evaluation of geor 1 as an additive for enhanced oil recovery

8/2/2019 Evaluation of GEOR 1 as an Additive for Enhanced Oil Recovery

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Evaluation of GEOR 1 as

an Additive for Enhanced

Oil Recovery

Prepared by:

Professor Andrew HurstDr Stephen Bowden

Dept Geology and PetroleumGeology,

University of Aberdeen,AberdeenScotland

06 July 2009


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Evaluation of GEOR 1 for EOR

3

Images of the beadpack before and after flooding with GEOR 1 in Table 1.1 and

1.2 show the recovery of oil from bypassed regions. Relative to other methods

GEOR 1 appeared efficient at accessing zones of bypassed oil. GEOR 1 was

originally developed to remove heavy oil residues to remediate contaminated

land and clean surfaces. In this application GEOR 1 acts rapidly, penetrating

asphaltic deposits to clean oil from surfaces. This ability appears to transfer to a

dynamic environment at the laboratory-scale, and would be crucial at the field

scale if it improved the access of an EOR fluid to oil bypassed by the initial water

flood.


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Table 1 Summary of results

Oil

Recovered

Watercut during

EOR

Primary

EOR

Extended

%EOR

Lowest

Average

Reduction

Image beforeEOR phase

Image after EOR

phase

Freshwater

GEOR 15 L/L

33

27

70

67

93

90

37(55)

40(60)

64

60

67

67

-10

-15

Coldwater

27

27

37

43

55

10(30)

16(37)

80

85

82

85

+ 5

+11

Hotwater>70 C80 85 C

27 40

46

13

16

65

64

85

78

-28

-28

Hotwater85 C

63 36(57)

55 71-38-10


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Table 1 Continued

Oil

Recovered

Watercut

during EOR

Primary

EOR

Extended

%

EOR

Lowest

Average

Reduction

Image before

EOR phase

Image after EOR

phase

Saltwater

GEOR 15 L/L 35 72 83

37(54) 40 51 -31

Coldwater 40 50 10(20)

50 66 +27

Oil Recovered = the % of oil initially in place recovered. Primary recovery = % recovered after

waterdrive; EOR = % recovered after equal volume of water to primary phase used to implement EORtechnique; Extended = % recovered after extension of EOR phase. Approximately equal pore volumes used

for each experiment. % EOR = % of oil initially in place recovered by first EOR technique, number in brackets is %enchantment in oil recovery.

Water cut during EOR . Note that for extended flooding there is no reduction, hence this number is

positive.

Water is entering from the top of the page and oil exiting from wells at the bottom. Coloured linesidentify regions of different shading, where shading is being used as a proxy for oil saturation. Blue is

highest saturation and yellow lowest.


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1.1 Introduction, aims and objectivesExperiments were designed and conducted to test under laboratory conditions

whether there is evidence that GEOR 1, a chemical additive, has the potential to

enhance the direct recovery of heavy oil from reservoir rocks. The background forthe experimental work is a history of successful applications of GEOR 1 to

dispersal of heavy-oil pollution, remediation of oil-contaminated sand and

cleaning and unblocking of oil transport infrastructure (pipelines and storage

tanks). The success of these downstream applications coupled with their cost

effectiveness and environmental friendliness encouraged Glensol, the

manufacturers of GEOR 1, to evaluate possible use of the additive to enhance oil

recovery from natural reservoir rocks. GEOR 1 was successfully tested by

Glensol as an extraction method for mined and quarried tar and oil sands. If

significant improvement in heavy-oil recovery is possible by using a chemical

additive it opens the way for step changes in the recovery of heavy oil both in

terms of recovery efficiency and cost per barrel of oil recovered.

The aim of this study is use simple laboratory experiments to verify that a low

concentration of GEOR 1 added to water can enhance the recovery of heavy oil

from reservoirs. Recovering heavy oil from the subsurface in a dynamic

environment is very different to extracting bitumen from sand at the surface.

Therefore specific objectives are required to benchmark any enhancement in

recovery observed for GEOR 1 compared to extended flooding with coldwater

and hotwater, with particular attention being paid to factors unique to flow through

porous media. These factors are the rate of oil recovery relative to chosen

benchmarks, and how much water is produced along with a given volume of oil.

Additional objectives were to observe the behaviour of GEOR 1 in both salt and

freshwater systems and differentiate GEOR 1 from previous methods of

chemical-enhanced oil recovery.

Specific questions to answer are:


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Can GEOR 1 enhance oil recovery?

Is GEOR 1 stable and effective in both fresh and salt water?

How efficient is GEOR 1 in comparison to alternative methods of EOR?

