Abstract: The present invention relates to the composition, preparation method and use of a solids-free drilling fluid system formulated with a mixture of divalent heavy brines, which is resistant to high pressures and high temperatures. The system has the special feature that it significantly reduces productive-formation permeability damage as it uses mixtures of different salts of water-soluble divalent metals to provide the features of density, polymers and special additives to provide the system with the physicochemical properties that any fluid for drilling, completing and repairing wells requires in order to fulfill the functions thereof and to provide heat resistance up to 200° C. A main feature of the present invention is that the composition that embeds the drilling/completing/repairing of oil wells fluid contains synthetic polymers and biopolymers that do not require large amounts of time, high shear speeds or heating for hydration thereof in divalent metal salt derived simple or binary brines.

Abstract: The present invention relates to the composition, preparation method and use of a solids-free drilling fluid system formulated with a mixture of divalent heavy brines, which is resistant to high pressures and high temperatures. The system has the special feature that it significantly reduces productive-formation permeability damage as it uses mixtures of different salts of water-soluble divalent metals to provide the features of density, polymers and special additives to provide the system with the physicochemical properties that any fluid for drilling, completing and repairing wells requires in order to fulfill the functions thereof and to provide heat resistance up to 200° C. A main feature of the present invention is that the composition that embeds the drilling/completing/repairing of oil wells fluid contains synthetic polymers and biopolymers that do not require large amounts of time, high shear speeds or heating for hydration thereof in divalent metal salt derived simple or binary brines.