**6. Applications of emulsion/microemulsion in oil industry**

## **6.1 Background**

It is to be expected that the future energy demand will be met by a global energy mix that is undergoing a transition from the current dominance of fossil fuels to a more balanced distribution of energy sources. After conventional waterflood processes, the part of the oil in the reservoir remains as a discontinuous phase in the form of oil globules trapped by capillary forces and is likely to be around 30% of the original oil in place (OOIP) [38], whereas another 40% is bypassed by the water. However, technically it is possible to improve this recovery efficiency by applying enhanced oil recovery (EOR) processes. Traditionally, oil recovery operations comprise three stages: primary, secondary, and tertiary. These stages describe the production from a reservoir in chronological manner. During primary recovery, which starts right from the earliest stages of production, the energy for displacing the oil to the production wells results from the use of natural energy present in the reservoir [39]. Continual withdrawal of the fluids from the reservoir, results in a decrease of the supporting energy. Consequently, it reaches a stage whereby further removal of fluids approaches the limits of a profitable operation. Here, it requires an intervention for increasing the reservoir energy and thus fostering production. This implies the initiation of the second stage, which entails the application of secondary recovery methods. The secondary recovery method results in the augmentation of the natural energy of the reservoir. One of the most popular secondary recovery methods is waterflooding. The estimations showed that the unproduced residual oil reserves from primary and secondary oil production methods are about two to three trillion barrels worldwide [40]. Given the tremendous amount of the unrecovered oil, the introduction of new intervention techniques is crucial. This entails the application of methods for tertiary recovery or enhanced oil recovery (EOR). Typically, the methods consist of injection of (nonreservoir) gases [40, 41], liquid chemicals and/or the use of thermal energy. This work focuses on the use of emulsions and/or microemulsions as effective method to improve oil recovery in the field. Previous experiences clearly indicate that emulsion and/or microemulsion-based EOR methods are an ideal, as well as a feasible alternative that can effectively recover this enormous resource base [42, 43].

### **6.2 Applications in enhanced oil recovery (EOR)**

In oil and gas industry, the approach to emulsion and/or microemulsion preparation has associated with the application of energy to a mixture of oil, water, and emulsifier. The emulsifier (i.e., surfactants or amphiphilic proteins) acts to stabilize the interfacial layer between the continuous and dispersed phase which has been generated through the addition of energy to the system. The injection of emulsions and/or microemulsion into oil reservoirs has been acknowledge as a potential tool for oil recovery due to the possibility of rheological, and thermodynamical properties of emulsions [44]. As reviewed by Muggeridge et al. [45] main objective of oil recovery is to improve both the microscopic displacement efficiency and the macroscopic sweep efficiency of the reservoir. The former regards the removal of oil at the pore level, while the latter is targeted at removing oil at the larger scale of the medium by avoiding oil trapping, a feature related to reservoir geological conformation and surface chemistry.

