Water in Oil Emulsion Stability that is used in Oil Drilling
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Water in Oil Emulsion Stability that is used in Oil Drilling
Background
The water-in-oil emulsion formation plays a vital role on the industry of oil. The activity of water-in-oil (W/O) emulsion occurs at different phases in the course of drilling, processing, production, as well as transportation of crude oil. Crude oil refers to a blend of aromatic hydrocarbons, aliphatic, oxygen, nitrogen, and sulfur that has compounds of asphaltenes and resins. In some cases, water-in-oil emulsions are the products of oil spillage. Spill workers often refer the emulsions to as “mousse” or “chocolate mousse,” because cleaning up the spilt oil appear to be challenging. During the formation of the emulsion of this nature, a dramatic change occurs in the physical characteristics of oil. It is worth to realize that asphaltenes and resins of crude oil produces the components that are interfacially active. Numerous studies have confirmed that the core mechanism of W/O emulsions’ asphaltenes is via the creation of the viscous film network that is cross-connected with an elevated mechanical rigidity (Nour & Yunus, 2006; Fingas & Fieldhouse, 2015). The oil viscosity often shifts from some few hundred mPa.s to 100,000mPa.s, and rise by a factor of between 500 and 1000 (Fingas & Fieldhouse, 2015). This scenario indicates the liquid product changing from a heavy and semisolid material. This foundational background results in the need to carry out this study that investigates the W/O emulsion stability that is used in oil drilling, focusing on how to get a stable water in oil emulsion and how to make a stable water in oil emulsion using mineral oil, SPAN 80, and oil EDC 95/11.
Problem Statement
The formation of water in oil emulsion has emerged to be an interesting activity in today’s oil industry because of the environmental and economic issues that come with it. The fact that the emulsions take place at different stages results in an increase in the production cost as well as the costs of transporting oil. There have been environmental issues that have occurred as a result of the hectic process of cleaning up the surrounding after the oil has spilled using methods like pumping, burning, use of sorbants, as well as the use of dispersants (Nour & Yunus, 2006). This problem has made emulsions hard to recover using the traditional recovery equipment of spillage, which has, in turn, made the process of drilling difficult. Undoubtedly, drilling is presently occurring in the environments that are harsh, associated with weather conditions that cannot be predicted as well as the complex geographical structures. The fields that have heavier deposits present further environmental issues when it comes to the extraction of oil.
Contamination resulting in drilling have also presented another problem that the oil refineries needs to deal with to have quality oil. Drilling of the wells into the ground is necessary prior to reaching the actual layer that contains oil. The product of this process is always contaminated oil, making it not suitable for transportation via pipelines. The solution to this issue called for the invention of oil-in-water (O/W) emulsions to get the pure oil for easy transportation (Saad et al., 2019). The most commonly used types of emulsions in the oil industry to clean oil comprise inverted and direct emulsions. While direct emulsions have been popular with extremely deviated wells and horizontal wells, stabilized indirect emulsions have gained wider applications in oil industry. Such emulsions have the features of enormous volumes of surfactants, which can cause destructions in the well. The solution to this problem has been the use of direct emulsion, though they have a limitation when it comes to drilling horizontal sections moving for distances that are longer. It also a drawback of having the difficulty in controlling the shales’ stability. These varied issues have compelled the majority of the oil refinery firms to consider changing from oil-in-water (O/W) emulsion methods to better techniques such as W/O emulsions to achieve the desired quality of oil during the drilling process.
The General Theory of the Formation of Emulsions
High quantity of water that accompanies the crude oil extraction is among the key issues affecting the oil industry. The formation of emulsions has an immense contribution to some laws that regulate the cost of pumping, production, and transportation of crude oil. Abdulredha et al. (2018) argue that emulsions are formed three primary reasons. They name the first reason as to bring about diffusion of a liquid into the other liquid because of the existence of mixing energy or turbulent flow. The second reason could be the enhancement of the interactions between two liquids that are immiscible, including water and oil. Moreover, the emulsifying agents present in the crude oil such as resins and asphaltenes calls for the formation of emulsions. Therefore, understanding the different reasons for forming emulsions is necessary in the development of the appropriate method than can help in cleansing the unpolished oil.
