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 + 3,9110-4M UO2(NO3)2 - 17 0,01M KCl + 3,0810-3M BaCl2 - 30 0,01M KCl + 1,7510-4M 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 • • • • • • • • • • 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.