The Role of Resins, Asphaltenes, and Water in WaterâOil Emulsion

Subscriber access provided by NEW YORK UNIV

Article

The Role of Resins, Asphaltenes, and Water in WaterOil Emulsion Breaking with Microwave Heating Taniya Kar, and Berna - Hascakir Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.5b00662 • Publication Date (Web): 29 May 2015 Downloaded from http://pubs.acs.org on May 31, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

The Role of Resins, Asphaltenes, and Water in Water-Oil Emulsion Breaking with Microwave Heating Taniya Kar, Berna Hascakir* Petroleum Engineering Department, Texas A&M University ABSTRACT The stability of the water-in-oil emulsions highly depends on the existence of the polar components and their interactions within the emulsions. Asphaltenes, resins, and water are the main polar components of the emulsions. As the stability of the emulsions increases, the emulsion breaking becomes more difficult and requires more energy and chemical input. With this study, we propose a significant reduction in energy and chemical use for efficient break up of water-in-oil emulsions through the application of microwave heating. To demonstrate this concept, we conduct experiments on different emulsions originated from Steam Assisted Gravity Drainage (SAGD) and Expanding Solvent-SAGD (ES-SAGD), and investigate how the polar components initially present in the emulsions affect the microwave efficiency. Water, a polar molecule, which is the main component in emulsions, was expected to allow the most efficient microwave absorption. However, our results show that asphaltenes and resins have greater role than the water component of emulsions during emulsion breaking with microwave heating.

1 ACS Paragon Plus Environment

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 23

INTRODUCTION Microwave heating is a highly controllable and versatile technique that directly affects polar molecules with more efficient energy transfer. The polar molecules absorb microwave radiation and oscillate.1 This way the electromagnetic radiation is converted to thermal energy.2 The amount of heat generation varies according to the magnitude of the microwave frequency and the dielectric properties of the polar molecules which are subjected to microwave radiation.3 The polarity of a molecule is quantified with the dipole moment of the molecule, which in turn, is determined by its molecular structure.4 For instance, carbon dioxide has a linear molecular shape. This molecular shape makes the vector sum of carbon-oxygen bond dipole moments zero. Therefore, the dipole moment of carbon dioxide is the zero Debye (D), consequently, carbon dioxide is non-polar. However, because the water molecule has bent molecular structure, the vector sum of the hydrogen-oxygen bond dipoles results in 1.85 D dipole moment which makes the water molecule polar.5 When the polarity is considered, high energy densities impacted through microwave heating and the highly controllable temporal and spatial characteristics of such a heating schedule may allow more efficient removal of the contaminants containing polar groups. Therefore, microwave heating has been implemented successfully before for the treatment of sewage sludge, wastewater, and organic wastes with high water content.6 Microwave has also been tested for the breaking up of water-in-crude oil emulsion recently in which mainly the effectiveness of microwave absorption has been discussed by considering only the existence of 2 ACS Paragon Plus Environment

Page 3 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

water, but the contribution of the other polar molecules present in crude oil, such as resins and asphaltenes, are not mentioned. 7, 8, 9, 10 While water is a polar molecule which is the main component of the water-in-oil emulsion, if the water-in-oil emulsion formation mechanism is considered, it is a known fact that asphaltenes are the other polar component which also have a major role in emulsion formation.11 Hence, the existence of both water and the complex molecular structure of asphaltenes make the water-in-oil emulsions good candidates for microwave treatment.12 Moreover, asphaltenes are not the only polar components of the crude oils, resins are also polar.13, 14 But, how the asphaltenes-resins interactions affect the overall polarity is not known. The presence of more than one polar group may affect the microwave absorption in a negative manner by reducing the overall dipole moment of the system.4 The determination of the polarity of a known molecule is relatively simple.5 However, the polarity determination will be complicated for a complex mixture which contains multiple polar groups with unknown molecular formulas. In this case, the overall polarity of the mixture should be estimated by considering also the interactions between the polar groups. The overall dipole moment of a complex chemical mixture; like water-in-oil emulsion, depends on the occurrence of polar groups in the mixture, their individual polarities, and their mutual interactions in the mixture.11, 15 Asphaltenes, resins, and water are the main polar components of water-in-oil emulsions.13, 14 The dipole moment of n-pentane (nC5) asphaltenes and resins originated from several crudes were calculated before by using several correlations. For heavy crude oils, they found that the dipole moment of the nC5-asphaltenes is around 6.9-7.0 D and


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 23

3.8-4.0 D for resins. 4 However, how the interactions of resins and asphaltenes in bulk oil affect the overall dipole moment of the crude oil system was not calculated. The separation of water from emulsions through microwave heating is not a new technique16. It has been tested both in the laboratory and also there has been some field practices17, 18. Most of the laboratory works studied the impact of the polar fractions of crude oils on the effectiveness of the microwave heating.

