**2.2 Characteristic of emulsion**

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

**117**

demulsifiers,

surfactants and brine.

inside the reservoir.

leads to higher recovery factor.

*Application of Emulsions and Microemulsions in Enhanced Oil Recovery and Well Stimulation*

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.

reservoirs and up to separation and treatment of oil and gas.

application in enhanced oil recovery and well stimulations.

• Emulsions are encountered at different steps of petroleum engineering related activities, starting from the moment the hydrocarbons are contained inside the

• The emulsions are normally considered as problematic when thinking about it from the oil processing and treatment point of view. In this case, an undesirably formed emulsion leads to slowing down oil/gas/water separation and process and, by such, increasing the cost of processing and treatment. In such a case, the emulsion need to be destabilized and broken by heating and/or using chemical

• Emulsions, from the other hand, may intentionally be formed and stabilized for

• Emulsion stability is affected by (1) the characteristics of the two immiscible phases (the continuous and dispersed phases), (2) the degree of the agitation to which the mixture is subjected, and (3) the concentration and type of emulsifiers.

• Microemulsions are generally composed of hydrocarbons, surfactants/co-

• Macro/microemulsions based enhanced oil recovery improve both the microscopic displacement efficiency and the macroscopic sweep efficiency, thus

• In enhanced oil recovery, the microemulsion flooding displays the unique properties of microemulsion systems, such as high viscosity and the ability to

• In well stimulation emulsified acids are used during matrix acidizing and acid fracturing to retard acid reaction with rocks, to generate deeper penetration

induce low interfacial tension, increasing oil extraction efficiency.

*DOI: http://dx.doi.org/10.5772/intechopen.84538*

*2.2.1 Effect of rheology on emulsion stability*

**Figure 3.** *Water-oil W/O emulsion identification based on stability index [6].*

*Application of Emulsions and Microemulsions in Enhanced Oil Recovery and Well Stimulation DOI: http://dx.doi.org/10.5772/intechopen.84538*
