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

There are numerous theories that have explained the creations of emulsions. The most prominent theory argue that emulsion occurs when the fluid droplets completely disperse in the other fluid that acts as a phase, and the two liquids must be immiscible under normal circumstances (Abdulredha et al., 2018). The emulsification of water and oil occurs successfully via shear motion. This process produces pure emulsification that is unstable and temporary because the liquids begins to form nearly immediately once the motion is halted. The prior researcher has suggested two distinct techniques for emulsification of oil and water, O/W and W/O, which rely on the phase of emulsion (Abdulredha et al., 2018). O/W arises when emulsion takes place in water where the droplets of oils are dispersed in water phases, while W/O is the product of the emulsion occurring in oil, with the molecules of water being dispersed in oil phase. The process of emulsion has helped in the generation of complex mixtures of emulsion such as oil-water-oil (O/W/O) or water oil water (W/O/W) emulsions.

Some theories have established the different types of emulsions in their investigations of the creation of W/O emulsions. Fingas and Fieldhouse (2014) established there are four W/O types resulting from the mixture of crude oil with water. They name these forms of emulsions as stable, unstable, meso-stable, and entrained W/O emulsions. These types came about after water resolution that was conducted over time with several rheological measurements. They were also discovered by the visual appearance of W/O products, both on the day during which the emulsions are formed and a week later (Fingas, 2014). The four types are extremely different from each other based on two or more measurements of water content, as well as the five rheological measurements.

The formation of emulsions have been studied based on the roles of the asphaltenes. Several researchers have noted that asphaltenes are the primary factors for the creation of W/O emulsions over four decades ago (Fingas, 2014). Undoubtedly, it was until recently that the specific asphaltenes roles in emulsions were defined. At the present, the basic concepts of W/O emulsions can be understood clearly because of the existence of numerous studies that have suggested numerous roles of asphaltenes. Fingas and Fieldhouse (2015) argue that the stabilization of W/O emulsions is paramount during the formation process. Research assert that the films of high-strength visco-elastic asphaltene form around the droplets of water in oil. It has also been evident that resins can also help in the formation of emulsions, though resins do not give the emulsions that are stable. Resins are used to increase the stability of asphaltene emulsion, where it serves as solvents of asphaltene and offers temporary stability when slow migration of asphaltene occurs. In general, numerous scientists have confirmed that the composition of oil forms a core factor in the formation of emulsion of W/O, which comprise the types as well as the amounts of resin, asphaltenes, together with the contents of the saturate.

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 theories 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 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 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 (2014), 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, 2014). 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.

The emulsions that have proved to be stable are the semi-solid substances (reddish to brown type).  The stable emulsions have an average content of water of between 70 percent and 80 percent on the day during which they are formed and nearly one week later (Fingas, 2014).  Notably, steady emulsions continue being in stable state for four or more weeks under conditions of the laboratory. The stable emulsions that have been previously studied have remained to be stable of over one year (Fingas, 2014). On the other hand, Meso-stable emulsions, start at almost 65 percent, but they lose a larger amount of this water within a short periods (in days). The entrained types of W/O then collect only approximately 40 percent of water, which merely loses this water at a slow rate in at least 12 months. However, the W/O types that are not stable pick up only a small water percentage, where no much variation occurs within a year. In this case, the viscosity of stable emulsion rises within one year, while others decrease or can only grow by small amounts. Fingas (2014) further argue that the unstable W/O types products undergo change and turn out to be more viscous as compared to being elastic. The research evidence indicate that the unchanging emulsion possesses the viscous similar to the elastic components within one year. Furthermore, all other types of W/O depict a higher component of viscosity as compared to the element of elasticity.

The study also establishes the characteristics of W/O types in providing the understanding the stability of emulsions. Research has identified a variety of properties when using oil in the formation of W/O types of emulsion during the start as compared to other three W/O forms. As an illustration, viscosities may be extremely high or low. The light fuels such as diesel fuel while heavy and viscous oil products include heavy residual oils. The entrained W/O types are black viscous liquids, having the water content of averagely between 40 percent and 50 percent on the first day when the formation starts, with the content of below 28 percent one week later (Fingas, 2014). The viscosity of this type of emulsions rise in a day of formation, with averages obtained in of two weeks and the other week later. Unstable W/O types of emulsions, on the other hand, have the oil that does not contain large amounts of water because of blending with water.

