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Properties of Oilfield Waters

Properties of Oilfield Waters. Lectures # 30 – 31 PETE 310. Topics. Brine composition and density Water (brine) compressibility Formation volume factor and Pb Viscosity Mutual solubilities (gas in water, water in gas). Water Production Issues.

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Properties of Oilfield Waters

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  1. Properties of Oilfield Waters Lectures # 30 – 31 PETE 310

  2. Topics • Brine composition and density • Water (brine) compressibility • Formation volume factor and Pb • Viscosity • Mutual solubilities (gas in water, water in gas)

  3. Water Production Issues • Oil and gas wells produce more water than oil (7 bbl/1 bbl oil in Texas) • Composition of co-produced water determines need for anti-scaling additives • Regulations limit disposal and beneficial use options • Environmental impact

  4. Oilfield Water Issues • Expensive Oilfield Water Management • Diversity of Oilfield Waters (amount, compositions) • Corrosion, Scale Control and Plugging • Microbiological Problems • Water Quality for Water-flooding, Steam Injection or Surface Disposal • Injectivity Decline in Water Injection Wells

  5. Cations Na+ K + Li + Ca ++ Mg ++ Ba ++ Fe ++ Sr ++ Anions Cl - SO4 = CO3 = CO3H - NO3 - Br - I - Dissolved Solids in Brines NaCl S A L T S

  6. Total Dissolved Solids (TDS)

  7. Measures of Solids Concentration rw is brine density which depends upon solids in solution

  8. Milliequivalents per liter Stiff Diagrams

  9. Typical Concentrations TDS = 68,030 ppm  6.8%  get rw convert to mg/l

  10. Periodic Table Info for each element here! More information here http://pearl1.lanl.gov/periodic/default.htm

  11. Conversions: mg per liter  milliequivalents per liter • See examples in text

  12. Conversions: mg per liter  milliequivalents per liter • Valence is # of charges (+ or -). Expressed as equivalent wt per g mole • Ca++ has ionic weight of 40.08 g/g mole • Equivalent weight is • 40.08 g/g mole/2 eq wt/g mole = 20.4 g/eq wt • Atomic weight divided equivalent weight is mg / meq • Milliequivalents per liter of calcium are • *** mg/l / 20.04 mg/meq = ***

  13. Bubble Point Pressure of Oilfield Water • Pb is the same as the Pb of the coexisting oil due to thermodynamic equilibrium

  14. Formation Volume Factor (Bw) • Depends upon pressure • Depends upon temperature • Depends upon gas in solution Offsetting – negligible effect -

  15. Works well even for brines up to 30% TDS Formation Volume Factor of Water (Bw)

  16. + Temperature Correction

  17. - Pressure Correction

  18. Effect of TDS on Brine Density

  19. Solubility of Hydrocarbons in Water

  20. Solubility of Methane in Water

  21. Effect of Salinity on solubility of gas in water

  22. Coefficient of Isothermal Compressibility (Cw)

  23. At a fixed T Viscosity of Water versus Pressure

  24. Water (Brine) Viscosity versus TDS At atmospheric pressure Increasing TDS

  25. Viscosity of Water at Reservoir Pressure

  26. Solubility of Water in Natural Gas (low pressure) Lb of water / MMSCF

  27. Solubility of Water in Gas (high P) Lb of water / MMSCF To evaluate dehydration requirements (equipment, chemicals) In natural gas processing

  28. Resistivity of Oilfield Water • Use in logging tools • Formation evaluation • Resistivity is inversely proportional to conductivity Rw = rA/L = [ohm/meters]

  29. Calculate Resistivity or TDS

  30. Gas-Water IFT

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