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Effect of produced water salinity on
wax precipitation in oil
TPG 4520 - Specialization Course
Carolin Gjengedal
Department for Petroleum Engineering and Applied Geophysics
June 10th, 2013
Outline
• Part 1: Background Information
• Part 2: Case Study
• Discussion
Wax
Napthenic
Hydrocarbons
General Formula of Paraffin
Paraffin Wax
Microcrystalline Wax
(Source: G. A Monsoori)
Colloidal Dispersion
Two-phase system
consisting of
particle/drops/bubbles
of one phase dispersed
in another continuous
phase.
• Emulsions: Liqiud dispersed in liquid
• W/O Emulsion
• Suspensions: Solid dispersed in liquid
• Wax
Dispersed
Phase
Continuous
Phase
(1 nm – 10 μm)
Van der Waals Forces
Attractive forces between atoms, molecules or
particles:
Rs
Attractive interaction
energy
Separation between particles: d
Between two spherical
Particles of the same radii, Rs
Rs
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)
Aggregation
- Colloidal Instability
Stable Suspension
Unstable Suspension
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 )
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
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)
Colloidal Stability & DLVO Theory
(Derjagin-Landau and Verwey-Overbeek)
• High zeta potential 
Large repulsion between particles
• Large Hamaker constant 
Large attraction between particles
Water
Type of Water
Fresh Water
Brackish Water
Seawater
Formation Water
TDS [%]
< 0,05
0,05 – 3
3–5
>5
Dissolved Salts In Seawater
[Na+]
TDS = Total Dissolved Solids
[Cl-]
(Source: Gudmundsson, 2009)
[SO42-]
[Mg2+]
[Ca2+]
[K+]
Water
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)
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
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 68-70 °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
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
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.
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
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
Summarized
• Ion concentration is affecting the zeta
potential, which again is reflecting a
suspensions stability
• Higher ion concentration will destabilize
water-wax suspensions
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
Discussion
• Wax precipitation depends almost entirely on the
temperature and temperature gradients.
(Kristofer Paso – Kjemi, NTNU)
References
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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. 1997.
Mansoori, GA. «Thermodynamics Research Laboratory.» The University of Illinois at Chicago.
http://tigger.uic.edu/~mansoori/TRL_html (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 2013. http://oceanplasma.org/documents/chemistry.html .
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.»
http://www.nbtc.cornell.edu/facilities/downloads/Zetasizer%20chapter%2016.pdf.

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