Fluid Loss
Some guar-based gels such as HPG (Hydroxypropyl Guar) show the same nonwall-building characteristics as HEC(Hydroethyl Cellulose) fluids in high permeability. However, guar gel tends to build a filter cake, and most tend to develop a better filter cake than the HEC fluids. This wall-building tendency has a complex leakoff function that is initially governed by viscous invasion of a non-Newtonian fluid and then changes over time to a system dominated by filter cake. This tendency to develop a filter cake with guar fluids is believed to be due to the high residue content of this fluid as compared to HEC. The filter-cake buildup and the deeper formation damage makes are drawbacks of ordinary guar for Fracture applications. HPG and CMHPG (Carboxymethylhydroxypropyl Guar) are usable Fracture fluids due to their lower gel-residue content.
