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chemical

Emulsion Stability (ES)

Purpose

Evaluate the quality and stability of an oil-based or synthetic-based mud emulsion by applying an alternating electric field across two electrodes immersed in the mud and recording the voltage at which current breakthrough occurs. A higher ES voltage indicates a tighter, more stable emulsion.

Equipment

  • Electrical stability tester (OFI or equivalent)
  • Calibration solution or reference fluid
  • Sample cup
  • Thermometer

Procedure

  1. Ensure the instrument electrodes are clean and free of mud or scale from previous tests.
  2. Verify instrument calibration using the manufacturer’s reference solution.
  3. Pour a well-mixed mud sample into the clean sample cup to the indicated fill level.
  4. Immerse the electrode probe into the sample; ensure both electrode tips are fully submerged.
  5. Record the sample temperature.
  6. Activate the instrument; the voltage ramps up automatically. Observe the meter or digital display.
  7. Record the voltage at which the instrument indicates current breakthrough (the ES reading).
  8. Repeat the measurement twice more; average the three readings and report.

Notes

  • Report ES as the average breakthrough voltage in volts (V).
  • ES is temperature-sensitive; always record and report the test temperature alongside the result.
  • A significant drop in ES compared to previous readings may indicate water contamination, emulsifier depletion, or base-oil dilution.
  • Clean electrodes thoroughly with solvent after each test to prevent carry-over between samples.