Paper: A New Clay Stabilizer For Use In Completion Fluids

The oil industry customarily has utilized various clay control additives to prevent formation damage caused by the hydration (swelling) or migration of clays. These additives include inorganic metal cations, (e.g. Zr+4, Al+3, Ti+4, et al.) synthetic polyacrylate polymer types, quaternary ammonium salts, and petroleum heavy ends. Clay stabilization using metal cations is accomplished by ion exchange with cations in the clay mineral lattice. These types of clay control agents are limited in application due to their general incompatibility with most polymers used to viscosify completion fluids. This incompatibility is particularly apparent in crosslinked stimulation fluid systems because the metal cations interfere with the crosslinking mechanism of the fluid. Quaternary ammonium salts are also used as clay control agents. They function in approximately the same manner as the metal cations. Synthetic polyacrylate polymers have been used as clay control agents in completion techniques. The polyacrylate function is two-fold. First, the polymer's cationic character under mildly acidic conditions exchanges with lower charged cations located on the clay mineral lattice. Secondly, because this polymer is a long chain molecule (due to molecular weight), it lines the pore wall which insulates the clays involved in the pore channels. Clay damage control through physical isolation of formation clays has been achieved by using petroleum heavy ends, and other similar materials. This method of clay stabilization has shown a degree of effectiveness. A major problem in using this method is due to economics. A number of clay stabilizers have been reported to fuse migrating clays. These systems are used primarily in sand consolidation, hydraulic fracturing and acidizing applications.