1. Effect of produced water salinity on wax precipitation in oil
TPG Specialization Course Carolin Gjengedal Department for Petroleum Engineering and Applied Geophysics
June 10th, 2013

2. Outline
Part 1: Background Information
Part 2: Case Study
Discussion

3. Wax Napthenic Hydrocarbons General Formula of Paraffin Paraffin Wax
Microcrystalline Wax
(Source: G. A Monsoori)

4. Colloidal Dispersion
Two-phase system consisting of particle/drops/bubbles of one phase dispersed in another continuous phase.
Dispersed Phase
Continuous Phase
Emulsions: Liqiud dispersed in liquid
W/O Emulsion
Suspensions: Solid dispersed in liquid
Wax
(1 nm – 10 μm)

5. Separation between particles: d
Van der Waals Forces
Attractive forces between atoms, molecules or particles:
Attractive interaction
energy
Between two spherical
Particles of the same radii, Rs Rs Rs
Separation between particles: d

6. The Electrical Double Layer
Variation in the ion density near a charged surface.
When a charged particle is present in an aqueous solution it is influenced by the ionic strengt in the solution.
Counter-Ion: Ion of opposite charge
Co-Ion: Ion of equal charge
(Source: G. Øye)

7. Aggregation - Colloidal Instability
Stable Suspension
Unstable Suspension

8. Zeta Potential Describing Colloidal Stability
Henry´s Equation:
ζ : Zeta potential. u : Electrophoretic mobility.
ε : Dielectric constant. η: Viscosity
κ: Debye-Hückel parameter
Rs: Particle radius
ƒ(κRs) : Henry’s function.
Used to calculate the Zeta Potential
(Zetasizer Nano Series )

9. Colloial Stability & DLVO Theory (Derjagin-Landau and Verwey-Overbeek)
Interaction energy between dispersed particles
Van der Vaals Attraction
ΦTot= ΦR+ΦA
Φ = Interaction energy
R = Repulsive
A = Attractive
Electrostatic Repulsion

10. Colloidal Stability & DLVO Theory (Derjagin-Landau and Verwey-Overbeek)
Total Ineraction Energy
Energy minimum : Coagulation – Instability
Energy barrier : Obstacle to Coagulation - Stable
Secondary minimum : Reversible Aggregation
(Source: G. Øye)

11. Colloidal Stability & DLVO Theory (Derjagin-Landau and Verwey-Overbeek)
High zeta potential 
Large repulsion between particles
Large Hamaker constant 
Large attraction between particles

12. Water Type of Water TDS [%] Fresh Water < 0,05 Brackish Water
0,05 – 3
Seawater
3 – 5
Formation Water
> 5
TDS = Total Dissolved Solids
(Source: Gudmundsson, 2009)

13. Ionic Components in Formation Water
Cations
Anions
Sodium
[Na+]
Chloride
[Cl-]
Magnesium
[Mg2+]
Sulfate
[SO42-]
Calcium
[Ca2+]
Bicarbonate
[HCO3-]
Potassium
[K+]
Carbonate
[CO32-]
Manganese
[Mn2+]
Hydroxide
[OH-]
Strontium
[Sr2+]
Borate
[BO3-]
Barium
[Ba2+]
Bromide
[Br-]
Iron
[Fe2+, Fe3+]
Phosphate
[PO43-]
(M. Abdou et al., 2011)

14. Paraffinic Hydrocarbons in Aqueous Suspensions
(S. N. Srivastava and D. A. Haydon, 1963)
Aggregation of paraffin wax suspension depending on electrolyte concentration
Aqueous Phase
Zeta Potential [mV]
0,01M KCl
- 55
0,01M KCl + 3,9110-4M UO2(NO3)2
- 17
0,01M KCl + 3,0810-3M BaCl2
- 30
0,01M KCl + 1,7510-4M Pb(NO3)2
- 21
0,02M KCl
- 46