**123**

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

The use of microemulsions is of high interest in many aspects of crude oil exploitation, especially in enhanced oil recovery (EOR). Macro- and microemulsion flooding is an efficient EOR recovery method due to its high extraction efficiency by reducing the oil-water interfacial tension [42]. A macroemulsion is a thermodynamics unstable heterogeneous mixture of oil and water with either oil droplet in water (an oil/water emulsion) or water droplets in oil (a water/oil emulsion). The droplets are stabilized by surfactants that absorb at the oil-water inter-phase, which makes that the interfaces are charged preventing the droplets to collide. On other hand, microemulsions are transparent homogeneous mixtures of hydrocarbons and water with large amounts of surfactants [24]. The microemulsions have recently been introduced in enhanced oil recovery processes in which chemicals, especially surfactants, are used to recover the oil from natural oil reservoirs. Since the discovery of microemulsions, they have attained increasing significance both in basic research studies and in the oil fields. In spite of intensive research on microemulsions, the theory behind understanding mechanisms (i.e., predictive power) for microemulsions is still lacking [43, 46, 47]. In addition, many difficulties are encountered in creating a suitable microemulsion film with temperature gradients required large, many ionic surfactants precipitating when contacted with brine, and most nonionic surfactants unsuitable. Other issues include adsorption of microemulsion components on rocks, and varying salinities and temperatures of the oil reservoirs. Over the past three decades, however, there has been sufficiently great progress made on the recovery of residual oil in particular chemical based enhanced oil recovery with microemulsions. Babadagli [48] has written a review about improvement of mature oil fields. According to his analysis, the most common chemical-based enhanced oil recovery method is the surfactant solution injection due to its relatively lower cost when compared to micellar or microemulsion injection. The way by which the injected chemical, in chemical based enhanced oil recovery (EOR), is a significant parameter for optimization of the EOR-method. Continuous injection of a chemical solution leads to increase operation costs and/or reduce the amount of treated material. Taking into account, injection of chemical solution considering the porous volume number (PV) is required in any efficient enhanced oil recovery (EOR) process. Thomas and co-workers (in: [48]) injected porous volumes (PV) of microemulsion in sandstone rock containing 35% of residual oil, noticing a linear relationship between the values of injected pore volume (PV) and the oil recovery. The Results of the study of Thomas and co-workers showed a 45% residual oil recovery when injecting around 10 pore volume (PV) of microemulsion. Santanna et al. [42] studied the application of different types of microemulsion for chemical based enhanced oil recovery (EOR), including different types of surfactants [42, 49, 50].

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

*6.2.1 Macro- and microemulsion flooding*

*6.2.2 Surfactant microemulsion flooding*

Microemulsions are generally composed of hydrocarbons, surfactants/cosurfactants and brine. Surfactants are considered to be the principal constituents of microemulsions and are adsorbed at the interface rather than in the bulk phase. Surfactants are classified into four groups based on the charge of the head group such as anionic, cationic, non-ionic and zwitterionic. Anionic surfactants such as sodium dodecylsulfate (SDS) are negatively charged in nature, but a small cation sodium ion occupies the counterpart. Anionic surfactants are most widely used in oil recovery process. Their adsorption phenomena in sandstone and carbonate are different. Their adsorption in sandstone is relatively lower than that of carbonate [49–51].

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

#### *6.2.1 Macro- and microemulsion flooding*

*Microemulsion - A Chemical Nanoreactor*

**6.1 Background**

resource base [42, 43].

**6.2 Applications in enhanced oil recovery (EOR)**

In oil and gas industry, the approach to emulsion and/or microemulsion preparation has associated with the application of energy to a mixture of oil, water, and emulsifier. The emulsifier (i.e., surfactants or amphiphilic proteins) acts to stabilize the interfacial layer between the continuous and dispersed phase which has been generated through the addition of energy to the system. The injection of emulsions and/or microemulsion into oil reservoirs has been acknowledge as a potential tool for oil recovery due to the possibility of rheological, and thermodynamical properties of emulsions [44]. As reviewed by Muggeridge et al. [45] main objective of oil recovery is to improve both the microscopic displacement efficiency and the macroscopic sweep efficiency of the reservoir. The former regards the removal of oil at the pore level, while the latter is targeted at removing oil at the larger scale of the medium by avoiding oil trapping, a feature related to reservoir geological conformation and surface

