WATER IN OIL EMULSION STABILITY THAT IS USED IN OIL DRILLING
Water in Oil Emulsion Stability that is used in Oil Drilling
Background
Water-in-oil emulsion formation plays a vital role in the oil industry. The activity of water-in-oil (W/O) emulsion occurs at different phases in the course of drilling, processing, production, and transportation of crude oil.
Crude oil refers to a blend of aromatic hydrocarbons, aliphatics, 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 to the emulsions as “mousse” or “chocolate mousse,” because cleaning up the spilled oil appears to be challenging.
During the formation of an emulsion of this nature, a dramatic change occurs in the physical characteristics of oil. It is worth realizing that asphaltenes and resins of crude oil produce the interfacially active components. Numerous studies have confirmed that the core mechanism of W/O emulsions’ asphaltenes is the creation of a viscous film network that is cross-connected with elevated mechanical rigidity (Nour & Yunus, 2006; Fingas & Fieldhouse, 2015). The oil viscosity often shifts from a few hundred mPa to 100,000 mPa and rises by a factor of between 500 and 1000 (Fingas & Fieldhouse, 2015). This scenario indicates that the liquid product is changing from a heavy to a semisolid material. This foundational background results in the need to carry out this study, which investigates the W/O emulsion stability that is used in oil drilling. Focusing on how to get stable water in oil emulsion and how to make 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 as 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 cost of transporting oil. There have been environmental issues that have occurred as a result of the hectic process of cleaning up the surroundings after the oil has spilled using methods like pumping, burning, the use of sorbents, 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 environments that are harsh, associated with weather conditions that cannot be predicted, as well as 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 has also presented another problem that the oil refineries need 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 unsuitable for transportation via pipelines.
The solution to this issue called for the invention of oil-in-water (O/W) emulsions to get 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 the oil industry. Such emulsions have the features of enormous volumes of surfactants, which can destroy the well.
The solution to this problem has been the use of direct emulsion, though it has limitations when it comes to drilling horizontal sections moving for distances. It is also a drawback of having difficulty controlling the shales’ stability. These varied issues have compelled the majority of 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
The high quantity of water that accompanies crude oil extraction is among the key issues affecting the oil industry. The formation of emulsions has made 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 for three primary reasons. They name the first reason as the diffusion of a liquid into another 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, call for the formation of emulsions. Therefore, understanding the different reasons for forming emulsions is necessary in the development of the appropriate method that can help in cleansing the unpolished oil.
The aspect of turbulence plays a significant role in emulsion formation. Notably, the mixing energy or disturbance was 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 systems that are similar to those of the fluid, where crude oil mixes with water. The authors point out that turbulence influences the break-up as well as the 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 contact 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 to 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, 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 are petroleum-based, which result in stabilized W/O emulsions. This article regards asphaltenes 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 asphaltenes contribute to the stability of W/O emulsions began more than four decades ago (Abdulredha et al., 2018). In general, this argument explains the reason for the increased usage of W/O emulsions as compared to traditional techniques such as O/W.
Stable Water in Oil Emulsion
The study of the rheology of emulsions seeks 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 to ensure 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.
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.