17, 19, 20

However, the laboratory scale experiments

were conducted on synthetic samples in which the known amount of asphaltenes and resins were blended to investigate the amount of polar groups on microwave efficiency or the processed oil sample was mixed with water to prepare water-in-oil emulsions. 18, 20 In this study, we investigate the effectiveness of microwave heating on the treatment of water-in-oil emulsions originated from Steam Assisted Gravity Drainage (SAGD) and Expanding Solvent-SAGD (ES-SAGD) by considering the effect of polar groups. SAGD is selected for this study, because it is an emerging Enhanced Oil Recovery (EOR) technology which has a rapid increase in application for bitumen extraction, especially in Alberta, Canada.21, 22 However, the greenhouse gas (GHG) emissions due to steam generation poses environmental problems, hence, the application of ES-SAGD gains attention to reduce the GHG emissions of SAGD and to increase oil production.23, 24 In ES-SAGD, the injection of a solvent along with steam dilutes the oil-in-place and effectively mobilizes the oil by reducing its viscosity and by allowing it to flow to the production well.19, 26 Still, the effectiveness of ES-SAGD over SAGD in terms of produced oil quality and the additional environmental impact of emulsion treatment for SAGD and ES-SAGD have not been fully investigated.


Page 5 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Thus, we first aim to characterize the emulsion types originated from SAGD and ES-SAGD and discuss the emulsion formation mechanism for different ES-SAGD scenarios. Chemical, mechanical, or conventional thermal methods are reliable and widely implemented emulsion breaking methods.27 However, if the higher volumes of produced water are considered, the chemical methods will require high amount of chemical use, which can be a problem due to the toxicity of the chemicals. The thermal methods can require high energy input, which can increase the cost of the process. And all of these treatment facilities may require large space due to high volumes of the produced water, which will generate additional environmental problems due to increase surface footprints of the surface facilities.

27, 28, 29

By

considering all of these drawbacks of existing and commonly used emulsion breaking methods, we propose a quick, energy and cost effective solution to break emulsions.

2, 30

Thus, we

investigate the effectiveness of microwave heating for emulsion treatment by considering the contribution of polar components in emulsions. Experimental One SAGD (E1) and three ES-SAGD (E2, E3, and E4) experiments were previously conducted at identical experimental conditions (75 psig at 165 °C) on a Canadian bitumen (8.65˚ API and 54,000 cP at 23 °C).23 Sand and clay mixture was used to prepare the reservoir rock. The clay has 90 weight % kaolinite and 10 weight % illite with 2.3 µm particle size.31 Several trial experimental studies for troubleshooting technical issues with the setup has been conducted before starting the main experiments.23


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 23

In the SAGD experiment (E1), steam was continuously injected for 12 hours at 18 L/min cold water equivalent rate. In the three ES-SAGD experiments (E2, E3, and E4), steam was coinjected with solvent at a constant steam/solvent (2:18) ratio for 9 hours. In E2, n-hexane was co-injected with steam. In E3, [n-hexane+toluene] mixture in equal amount (1:1 L/min injection rate) was co-injected with steam. In E4, n-hexane and toluene were cyclically injected with steam; [n-hexane + steam] and [toluene + steam] with one hour cycles. E4 ended with [n-hexane + steam] injection in the 9th hour. The total experimental time was decided according to the oil production rate. Note that n-hexane is asphaltene insoluble and toluene is asphaltene soluble solvents.32 Therefore, we were expecting less asphaltenes in the emulsions originated from E2 but more for E3 and E4. The produced oil sample originated from E4 was collected from toluene cycle. Hence, we were expecting the highest asphaltene content in the produced oil sample originated from E4. In this study, the produced oil samples originated from all experiments and original bitumen were first characterized to identify the emulsion type and then, the produced oil samples were subjected to microwave treatment. The scope of this study is to characterize the emulsions originated from SAGD and ES-SAGD and to investigate the effectiveness of microwave treatment for emulsion breaking. Thus, the detailed description of the experimental procedure for SAGD and ES-SAGD can be found in the previously published technical papers.23, 33 Emulsion characterization: The produced oil samples originated from SAGD and ES-SAGD experiments were visualized with the Meiji Techno Japan- Microscope (100X magnification) and 6 ACS Paragon Plus Environment

