Addressing the Growing Energy Demand: The Role of Enhanced Oil Recovery (EOR) Techniques

1. Introduction

As population increases, the demand for energy consumption also increases [1]. The discovered petroleum reserves are the main sources for providing fuel to the world. Crude oil is one of the most important raw materials, that is used on a daily basis for various proposes [2]. The majority of the world’s daily oil production comes from mature reservoirs, where increasing oil recovery from such reservoirs is the main concern for oil industries. Therefore, employing efficient enhanced oil recovery (EOR) approaches will be effective to meet the growing energy demand in the future [3]. The amount of success or failure of a process for EOR can be determined by microscopic/macroscopic displacement efficiency in porous media.

On the one hand, in order to increase the microscopic displacement efficiency, interfacial tension between crude oil and water should be decreased, and that can be obtained by compositions of crude oil [4]. The compositions of crude oil refer to the surface-active components (polar components) which have been identified mainly as acidic, basic, and other components [5-7]. In terms of acidic components, carboxylic acids (naphthenic acids) have been discovered as vital in crude oil [8]. Stearic acid is a long chain fatty acid, which acts as the carboxylic group in the reservoirs and strongly adsorbs into the calcite surface from the oil phase, compared to short chain fatty acids [9-10]. In respect to the basic components, quinoline has been found in crude oil as a polar component [11]. There have been several published researches in regard to reducing the interfacial tension with surface-active components. Standal et. al., [13] carried out another experiment in interfacial activity for polar components in oil/water model systems, where 1-naphtoic acid, 5-indanol, and quinoline components were utilised. The results showed that, there was no changes in the interfacial tension for the 1-naphtoic acid/oil/water system as a function of pH and concentration, whereas 5-indanol/oil/water system showed that, there is a reduction of interfacial tension. In addition to this, the system of quinoline/oil/water leads to reduce the interfacial tension slightly, compared to 5-indanol/oil/water system. Spilda et. al., [14] investigated that, the interfacial tensions between octanoic acid–octylamine mixtures in isooctane–water systems and the results suggested that, the interfacial tension significantly decreased, when the mixture of octanoic acid and octylamine were used at the interface, compared to using one of them alone. In addition to this, the importance of surface-active components in crude oil reduces the interfacial tension, and salts also have been proposed by several authors to change the interfacial properties.

Questions

On the other hand, in order to increase the macroscopic displacement efficiency, the mobility ratio of injected fluid should be decreased, that can be obtained by chemical flooding injection, which involves the injection of various chemicals especially polymer and biopolymers [16]. An example of such polymers is polyacrylamide (PAM), which is used in oil industries to increase the viscosity of the injected water [17]. It should be noted that, microbial enhanced oil recovery (MEOR), has been recommended as an effective alternative to EOR, which can be implemented in the reservoir to enhance residual oil mobilisation [18]. Biopolymers have been potentially used in MEOR for plugging of high permeability zones and increasing the viscosity of the displacing water towards sweep efficiency. Xanthan gum is one of the biopolymers, that has been proposed to extensive researches in oil companies and authorities [19]. Rheological properties of polyacrylamide (PAM) and partially hydrolysed polyacrylamide (HPAM) solutions were studied by Katarzyna and the results indicated that, both PAM and of HPAM are described as Newtonian behaviour, where the viscosity can be changed by share rate, temperature, and salinity [20]. Similar observations were reported for viscosity changes, when biopolymer (xanthan gum) was used [21]. It should be noted that, polymers also can influence the interfacial tension. Wei et. al., [22] investigated that, the effect of different polymer concentration on the dynamic IFT of 0.3 wt% benzyl substituted alkyl sulfobetaine (BSB) against n-decane and their results suggested that, the interfacial tension was increased gradually with the increasing polymer concentration, which was in line with the outcome of the research by Ma et. al., [23].

The aim of this study is to determine the effect of acidic and basic components as oil surface-active components on the physiochemical properties such as interfacial tension, viscosity, and emulsion stability by added PAM and xanthan gum as a polymer and biopolymer respectively in the presence of seawater at ambient and 80 oC temperature.

2. Results and Discussion

2.1 Emulsion stability of the distilled water/n-decane mixtures with different components

Figure 1 illustrates that, the emulsion stability of the distilled water/n-decane mixtures at 25 and 80 oC. As it can be seen in Figure 1 (A), in general, the time separation of the distilled water/n-decane with added PAM is much quicker than xanthan gum, while the concentration of PAM (5000 ppm) is almost three times more than xanthan gum (1500 ppm). This time is even faster by adding acidic and basic components, within the n-decane. However, acidic components have more effects on the emulsion stability, compared to basic one. Furthermore, the shortest time separation between two phases was observed, when salt was added. As it is shown in Figure 1 (B), a similar pattern was observed at high temperature. However, as the temperature increased from 25 to 80oC, the emulsion stability becomes faster. For instance, it takes minimum 150 minutes to reach the emulsion stability of PAM solution, when the temperature is 25oC, whereas, 120 minutes is required, when the temperature increases to 80 oC. Literature suggests that, increasing temperature will affect the critical micelle concentration (CMC), the adsorption kinetics of surfactant molecules, the mutual solubility of the solvents, and the distribution of the surfactants between oil and water towards to reach emulsion stability faster [25-26].

