BAKER HUGHES - Drilling Fluids Reference Manual

BOREHOLE PROBLEMS
2. Mix slurry volume equivalent to or greater than open-hole volume below point of loss. For 100 bbl
of slurry, add 154 sacks of MILGEL, 154 sacks of cement, and 72 bbl of diesel.
3. Pump 5 bbl of diesel in front of slurry to serve as a buffer between drilling fluid and squeeze slurry.
Start pumping slurry and continue until slurry reaches bit (follow slurry with another 5 bbl diesel
spacer). After slurry reaches the bit, close preventers and begin pumping drilling fluid into annulus at
rate of 2 bbl/min while displacing slurry, from drillpipe, at a rate of 4 bbl/min. After pumping ½ of
slurry, reduce pump to ½ speed (1 bbl/min annulus and 2 bbl/min on drillpipe). After pumping ¾ of
slurry, attempt “hesitation” squeeze pressure of approximately 100 to 500 psi. Under-displace slurry
so that approximately 1 bbl remains in drillpipe.
4. Pull out of hole and wait eight to ten hours to allow slurry to set.
Diesel oil-bentonite squeezes (400 lb of MILGEL per bbl of diesel) are run in a similar manner,
but will have a lower set strength than diesel oil-bentonite-cement squeezes.
WATER ORGANOPHILIC CLAY PLUG
In oil based drilling fluids, the reverse of an oil bentonite plug is used, the water organophylic
clay plug (reverse gunk squeeze). In oil based drilling fluids, a clay which has been chemically
treated to render it oil dispersible is used to provide viscosity. This Organophylic clay will not
yield in water but will yield in oil in the presence of water. Thus, if a high concentration of
Organophilic clay dispersed in water is pumped to the loss zone, on contact with oil based drilling
fluid, it will form a strong solid material.
1. The gel used in the reverse gunk-squeeze will yield with OBM, and should therefore not
come into contact with OBM until the gunk exits the drill string. Preventing OBM from
entering the batch tank and associated lines is imperative.
2. For the reverse gunk squeeze to work properly, the bit must be located just above the loss
zone so that the gunk will yield in the loss zone.
3. Pumping OBM down the annulus, simultaneously with pumping down the drill string,
will ensure that the gunk mixes with the OBM, and prevents the gunk from being
squeezed into a zone above the bit, which could stick the drill string.
4. Performing an open hole squeeze with the drill string across permeable zones can result
in differential sticking of the drill string. Therefore, it is important to keep the squeeze
pressure on the annulus low, and minimize the time the drill string is stationary. Do not
reciprocate the drill string while the annular preventer is closed, as the gunk may mix
across the BHA and stick the pipe.
5. This type of pill cannot be reversed out of the pipe.
Mixing Procedure
1. Ensure that the cementing unit and cementing batch tank are clean.
2. Mix reverse gunk pill in the cementing batch tank:
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 7-27