Page 7 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

ProgRes CT5- Camera. Then, the amounts of water, clays, and SARA (saturates, aromatics, resins, and asphaltenes) fractions in the produced oil samples were determined. The water content of the original bitumen sample and the produced oil samples were determined by heating the samples in a Thermogravimetric Analyzer (TGA) and Differential Scanning Calorimetry (DSC) at an identical heating rate (10 °C/min) till reaching 200 °C for all the samples. On separate produced oil samples, SARA fractionation was carried out by following an ASTM method.34 SARA fractionation starts with asphaltene separation and according to the ASTM standard that we used, the n-pentane insoluble portion of bitumen is called asphaltenes. The structural analyses of both bulk samples (produced oil and original bitumen) and their SARA fractions were attained with an Agilent Fourier Transform Infrared (FTIR) spectroscopy equipment. FTIR results confirmed the existence of clay only in the bulk produced oil samples and asphaltene fractions. Clays then, were separated from the bulk oil and from the asphaltenes, by using solvent extraction and filtration. Filter size was selected less than the clay size (2.3 µm).31 Because toluene is an asphaltene solvent, toluene was used as the solvent to separate asphaltenes from clays.32, 35 The clays in the bulk oil samples were also separated to observe the clay-oil interaction by following the same procedure. Microwave Treatment of Emulsions: The produced oil samples were subjected to microwave heating at 2,450 MHz microwave frequency and 900 W microwave power at atmospheric pressure. The microwave heating experiments were repeated two times for all experimental samples, but the optimization of the heating and soaking periods are conducted only on one


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 23

sample. The optimum heating and soaking schedules were selected as 1 minute heating + 1 minute soaking + 1 minute heating. This optimized heating and soaking schedule was applied to all of the samples. Experimental temperatures varied from experiment to experiment, but the final temperatures were detected between 150-200 °C. The effectiveness of microwave treatment was examined with the microscopic images gathered after the treatment and the images were compared to the before treatment images. Furthermore, the water content of the microwaved samples was determined with TGA/DSC experiments by following the same procedure described previously for the initial samples. Experimental Results and Discussion Characterization of Emulsions: Produced oil samples were first examined visually (top pictures in Figure 1) and then, the microscopic images were acquired at 100X magnification for each sample (bottom microscopic images in Figure 1).

Figure 1. Pictures (on top) and microscopic images (at the bottom) of the original bitumen and the oil-water emulsions


Page 9 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

The produced oil samples show stable emulsion content at different sizes and types.13 Emulsions originated from the base SAGD experiment (E1) have the greatest water droplet size which is in triple form (oil-in-water-in-oil emulsion). The size of the water droplet is smaller in E2, and the smallest and more dispersed water droplets in oil-phase are observed for E3 and E4. The coalescence of the smaller water droplets dispersed in the oil-phase can be more difficult than the agglomeration of the bigger droplet sizes (E1). However, the emulsion originated from E1 has triple type of emulsion which can be more difficult to break than the emulsions observed in E2, E3, and E4.36 The water content of the bulk original bitumen and the produced oil samples originated from E1, E2, E3, and E4 was determined with ThermoGravimetric Analyzer (TGA) and Differential Scanning Calorimetry (DSC) by applying a constant heating rate (10 °C/min) under air injection till reaching 200°C. The weight loss observed between 125 °C to 142 °C for each experimental sample is associated with the water content of each sample (Figure 2-A). Because at the same temperature values in where the weight loss is observed in TGA graphs (Figure 2-A), the DSC curves indicate an endothermic peak, which is due to the vaporization of water (Figure 2-B).37, 38 This weight loss in TGA graphs is used to calculate the water content of the samples. For reference, TGA and DSC curves for distilled water are presented in the same figures with red dashed lines which enable to observe the water behavior alone.


Energy & Fuels

Original Bitumen

E1 1.7

80

1.3

Heat Flow, µV/mg

100

60 40 20

E2

E3

E4 6 4

0.9 2

0.5 0.1

0 -0.3

0

-0.7

25

45

65

85 105 125 145 165 185 Temperature, °C

A-Weight Loss for Bulk Oil Samples Before Microwave Heating (TGA)

-2

µV/mg Heat Flow for Distilled Water, µm/mg

Distilled Water

Weight %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 23

25 45 65 85 105 125 145 165 185 Temperature, °C

B-Heat Flow for Bulk Oil Samples Before Microwave Heating (DSC)

Figure 2. TGA (A) and DSC (B) curves obtained to determine the water content of produced oil and original bitumen samples. For reference, the TGA/DSC curves for distilled water are also presented with red dashed curves.

