OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: 832-320-7300 / Fax: 713-880-9886 / www.ofite.com
2
The OFITE Electrical Stability Meter (ES) is a sine wave instrument. It is
manufactured in accordance with the American Petroleum Institute (API)
“Recommended Practice Standard Procedure for Field Testing Oil-Based
Drilling Fluids”, 13B-2. It is accurate, compact, and portable and is intended
for routine field and laboratory use to measure the relative electrical strength
of drilling fluids having a continuous oil phase.
The ES Meter is self contained and consists of a meter and probe, and it
operates on four 9 volt alkaline batteries which are readily obtainable. Two
calibration standards (high and low) are included with each unit to ensure ac-
curacy.
The dielectric breakdown voltage is the point at which the drilling fluid be
-
comes electrically conductive. The DC power source of the batteries pro-
vides an AC voltage to the electrodes at a low frequency. The unit provides a
constant rate of voltage increase until the emulsion becomes electrically con-
ductive. A current flow of 61 micro amps (61 mA) across the electrodes will
cause the display to stop and the reading will be held as long as the switch is
depressed. The reading is called the electrical stability, emulsion stability or
ES value of the fluid.
The electrical stability value will decrease with increasing testing temperature.
The recommended API test temperature is 120°F ± 5° (49°C ± 3°).
The chemical composition and the shear history of a drilling fluid control the
absolute magnitude of the ES in a complex fashion. Therefore, interpreting
the oil-wet state of a mud from a single ES measurement is not appropriate.
Only trends in ES should be used in making treatment decisions.
Intro
Description