**6. Applications of emulsion/microemulsion in oil industry**

It is to be expected that the future energy demand will be met by a global energy mix that is undergoing a transition from the current dominance of fossil fuels to a more balanced distribution of energy sources. After conventional waterflood processes, the part of the oil in the reservoir remains as a discontinuous phase in the form of oil globules trapped by capillary forces and is likely to be around 30% of the original oil in place (OOIP) [38], whereas another 40% is bypassed by the water. However, technically it is possible to improve this recovery efficiency by applying enhanced oil recovery (EOR) processes. Traditionally, oil recovery operations comprise three stages: primary, secondary, and tertiary. These stages describe the production from a reservoir in chronological manner. During primary recovery, which starts right from the earliest stages of production, the energy for displacing the oil to the production wells results from the use of natural energy present in the reservoir [39]. Continual withdrawal of the fluids from the reservoir, results in a decrease of the supporting energy. Consequently, it reaches a stage whereby further removal of fluids approaches the limits of a profitable operation. Here, it requires an intervention for increasing the reservoir energy and thus fostering production. This implies the initiation of the second stage, which entails the application of secondary recovery methods. The secondary recovery method results in the augmentation of the natural energy of the reservoir. One of the most popular secondary recovery methods is waterflooding. The estimations showed that the unproduced residual oil reserves from primary and secondary oil production methods are about two to three trillion barrels worldwide [40]. Given the tremendous amount of the unrecovered oil, the introduction of new intervention techniques is crucial. This entails the application of methods for tertiary recovery or enhanced oil recovery (EOR). Typically, the methods consist of injection of (nonreservoir) gases [40, 41], liquid chemicals and/or the use of thermal energy. This work focuses on the use of emulsions and/or microemulsions as effective method to improve oil recovery in the field. Previous experiences clearly indicate that emulsion and/or microemulsion-based EOR methods are an ideal, as well as a feasible alternative that can effectively recover this enormous

**122**

chemistry.

The use of microemulsions is of high interest in many aspects of crude oil exploitation, especially in enhanced oil recovery (EOR). Macro- and microemulsion flooding is an efficient EOR recovery method due to its high extraction efficiency by reducing the oil-water interfacial tension [42]. A macroemulsion is a thermodynamics unstable heterogeneous mixture of oil and water with either oil droplet in water (an oil/water emulsion) or water droplets in oil (a water/oil emulsion). The droplets are stabilized by surfactants that absorb at the oil-water inter-phase, which makes that the interfaces are charged preventing the droplets to collide. On other hand, microemulsions are transparent homogeneous mixtures of hydrocarbons and water with large amounts of surfactants [24]. The microemulsions have recently been introduced in enhanced oil recovery processes in which chemicals, especially surfactants, are used to recover the oil from natural oil reservoirs. Since the discovery of microemulsions, they have attained increasing significance both in basic research studies and in the oil fields. In spite of intensive research on microemulsions, the theory behind understanding mechanisms (i.e., predictive power) for microemulsions is still lacking [43, 46, 47]. In addition, many difficulties are encountered in creating a suitable microemulsion film with temperature gradients required large, many ionic surfactants precipitating when contacted with brine, and most nonionic surfactants unsuitable. Other issues include adsorption of microemulsion components on rocks, and varying salinities and temperatures of the oil reservoirs. Over the past three decades, however, there has been sufficiently great progress made on the recovery of residual oil in particular chemical based enhanced oil recovery with microemulsions. Babadagli [48] has written a review about improvement of mature oil fields. According to his analysis, the most common chemical-based enhanced oil recovery method is the surfactant solution injection due to its relatively lower cost when compared to micellar or microemulsion injection. The way by which the injected chemical, in chemical based enhanced oil recovery (EOR), is a significant parameter for optimization of the EOR-method. Continuous injection of a chemical solution leads to increase operation costs and/or reduce the amount of treated material. Taking into account, injection of chemical solution considering the porous volume number (PV) is required in any efficient enhanced oil recovery (EOR) process. Thomas and co-workers (in: [48]) injected porous volumes (PV) of microemulsion in sandstone rock containing 35% of residual oil, noticing a linear relationship between the values of injected pore volume (PV) and the oil recovery. The Results of the study of Thomas and co-workers showed a 45% residual oil recovery when injecting around 10 pore volume (PV) of microemulsion. Santanna et al. [42] studied the application of different types of microemulsion for chemical based enhanced oil recovery (EOR), including different types of surfactants [42, 49, 50].

#### *6.2.2 Surfactant microemulsion flooding*

Microemulsions are generally composed of hydrocarbons, surfactants/cosurfactants and brine. Surfactants are considered to be the principal constituents of microemulsions and are adsorbed at the interface rather than in the bulk phase. Surfactants are classified into four groups based on the charge of the head group such as anionic, cationic, non-ionic and zwitterionic. Anionic surfactants such as sodium dodecylsulfate (SDS) are negatively charged in nature, but a small cation sodium ion occupies the counterpart. Anionic surfactants are most widely used in oil recovery process. Their adsorption phenomena in sandstone and carbonate are different. Their adsorption in sandstone is relatively lower than that of carbonate [49–51].

