging mechanism in pipes with diameter reduction is proposed. Further, in combination with the hydrate deposition difference between the inside and outside of the arc-shaped low-speed area, a new numerical model is established for hydrate plugging prediction in the pipe with diameter reduction, which can predict the growth and evolution of the hydrate deposition layer accurately with the consideration of the diameter's reduction. The results of this work provide a valuable guidance for the targeted prevention and management of hydrate plugging in flowlines with diameter reductions.

Automated summary

Research shows that diameter reductions in flowlines can facilitate the deposition of hydrate particles on pipe walls and the formation of a hydrate deposition layer. Fluid shear force causes hydrate sloughing during the growth of the deposition layer. Increasing diameter reduction or subcooling leads to significantly increased hydrate deposition, resulting in shorter time for hydrate plugging.