How does GEOR 1 improve upon other chemical methods of EOR?

Positive outcomes for the experiments above provide a basis for planning and

designing field tests of GEOR 1 in conventional heavy-oil reservoirs. The

experiments are designed to give oil-field operators a clear indication of the likelybenefit of using GEOR 1 in a commercial context.


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1.2 Previous chemical EOR

Although there is a considerable literature on chemicals that enhance oil recovery

there have been few successful commercial projects. General textbooks on

reservoir engineering tend to characterise chemical methods of enhanced oil

recovery as being economically marginal and technically complex, although

rarely for a common reason.

Foremost is that the cost of the surfactants can be expensive relative to the value

of any increase in oil recovery. This is further compounded by the possible loss of

surfactants to the reservoir formation during floods. Furthermore in many field

situations it has been difficult to bring the injected water containing EOR-chemicals into contact with bypassed oil the injected water containing EOR

chemicals simply flows around regions that contain residual oil.

Technical problems are caused the sensitivity of surfactant properties?? to

differing reservoir formation water chemistry and mineralogy, which necessitate a

design stage to specifically tailor a combination of surfactants and their co-

surfactants for particular reservoir characteristics. A miscalculation or false

assumption about reservoir rock and fluid properties at an early design stage has

the potential to cause failure for a chemical EOR project at the field scale.

Therefore in addition to the costs of implementing a field-scale EOR project a

considerable investment is also necessary at the design stage, thus a chemical

EOR project is inherently risky, may take along time to bring to fruition and even

longer to pay back a financial investment.

The chemical composition of GEOR 1 is confidential and thus it is hard to place

within the schemes typically used to characterise chemical EOR techniques.

Previous characterisations of EOR treatments similar to GEOR 1 include low and

high concentration surfactant floods, techniques that form surfactants using

chemicals already present in the oil (alkali flooding) and those that use


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microbially produced biosurfactants. Although GEOR 1 is used at low

concentrations, and forms water in oil micro emulsions, the producers of GEOR 1

believe that GEOR 1 does not fit easily within any currently used classification.


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2.0 Experimental method

A microfluidic beadpack was adapted to allow the preliminary evaluation of water

flooding with GEOR 1 as a method of enhanced oil recovery for heavy oil. During

experiments the bead-pack was flooded with heavy oil and to promote the aging

of the system to an oil-wet state it was warmed at 30 C. The device was cooled

to room temperature before use. Two or more phases of recovery were used.

The first phase comprised primary recovery by water drive. During this stage

coldwater (20 C) was used. Second and subsequent phases comprised flooding

by one of three techniques; 1) coldwater (20 C), 2) hotwater between 70 to 85

C or 3) water with a 5 L/L (5 ppm) concentration of GEOR 1. The beadpack

was videoed during the experiments and still-images were point-counted tomeasure water saturation and the volume of fluids exiting the bead pack. The

methodology is summarised in figure 2.1. Table 1 lists the experiments

performed for the evaluation of GEOR 1 as a heavy oil recovery additive and the

details of additional experiments whose results are presented here for evaluation

purposes.

Table 2.1 Experiments used for report

Water type EOR method Other details

Freshwater GEOR 1 5 L/L concentrationGEOR 1 duplicate

Coldwater comparison

Hotwater comparison experiments at 70, 80 and 85 C

Saltwater GEOR 1 5 L/L concentration

Coldwater comparison

Heavy Oil and Water

The oil used is from Siljian (Sweden) and has an asphaltene + resin content of 36

%, an API value of 18 o/ ~10 000 cp. Tap water (TDS < 500 mg/L) was used for

freshwater floods and seawater for saltwater floods (TDS ~ 35 000 mg/L). The

same stock solution of GEOR 1 was used to make up saltwater and freshwater


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solutions of 5 ppm concentration. GEOR 1 was not explicitly tailored or adapted

for the heavy oil and bead pack used in this study.

1) Channel withbead trap

2) Channel packed withbeads

3) Oil flown intochannel

4) Water flown intochannel

5) Volume of oil and water in drainingwells counted

800 m

6) Before and after images of gravel pack analysed






m


Bead diameter/ Grain size: 22 m

Porosity: ~ 46 %

~ 48 m






800 m







m



Porosity: ~ 46 %

~ 48 m






800 m







m



Porosity: ~ 46 %

~ 48 m


Porosity: ~ 46 %

~ 48 m

Figure 2.1 Photo graphs of device, and device before and after heavy oil is emplaced. Schematic diagram of

method, showing different stages of an experiment.


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Further details

The device used in this study is not a micromodel but a micro-scale beadpack.

