*2.2.1 Effect of rheology on emulsion stability*

*Microemulsion - A Chemical Nanoreactor*

**2.2 Characteristic of emulsion**

phase is noticed over time (**Figure 3**).

emulsion.

inside the primary oil phase. The presence of impurities in the oil phases, which act as emulsifiers, will increase the possibility of forming W/O emulsion with stability proportional to the degree of turbulence and the concentration of the emulsifiers. O/W emulsion, from the other hand, is more frequently recognized at water outlets downstream to two phase separators and at the inlet of three phase separators and free water knock out (FWKO) facilities. This type of emulsions should be treated properly before it reaches the first pump station for long distance transportation. The main problem arise from flowing of this type of emulsions in pipelines is the corrosion of internal wall of the pipeline due to presence of water. However, presence of emulsions inside pipeline may also be useful as it facilitates smooth transportation of high viscous crude. Because of that heavy and waxy crude oils may intentionally emulsified with water to form (O/W)

The main characteristic upon which emulsions are valued is the emulsion stability. Emulsion stability is directly related to the degree of the emulsion tightness and the force of bond between the primary phase and the dispersed phase. High stability is sometimes desired for some applications and processes, whereas it causes problems in others. The applications where high stable emulsions are needed in petroleum industry include enhanced oil recovery (EOR), well stimulation, and heavy/waxy crude transportation. The applications where high stable emulsions are problematic are downstream operations. Highly stable emulsion causes a lot of problems in separation and treatment processes where longer time and more cost are needed to ensure efficient separation and high sale value for the

treated hydrocarbons. Emulsion stability is affected by the characteristics of the two immiscible phases (the continuous and dispersed phases), the degree of the agitation to which the mixture is subjected, and the concentration and type of emulsifiers. Thermal stability can be measured in lab using different techniques or can be quantified using the stability indexed as discussed before. The simplest and more accessible measurement technique is the bottle test. A small amount of the emulsion is placed in a scaled bottle and the separated amount of the dispersed

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**Figure 3.**

*Water-oil W/O emulsion identification based on stability index [6].*

The effect of different flow properties on emulsion has been studied by many researchers [8–10]. The rheology of an emulsion involves the study of the flow of the emulsion itself. Therefore, it concerns with the viscosity of the emulsion. Some of the rheological properties are temperature, dispersed phase volume fraction, the inclusion of surfactant in emulsion and the chemical constituent that exists in each section. All of these properties affect the viscosity of emulsion which is usually measured. It was also revealed that the viscosity becomes substantially lesser as the volume fraction of water was lowered. Even more so, the viscosity is also firmly influenced by temperature [11]. The temperature when it is intensifying at a certain degree it will cause a cracking between the bond with solid components as it will not allow the components which contain in crude oil to have the opportunity to combine and agglomerated. Eventually, less viscous emulsion in obtained. Additionally, other factors that affect the rheology are the shear rate. Greater shear rates result in lower viscosity as there will be less flow ability interruption in the emulsion [2]. Although shear rate is considered to affect the rheology, Keleşoğlu et al. [12] proclaimed that shear rate does not apply to an emulsion with a volume fraction that is less dispersed. Out of all the factors states, temperature is one of the significant parameter that can highly affect the viscosity of emulsion.

