OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: 832-320-7300 / Fax: 713-880-9886 / www.ofite.com
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Intro
The OFI Testing Equipment (OFITE) High Temperature High Pressure
(HTHP) Filter Press is designed to evaluate the filtration characteristics of
drilling fluids, cement slurries, fracturing fluids, and completion fluids under
elevated temperatures and pressures. Evaluating fluids under HTHP condi
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tions similar to the downhole environment is of paramount importance. Fluid
properties must be monitored while under high temperatures and pressures
as filtration behavior and wall cake building characteristics of permeable
formations change with changing environments. These characteristics are
affected by the shape, type, and quantities of solids present in the fluid and
their physical and electro-chemical interactions, all of which are affected by
changing temperatures and pressures.
OFITE manufactures and provides HTHP filtration units in two basic sizes,
175 mL and 500 mL capacities. Both are used extensively throughout the
world and in all environments, but in general the 175 mL units are designed
for field portability, while the larger 500 mL units are designed for laboratory
usage at higher temperatures and pressures. All OFITE Filtration devices fully
conform to American Petroleum Institute (API) specifications.
A complete HTHP Filter Press consists of a controlled pressure source, usu
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ally Nitrogen pressurization or Carbon Dioxide bulbs for the 175 mL units.
Top and bottom pressure manifolds are provided to simulate the differential
pressures found in a down-hole environment, and to prevent evaporation
of the base fluid if exceeding the boiling point of that fluid. The test cells are
provided in a variety of assemblies, depending upon the type of fluid tested,
the filter media, and the temperatures and pressures desired. The test cells
are encased inside a heating jacket, which is adjustable.
A variety of filter media are available, the most common being standard API
filter paper, cement screens, and ceramic filters. The ceramic filters may be
obtained to match the pore throat or permeability of the formation. Natural for
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mation filters or cores may also be used of differing pore throat / permeability
sizes. Slotted disks of varying sizes are frequently used for lost circulation
materials studies.
The 175 mL has a maximum temperature of 350°F (177°C) and the 500 mL
heating jackets are capable of reaching 400°F (204°C). However, lower
fluid volumes due to fluid expansion at higher temperatures, limit the 175 mL
units to a useful working temperature of 300°F (149°C). Anyone running tests
above 350°F (177°C) must substitute a complete set of o-rings after each and
every test.