A new model was developed to describe water leakoff from formed Cr(III)-acetate-HPAM gels during extrusion through fractures. This model is fundamentally different than the conventional filter cake model that was used during hydraulic fracturing. Even so, the model accurately predicted leakoff during extrusion of a guar-borate gel. Thus, the new model may be of interest in hydraulic fracturing. Contrary to the conventional model, the new model correctly predicted the occurrence of wormholes and stable pressure gradients during gel extrusion through fractures.
This work was motivated by an attempt to understand propagation of formed gels as they extrude through fractures during water shutoff treatments. Formed gels lose water during extrusion through fractures. This water leaks off through the fracture faces and controls the rate of gel propagation. Leakoff also controls the rate of fracture growth during hydraulic fracturing and during produced water re-injection.