Methods of Water-in-Oil Emulsion Formations
Old Frameworks

The processes of emulsification examined above were not in existence until the past one and a half decades, which have since been transformed into equations of modelling. The diverse W/O types determine that one simple equation does not sufficiently forecast the formation of emulsions. In earlier years, the data on the kinetics of creation at the sea, among other modeling information was not adequate (Fingas, 2014). Today, the formation of emulsion stems from surfactant-like activity of the resin compounds and polar asphaltene. The old models depict that asphaltenes formed much more stable emulsions as the similar compounds behaved like surfactants when not in solution. It was realized that the emulsions start forming when the desired viscosity and chemical conditions were achieved and sea energy was sufficient. It was further observed that the formation of three different water-in-oil types occur based on the type of oil together with its constituents. Nevertheless, some oils canton form any W/O types, resulting in a fourth type of W/O that has called for further exploration.

In ancient days, the emulsion formation rate was presumed to be of the first-order nature as time advanced. The logarithmic or exponential curve were used to approximate this rate (Fingas, 2014). One of the assumptions was the physical one, stating that all oils pick up water on a basis of the first-order. This assumption was widely employed in oil spill frameworks despite not being consistent with the knowledge of how formation of emulsions takes place. The study reveals that the old models proved not to be reliable and offer the formation predictions that are not accurate.

New Frameworks

The new models were invented to address the limitations that were encountered in the old models. Current researchers have recently developed some latest models to predict the formation of W/O emulsions. These frameworks have proved to be efficient since they utilize empirical data in the formation prediction of emulsions by use of a nonstop function, which also utilize the chemical and physical characteristics of oil (Fingas, 2014). The properties of emulsifications of more oils were also determined, while the properties of some oils in the current set of oil measured once again. This series of measurements resulted in the recalculations of the old models with because of obtaining reliable data on a given set of discrete samples.

The latest models have resulted in the formation of stabilized W/O emulsions using asphaltenes, where the resin participation also occurs. Fingas (2014) present the evidence of this type and other types which indicate that the whole distribution effects of Saturates, Aromatic, Resins, and Asphaltene (SARA) on the emulsions of formation. Asphaltenes have been used as prime stabilizers while resins are the secondary agents in the emulsion formation, especially where the concentration of the aromatics and saturates occur at some level and when the accurate viscosity and density are used. Most importantly, the empirical information that encompasses the data on the oil content, density, viscosity, as well as the W/O type stability that is formed were utilized in the development of mathematical correlation.

The current models suggest the need for a transformation for the adjustment of the information to one decreasing or increasing role. The model suggested by Fingas (2014) show that regression techniques do not respond rightly to a function that change both inversely and directly with the parameter that is targeted. The majority of parameters possess an optimal value associated with class, implying that the values possess a peak function based on class or stability. The new model has made the rectifications in the values of the old models leading to an increase in the regression coefficient. The framework also employs arithmetic approach which helps in the conversion of the values ahead of the peak to the values that appear at the back of the peak, leading a simple decreasing function (Fingas, 2014). These adjustments has made the optimal value to utilize a peak function, where the fit of the peak function fit is obtained from software called TableCurve.

The transformed values have immensely contributed to the development of new model proceeding where a multiple linear equation has been fit to the information. The model has been able to attain the functionalities of logarithmic, exponential or square curves through the correlation to the actual value of the input features in addition to their expanded values. In this case, the functionalities are treated as the exponential of the initial figure, together with their expanded values, using ln (the natural log). Every parameter relates to the index of stability in five different sets of mathematical accounts, which resembles the method of standard Gaussian expansion regression (Fingas, 2014).

 

Determination of Stability

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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.

Fingas, M.F. (2014). Water-in-oil emulsions: formation and prediction. Spill Science, 1-13. https://doi.org/10.14355/jpsr.2014.0301.04.