To observe the interaction of water and clays with individual oil components, the bulk produced oil samples were subjected to SARA fractionation by using ASTM D2007-11 standard. The bulk oil samples, their asphaltenes, and deasphalted components (saturates, aromatics and resins) are characterized with Fourier Transform InfraRed (FTIR) spectroscopy (Figure 3).


Page 11 of 23

1

0.5

Distilled Water Clay Sand n-hexane toluene

0.4

E1

E2

E3

E4

0.4

0.2

Absorbance, %

0.6

Original Bitumen

0.4

Absorbance, %

Absorbance, %

0.8

0.3 0.2

0.3 0.2 0.1

0.1

0

0

0 3500

2500 1500 Wavenumber, cm-1

500

3500

A-Reference Samples

0.4

Original Bitumen

E1

E2


3500

500

B-Produced Oil E3

E4

0.4

Original Bitumen

E1


500

C-Asphaltenes E2

E3

E4

0.7

Original Bitumen

E1

E2

E3

E4

0.6

0.2 0.1

Absorbance, %

0.3

0.3

Absorbance, %

Absorbance, %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

0.2

0.1

0.5 0.4 0.3 0.2 0.1

0 3500


D-Saturates

500

0

0 3500


500

E-Aromatics

3500


500

F-Resins

Figure 3. FTIR spectrum for A- Reference Samples, B-Produced Oil, C-Asphaltenes fraction, DSaturates fraction, E-Aromatics fraction, and F-Resins fraction Figure 3-A represents the reference samples used to prepare the oil-sand mixture and also the spectra of n-hexane and toluene, which were coinjected with steam during ES-SAGD experiments. Figure 3-B shows the produced oil FTIR spectra before water and clay removal. Figure 3-C through Figure 3-F present the FTIR spectra of the asphaltenes, saturates, aromatics, and resins fractions of the original bitumen and produced oil samples, respectively. The saturate (Figure 3-D) and the aromatic (Figure 3-E) fractions of the samples do not show significant variations in the molecular structure. However, the FTIR spectra of resins show variations. In E4, toluene signature (purple curve in Figure 3-A) is observed at 3020 cm-1, 1495 cm-1, 727 cm-1, and 694 cm-1 wavenumbers (Figure 3-F).39 Note that the analyzed produced oil sample from E4 was taken from the toluene cycle. This result may indicate that the injected


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 23

toluene interacts more with resins rather than aromatics (compare Figure 3-E and Figure 3-F to Figure 3-A purple curve). In E3, also, toluene was used, but in this experiment, toluene was mixed with n-hexane and then, co-injected with steam. Toluene-resins interaction in E3 (Figure 3-F) still exists but not as significant as in E4. Because in E3, the solvent ratio was 1/1:18 (toluene/n-hexane:steam), but the sample examined from E4 was exposed to higher amount of toluene (2:18 (toluene:steam) ratio). The asphaltene fraction of the samples has significant absorbance peaks at around 3293 cm-1 and 1637 cm-1 (Figure 3-C) which indicate the existence of water

39

(similar absorbance peaks

can be observed in the distilled water spectrum; blue curve in Figure 3-A). The characteristic clay peaks are at 3688, 3651, 3621, 1115, 1026, 1003, and 910 cm-1 wavenumbers, which have been observed in both bulk produced oil and in their asphaltene fractions (the red curves in zoomed graphs in Figure 3-C represents reference clay spectrum taken from Figure 3-A). The peaks, observed in the fingerprint region from 1026-600 cm-1, represent Si-O and Al-OH functional groups, which can again be associated to clay presence mainly (Figure 3-C, right zoomed graph).39, 40 These characteristic peaks are observed in almost all produced oil samples (Figure 3-B) but not in the original bitumen (black curve in Figure 3-B). The most significant clayoil interaction is observed for E3 in which toluene and n-hexane mixture is coinjected with steam (green curve in Figure 3-B). However, the clay-asphaltene interaction is observed less for E3 (compare Figure 3-B to Figure 3-C for E3). Hence, the clay might also interact with the other components and most probably with resins.14 In almost all produced bulk samples and in their asphaltenes, significant clay and water absorbance peaks are observed in FTIR spectra (Figure 3-C). The FTIR spectra of the saturates, 12 ACS Paragon Plus Environment

Page 13 of 23

aromatics, and resins fractions do not indicate any peak related to the existence of water or clay in these fractions after SARA separation by following the ASTM method. Hence, it has been concluded that only the asphaltenes fraction of the samples interacts with clay and water mainly. However, during resins separation, clays might be filtered.34 Thus, water or clay might be removed during the fractionation of deasphalted oil into saturates, aromatics, and resins, so that they could not be observed with FTIR analyses. However, the clays and water attached to the asphaltenes are not easy to remove and toluene extraction was used to separate the clays from bulk produced oil samples and from their asphaltenes. By combining TGA/DSC results summarized in Figure 2 to determine water content of emulsions and the filtration method to determine the clay amount in emulsions, the weight percent of SARA fractions obtained with ASTM method34 were corrected and the results are summarized in Figure 4 for all produced oil samples and original bitumen.