#### *6.2.3 Mechanism of surfactant microemulsion flooding*

In microemulsion flooding, the reservoir is flooded with water containing a small percentage of surfactant and other additives such as hydrocarbon, mediumchain alcohol and brine. The surfactant plays a key role in forming the exact type of microemulsion that reduces the interfacial tension of the target oil [29, 52]. This is critical to both mobilize oil and enable it to escape from the reservoir rock. In general, whenever a waterflood has been successful, microemulsion injection will be applicable, while in many cases where water injection has failed due to its poor mobility relationships, microemulsion flooding can still be successful mainly because the required mobility control.

#### *6.2.4 Interfacial tension reduction*

In enhanced oil recovery, the microemulsion flooding displays the unique properties of microemulsion systems, such as high viscosity and the ability to induce low interfacial tension, increasing oil extraction efficiency. [42] According to Austad and Strand [53, 54], very low interfacial tensions may be reached with microemulsion systems. As stated by Gurgel et al. [55] microemulsions are potential candidates in enhanced oil recovery, especially because of its ultra-low interfacial tension values, attained between the contacting oil and water microphases that form them. Under such circumstances, microemulsions flow more easily through the porous medium, which enhance oil extraction performance rates. Babadagli [48] has written a review about improvement of mature oil fields. According to his review, the most common chemical injection technique, as an enhanced oil recovery method, is the surfactant solution injection due to its relatively lower cost when compared to microemulsion injection. The way by which the fluid is injected, when the chemical method is applied, is an important parameter for optimization of the technique. Continuous injection of a chemical solution may increase operation costs and reduce the amount of treated material. In view of this, injection of chemical solution considering the porous volume number (PV) is required in any efficient recovery process. Thomas et al. (in: [48]) injected porous volumes of microemulsion in sandstone plugs containing 35% of residual oil, observing a linear relationship between the values of injected PV and the oil recovery. Results typically showed a 45% residual oil recovery when injecting 10 PV of microemulsion. Santanna and co-workers [42] studied the application of different types of microemulsion for enhanced oil recovery, one was prepared with a commercial surfactant (MCS), and another contained a surfactant synthesized in laboratory (MLS). The experiments consisted of the injection of fluids into cylindrical plug samples. During the microemulsion flooding, samples were collected as a function of time and the mass of oil recovered by the microemulsion was determined. The chemicals used to prepare the microemulsion systems were commercial anionic surfactant (soap-sodium salt) obtained from fatty acids; anionic surfactant (soap–sodium salt) synthesized in laboratory, extract from fatty acids (100 wt.% of vegetable oil containing 12 carbon atoms); isoamyl alcohol; pine oil; and distilled water. From the results obtained, one could conclude that the use of microemulsion prepared with the commercial MCS allowed for recovery indexes as high as 87.5%, whilst the use of the MLS microemulsion permitted recovery indexes as high as 78.7%. This was because the difference in microemulsion viscosities, corroborated by the fact that the MCS-based microemulsion (32 cP viscosity) could recover more oil than the MLS-based microemulsion (27 cP viscosity).

**125**

**Table 2.**

using the following formula:

