The new generation of Drill-In Fluids have been developed to mitigate the potential of damage the producing formation and eliminate the need for post-completion cleanup. However depending on the reservoir features and the architecture selected for completing the well a significant reduction of the well productivity or injectivity can be caused by filtercake formation. The common approach is the application of breakers such as acids, strong oxidizers or enzymes. When an oxidizer treatment is the preferred option, high concentration solutions are usually applied at temperatures higher than 50-60 °C. Recently, the requirement of an effective oxidant breaker, as an alternative to acid, in low temperatures acid-sensitive reservoirs promoted an extensive research activity, which lead to a new cleanup treatment capable of effectively reducing the damage induced by the polymers which form the filtercake.
In this paper the performance at laboratory-scale of a new oxidizing agent is reported and some guidelines for its application including the possibility to delay its action are provided. The new breaker system consists of two components: a solution of hydrogen peroxide at a very low concentration (1-2% v/v) and an iron complex activator.
By coreflooding tests the effectiveness of this breaker to remove the external filtercake and the polymers, which entered the formation, was identified. Experimental results showed that this type of oxidants can degrade the polymers contained in the filtercake also at temperatures as low as 35°C, generating non-damaging by-products characterized by very low molecular weight. A delayed action of the breaker can be obtained by modifying the oxidizer concentration and the type of iron complex. Finally some results on the behaviour of the developed system in heavy brines including CaCl2 and CBr2 are presented.