Microfluidic tools for studying coalescence of crude oil droplets in produced water

Abstract

The major contaminant targeted during the treatment of the oilfield produced water is dispersed oil.The efficiency of most separation processes highly relies on the size of the droplets, which can be increased through coalescence. Crude oil has a complex and field-dependent composition, which can affect the interfacial properties of the drops, and consequently the merging process in different ways. This study focused on the development of microfluidic techniques for investigating coalescence between crude oil drops. The experiments were performed with six diluted crude oils and three neat oils, the latter in the presence of an oil-soluble surfactant. The composition of the water phase was systematically varied (pH, ionic composition, presence of dissolved components). In general, crude oil droplets coalesced more readily in lower or neutral pH. The addition of dissolved Fluka acids to the water phase had a unique effect on each crude oil, reflecting their composition.What is more, this effect was similar to the presence of water-soluble crude oil components in the aqueous phase. The pressure did not have a significant effect on the coalescence, which was explained by the lack of the lightest components (C1-C4) in the system. In summary, the results revealed several trends, however it was clear that the coalescence highly depended on the oil composition. This underlined the necessity for experimental methods, such as microfluidics, which allow for quick assessment of the stability of crude oil droplets.

Microfluidic Droplet Detection via Region-Based and Single-Pass Convolutional Neural Networks with Comparison to Conventional Image Analysis Methodologies

“…Therefore the experimental methodologies used will only be discussed briefly and the reader is kindly referred to our prior published work for greater detail. The datasets for each specific type of analyzed phenomena were from the following sources: flow cells [51,52] and coalescence events [53]. The analysis performed for droplet generation, polydisperse flow cells, micrographs and porous media is unpublished.…”

“…For flow cells, this data was then exported to Matlab, where a custom script produced size distributions and coalescence frequencies. This procedure is described in greater detail elsewhere [51,54].…”

“…Subsequent to droplet generation in microfluidics, the various types of downstream droplet interaction are numerous and often the end goal of a microfluidic experiment, depending on the application. In most of our previous reports [51,65], we focused on their coalescence or generally the interactions with other droplets. Here, we will showcase the analysis capabilities and symmetry to prior techniques using various CNNs on systems of freely flowing droplets, where the average diameter is smaller than the relatively large width (approximately 500 µm) of non-constrained flow cells.…”

“…After passing through the coalescence chamber, many of the initially monodisperse droplets can merge together and re-emerge as larger droplets later in the flow cell. Since the area of the droplets increase proportionally to the number of coalescence events, it is common to use size classes instead of actual droplet sizes [71,51]. The size classes are deteremined as follows: size class 1 is the the initial droplet size, size class 2 is the droplet formed after coalescence of two size class 1 dropslets, size class 3 is created by coalescence between size class 1 and 2 droplets, and so on.…”

Prediction of spontaneous imbibition in fractal porous media based on modified porosity correlation

“…The phenomenon of spontaneous imbibition, which is driven by capillary pressure, has an important function in different technical applications, such as oil recovery (Gao et al, 2018), carbon dioxide storage by capillary trapping (Arshad et al, 2016), paper sensors (Elizalde et al, 2015), inkjet printing (Wijshoff, 2017), heat pipe wicks (Nishikawara et al, 2018), or microfluidic devices (Dudek et al, 2018). There is great research interest in spontaneous imbibition in porous media (Ashraf et al, 2019).…”