*6.3.1 Assessment of stimulation efficiency*

*Emulsified acids with continuous phase of three types of oil [56].*

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

Matrix acidizing is a well stimulation technique used to eliminate formation damage and/or increase permeability in sandstone and carbonate reservoir. This eventually leads to the improvement of the reservoir inflow performance, which will turn in enhancing wells productivity [56]. Matrix acidizing is performed by injecting acid solution with a prescribed concentration into the formation from surface. The typical acid used for carbonate reservoirs is hydrochloric acid with concentration of 15%, whereas for sandstone reservoirs a mixture of hydrofluoric/ hydrochloric acid solution with a concentration 3% HF/12% HCl is used. The efficiency of matrix acidizing process is highly dependent on the distance the acid can penetrate inside the reservoir, which is inversely proportional to the rate of reaction between the acid and the rock. Fast acid reaction yields less penetration distance inside the formation, and hence, the acidizing operation will get less efficient. Therefore, different methods are implemented to retard the acid-rock reaction. One way to do so is by emulsifying the acid solution with a hydrocarbon oil (diesel oil or xylene) with the assistance of an emulsifying agent. This process results in producing an emulsifying acid fluid that more favorable than the ordinary acids because the hydrocarbon oil phase provides a diffusion barrier causing the slow release of acid and deeper penetration [57]. The emulsified acid is considered efficient if it can slow down the reaction rate (i.e., retard the acid) and generate a successful stimulation operation (expressed as increase in the rock permeability). Both effects can be assessed experimentally using core samples from the target rock. The acid retarding effect can be investigated by comparing the solubility of the rock in the blank acid with that in the emulsified acid. Assessment of emulsified acid retarding efficiency (acid solubility test): the acid solubility test is conducted to measure the amount of rock soluble by using the emulsified acid. Mohsin and his co-workers [56] conducted acid solubility test for an Indiana Limestone core sample in hydrochloric acid oil emulsified acid at ambient and 70°C. Approximately 1 g powder of the rock placed in a volume of 150 cc of the emulsified acid for a period of 60 min without stirring at the desired temperature. Hydrochloric acid solution with 15% concentration has been used to formulate three types of emulsified acids each with different type of oil phase (diesel oil, palm oil, and *Jatropha* oil). The solubility value, expressed in percentage, was calculated for each emulsified acid

SA%= W1 − W2/(W1 × 100) (1)

The stimulation efficiency is investigated experimentally using core flooding lab. A core sample from the stimulated rock is placed inside the core holder of the

**Emulsion type Initial weight (W1), g Final weight (W2), g Average solubility (70°C)**

*Jatropha* oil-based 1 0.050033 94.99 Diesel oil-based 1 0.0285 97.15 Palm oil-based 1 0.02076 97.924

The solubility values at temperature of 70°C are shown in **Table 2**.

**6.3 Emulsion and microemulsion applications in well stimulation**

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

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

## **6.3 Emulsion and microemulsion applications in well stimulation**

Matrix acidizing is a well stimulation technique used to eliminate formation damage and/or increase permeability in sandstone and carbonate reservoir. This eventually leads to the improvement of the reservoir inflow performance, which will turn in enhancing wells productivity [56]. Matrix acidizing is performed by injecting acid solution with a prescribed concentration into the formation from surface. The typical acid used for carbonate reservoirs is hydrochloric acid with concentration of 15%, whereas for sandstone reservoirs a mixture of hydrofluoric/ hydrochloric acid solution with a concentration 3% HF/12% HCl is used. The efficiency of matrix acidizing process is highly dependent on the distance the acid can penetrate inside the reservoir, which is inversely proportional to the rate of reaction between the acid and the rock. Fast acid reaction yields less penetration distance inside the formation, and hence, the acidizing operation will get less efficient. Therefore, different methods are implemented to retard the acid-rock reaction. One way to do so is by emulsifying the acid solution with a hydrocarbon oil (diesel oil or xylene) with the assistance of an emulsifying agent. This process results in producing an emulsifying acid fluid that more favorable than the ordinary acids because the hydrocarbon oil phase provides a diffusion barrier causing the slow release of acid and deeper penetration [57]. The emulsified acid is considered efficient if it can slow down the reaction rate (i.e., retard the acid) and generate a successful stimulation operation (expressed as increase in the rock permeability). Both effects can be assessed experimentally using core samples from the target rock. The acid retarding effect can be investigated by comparing the solubility of the rock in the blank acid with that in the emulsified acid. Assessment of emulsified acid retarding efficiency (acid solubility test): the acid solubility test is conducted to measure the amount of rock soluble by using the emulsified acid. Mohsin and his co-workers [56] conducted acid solubility test for an Indiana Limestone core sample in hydrochloric acid oil emulsified acid at ambient and 70°C. Approximately 1 g powder of the rock placed in a volume of 150 cc of the emulsified acid for a period of 60 min without stirring at the desired temperature. Hydrochloric acid solution with 15% concentration has been used to formulate three types of emulsified acids each with different type of oil phase (diesel oil, palm oil, and *Jatropha* oil). The solubility value, expressed in percentage, was calculated for each emulsified acid using the following formula:

