Wax and Wax–Hydrate Deposition Characteristics in Single-, Two-, and Three-Phase Pipelines: A Review

Abstract

In the oil pipeline transportation system, wax deposition will reduce the effective circulation area, weaken the overall pipeline transportation capacity, and even block the pipeline, which seriously threatens the safety of the pipeline flows. In the actual production of oil fields and the transportation of oil products, except for the single-phase waxy crude oil, under most conditions, operations are performed using multiphase mixed transportation, so it is necessary to determine the wax deposition characteristics in those pipeline systems. In this Review, three new wax deposition mechanisms proposed in recent years and several typical experimental devices were summarized, the wax deposition in oil–water and oil–gas flow systems and the wax–hydrate coupling deposition in oil–gas–water flow system flows were concluded; the mathematical models were also categorized based on the three flow systems. Meanwhile, it highlighted the fact that, in the two-phase flow, because of the complexity of the flow pattern and the presence of the second interface on the wax deposition process, independent theoretical research on the mechanism of wax deposition is particularly necessary; based on this, a more-accurate wax deposition prediction model can also be developed. For the coupled deposition of wax-hydrate in the three-phase flow system, experimental instruments such as FBRM, PVM and molecular dynamics simulations could be used to study the distribution characteristics and interaction rules of wax crystals and hydrate particles from a microscopic perspective. On the other hand, the mechanism of wax crystal and hydrate coupling deposition by additives such as antiwax agents, hydrate inhibitors, antipolymerization agents, and pipeline transportation conditions can be investigated experimentally to better control the deposition process during pipeline operation and ensure the safe flow in the transportation system.

Hydrate Deposition Model and Flow Assurance Technology in Gas-Dominant Pipeline Transportation Systems: A Review

“…19−24 Liang et al 25 used X-ray computed tomography to obtain the three-dimensional morphology and parameters of the hydrate shell over time and, from this, the mass transfer characteristics of hydrate molecules and guest molecules during the hydrate formation process. Ravichandran et al 26 proposed a pseudosteady-state mechanical model to predict the amount of 34 1934−2018 the methods adopted and contributions made by each experimental group in the cold flow technology of rehydrating were summarized; the deposition mechanism of the hydrate wall and the method for measuring the parameters of fluid cold flow converting into a hydrate slurry were further studied Liu et al 35 1955−2020 the new wax deposition mechanism and typical experimental devices proposed in recent years are summarized; the experimental studies and prediction models of wax deposition or wax−hydrate coupling deposition in single-, two-, and three-phase flows are classified Wang et al. 36 1940−2020 this paper reviews a series of extensions and improvements of the Chen−Guo model to eliminate the original limitations, applicable to different complex systems, including structural H and semi-enclosed hydrates, sulfur-containing gas/inhibitor/accelerator systems, oil-in-water emulsion systems, and porous systems Shi et al 37 1983−2021 the application of traditional hydrate management strategy and risk hydrate management strategy in China is summarized; the research on hydrate thermodynamics and kinetics, hydrate particle aggregation, deposition, and plugging mechanism, and hydrate plugging risk prediction and evaluation methods were systematically reviewed Aman et al 15 1811−2021 the development and evolution of hydrate blockage mechanism in the oil-dominated system and the progress in the development technology of low-dose hydrate inhibitors brought about by the exploration process were introduced historically; on the basis of the blockage mechanism of the first gas-dominated system, the experimental study on the Chinese flow loop of the gas-dominated system is summarized…”

Advances in and Perspectives on Strategies for Improving the Flowability of Waxy Oils

“…), combined with the precipitation of wax crystals. Therefore, the rheological and interfacial properties of crude oil and its emulsions need to be tested and predicted, and the deposition of hydrates, waxes, and scales need to be simulated to ensure the safety of production facilities and crude oil flow. − …”

Effect of Wax Composition and Shear Force on Wax Aggregation Behavior in Crude Oil: A Molecular Dynamics Simulation Study

“…In the process of pipeline transportation, the wax in the oil will exhibit a complex aggregation behavior with changes in temperature, pressure and external forces, which often precipitates from oil with the change in phase state, resulting in wax deposition, thereby reducing the oil flow area and increasing the flow rate in the pipeline, which greatly affects the safe operation of the pipeline. Therefore, wax deposition has always been a technical problem that needs to be solved by pipeline workers [ 1 , 2 , 3 ].…”