Abstract
Fines migration is a well known problem in sandstone formations, where clay particles are released when come in contact with fresh water or high pH fluids. In its nature state, each clay platelets is surrounded by an atmosphere of cations. These positive charges neutralize the negative charges of the platelets and hold the platelets in electrostatic equilibrium. Beside the electrostatic interactions between colloidal entities, dispersion forces often called the London-van der Waals forces, which are always attraction forces, exist between particles. To mitigate the migration problem, it was required to control these forces.
A new inorganic Al/Zr-based clay stabilizer was used to mitigate fines migration problem. Its effectiveness was proven experimentally in Berea sandstone cores with permeability of 65–100 md, Berea sandstone is rich in kaolinite. It showed also great effectiveness when come in contact with high pH fluids. Coreflood tests were conducted at various temperatures up to 300°F. Effluent samples were collected, and the concentrations of different cations were measured using ICP.
Experimental results showed that the stabilizer was effective in mitigating fines migration in Berea cores up to 300°F. The amount of Al/Zr retained in the core effluent was found to be a function of clay content. Various forces acting on clay particles were defined using Derjaguin and Landau, Verwey and Overbeek theory. The mechanism of stabilizing clay using the new chemical is well explained by DLVO theory. The results of this work will help production engineers to design clay stabilizer treatment used in the field.
