BAKER HUGHES - Drilling Fluids Reference Manual

RESERVOIR APPLICATION FLUIDS
Lab Validation
Bridgewise calculations have been validated in
the permeability lab using cores of known pore
size. Bridging efficiency evaluations based on
long-term mud-off times (24-48 hours) were used
to demonstrate the performance of various PSD
blends.
In a recent drill-in fluid evaluation, tests were
conducted on a field core having a pore diameter
range between 3 to 35 μm (d50 = 20 μm).
Bridgewise calculations suggested that MIL-
CARB and FLOW-CARB 10 would be the
optimum product mix for this core. The core was
tested and similar cores were tested with blends
suggested by the Abrams and Kaeuffer rules. The
lab results confirmed that the Vickers Rule
provided the best recommendation for controlling
spurt and total filtrate volumes relative to the
other PSD blends. More significantly, after 48
hour dynamic and static exposure tests were
completed, higher regain permeability results were also achieved.
Clear Brine ESD Calculator (Equivalent Static Density)
Introduction:
When planning for a completion, or while on location, the brine engineer must be able to predict
the effective hydrostatic pressure exerted by the brine completion fluid in the wellbore. He must
know what fluid density to procure in order to have the effective downhole density required to
balance formation pressures under static conditions. Brine fluids can expand and therefore their
densities are reduced as fluid temperatures increase. Since the temperature of the wellbore
increases with depth, the effective hydrostatic pressure of the brine column changes as the
temperature changes. Conversely, brine fluids are somewhat compressible, offsetting some of the
effect of thermal expansion. Thus, the net change in the brine column density must be calculated in
advance to ensure adequate well control and to minimize client completion fluid costs.
The temperature/pressure correction software program for clear brine developed by Baker Hughes
Drilling Fluids is known as the Clear Brine ESD Calculator. Baker Hughes Drilling Fluids’
Technology Group developed this calculator in response to the needs of field operations.
Background:
Before the development of the ESD Calculator, the industry used theoretical models to calculate
the changes in density of brine due to temperature and pressure changes. The results derived from
these models have not always been in close agreement with experimentally determined values at
elevated temperatures and pressures for most of the brine blends used in the field. Furthermore, the
change in density versus temperature and pressure are different for each brine type or blend.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 6-106