24.1

Weight Percent, wt%

31.1

Weight Percent, wt%

39.1

34.3 21.3 25.1 18.8 18.7 21.9

E4

14.3

E3

20.0

E2

Resins

Asphaltenes

0 Saturates

E1

27.9 31.8 26.8

OIL

16.0

CLAY

10

25.3

0

Water Content Original Bitumen

20 11.0

7.85 13.94 10.57 14.25

10.6

0

30

25.2

40

45.74 31.77 19.8

60

40 23.6

46.41 54.29 69.63 31.75

80

20

43.9

89.4

100

54

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Aromatics

Original Bitumen

E1

E2

E3

E4

A- Water & Clay Contents of the Produced Oils B- SARA fractionations of Oil Component Only

Figure 4. The weight percent of Water, Clay, and Oil on the left and Saturates, Aromatics, Resins, and Asphaltenes in only oil component on the right


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 23

It has been observed that both water and clay contribute the formation of stable emulsions.13, 19, 41

The greatest water content (54 wt %) with the greatest clay content (14.25 wt %) is

observed in the emulsions originated from E1 in which only steam was injected for 12 hours. In ES-SAGD experiments (E2, E3, and E4), the water content increase is observed with the increase in asphaltene content (compare Water Content in Figure 4-A to Asphaltenes in Figure 4-B). The highest water content among all ES-SAGD experiments is reported for E4. Note that in E4, the injection is cycled between [toluene + steam] and [n-hexane + steam]. The sample analyzed for E4 was taken from the toluene cycle; [toluene + steam]. Because toluene is asphaltene soluble, more asphaltenes are found in the produced oil of E4 than the other ES-SAGD samples. The higher asphaltene content present in the produced oil of E4 results in an increase in water content of produced oil sample. However, in E2, because n-hexane is insoluble in asphaltenes, less asphaltenes are produced in the emulsions, consequently, less water is found in the emulsions. In other words, the asphaltene-water interaction is minimized with the use of asphaltene insoluble solvent during ES-SAGD. 42 The asphaltene-water interaction shows a linear relation (Figure 5). Note that the water content given in Figure 4-A was obtained through TGA/DSC experiments and the asphaltene content in produced oil summarized in Figure 4-B for all experiments was measured by following an ASTM standard. These two parameters obtained with the application of two different experimental analysis on the same samples resulted in a perfect linear relationship.


Page 15 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 5. Linear relationship plotted between asphaltene content in the produced oil (x-axis) and water content in the produced oil (y-axis) for E1, E2, E3, and E4. Microwave Treatment of Emulsions: Produced oil samples from E1, E2, E3, E4, and the original bitumen sample were subjected to microwave heating. One minute heating-one minute soaking-one minute heating schedule was applied to all samples. The microwave efficiency was first investigated with the microscopic images (Figure 6). In Figure 6, the “BEFORE” microscopic images are taken just before the microwave treatment and the “AFTER” microscopic images are taken just after the microwave treatment. The most significant difference in the “BEFORE” and the “AFTER” microwave heating images was observed for E1.


Energy & Fuels

Figure 6. Microscopic images of the produced oil samples before (top images) and after (bottom images) microwave treatment Original Bitumen

E1

100

Heat Flow, µV/mg

80 60 40 20 0 25

45

65

85 105 125 145 165 185 Temperature, °C

A-Weight Loss for Bulk Oil Samples After Microwave Heating (TGA)

E2

E3

E4

2.9 2.5 2.1 1.7 1.3 0.9 0.5 0.1 -0.3 -0.7

6 4 2 0 -2

Heat Flow for Distilled Water, µm/mg µV/mg

Distilled Water

Weight %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 23

25 45 65 85 105 125 145 165 185 Temperature, °C

B-Heat Flow for Bulk Oil Samples After Microwave Heating (DSC)

Figure 7. TGA (A) and DSC (B) curves obtained to determine the water content of produced oil and original bitumen samples after microwave treatment. For reference, the TGA/DSC curves for distilled water are also presented with red dashed curves.