15. Electro kinetic Properties of Paraffin Suspensions In Water & Electrolyte Solutions (E. Chibowski et al., 2005)
PREPARATION
100 mL of water or electrolyte solution was heated to °C
0,1 g of pharmaceutical paraffin wax was added. The paraffin melted at this temperature
The content was homogenized
The suspension of solid particles of paraffin was obtained by cooling
ELECTROLYTES
NaCl
LaCl3
Natural pH of the suspension
In water: 6.6 (+- 0.2)
In NaCl: 6,8
In LaCl3: 6,64-6,68

16. Electro kinetic Properties of Paraffin Suspensions In Water & Electrolyte Solutions (E. Chibowski et al., 2005)
MEASUREMENT POINTS:
40 min
50 min
60 min
70 min
80 min
90 min
120 min
24 h
SOLUTIN pH:
pH = 4
pH = Neutral
pH = 10

17. Electro kinetic Properties of Paraffin Suspensions In Water (E
Electro kinetic Properties of Paraffin Suspensions In Water (E. Chibowski et al., 2005)
Zeta potentials of paraffin particles in water at different pH and time.
Bars = Standard errors.

18. Electro kinetic Properties of Paraffin Suspensions In Electrolyte Solutions (E. Chibowski et al., 2005 )
Zeta potensials of paraffin particles in 10-4 M NaCl at different pH and time
Zeta potensials of paraffin particles in 10-4 M LaCl3 at different pH and time

19. Electro kinetic Properties of Paraffin Suspensions In Electrolyte Solutions (E. Chibowski et al., 2005 )
Zeta potensials of paraffin particles in 10-3 M NaCl at different pH and time
Zeta potensials of paraffin particles in 10-3 M LaCl3 at different pH and time

20. Summarized
Ion concentration is affecting the zeta potential, which again is reflecting a suspensions stability
Higher ion concentration will destabilize water-wax suspensions

21. Discussion
Salt will have almost no influence on wax precipitation because the salt is sustained in the aqueous phase, and wax is sustained in the oil phase.
The wax will not be in contact with the salt in the water phase, and the salt will not be in contact with wax in the oil phase

22. Discussion
Wax precipitation depends almost entirely on the temperature and temperature gradients.
(Kristofer Paso – Kjemi, NTNU)

23. References
Chibowski, Emil, Agneszka Ewa Wiacek, Lucna Holysz, og Konrad Terpilowski. «Investigation of the Electrokinetic Properties of Paraffin Suspension. 1. In Inorganic Electrolyte Solutions .» Paper, Department of Physical Chemistry, Faculty of Chemistry, Maria Curie-Sklodowska University, 2005.
Guðmundsson, Jón Steinar. TPG 4135, Prosessering av Petroleum, Grunnleggende enhetsoperasjoner i produksjon av olje og gass. . Trondheim: Department of Petroleum Engineering and Applied Geophysics, 2009.
Hiemenz, Paul C, og Raj Rajagopalan. Principles of Colloid and Surface Chemistry
Mansoori, GA. «Thermodynamics Research Laboratory.» The University of Illinois at Chicago. (funnet June 9, 2013).
Medhat, Abdou, et al. Finding Value in Formation Water. Report, Schumberger, Oilfield Review Spring, 2011.
Nelson, Jessica DeGroote, Drucker, Jarrett A, Andrew A Haefner, og Robert A Wiederhold. «Varying electro-kinetic interactions to achieve predictable removal rates and smooth surfaces on ZnS .» 2009.
Ocean Health . Ocean Health. 9 June
Sirvastava, S. N, og D. A Haydon. «Estimate of the Hamaker COnstant For Paraffinic Hydrocarbons in Aqueous Suspensions.» Paper, Department of Colloid Science, University of Cambridge, 1963.
Gisle Øye, Lecture notes in TKP4115 Surface- and Colloid Chemistry
Zetasizer Nano Series. «Zeta Potential theory.»