The key difference between the two techniques is that the beadpack creates true

3D tortuousity. The sodalime glass-beads used for experiments are a high

sphericity 22 micrometer diameter particle-size standard. Beads were introduced

through a channel 500 micrometers in breadth and ~46 micrometers in depth

until a pack of suitable length accumulated behind a gap filter. A picture of the

device and an image of the channel packed with beads is shown in figure 2.2.

Prior to use the pack was flushed with the water appropriate to the experiment

and the oil flown in to the pack at high flow rates/pressures. Prior to each

experiment the device was warmed to 30 oC to promote the adhering of oil onto

the beads to create an oil wet system.

During experiments the beadpack and the draining wells were videoed. Image

stills were point-counted to obtain water saturation and fractional watercut. When

measuring fractional water-cut, blocked-wells were excluded from calculation of

the parameter.

The device was fabricated at the James Watt-Nano Centre at the University of

Glasgow in cooperation with Professor Jonathan Cooper, experiments were

performed at the Dept of Geology and Petroleum, University of Aberdeen.


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3.1 Heavy oil production using different EOR techniques

Fluid flow during experiments was driven by the circulation of water with the data

collected including the volume of water injected into the device, the percentage of

water in the beadpack and the percentage of water exiting through the draining

wells1. These three measurements represent the time taken to recover a given

quantity of oil, the amount of oil recovered out of the total available and the

proportion of oil recovered relative to water.

The amount of oil produced per volume of injected water is plotted in figures 3.1.

and 3.2. Extended phases of recovery are denoted by dashed lines, but the

following discussion refers to the first phase of enhanced oil recovery. Relative toflooding with hotwater and coldwater, flooding with GEOR 1 brought forward

production significantly. This is illustrated in figures 3.1.and 3.2 by GEOR 1

attaining its maximum displacement of oil for the circulation of lower pore

volumes in comparison to the hot- and coldwater experiments. Although the

overall volume of oil displaced is similar for both hotwater and GEOR 1, the key

difference is that GEOR 1 attains this far more rapidly (a Welge displacement

efficiency calculation suggests that to recover 70 % of the oil initially in place

more than 50 pore volumes of cold-freshwater would have to be circulated).

Fractional water-cut is a measure of the proportion of water produced relative to

oil. Because of the viscous and asphaltic nature of the heavy oil used during the

experiments water is significantly more mobile than oil during the primary water-

flooding. This is particularly notable for the cold-freshwater experiment where the

watercut was very high from an early stage in the experiment (figure 3.3). This

continued during extended flooding with cold-freshwater. In contrast coldwater

flooding with GEOR 1 added significantly reduced or suppressed the fractional

water-cut.

1The higher the amount of water in the bead pack the greater the amount of oil displaced andrecovered. Similarly; either water or oil is exiting the device so the greater the percentage ofwater exiting the device the lesser the percentage of oil recovered.


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Watersaturation

5 ppm Glensol

PrimaryRecovery

Hot water 75 to 80 C

Hot water 85+ C

Cold water

0

0.2

0.4

0.6

0.8

1

50

Pore volume injected subsequent to water break through

0 5 10 15 20 25 30 35 40 45

5 ppm Glensol

Cold water

0

0.2

0.4

0.6

0.8

1

Watersaturation

5 ppm Glensol

PrimaryRecovery


Hot water 85+ C

Cold water

0

0.2

0.4

0.6

0.8

1

50


0 5 10 15 20 25 30 35 40 45

5 ppm Glensol

Cold water

0

0.2

0.4

0.6

0.8

1

Figures 3.1 and 3.2. Graphs illustrating the recovery of oil by displacement with water. All unfilled

symbols e.g. , etc refer to data for primary recovery phases. Shades symbols: = data obtained for

Glensol; = data obtained for cold water; + = data for hot water experiments. Dashed lines show extended

flooding with Glensol.


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Making a comparison between the hotwater and GEOR 1 flood experiment is a

little more complicated due to differential changes in volume in the oil phase

brought about by the two EOR techniques. It is likely that the overall reduction in

water-cut brought about by GEOR 1 is at least equitable to that of the hotwater

method if not greater. The minimal water-cut values attained by both techniques

are about 60 % for the freshwater/heavy oil system (figure 3.3.).

The saltwater/heavy oil system exhibited higher recoveries of the oil in place. The

presence of saltwater changes how heavy oil interacts with solid surfaces

(lowering the contact angle between the oil and water phases on wetting

surfaces). For an oil-wet system the decrease in contact angle or wetting

preference in saltwater can increase the mobility of the oil phase causing it to be

more easily mobilised than in a freshwater/heavy oil system. The effect of this

change in wetting preference can be seen by comparing figure 3.1 and 3.2,

where considerably more oil is mobilised during flooding with saltwater than with

freshwater.

