Advanced strategies for mitigation of

asphaltene deposition

Department of Chemical and Biomolecular Engineering

Francisco “Paco” Vargas

* fvargas@rice.edu 8 vargas.rice.edu

2

v  Polydisperse mixture of the heaviest and most polarizable fraction of the oil

v  Defined in terms of its solubility

ü  Miscible in aromatic solvents, but insoluble in light paraffin solvents

v  Deposition mechanism and molecular structure are not completely understood

v  Behavior depends strongly on P, T and {xi }

(a) n-C5 asphaltenes (b) n-C7 asphaltenes

J. Buckley, NMT

http://tigger.uic.edu/~mansoori/Asphaltene.Molecule_html

Background

Asphaltene Deposition

Prediction

PRECIPITATION is a necessary but NOT a sufficient condition for DEPOSITION

4

Q. Ge, Y.F. Yap, F.M. Vargas, M. Zhang & J. Chai. 9th ICHTFMT, Malta 2012

Pres

sure

Temperature

Reservoir [A]

A

B

Wellhead [B]

C

D C

AOP

BP

Reservoir

Stable

Unstable

VLLE

D

Background (continued)

NIR Spectroscopy

Constant T and Composition

Determination of Asphaltene Onset Pressure

5

NIR Spectroscopy

Constant T and Composition

+ HPM

Determination of Asphaltene Onset Pressure

On the Prediction of Asphaltene Precipitation

Advanced EOS Modeling

Case Study: Fluid B1, Comparison SRK Vs PC-SAFT

-

2,000

4,000

6,000

8,000

10,000

0 100 200 300 400

Temperature,°F

Pressure,psia

-

2,000

4,000

6,000

8,000

10,000

0 100 200 300 400

Temperature,°F

Pressure,psia

+ 5% gas (fit) + 30% gas (prediction)

PC-SAFT SRK+P

7

Modeling using PC-SAFT

Advanced EOS Modeling

-

2,000

4,000

6,000

8,000

10,000

0 100 200 300 400

Temperature,°F

Pressure,psia

-

2,000

4,000

6,000

8,000

10,000

0 100 200 300 400

Temperature,°F

Pressure,p

sia

-

2,000

4,000

6,000

8,000

10,000

0 100 200 300 400

Temperature,°FPressure,psia

-

2,000

4,000

6,000

8,000

10,000

0 100 200 300 400

Temperature,°F

Pressure,psia

-

2,000

4,000

6,000

8,000

10,000

0 100 200 300 400

Temperature,°F

Pressure,psia

+ 10% gas

-

2,000

4,000

6,000

8,000

10,000

0 100 200 300 400

Temperature,°F

Pressure,p

sia

predicted + 5% gas

fitted

+ 15% gas predicted

+ 30% gas predicted

Cas

e St

udy:

Flu

id B

Asphaltene Deposition

Prevention

A GAME CHANGER is REQUIRED

Current testing procedures to assess the performance of asphaltene inhibitors

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ADT HPHT - SDS

Ambient conditions

Asphaltene Inhibitors

SEM image of Asphaltene Aggregate

5 µm

Asphaltene Microstructure (SEM)

Effect of Dispersants on Asphaltene Aggregation and Precipitation

010203040506070

0.0

0.2

0.4

0.6

0.8

1.0

1.2

30 40 50 60 70 80 90 100

Heptane Concentration / (vol. %)

Nor

mal

ized

Lig

ht in

tens

ity

Crude Oil Concentration / (vol. %)

Crude Oil SDisp 9 2000ppm 25C 24h

Precipitation onset with and without inhibitor

010203040506070

0.00001

0.0001

0.001

0.01

0.1

1

10

30 40 50 60 70 80 90 100

Heptane Concentration / (vol. %)

Nor

mal

ized

Lig

ht in

tens

ity

Crude OIl Concentration / (vol. %)

Crude Oil S

Disp 9 2000 ppm 25°C 24h

12

28.8 vol. % Precipitation onset

with inhibitor 22.4 vol. %

Precipitation onset without inhibitor

Direct Method Indirect Method

13

020406080100

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

0 20 40 60 80 100

Heptane Concentration / (vol. %)

Nor

mal

ized

Lig

ht in

tens

ity

Crude OIl Concentration / (vol. %)

Blank 25°C 1hDisp 8 500ppm 25°C 1hDisp 9 500ppm 25°C 1hDisp 15 500ppm 25°C 1h

020406080100

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

0 20 40 60 80 100

Heptane Concentration / (vol. %)

Nor

mal

ized

Lig

ht in

tens

ity

Crude OIl Concentration / (vol. %)

Blank 25°C 1hDisp 8 70ppm 25°C 1hDisp 9 70ppm 25°C 1hDisp 15 70ppm 25°C 1h

Effect of Dispersants Dosage on Asphaltene Aggregation

Low Dosage High Dosage

020406080100

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

0 20 40 60 80 100

Heptane Concentration / (vol. %)

Nor

mal

ized

Lig

ht in

tens

ity

Crude OIl Concentration / (vol. %)

Blank 25°C 1h

Disp 8 70ppm 25°C 1h

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

Nor

mal

ized

Lig

ht in

tens

ity

Crude OIl Concentration / (vol. %)

020406080100

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

0 20 40 60 80 100

Heptane Concentration / (vol. %)

Nor

mal

ized

Lig

ht in

tens

ity

Crude OIl Concentration / (vol. %)

Blank 25°C 1h

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Asphaltene Dispersants - Efficiency

!"#=%&&∗ (%− *+,-↑!./0. 23+456-7.38 / *+,-↑96-8:  )

Asphaltene deposition in micromodels

However….

