Influence of Adding Asphaltenes and Gas Condensate on CO₂ Hydrate Formation in Water–CO₂–Oil Systems

Abstract

Gas hydrate formation is a huge flow assurance problem in offshore production of oil and gas. However, there have been some reported cases in oil-dominated systems where the hydrates do not form, even though the high-pressure and low-temperature environments induce favorable thermodynamic conditions. The reason for this unexpected result seems to be related to the presence of natural chemical compounds in crude oils that prevent the hydrates’ nucleation and agglomeration. Because the number of works in this specific topic are scarce, in the present work, we study the role played by saturates (hydrocarbon compounds) and asphaltenes (heterocyclic compounds), which are commonly present in crude oil, on hydrates that are formed from CO2 molecules in water–CO2–oil systems. Our tests were carried out in an assembly composed of a rotational rheometer with a magnetic pressure cell, which was connected to a high-pressure system. Our main results are displayed in terms of viscosity as a function of time at constant shear rate, pressure, and temperature. In this kind of experiment, hydrate formation is associated with a jump of viscosity. Our data suggest that asphaltenes retard the CO2 hydrate nucleation and formation in the crude oils studied in this work.

Investigation on Hydrate Formation and Growth Characteristics in Dissolved Asphaltene-Containing Water-In-Oil Emulsion

“…It is quite different from Sandoval’s conclusion, whose experimental mass fraction of powder asphaltene ranged from 0.0874 to 2.8 wt %. Furthermore, asphaltene exists in a dissolved phase in this work compared with the particulate phase.…”

“…Stoporev utilized an autoclave to test the hydrate formation kinetics of water-in-oil emulsion and also found that the oil–water system containing asphaltenes could decelerate the nucleation rate and increase the induction time. This conclusion is consistent with that of Sandoval, who determined the positive correlation between the amount of asphaltenes and the induction time when investigating the effect of powder asphaltene on carbon dioxide hydrate formation. Morrissy used the micromechanical force (MMF) apparatus to explore the growth rate of cyclopentane hydrate films and proposed that natural surface activity components in oil may be adsorbed on the water–cyclopentane interface, which destroys the assembly of hydrate crystals, exhibiting a palpable decrease in the growth rate of hydrate films.…”

“…In the first section of this paper, numerous scholars have introduced that asphaltene could affect the formation kinetics of hydrate and inhibit the formation of hydrate. Sandoval proposed that the quality of powder asphaltene is proportional to the induction time, but he did not investigate the effect of low-concentration dissolved asphaltene on the induction time of hydrate formation. The microscopic induction time is defined as the time starting from the hydrate equilibrium state to the appearance of the first critical nucleus .…”

Effect of Asphaltenes on the Kinetics of Methane Hydrate Formation and Dissociation in Oil-in-Water Dispersion Systems Containing Light Saturated and Aromatic Hydrocarbons

“…This happens due to the arrangement and solubility of asphaltenes at the interface or hindering of the guest−host interaction, 40 or both. 41 On the contrary, there are studies that have reported a decrease in the hydrate inhibition tendency with increased asphaltene content or even promotion. For example, the authors observed an increase in agglomeration and a decrease in supercooling with an increase in the asphaltene content in the system.…”

“…Asphaltene has been shown to increase hydrate induction and growth time in water–CO 2 –oil systems but does not avoid hydrate formation, typically working as a kinetic hydrate inhibitor (KHI). This happens due to the arrangement and solubility of asphaltenes at the interface or hindering of the guest–host interaction, or both . On the contrary, there are studies that have reported a decrease in the hydrate inhibition tendency with increased asphaltene content or even promotion.…”