BAKER HUGHES - Drilling Fluids Reference Manual

FLUIDS ENVIRONMENTAL SERVICES
surface, or conversely the efficiency will decrease if the filter media flexes under the build up of
differential pressure and the release of captured debris takes place.
Hydrocarbon Absorption Filter Elements
Hydrocarbon absorption filters are made of treated polypropylenes or polymers and are modified so
that they chemically bond to hydrocarbons. Some of these filters will begin to release the
hydrocarbons once they are saturated, while others will absorb the hydrocarbons into the polymeric
structure until they solidify and prevent any further flow through the filters.
Analysis Equipment
Turbidity (NTU) Turbidity Meters
The Portable Turbidity Meter operates on the nephelometric principle of turbidity measurement. The optical
system includes a tungsten-filament lamp, a 90 0 detector to monitor scattered light and a transmitted light
detector. The instrument’s microprocessor calculates the ratio of the signals from the 90 0 and transmitted light
detectors. The ratio technique corrects for interferences from color and compensates for fluctuations in lamp
intensity, providing long term calibration stability.
A turbidity Meter is used to measure the level of turbidity or cloudiness of a fluid. The readings will
not give any indication of what is causing the fluid to be turbid, however it can be concluded that a
high reading warrants further testing using more sophisticated equipment. The turbidity meter is a
useful tool for quick analysis and should only be used to provide an indication of changing
cleanliness rather than a conclusion that the fluid is within the cleanliness specification required.
Percent Solids Laboratory Centrifuge
The electric bench top centrifuge is used to provide a visual assessment of the amount of particulate in the fluid.
They are best suited to measuring solids or oil in heavily contaminated fluids as the final readings are taken
visually and are useful when determining the solids content trend during a wellbore clean-up. The laboratory
centrifuge is also relatively easy to operate and requires no more than a 5 minute spin cycle to determine a
reasonably accurate reading. A 100ml sample is poured into a glass vial that is placed in a counter balanced
receptacle where it is spun at speed creating high gravitational forces that separate the different constituents by
their densities e.g. oils to the top, water or brine in the middle and solids at the bottom of the glass vial. The
glass vial is calibrated so that the user can determine the level of contamination as a percentage of the total
volume tested.
Particle Counting and Size Distribution Laser Analyzers
A laser particle analyzer is used to count the number of particles in filtered fluids within pre-set size
bands ranging from 2 microns to 200 microns. These units are best suited for measuring particles in
filtered fluids if accurate readings a re to be achieved. Unfiltered fluids can cause blockages in the
internal components of thes e instruments.
During well stimulation work and gravel packing the requirement is normally for a pre-filtered fluid
that is filtered to 2 micron absolute with 99.9% removal efficiency.
A laser analyzer is sensitive enough to measure the
will print the readings for future safekeeping.
remaining particles at various micron sizes and
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 14-62