Blank In08 Deposition as a function of Inhibitor Concentration

Probing Asphaltene Deposition Inhibition

0 ppm 500 ppm

10 min

23 min

Flow time

Commercial Inhibitor concentration

Flow rate : 60 µl/min

Using Micromodels

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Novel system to probe asphaltene deposition

Effluent

Ultrasonic water bath

Syringe pump Crude oil or model oil

Syringe pump Precipitant

PTFE Column

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020406080100

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

0 20 40 60 80 100

Heptane Concentration / (vol. %)

Nor

mal

ized

Lig

ht in

tens

ity

Crude OIl Concentration / (vol. %)

Blank 25°C 1hDisp 8 500ppm 25°C 1hDisp 9 500ppm 25°C 1hDisp 15 500ppm 25°C 1h

020406080100

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

0 20 40 60 80 100

Heptane Concentration / (vol. %)

Nor

mal

ized

Lig

ht in

tens

ity

Crude OIl Concentration / (vol. %)

Blank 25°C 1hDisp 8 70ppm 25°C 1hDisp 9 70ppm 25°C 1hDisp 15 70ppm 25°C 1h

Effect of Dispersants Dosage on Asphaltene Aggregation

Low Dosage High Dosage

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Asphaltene Deposition | Effect of Chemicals

Crude Oil S treated with three commercial asphaltene dispersants

y = 1.7792x + 40.261R² = 0.9716

0

20

40

60

80

100

120

140

0 10 20 30 40 50

Asp

halte

ne D

epos

it (m

g)

Dispersive Performance - Efficiency DPE (%)

Blank

Disp 8

Disp 9

Disp 15

Linear (Series3)

Amount of Deposited Asphaltenes Vs Dispersive Performance

Mechanism for Asphaltene Deposition

Effect of Corrosion on Asphaltene Deposition

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Ø  Corrosion results in the formation of rust on pipeline walls and the variation of surface roughness

Ø  Study the effect of rust attaching on metallic surfaces on asphaltene deposition

Ø  Investigate the effect of surface roughness on asphaltene deposition

(a) Original sphere (b) Corroded sphere (with rust) (c) Sphere with higher surface roughness(without rust)

(b) (b)

1000 µm 100 µm

(a)

1000 µm 100 µm

(c)

1000 µm 100 µm

* Images were taken by using HIROX KH8700 3D Digital Microscope

Fe(III)-induced asphaltene deposition

Deposited asphaltenes, % of total infused asphaltenes

Without emulsified water With emulsified water

Effect of water 23.4 ± 1.4 24.9 ± 1.5

Without Fe(III) With Fe (III)

Effect of Fe (III) 24.9 ± 1.5 36.2 ± 1.4

Without EDTA With EDTA

Effect of EDTA 36.2 ± 1.4 7.6 ± 0.5

Although EDTA reduced asphaltene deposition on carbon steel, it increased deposition on PTFE by 170%.

Asphaltene Deposition

Remediation

Best Practices of Deposit Removal using Solvents

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Good Solvent

Asphaltene Deposition Removal

Poor Solvent followed by Good Solvent

Using solvent wash

Immediate Treatment

Treatment after 6 days

Experiments by Nate Lin & Lisa Biswal – Rice University

After 67%heptane and 33% toluene washed (Poor solvent)�

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Before washing�

Washed with poor solvent�

Asphaltene Deposition Removal

Experiments by Nate Lin & Lisa Biswal – Rice University

Take-home ideas

•  Asphaltene precipitation is a fully reversible process. Deposition and aging might not be.

•  Asphaltene precipitation is a necessary but not a sufficient condition for deposition (which is the actual problem in oil wellbore).

•  Current experimental techniques (NIR and HPM) are not sensitive enough to detect the true onset of asphaltene precipitation.

•  PC-SAFT is an excellent model to predict the precipitation of asphaltene and design and validate HPHT experiments – not so easy to use, though.

Take-home ideas (continued)

•  Selection of Asphaltene Deposition Inhibitors is not a trivial task: Chemicals might make the problem WORSE.

•  Most of the current commercial chemical tests are done under unrealistic conditions.

•  New generation of inhibitors must be based on other mechanisms – Dispersion might not be the way to go.

•  Surface roughness and iron ions produced by corrosion increase asphaltene deposition.

•  EDTA can reduce asphaltene deposition on metal surfaces but increase deposition on PTFE coatings.

•  When removing asphaltene deposits using solvent wash, the right solvent must be used from the beginning.

Advanced strategies for mitigation of

asphaltene deposition

Department of Chemical and Biomolecular Engineering

Francisco “Paco” Vargas

* fvargas@rice.edu 8 vargas.rice.edu