2.2 Interfacial tension (IFT) measurements

Table 3 shows the reference point of pure n-decane with distilled water and the reduction in IFT, when acidic and basic components were dissolved in n-decane.

2.2.1 Effect of acidic/basic components and salinity on IFT with added polymer and biopolymer

Figure 2 shows that, the effectiveness of the acidic and basic components under the influence of added polymer and biopolymer to the solutions at ambient temperature. In general, it can be seen that, polymer had a significant reduction on IFT, compared to biopolymer. The addition of basic and acidic components to the n-decane reduced the IFT. In terms of the acidic component with the polymer and biopolymer effect, the results showed that, the IFT was reduced to 1 mN/m and 11.9 mN/m, respectively. Similar results were observed on IFT reductions, when the basic component was used but not effective like the acidic one. Additionally, as it has been shown in Table 3, although there was a reduction on IFT by adding seawater, and based on Figure 2, there was an increase on IFT, when polymer and biopolymer were added under the influence of seawater.

2.2.2 Effect of temperature on IFT

Figure 3 shows that, the effect of temperature on IFT at different systems. As it is illustrated in this Figure 3, as temperature increases, the IFT also increases. It should be noted that, the increase on IFT for the polymer is much more than the biopolymer.

2.2.3 Effect of aging time on IFT

Figure 4 illustrates the effect of aging time on IFT at different systems. It can be seen that, there is a direct relationship between time and increasing in IFT. In fact, as time increases, the IFT also increases.

2.3 Viscosity measurements

2.3.1 Effect of acidic/basic components and salinity on viscosity with added polymer and biopolymer

Figure 5 shows that, the viscosity behaviour of polymer/biopolymer systems containing acids components and seawater. In general, the viscosity decreases by increasing the shear rate for all systems. Furthermore, it is observed that, the viscosity of biopolymer is almost two times bigger than the polymer in low shear rates (see figure 5B at the shear rate 3 S-1). As shown by the results, the acid component did not change the viscosity. However, the viscosity was decreased slightly by adding seawater up to 10 and 5 cP for biopolymer and polymer respectively. The same results were observed in the case of the basic component.

2.3.2 Effect of aging time on viscosity

In order to investigate the retention time and its influence on the viscosity of the system, polymer and biopolymer solutions with 100 rpm were tested in four-time intervals of 1, 2, 10, and 20 days at ambient temperature. As it can be seen in Figure 6, there was no changes by time for polymer/n-denane and biopolymer/n-decane, while there was a slight reduction of viscosity when seawater was added.

Summery

1. The emulsion stability of the polymer/oil is much quicker the biopolymer/oil.
2. Acidic/basic components and seawater can reduce the time separation of two phases (water/oil)
3. Polymer and biopolymer can reduce the IFT between oil and water.
4. Acidic component has more effect on reduction of IFT compared to basic one.
5. The IFT increases by time for all systems.
6. The viscosity of biopolymer is much higher than polymer, while the concentration of polymer (5000 ppm) three times bigger than biopolymer (1500 ppm).
7. Acidic and basic components do not have an effect on viscosity at ambient temperature, while seawater has been found effective slightly.

Training and other activities

I have attended at Teesside University’ courses, where I improve my study skills through undertaking several modules including initial research training, and research standards. Furthermore, I have gained significant experience in academic writing skills including accuracy, paraphrasing, style and register, structuring academic texts, and presentations at Teesside University. I have attended in several conferences, which was located at Teesside University including postgraduate research conference, and environmental geology. In addition, I have undertaken several teachings regarding my topic to get more familiar such as programming (Eclipse), recovery efficiency, gas, thermal, and chemical flooding for enhanced oil recovery.

I will attend the conference, that is located in Japan this year, which is related to the biopolymer application in industry. Furthermore, I have registered for “New to Teaching Workshop Invitation” in March 2019.

Overall plan

In this research, we aim to synthesise and characterise polymer (PAM) and biopolymer (Xanthan gum) and study their performance as a displacing fluid in EOR under influence of surface-active components on the crude oil. The research will be carried out in three stages, where each stage takes 1 year.

Stage one: Rheological properties

A. Emulsion stability of the distilled water/n-decane mixtures with different components: As we are dealing with two phases, it is important to know how long is required to separate oil and water from each other especially when polymer and biopolymer are added to the solutions.

B. Interfacial tension measurements: In order to increase the microscopic displacement efficiency, interfacial tension between crude oil and water should be decreased. In this case, several aspects such as the effect of biopolymer and biopolymer, surface active components (acids and bases), salinity, temperature, and aging time on IFT have been investigated.

C. Viscosity measurements: In order to increase the macroscopic displacement efficiency, the mobility ratio of injected fluid should be decreased. Similar procedures in the line of IFT measurements were carried out to achieve this goal such as the effect of biopolymer and biopolymer, surface active components on the viscosity.

Stage two: Core flooding

Stage three: Modelling

In this stage, we will introduce a model, as a reservoir and then determine the properties of the reservoir such as dimension, injector and producer of the reservoir. After that, one type of polymer/biopolymer/biosurfactant will be injected into the injection process with assuming having a fractured reservoir to see the outcome of the recovery factor.

Next year

The research will carry out in terms of core fooling in order to determine the oil recovery factor from the fractured reservoirs.