BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
At differential pressures in excess of 200 psi, the calcium carbonate bridging particles can form strong
adherence between them and be very difficult to disperse and remove from the filter surface. The
dispensability of these particles can be greatly increased by placing a parting agent or barrier between
them during cake formation. One of the most effective methods of accomplishing this is to coat the
particles with certain organic water soluble polymers prior to filtration. This has been accomplished
in the PERFFLOW ® systems as evidenced by the high return permeability results.
Figure 1–17 shows a photomicrograph of filter cake from a 17 lb m /gal PERFFLOW fluid while that of
a sized salt fluid is shown in Figure 1–18. Note the granular and irregular packing of the calcium
carbonate particles in Figure 16. In contrast, note the highly oriented cubic salt crystals in Figure
1-18. This difference in packing will result in much less surface area for particle adhesion in the
calcium carbonate cake. This appears to be a major factor in the ease of dispersability of the
PERFFLOW filter cake upon production as compared to the sized salt filter cake.
Figure 1-17
SEM Photomicrograph – 17 lb/gal PERFFLOW
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 1-41