Spe Emulsions By Brendan Graham

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Spe Emulsions By Brendan Graham

  1. 1. Oil/Water Emulsions Formation Prediction and Measurement Dr. Dr Brendan Graham University of Western Australia Centre for Petroleum, Fuels & Energy Fluid Science Division
  2. 2. Outline • Introduction to Oil/Water Emulsions – Formation, Issues, Remediation • Measurement Techniques – Techniques, Issues • UWA Apparatus – Address shortcomings • Multi Phase Flow Meters – Types, Issues
  3. 3. Production Issues • Lost Production – Down hole • Transportation issues – Viscosity • Treatment costs – Chemical, Electrical • Need to know risk of formation
  4. 4. Relative Viscosity of Emulsions 4
  5. 5. Emulsion Viscosity • Viscosity of emulsions depends on – Viscosities of the oil & water – The volume fraction of the dispersed water – The droplet size distribution – The temperature p – The shear rate – facilities design implications – The amount of solids present 5
  6. 6. Crude Oil/Water Emulsions • Three criteria to form an emulsion – Two immiscible phases p – Agitation to disperse one liquid into droplets – Emulsifier to stabilise droplets • Emulsions are problem only if stable on production time scale
  7. 7. Sources of shear • Gas lift wells – Gas injection p j points • Pumping wells – Pump and tubing • Gas evolution – Perforations, screens, chokes, flow lines
  8. 8. Emulsion Stability • Two common types of emulsifiers – Surfactant or surface active agent • Reduces surface tension • Forms viscous barrier • Repulsion of electrically charged droplets – Fine solid particles • Sand, silt, FeS, asphaltenes 8
  9. 9. Emulsifiers • Naturally occurring – Higher boiling point fractions – asphaltenes resins asphaltenes, resins, organic acids & bases • Introduced surfactants – Drilling fluids, stimulation chemicals, EOR surfactants – Injected chemicals for wax scale control wax, 9
  10. 10. Minimisation Techniques • Use downhole chokes – Higher temperatures g p – Lower pressure differential • Minimise points of flow disruption – Smooth flow lines – Pumps in working order • Injected chemicals – Minimise use – Check for compatibility
  11. 11. Will an oil form an emulsion? Will my demulsifier work?
  12. 12. Laboratory Techniques • Bottle Shaker/Rocker • Blender (D ASTM 1401) – Originally made for non crude oil application – Routinely modified for different applications
  13. 13. Case Study Results • Looking at real report data • Issues – Measurement accuracy – Reproducibility
  14. 14. 30:70 Oil:Brine Low Agitation
  15. 15. 30:70 Oil:Brine High Agitation
  16. 16. • Accuracy of Measurement – Phase levels not correct – Subjective determination of levels
  17. 17. Reproducibility
  18. 18. Current Test Conditions • Shear conditions not representative of real world shear experienced by oil/water • Overestimate emulsion formation tendency • Results quite subjective, user dependent • Determines demulsifier choice and dosing amount • N d more representative method Need t ti th d
  19. 19. UWA solution • Objective measurement technique • User independent • Based on amount of energy required for emulsion formation
  20. 20. Emulsion Dynamometer • V i bl speed rotor Variable d t • Measure force transmitted through solution • Determine energy inputted into system
  21. 21. Effect of Shear Rate orce (N) Fo Time (s)
  22. 22. Reproducibility 0.1 Sample 1 0.09 Sample 2 Sample 3 0.08 0.07 0.06 Force 0.05 0.04 0.03 0.02 0 02 0.01 0 0 10 20 30 40 50 60 Time (s)
  23. 23. Addition of Surfactant Increased Energy Input Slippage Ons Time [(log (s)] ( Decreased Energy Input Increased Viscosity set Surfactant Concentration (mg/10mL water)
  24. 24. Applications of Emulsion Dynometer • Determine energy required for emulsion formation • Test demulsifier efficacy based on energy applied to system • Compare to CFD models to determine amount of shear experienced in p p production
  25. 25. Multiphase Meters • Used to determine flow rates of oil/water in pipelines • Need to determine phase fractions – Gamma rays – Microwave – Electrical impedance
  26. 26. Electrical Impedance • Based on Bruggeman Equation Measured 13 ε w − ε mix ⎛ ε o ⎞ ⎜ ε ⎟ = 1 − φw ×⎜ ε w − ε o ⎝ mix ⎟⎠ Calculated Assigned Values
  27. 27. Measure & calculate εr (= n2) for oil & emulsion Characterization of oil (SCN components) ℘SCN = 0.3341M SCN + 0.4208 ε −1 calculate εoil : = ρ ∑ z SCN℘SCN ε +2 Measured εoil (Capacitor) Calculated εoil 2.44 ± 0.06 2.1
  28. 28. Relation of Measured to Calculated Data Then measure εwater & εmix for known water cuts (φw) f k t t to test Bruggeman eqn Errors of 10-15% compared to Bruggeman eqn used by industry in MPFMs
  29. 29. Summary • Current laboratory results not reproducible and subjective • MPFM have errors of 10-15% • Need for careful evaluation of results
  30. 30. Questions ?
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