Hydrate deposition characteristics analysis and structural optimization design of reduced-diameter pipe based on an improved model

Abstract

High-pressure and low-temperature conditions in deep-water development are probably going to cause serious hydrate deposition problems. Current studies on hydrate migration and deposition are mainly centered on through-diameter conditions, and relatively few studies have been carried out for reduced-diameter conditions. Meanwhile, the effect of heat transfer between the particle-fluid-wall in the pipe on hydrate particle deposition is usually neglected, resulting in discrepancies between results and reality. Here, an improved hydrate deposition-stripping model is developed based on hydrate particle adhesion and rebound as well as deposition and stripping criteria, and combined with the inter-phase heat transfer characteristics. The effects of several important parameters, such as thermophoretic force and pipeline structure, on the deposition characteristics of micron-sized hydrate particles were investigated, and the deposition mechanism of hydrate in special pipelines was revealed. Also, the combination of calculation results provides new ideas for the design of oil and gas pipes. Based on the enhanced mechanism of hydrate particle deposition in the reduced-diameter pipe proposed in this paper, a new parameter of hydrate particle deposition enhancement rate (ξh) is defined to characterize the integrated enhancement effect of reduction structure and heat transfer in the pipe on hydrate particle deposition, and a new correlation calculation method is provided for it. The results can provide a valuable reference for efficient and accurate calculation of hydrates.