The study of the interaction between hydrate formation and wax precipitation in water-in-oil (W/O) emulsions is of great significance for the security of development in deep-water waxy oil and gas fields. Experiments of natural gas hydrate formation in W/O emulsions containing wax crystals were performed in a high-pressure autoclave. The macro-parametric data, including pressure, temperature, hydrate induction time, hydrate growth amount and rate, were compared and analyzed. Results indicated that the stage behavior of hydrate formation process was not affected by the precipitated wax crystals in W/O emulsions. The mass transfer resistance of hydrate nucleation was enhanced in waxy W/O emulsions. Hence, the hydrate induction time was prolonged and could be estimated by a semiempirical crystallization model developed based on the Freundlich adsorption isotherm theory. Meanwhile, the precipitated wax crystals in W/O emulsions affected the porosity of the hydrate shell, leading to a decrease in the average hydrate growth rate, but the total hydrate growth amount increased compared to the emulsified systems without wax crystals. The effect of hydrate formation and dissociation on the wax precipitation was studied, combined with the data analysis obtained from the polarizing microscopic observation. More wax crystals precipitated in the systems after hydrate dissociation compared to the systems without hydrate formation. The fractal box dimension of the precipitated wax crystals was relatively larger affected by hydrate formation and dissociation, implying that the structure of precipitated wax crystals was more intricate.

Clarifying the interaction effect between hydrate and wax is of great significance to guarantee operation safety in deep water petroleum fields. Experiments in a high-pressure hydrate slurry rheological measurement system were carried out to investigate hydrate formation and slurry viscosity in the presence of wax crystals. Results indicate that the presence of wax crystals can prolong hydrate nucleation induction time, and its influence on hydrate growth depends on multiple factors. Higher stirring rate can obviously promote hydrate growth rate, while its influence on hydrate nucleation induction time is complicated. Higher initial pressure will promote hydrate formation. Gas hydrate slurry shows a shearthinning behavior, and slurry viscosity increases with the increase of wax content and initial pressure. A semiempirical viscosity model showing a well-fitting is established for hydrate slurry with wax crystals by considering the aggregation and breakage of hydrate particles, wax crystals, and water droplets.

Three ruthenium complexes bearing backbone-monosubstituted CAACs were prepared and displayed dramatic improvement in catalytic efficiency not only in RCM reaction but also in the ethenolysis of methyl oleate, compared to those bearing backbone-disubstituted CAACs.

Pipeline blockage caused by hydrates and wax in subsea pipelines is a major hazard for flow assurance in the petroleum industry. When hydrates and wax coexist in a flow system, the plugging risk is more severe. The effects of wax on hydrate formation, agglomeration process, flow properties, and plugging mechanisms were studied in a high-pressure flow loop using water-in-oil (w/o) emulsion systems. The flow properties of the system with the presence of wax were entirely different from those of the system without wax under the same experimental conditions. Three types of plugging were observed in the flow loop: rapid plugging, transition plugging, and gradual plugging. The interaction relationships between wax crystals, water droplets, and hydrate particles and the formation of wax−hydrate aggregates were proposed based on the particle video measurement (PVM) probe observation and the analysis of the fluid viscosity. The mechanisms of different plugging scenarios were presented, which were highly correlated with the temperature and initial flow rate. The presence of wax would impact on the agglomeration process of hydrate particles leading to a catastrophic decrease in the transportation ability and an extremely high plugging risk after hydrate formation in the pipeline.

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