$$\mathbf{SA}\,\% = \mathbf{W1} - \mathbf{W2}/(\mathbf{W1} \times \mathbf{100})\tag{1}$$

The solubility values at temperature of 70°C are shown in **Table 2**.

#### *6.3.1 Assessment of stimulation efficiency*

The stimulation efficiency is investigated experimentally using core flooding lab. A core sample from the stimulated rock is placed inside the core holder of the


**Table 2.**

*Emulsified acids with continuous phase of three types of oil [56].*

*Microemulsion - A Chemical Nanoreactor*

because the required mobility control.

*6.2.4 Interfacial tension reduction*

*6.2.3 Mechanism of surfactant microemulsion flooding*

In microemulsion flooding, the reservoir is flooded with water containing a small percentage of surfactant and other additives such as hydrocarbon, mediumchain alcohol and brine. The surfactant plays a key role in forming the exact type of microemulsion that reduces the interfacial tension of the target oil [29, 52]. This is critical to both mobilize oil and enable it to escape from the reservoir rock. In general, whenever a waterflood has been successful, microemulsion injection will be applicable, while in many cases where water injection has failed due to its poor mobility relationships, microemulsion flooding can still be successful mainly

In enhanced oil recovery, the microemulsion flooding displays the unique properties of microemulsion systems, such as high viscosity and the ability to induce low interfacial tension, increasing oil extraction efficiency. [42] According to Austad and Strand [53, 54], very low interfacial tensions may be reached with microemulsion systems. As stated by Gurgel et al. [55] microemulsions are potential candidates in enhanced oil recovery, especially because of its ultra-low interfacial tension values, attained between the contacting oil and water microphases that form them. Under such circumstances, microemulsions flow more easily through the porous medium, which enhance oil extraction performance rates. Babadagli [48] has written a review about improvement of mature oil fields. According to his review, the most common chemical injection technique, as an enhanced oil recovery method, is the surfactant solution injection due to its relatively lower cost when compared to microemulsion injection. The way by which the fluid is injected, when the chemical method is applied, is an important parameter for optimization of the technique. Continuous injection of a chemical solution may increase operation costs and reduce the amount of treated material. In view of this, injection of chemical solution considering the porous volume number (PV) is required in any efficient recovery process. Thomas et al. (in: [48]) injected porous volumes of microemulsion in sandstone plugs containing 35% of residual oil, observing a linear relationship between the values of injected PV and the oil recovery. Results typically showed a 45% residual oil recovery when injecting 10 PV of microemulsion. Santanna and co-workers [42] studied the application of different types of microemulsion for enhanced oil recovery, one was prepared with a commercial surfactant (MCS), and another contained a surfactant synthesized in laboratory (MLS). The experiments consisted of the injection of fluids into cylindrical plug samples. During the microemulsion flooding, samples were collected as a function of time and the mass of oil recovered by the microemulsion was determined. The chemicals used to prepare the microemulsion systems were commercial anionic surfactant (soap-sodium salt) obtained from fatty acids; anionic surfactant (soap–sodium salt) synthesized in laboratory, extract from fatty acids (100 wt.% of vegetable oil containing 12 carbon atoms); isoamyl alcohol; pine oil; and distilled water. From the results obtained, one could conclude that the use of microemulsion prepared with the commercial MCS allowed for recovery indexes as high as 87.5%, whilst the use of the MLS microemulsion permitted recovery indexes as high as 78.7%. This was because the difference in microemulsion viscosities, corroborated by the fact that the MCS-based microemulsion (32 cP viscosity) could recover more oil than the MLS-based

**124**

microemulsion (27 cP viscosity).

