HIGH-PRESSURE/HIGH TEMPERATURE SOLIDS-FREE FLUID SYSTEM FOR DRILLING, COMPLETING AND REPAIRING OIL AND GAS WELLS

摘要

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, which system can be used for drilling, completing and repairing petroleum wells and, more specifically, for drilling, completing and repairing the productive zone of offshore, onshore and lake-based wells that produce hydrocarbons (crude oil, gas and mixtures of oil/gas and condensates). Said system has the special feature that it significantly reduces productive-formation permeability damage since it uses mixtures of different salts of water-soluble divalent metals to provide the characteristics 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 fulfil the functions thereof, and, above all, to provide heat resistance up to 200°C, providing lubrication and inhibiting hydration of any clays present in the productive-formation pores. A primordial feature of the present invention is that the composition that incorporates the petroleum-well-drilling/-completing/-repairing fluid contains synthetic polymers and biopolymers, for enhancing viscosity and controlling filtration losses, that do not require large amounts of time, high cutting speeds or heating for hydration thereof in divalent-metal-salt-derived simple or binary brines.