An improved model for predicting hydrate formation and deposition in horizontal annular flow

Abstract

The formation and deposition of hydrates in pipelines form flow barriers, which affect the safety of offshore oil and gas transportation. In this study, an improved model of hydrate formation and deposition is established by considering the non-uniform distribution of liquid film and droplets resulting from gravity, which is a non-negligible factor in the accurate prediction of hydrate deposition in horizontal annular flow. The uneven distributions of the hydrate deposit thickness along the radial and axial directions in a horizontal annular flow were calculated using the proposed model. Three different deposition characteristics of hydrates along the radial direction were found: concave W-type, convex W-type, and Ω-type. Meanwhile, the radial hydrate deposit thickness gradually increased as the gas flow rate increased. With an increase in the liquid flow rate, a greater axial distance between the pipe section and inlet results in a clearer increase in the radial hydrate deposit thickness. In addition, a peak value of the hydrate deposit thickness occurs at a certain position in the axial direction. This study provides a theoretical basis for the prediction and prevention of hydrate blockages during offshore gas transportation.