The behaviour of GEOR 1 in a saltwater system is important in two respects: 1)

does GEOR 1 have an effect above that of using cold-saltwater alone and 2) is

GEOR 1 stable in both a fresh and saltwater environment? Firstly; flooding with

GEOR 1 in a saltwater system brought forward production significantly and

recovered more oil than cold-saltwater alone, but most notably it reduced water-

cut by about 40 % (figure 3.4). Secondly, the same GEOR 1 batch enhanced oil

recovery in both freshwater and saltwater/ heavy oil systems. This is highly

significant because it broadens the scope of applicability for GEOR 1-flooding as

an EOR-technique. Previous surfactant flood and EOR techniques that utilisedmicellar solutions have been highly sensitive to formation water chemistry

requiring a pre-flush to condition formations or the tailoring of surfactants for

specific formation water chemistries. For both salt- and freshwater a GEOR 1

flood recovered 70 % of the oil in place.


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5 ppm Glensol


Hot water 85+ C

Fractionalwater

cut

50


0 5 10 15 20 25 30 35 40 450

0.2

0.4

0.6

0.8

1

0

0.2

0.4

0.6

0.8

1

5 ppm Glensol


Hot water 85+ C

Fractionalwater

cut

50


0 5 10 15 20 25 30 35 40 450

0.2

0.4

0.6

0.8

1

0

0.2

0.4

0.6

0.8

1

Figure 3.3 and 3.4. Graph of the fraction of water exiting the device. All unfilled symbols e.g. , etc

refer to data for primary recovery phases. Shades symbols: = data obtained for Glensol; = data

obtained for cold water; + = data for hot water experiments. Dashed lines show extended flooding withGlensol.


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3.2 Further analysisAnalysis of fractional flow curves provides a means to predict how water flooding

could operate at a bigger scale and also helps to characterise processes and

mechanisms that are enhancing oil recovery during a GEOR 1 flood.

The simplest estimate of water flood efficiency is the mobility ratio, a parameter

that balances the viscous forces of one fluid phase against another; a mobility

ratio less than 1 characterises an efficient water flood regime and a ratio much

greater than 1 is an inefficient water flood. The mobility ratio estimated for the

cold-freshwater experiment is approximately 500 following water breakthrough.

0

20

40

60

80

100

fractionalwatercut%

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

Wct%

M=

25

M=2.5

M=0.2

5M

>499

Primary Recovery Extended water flood

Sea water

Fresh water

0 0.2 0.4 0.6 0.8 1

Water saturation

0

20

40

60

80

100

fractionalwatercut%

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

Wct%

M=

25

M=2.5

M=0.2

5M

>499

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

Wct%

M=

25

M=2.5

M=0.2

5M

>499

Primary Recovery Extended water flood

Sea water

Fresh water

0 0.2 0.4 0.6 0.8 1

Water saturation Figure 3.5. Fractional flow behaviour of beadpack. = data for primary and advanced stages of cold-

freshwater flood (solid blue line); = data for primary and advanced stages of cold-saltwater flood

(dashed blue line). Inset shows behaviour for idealised mobility ratios. Wct % = fractional water cut and M= mobility ratio.


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The fractional water-flow behaviour for the coldwater experiments are shown in

figure 3.5. After a small amount of heavy oil has been produced (water has

displaced oil from the beadpack thus increasing water saturation), water-cut

values are high. For comparative purposes fractional water-cut curves are also

shown for idealised systems with lower mobility ratios. Comparison of these

systems to the one used for experiments highlights the difficulty of producing

heavy oil: if a watercut of 80 % represented the operating limit for a given field,

then production of a heavy oil deposit with the characteristics of the micro-

beadpack would have to cease after production of less than 10 % of the movable

oil in place. For the lowest mobility ratio illustrated, with a low viscosity oil this

would be about 50 % of the oil in place.

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

70 oC80 oC85 oC

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

Wct%

Water

wetO

ilwet

fractionalwater

cut%

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

70 oC70 oC80 oC80 oC85 oC85 oC

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

Wct%

Water

wetO

ilwet

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

Wct%

Water

wetO

ilwet

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

Wct%

Water

wetO

ilwet

fractionalwater

cut%

Figure 3.6. Fractional flow behaviour during thermal EOR, note wetability inversion at highest

temperature. Blue line from figure 3.5. Redlines = thermal EOR data.. = data for hot water at 70 oC, + =

80 oC and = data for 85o C.


