Probing the Coalescence Mechanism of Oil Droplets in Fluids Produced by Oil Wells and the Microscopic Interaction between Molecules in Oil Films

Abstract

The microscopic interactions between oil droplets during the coalescence process have an important impact on the stability of the emulsion. In this paper, a model that can present the phenomenon of coalescence of oil droplets was established. Experiments were carried out to evaluate the stability of the emulsion. Combined with molecular dynamics simulation technology, the coalescence behaviors of emulsified oil droplets in fluids produced by oil wells were studied. Factors affecting the coalescence of emulsified oil droplets were analyzed. The results show that the fluid velocity was relatively high at the position where two oil droplets were close to each other. After the coalescence of oil droplets was completed, the emulsion system became stable. There was no obvious correlation between oil droplet size and coalescence time. When two adjacent oil droplets with different radii coalesced, the larger oil droplet moved a shorter distance overall. At the initial moment, there was a clear boundary between the oil film and the water phase. The longer the carbon chain, the more stable the emulsion. Among the following four crude oil molecules with the same number of carbon atoms, chain-like saturated hydrocarbons were the most stable, followed by chain-like carbon–carbon double bonds in component crude oil. Crude oils containing chain-like carbon–carbon triple bonds were the third most stable. Cyclane were the least stable. An increase in the asphaltene content was an important reason for the enhancement of the emulsifying ability and stability in the emulsion system. This work can help improve oil–water separation efficiency, thus reducing storage and transportation burden of crude oil.

Molecular Dynamics Computational Study of Sustainable Green Surfactant for Application in Chemical Enhanced Oil Recovery

“…This reduction in interactions can have an impact on emulsion stability. 47 Similar behavior was also observed at 95 ns, represented by dashed line c, for all three systems. Figure 6 provides images at 63, 78, and 95 ns for all systems.…”

“…However, the high distance observed in the same system at 63 ns, represented by the green dashed line in Figure , can be attributed to a decrease in interactions among the oil molecules as they coalesce during the oil droplet emulsification process. This reduction in interactions can have an impact on emulsion stability . Similar behavior was also observed at 95 ns, represented by dashed line c, for all three systems.…”

A Study on the Oil-Bearing Stability of Salt-Resistant Foam and an Explanation of the Viscoelastic Phenomenon

“…This conclusion can be inferred from Figure 8; the concentration of oil at point B almost no longer changes after 180 s, while the oil concentration at points A, C, and D slowly decreases. When the area of "oil film" exceeds 15% of the surface area on a single bubble, the balance is broken, and the pressure of the internal gas forms a stress focus on the surface, thus causing the bubble burst [20]. It is worth noting that the impact by a single bubble bursting in this case will form a chain effect on the bubbles around it, and then cause a series of bubbles to burst at the same instant (instead of the bursting of the bubble columns at the gradual decline).…”

Unstable Coalescence Mechanism and Influencing Factors of Heterogeneous Oil Droplets

“…The ions and pH value of the formation water also change the time of oil droplet coalescence [21]. More research has mostly investigated the separation effect of emulsions from the standpoint of the oil-water separation mode [22][23][24]. In our previous work, molecular dynamics simulation and microscope observation experiments studied the stability of different surfactant emulsions in the demulsification process and the microscopic mechanism of molecules in the oil film [25,26].…”