The aspect of turbulence plays a significant role in the emulsion formation. Notably, the mixing energy or disturbance as the initial factor that led to the creation of emulsions. According to Abdulredha et al. (2018), the existence of turbulence in the pipeline flow assists in the formation of emulsion because of the two flow system that is similar to that of the fluid, where crude oil mixes with water. The authors point out that turbulence influences break-up as well as coalescence of emulsions (Abdulredha et al., 2018). During the flow of the oil in the pipeline, the suppression of turbulence also takes place as a result of the contant between the droplets of emulsion and other fluids at a constant stage. In scientific perspective, turbulence suspension arises as a result of the kinetic energy of one fluid, which has a single stage, turns out to be higher as compared to other two-phase liquid at the flow rate of the fluid. Moreover, there is the transfer of part of the kinetic energy to emulsions from the stream that is two-phased, making this kind of energy less as opposed to single-phased kinetic energy. Similarly, the turbulent strength decreases when the kinetic energy or power flows from single-phased to the particle. This article is relevant in this research because it provides an understanding of the impact of turbulence on emulsion to help in the selection of the method that can match it to solve the issues associated with oil in the course of drilling.
Resins and asphaltenes and other elements, which are also known as functional molecules, have an influence on the creation of emulsions. The molecules of this nature have heteroatoms, like oxygen, sulfur, and nitrogen. According to Subramanian et al. (2017), these components lead to basic and acidic characteristics in the fluids that petroleum-based, which result in the stabilized W/O emulsions. This article regards alphaltenes as the components with the strongest stability of W/O emulsion since they possess polycyclic aromatic and aromatic hydrocarbons. The knowledge of the fact that alphaltenes contribute to the stability of W/O emulsions begun more than four decades ago (Abdulredha et al., 2018). In general, this argument explains the reason for the increased usage of the W/O emulsions as compared to the traditional techniques such as O/W.
Stable Water in Oil Emulsion
The study of rheology of emulsions seek to examine the stability in W/O. As argued earlier, asphaltenes and resins have been established as the strongest stabilizers of emulsions (Abdulredha et al., 2018). According to Fingas and Fieldhouse (2015), the emulsions that have stabilized using surfactant films, including and asphaltenes and resins act in a similar manner as the hard-sphere dispersions, depicting viscoelastic behavior. In the formation of emulsion, the relaxation time is determined, which appears to be increasing as the volume fraction of the discontinuous stage increases. The authors observed that the stability of emulsion heavily relies on the rheological features of the interface of water–oil, where an elevated elasticity also leads to an increase in the stability level (Fingas & Fieldhouse, 2015). These findings resonate with the previous studies suggesting that the W/O emulsions are stabilized using both resins and asphaltenes, though there is a need for ensuring that the content of resin slightly exceeds the asphaltene content for greater stability.
Modeling of Water-in-Oil Emulsion Formations
References
Abdulredha, M.M., Hussain, S.A. & Abdullah, L.C. (20180. Overview on petroleum emulsions, formation, influence and demulsification treatment techniques. Arabian Journal of Chemistry, https://doi.org/10.1016/j.arabjc.2018.11.014.
Fingas, M.F. & Fieldhouse, B. (2015). Water-in-oil emulsions: Formation and prediction, chap.8. In “Handbook of Oil Spill Science and Technology, First Edition.” John Wiley & Sons.
Nour, A. & Yunus, R.M. (2006). Stability investigation of water-in-crude oil emulsion. Journal of Applied Sciences, 6(14):2895-2900.
Saad, M.A., Kamil, M., Abdurahman, N.H., Yunus, R.M., & Awad, O.I. (2019). An overview of recent advances in state-of-the-art techniques in the demulsification of crude oil Emulsions. Processes, 7(240): 1-26. https://doi.org/10.3390/pr7070470.
Subramanian, D., May, N., & Firoozabadi, A. (2017). Functional molecules and the stability of water-in-crude oil emulsions. Energy Fuels, 31(9): 8967–8977.