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Figure 3.6 presents the results for the thermal EOR experiments. An initial a drop

in oil viscosity for temperatures in the 70 to 80 oC range increases recovery

marginally, but at temperatures greater than 85 oC a completely different

fractional flow behaviour results. The concave upwards graph is characteristic of

the fractional flow behaviour observed for low viscosity water-wet systems and

describes a situation where increased oil recovery is accompanied by relatively

minor increases in fractional water-cut.

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

Fresh water Glensol

Sea water Glensol

fractionalwatercut%

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Water saturation

Fresh water Glensol

Sea water Glensol

fractionalwatercut%

Figure 3.7. Fractional flow behavior under Glensol flood.& = data for 1st and 2nd stages of EOR

with Glensol in freshwater. = 1st

and 2nd

stages ofEOR with Glensol in saltwater.

From figure 3.7 it is clear that flooding with GEOR 1 improves the fractional flow

regime; arrival of the GEOR 1 flood-front at the end of the beadpack is marked by

a reduction in water-cut as an oil bank is mobilised and moved through the

beadpack. This effect is most pronounced for the saltwater experiment. However


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late stage extended flooding with GEOR 1 in saltwater is characterised by an

increasing water-cut, but the shape and gradient of the line on figure 3.7 does

not suggest a change in wettability as was observed for the thermal method.

Although the extended floods using GEOR 1 in freshwater do not water-out

during the duration of the experiment, eventually this would occur.

Flooding with a low concentration of GEOR 1 may increase recovery via a range

of mechanisms:

1) An increase in heavy oil mobility caused by strong and rapid surfacting

action; GEOR 1 has been shown (by Glensol) to act rapidly on asphalt

associated with tar-sands and pipe-line precipitated asphaltenes where it

rapidly penetrates through oil residues to reach the oil-surface interface.

Results presented here suggest that the same effect occurs in a dynamic

environment. This gives GEOR 1 not only access to residual oil, but

access to heavy asphaltic oil in marginally tighter regions of the beadpack

that would be difficult to mobilise using water alone.

2) The formation of water in oil microemulsions with reduced oil viscosity.

Microemulsions have a much reduced viscosity and swell to form a

continuous mobile oil phase. This process is most evident for the saltwater

experiments and is expressed as a notable decrease in water-cut and an

increase in recovery.

3) If GEOR 1 viscosifies water it may also increase overall recovery by

stabilising the flood-front and being better able to mobilise oil. This wouldaid sweep efficiency and increase overall recovery.


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phase. A thermal method would be expected to mobilise heavy oil in such

regions by the conduction of heat, which does not depend on mass transfer to

lower viscosity. A chemical EOR method requires physical contact with the by-

passed or residual oil to mobilise it. The mobilisation of heavy oil in these regions

by GEOR 1 is therefore notable and attests to the rapid and deep surfacting

action of GEOR 1.


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4.0 Conclusion

The presence of very low concentrations of GEOR 1 in injected water

significantly enhances the recovery of heavy oil during waterflood. Heavy oil

production is brought forward relative to coldwater flooding with fresh and saline

water with high recoveries obtained more rapidly when flooding with GEOR 1

than with hotwater or coldwater benchmarks. The positive affect of GEOR 1 in

both fresh and saltwater highlights its robustness as an additive.

To the best of our knowledge GEOR 1 has unique properties as a chemical

additive as it is efficient and effective in salt- and freshwater when used at low

concentrations sets it apart from previous chemical methods of enhanced oilrecovery. GEOR 1 is cost effective and not designed to be recovered for

reinjection thus mitigating an important element of economic risk in EOR projects.

For example, where loss of surfactant by adsorption onto reservoir surfaces is

encountered during surfactant flooding this could feasibly be mitigated by

increasing the concentration of GEOR 1 in the injected water as the GEOR 1

itself is not an unreasonable cost increment or environmentally sensitive in an

EOR project. Because the GEOR 1 additive can be used in a variety of reservoir

formation water chemistries it should be possible to simplify programes of

additive treatment in field applications. This potentially reduces the costs and

risks typical of previous chemical methods of enhanced oil recovery which

required extensive design and compatibility studies.

The experimental results far exceeded our expectations for GEOR 1 and more

importantly demonstrated that the additive out-performs cold- and hot-water

floods in fresh- and salt-water. Our bead-pack experiments are a simplification of

natural reservoir conditions however, they provide an important insight into the

utility of GEOR 1, which encourages us to recommend designing an immediate

field trial.

evaluation of geor 1 as an additive for enhanced oil recovery

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