STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

706 Drilling and Well Completions
Table 4-62
Checklist of Completion and Workover Fluids Considerations [26]
Factor Considered
1. Mechanical
Annular velocity
Mixing facilities
Annular space
Circulation frequency
Corrosion
Fluid components
2. Formation
Permeability damage
Formation pressure
Clay content
Vugular formation
Formation sensitivity
Temperature
Completion and Workover Fluid Considered
Higher annular velocity-low viscosity system or low annular
velocity-higher viscosity systems can be selected. Annular
velocity can be substituted for viscosity in lifting particle.
Annular velocity at 150 Wmin should be sufficient for
borehole cleaning with 1 cp viscosity clear salt water.
If mixing facilities are poor to produce adequate shear, the
completion/workover fluid should be prepared and maintained
with very small amounts of material.
The size of bottom hole equipment (liners, packers, etc.)
reduces annular space and increases pressure losses. The
fluid must maintain rheological properties which reduce
pressure losses.
In the completion and workover operations, there are long
periods when fluid in the hole is not circulated. Fluid
suspension and thermal stability should be determined in
order to evaluate the necessary circulation frequency.
Some workover fluids can produce high corrosion rates.
Corrosion control can be accomplished through H control,
inhibitors or bactericides. The practical corrosivity limit is
0.05 Ib/ft2 per operation.
Solubility at fluid components at the well bore conditions
(pressure and temperature) should be considered. Glazing at
jet and bullet tracks should not occur while perforating.
Fluid solids should be kept as low as possible. Fluid should
not contain solids larger than two microns in size unless
bridging material.
Density control with calcium carbonate, iron carbonate,
barium carbonate, ferric oxide.
Fluid inhibition with electrolyte additive.
In order to prevent "seepage loss" of circulation to the
vugular formation, bridging the formation-by properly sized,
acid-soluble on oil-soluble resin particles as well as colloidal
particles-should be considered.
Formations can be oil wet or water wet. The fluid filtrate
depends on what is the continuous phase of the completion
fluid. Thus the formation wettability can be reduced by
wettability charge. This effect can be controlled either by
proper fluid selection or by treatment with water wetting
additives.
In high temperature wells, the temperature degradation of
polymens should be considered.