Integration of cold finger, DSC and HTGC techniques to study the physico-chemical properties of wax deposits

The cold finger apparatus is widely employed for practical screening of wax deposition and inhibitor performance, however, it is typically restricted to macroscopic metrics such as deposit mass or thickness. In this work, the cold finger was coupled with high-temperature gas chromatography (HTGC) and differential scanning calorimetry (DSC) to investigate wax deposition from a mechanistic perspective using model waxy fluids, systematically exploring two experimental variables scarcely addressed in the literature: the total wax concentration and the macrocrystalline/microcrystalline wax ratio in the stock solution. The results show that increasing wax concentration enhances the deposition driving force and increases the paraffin content in the deposits. Deposits formed from diluted solutions are proportionally enriched in heavier paraffins, whereas those formed from concentrated solutions more closely reflect the stock composition, indicating differences in solubility-driven selectivity and deposition kinetics. DSC analysis revealed that highly polydisperse systems exhibit higher WATs due to multiple independent crystalline populations and an increased number of nucleation sites, whereas increasing microcrystalline content leads to lower crystallization enthalpies, indicating smaller and less ordered crystalline domains. Cocrystallization of distinct wax populations significantly alters the physico-chemical behavior of the deposits. Overall, wax concentration is primarily related to the deposition driving force and extension of wax deposition, while wax polydispersity controls the crystalline morphology and nucleation behavior. These findings demonstrate that coupling cold finger experiments with HTGC and DSC can provide an expanded physico-chemical framework for interpreting wax deposition, which can support the rational development of flow assurance strategies and selection of chemical inhibitors. • The cold finger apparatus was coupled with HTGC and DSC to provide physico-chemical insight into wax deposition. • Wax concentration relates with deposition driving force, affecting deposition extent and solubility-driven selectivity. • Wax polydispersity influences nucleation behavior, the number of crystalline populations and deposit crystalline morphology. • Model waxy fluids provide frameworks for future studies involving other crude oil components or chemical additives.