Page 17 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

The water content of the microwaved samples was determined by TGA/DSC experiments by following the same procedure applied to the original samples (Figure 2 and Figure 7). The water amount in each sample is decided on the basis of the endothermic peak observed in DSC curves (Figure 7-B). The heat flow curve belonging to distilled water is also presented in the same figure to observe the behavior of water only. It is observed that for E1 and E4, water is effectively removed from produced oil samples via evaporation (Figure 7-A). However, water is not removed effectively for E2 and E4, instead, an increase in weight of water content in the bulk-microwaved sample is observed. There might be two possible reasons behind this increase. First, this can be due to the formation of water upon the cracking of heavy hydrocarbons by oxygen exposure that oxygen may exist in the microwave cavity. Second, the weight losses might be also due to the evaporation of light hydrocarbons formed due to microwave cracking. 2, 30 No direct relation is observed between the asphaltene content and the remaining or removed water content in produced oil after microwave treatment. However, asphaltenes are not the only polar components of the crude oils, resins are also polar

14

and it is a known fact that

microwave energy is absorbed more effectively by polar molecules.1 Therefore, resins to asphaltenes ratio (R/A) for the original bitumen and produced oil before microwave treatment is calculated from the data provided in Figure 4 and a correlation is observed between resins to asphaltene ratio and the water remaining in the samples after microwave heating (Figure 8). The water remained in the emulsions show the effectiveness of the microwave treatment; the lower the remained water, the higher the microwave efficiency.


Energy & Fuels

0.9

Water Remained after MW wt% Resins/Asphaltenes

105

0.8

85

0.7

65

0.6

45

0.5

25

Resins/Asphaltenes

125

Water weight percent, wt%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 23

0.4 E1

E4

Original Bitumen

E2

E3

Figure 8. Relation between water remained after microwave heating in oil samples and the resins to asphaltene ratio of the bulk samples before microwave heating It is observed that as the resins to asphaltenes ratio (R/A) decreases, the microwave efficiency increases (Figure 8). The linear correlation between resins to asphaltenes ratio and microwave efficiency shows that the maximum microwave efficiency (100% water removal) can be maintained when resins to asphaltenes ratio is equal to 0.33, in which higher overall dipole moment can be obtained. Note that the dipole moments of resins and asphaltenes are higher than that of water4, 5, hence, microwave energy is absorbed more by the resins and asphaltenes. Conclusion The water content of the water-oil-emulsions might be controlled by the amount of asphaltenes, aromatics, and clay fraction of the emulsions. However, the microwave effectiveness is controlled by the polar fractions of crude oil; resins and asphaltenes.


Page 19 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

The ES-SAGD with n-hexane experiment (E2) (asphaltene insoluble solvents) resulted in less emulsions in produced oil when compared to the other cases. However, the amount of water in produced oil is found high (19.8 wt%), therefore, these emulsions still require to implement surface separation. But these types of emulsions seem to be unsuitable for microwave heating if this same microwave heating procedure is implemented. On the other hand, the response of the emulsions originated from SAGD, which has the highest water content (54 wt%), to microwave heating is significantly positive. Thus, we found that the emulsion breaking through microwave heating does not depend only on the water content but also on the resins and asphaltenes contents of the emulsions and their mutual interactions. Our results suggest that due to the interactions between polar fractions, the dipole moments of resins and asphaltenes can be, at least partially, cancelled out. Hence, the greater the differences between the amounts of asphaltenes and resins in emulsion, the higher the overall dipole moment. Consequently, with the higher overall dipole moment, the microwave efficiency increases. Because asphaltenes and resins have higher dipole moments than water molecules, microwave radiation is preferentially first absorbed by the polar fractions of oil; resins and asphaltenes. The emulsion breaking occurs by the heat transfer due to conduction or convection; first, heat is generated by the oscillation of polar fractions and then, heat is transferred to water. If a sufficient amount of heat is transferred to water by the oscillation of polar molecules, water could be effectively removed from emulsions.


Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 23

Acknowledgements We acknowledge the financial support and opportunity provided by Texas A&M University to conduct experiments in Ramey Thermal Recovery Laboratory. We also acknowledge the members of Heavy Oil, Oil shales, Oil sands, & Carbonate Analysis and Recovery Methods (HOCAM) Research Team at Texas A&M University, Petroleum Engineering Department, for their help. REFERENCES [1] Dallinger, D., Kappe, C. O. Microwave-Assisted Synthesis in Water as Solvent. Chemical Reviews, 2007, 107(6), pp 2563-2591. [2] Hascakir, B., Akin, S. Recovery of Turkish Oil Shales by Electromagnetic Heating and Determination of the Dielectric Properties of Oil Shales by an Analytical Method. Energy & Fuels, 2010, 24(1), 503-509. [3] Kappe, C. O. Controlled Microwave Heating in Modern Organic Sysnthesis. Angewandte Chemie, International Edition 2004, 43, 6250-6284. [4] Goual, L., Firoozabadi, A. Measuring Asphaltenes and Resins, and Dipole Moment in Petroleum Fluids. AIChE Journal, 2002, 48(11). [5] Oxtoby D. W., Pat Gillis, and Butler L. J., Principles of Modern Chemistry. Cengage Learning 8th Edition, 2015, p 111. [6] Menendez, J. A., Inguanzo, M., Pis, J. J. Microwave-induced pyrolysis of sewage sludge. Water Research, 2002, 36, 3261-3264. [7] Binner, E. R., Robinson, J. P., Silvester, S. A., Kingman, S. W., Lester, E. H. Investigation into the mechanisms by which microwave heating enhances separation of water-in-oil emulsions. Fuel, 2014, 116 (2014) 516-521. [8] Evdokimov, I. N., Losev, A. P. Microwave treatment of crude oil emulsions: Effects of water content. Journal of Petroleum Science and Engineering, 2014, Volume 115, Pages 2430. [9] da Silva, E. B., Santos, D., de Brito, M. P., Guimaraes, R. C. L., Ferreira, B. M. S., Freitas, L. S., de Campos, M. C. V., Franceschi, E., Dariva, C., Santos, A. F., Fortuny, M. Microwave demulsification of heavy crude oil emulsions: Analysis of acid species recovered in the aqueous phase. Fuel, 2014, Volume 128, Pages 141-147.


Page 21 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

[10] Martinez-Palou, R., Ceron-Camacho, R., Chavez, B., Vallejo, A. A., Villanueva-Negrete, D., Castellanos, J., Karamath, J., Reyes, J., Aburto, J. Demulsification of heavy crude oil-inwater emulsions: A comparative study between microwave and thermal heating. Fuel, 2013, Volume 113, Pages 407-414. [11] Fingas, M. Water-in-Oil Emulsions: Formation and Prediction. Journal of Petroleum Science Research, 2014, Volume 3 Issue 1, January 2014. [12] Turton, R. The Physics of Solids. New York: Oxford University Press, 2000. [13] Mullins, O. C., Sheu, E.Y., Hammami, A., Marshall, A. G. Asphaltenes, Heavy Oils, and Petroleomics. Springer Science and Publishing Media, New York, 2007, ISBN10:0-387-317341. [14] Spiecker, P. M., Gawrys, K. L., Trail, C. B., Kilpatrick, P. K. Effects of petroleum resins on asphaltene aggregation and water-in-oil emulsion formation. Colloids and surfaces A: Physicochemical and engineering aspects, 2003, 220(1): 9-27. [15] Novick, S. E., Davies, P. B., Dyke, T. R., Klemperer, W. Polarity of van der Waals molecules. Journal of the American Chemical Society, 1973, 95(26), pp 8547-8550. [16] Klaila, W. J. Method and apparatus for controlling fluency of high viscosity hydrocarbon fluids, 1983. US Patent, 4,067,683. [17] Fang, C.S., Lai, P.M.C., Microwave Heating and separation of water-in-oil emulsions. Journal of Microwave Power and Electromagnetic Energy, 1995, 30(1), pp 46-57. [18] Rajakovic, V., Skala, D., Separation of water-in-oil emulsions by freeze/thaw method and microwave, Separation and Purification Technology, 2006, 49, pp 192-196. [19] McLean, J. D., Kilpatrick P.K., Effects of asphaltene aggregation in model heptanetoluene mixtures on stability of water-in-oil emulsions, Journal of Colloidal and Interface Science, 1997, 196, pp 23-24. [20] Xia, L., Lu, S., Cao, G., Stability and demulsification of emulsions stabilized by asphaltenes or resins, Journal of Colloidal and Interface Science, 2004, 271, 504-506. [21] Butler, R.M., McNab, G.S., Lo, H.Y. Theoretical studies on the gravity drainage of heavy oil during in-situ steam heating. 29th Canadian Chemical Engineering Conference, 1979, Sarnia, Ontario, Canada. [22] Huc, A. Heavy Crude Oils. From Geology to Upgrading: An Overview. France, Paris: Editions Technip, 2011. [23] Mukhametshina, A., Hascakir, B. Bitumen extraction by expanding solvent-steam assisted gravity drainage (ES-SAGD) with asphaltene solvents and non-solvents. SPE Heavy Oil Conference-Canada, 2014, 10-12 June, Calgary, Alberta, Canada. SPE 170013-MS. [24] Nasr, T.N., Beaulieu, G., Golbeck, H., Heck, G. Novel Expanding Solvent-SAGD Process “ES-SAGD”. Journal of Canadian Petroleum Technology, 2003, 42(1). PETSOC-03-01-TN-P. 21 ACS Paragon Plus Environment

Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 23

[25] Nasr, T. N., Kimber, K. D., Vendrinsky, D. A. Process Enhancement in Horizontal Wells Through the Use of Vertical Drainage Channels and Hydrocarbon Additives. Western Regional Meeting, 1991, Long Beach, California, USA, 20-22 March. SPE-21794-MS. [26] Mokrys, I. J., Butler, R. M. In-Situ Upgrading of Heavy Oil and Bitumen by Propane Deasphalting: The VAPEX Process. Production Operations Symposium, 1993, Oklahoma City, OK, USA. 25452-MS. [27] Sarathi, P. S., Olsen, D. K., Practical aspects of steam injection processes a handbook for independent operators, 1992, NIPER-580 (DE92001070), pp 358-365. [28] Prats, M., Thermal Recovery, 1982, SPE Monograph Series, Vol. 7, pp 193-197. [29] Green, D. W., Willhite, G. P., Enhanced Oil Recovery, 1998, SPE Textbook Series, Vol.6, pp 283. [30] Hascakir, B., Acar, C., Akin, S., Microwave Assisted Heavy Oil Production: An Experimental Approach, Energy and Fuels, 23(12), pp 6033-6039, 2009. [31] Unal, Y., Kar, T., Mukhametshina, A., Hascakir, B. The Impact of Clay Type on the Asphaltene Deposition during Bitumen Extraction with Steam Assisted Gravity Drainage. SPE International Symposium on Oilfield Chemistry, 2015, 13-15 April, The Woodlands, Texas, USA, SPE-173795-MS. [32] Speight, J. G. The Chemistry and Technology of Petroleum, 3rd ed.; Marcel Dekker: New York, 1999 and references therein. [33] Mukhametshina, A., Morrow, A., Aleksandrov, D., Hascakir, B. Evaluation of Four Thermal Recovery Methods for Bitumen Extraction. SPE Western North America and Rock Mountain Joint Regional Meeting, 2014, 16-18 April, Denver, CO, USA, SPE 169543-MS. [34] ASTM. D2007-11: Standard Test Method for Characteristic Groups in Rubber Extender and Processing Oils and Other Petroleum-Derived Oils by the Clay-Gel Absorption Chromatographic Method. 2011. [35] Amyx, J.W., Bass, D.M., Whiting, R.L. Petroleum Reservoir Engineering. (Vol. 1), McGraw-Hill College, 1960, ISBN 07-001600-3: 103-104. [36] Kokal, S. L. Crude oil emulsions: A state-of-the-art review. SPE Production & facilities, 2005, 20[01]: 5-13. SPE 77497. [37] Chen, K., Liu, H., Guo, A., Ge, D., Wang, Z. Study of the Thermal Performance and Interaction of Petroleum Residue Fractions during the Coking Process. Energy Fuels, 2012, 26[10], pp 6343-6351. [38] Jones, F., Tran, H., Lindberg, D., Zhao, L., Hupa, M. Thermal Stability of Zinc Compounds. Energy Fuels, 2013, 27(10), pp 5663-5669. [39] Bellamy, L.J., The infrared Spectra of Complex Modules, Advances in Infrared Group Frequencies, Second Edition, 1980, Volume II. 22 ACS Paragon Plus Environment

Page 23 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

[40] Saikia, B. J. and Parthasarathy, G. Fourier transform infrared spectroscopic characterization of kaolinite from Assam and Meghalaya, Northeastern India. Journal of Modern Physics, 2010, 1(04): 206. [41] Kar, T., Williamson, M., Hascakir, B., The Role of Asphaltenes in Emulsions Formation for Steam Assisted Gravity Drainage (SAGD) and Expanding Solvent-SAGD (ES-SAGD), 2014 SPE Heavy and Extra Heavy Oil Conference-Latin America, 24-26 September 2014, Medellin, Colombia, SPE-171076-MS. [42] Kar, T., Yeoh, J., Ovalles, C., Rogel, E., Benson, I.P., Hascakir, B. The Impact of Asphaltene Precipitation and Clay Migration on Wettability Alteration for Steam Assisted Gravity Drainage (SAGD) and Expanding Solvent-SAGD [ES-SAGD]. 2015 SPE Heavy Oil Conference, 9-11 June, 2015 Calgary, Alberta, Canada, SPE-174439-MS.


The Role of Resins, Asphaltenes, and Water in WaterâOil Emulsion

Recommend Documents

The Role of Resins, Asphaltenes, and Water in WaterâOil Emulsion