#### **Figure 8.**

*The cores used for investigating the diesel-based and Jatropha-based emulsified acids [56].*

#### **Figure 9.**

*Filtrate from Jatropha oil-based emulsion (on left side) and filtrate from diesel oil-based emulsion (on right side) [56].*

#### **Figure 10.**

*Pressure drop profiles by the end of the acidizing using (a) diesel based emulsified acid, and (b) Jatropha based emulsified acid [56].*

core flooding lab and the reservoir condition can be simulated by setting the pressure and temperature of the core flooding lab at values similar to the real conditions of the reservoir. The core flooding equipment FES 350 has been used by Mohsin and his co-workers [56] to investigate the stimulation efficiency of the diesel-based and *Jatropha*-based emulsified fluids described in **Table 2** at a temperature of 7°C, a back pressure of 700 psi, confining pressure of 1300 psi, and injection rate of 0.5 cc/min. Two carbonate cores, shown in **Figure 8**, were immersed first with

**127**

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

brine to determine permeability of the core by recording the differential pressure points using Darcy's law, as the fluid moves across the core. The 15 wt% HCl emulsified acid was then injected until pressure drop was observed indicating the breakthrough. The cores were then flushed with brine to remove stimulation fluid and was cleaned, dried and was measured for weight, porosity and permeability. **Figure 9** shows filtrate from *Jatropha* oil-based emulsion (on left side) and filtrate

**Figure 10** shows pressure drop profiles of the cores shown in **Figure 8** by the

• An emulsion may be defined as a biphasic system consisting of two immiscible liquids, one of which (the dispersed phase) is finely and uniformly dispersed

• The main characteristic upon which emulsions are valued is the emulsion

• Emulsion stability is directly related to the degree of the emulsion tightness and

• 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

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

• It is to be expected that the future energy demand will be met by a global energy mix that is undergoing a transition from the current dominance of fossil fuels to

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

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

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

a more balanced distribution of energy sources.

low interfacial tension, increasing oil extraction efficiency.

the force of bond between the primary phase and the dispersed phase.

as globules throughout the second phase (the continuous phase).

end of the acidizing with the *Jatropha* oil-based (a) and the diesel oil-based (b) emulsified acids. Both the two pressure profiles figures indicate reaching the end of the core by the acidizing medium while creating the conduit and both cores achieved almost similar pressure drop. However, diesel laced acid achieved slightly higher pressure drop (1.6 psi), whereas *Jatropha* oil-based emulsified acid achieved one peak pressure drop at 1.5 psi. This stipulates higher consumption of the diesel-based acid and possibility of increase residue production due to acid

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

from diesel oil-based emulsion (on right side).

reactivity.

**7. Conclusions**

stability.

emulsifiers.

tants and brine.

to higher recovery factor.

inside the reservoir.

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

brine to determine permeability of the core by recording the differential pressure points using Darcy's law, as the fluid moves across the core. The 15 wt% HCl emulsified acid was then injected until pressure drop was observed indicating the breakthrough. The cores were then flushed with brine to remove stimulation fluid and was cleaned, dried and was measured for weight, porosity and permeability. **Figure 9** shows filtrate from *Jatropha* oil-based emulsion (on left side) and filtrate from diesel oil-based emulsion (on right side).

**Figure 10** shows pressure drop profiles of the cores shown in **Figure 8** by the end of the acidizing with the *Jatropha* oil-based (a) and the diesel oil-based (b) emulsified acids. Both the two pressure profiles figures indicate reaching the end of the core by the acidizing medium while creating the conduit and both cores achieved almost similar pressure drop. However, diesel laced acid achieved slightly higher pressure drop (1.6 psi), whereas *Jatropha* oil-based emulsified acid achieved one peak pressure drop at 1.5 psi. This stipulates higher consumption of the diesel-based acid and possibility of increase residue production due to acid reactivity.
