A new biodegradable member of the chelating family of breaker fluids has been developed for treating oil and gas wells over a wide temperature range in environmentally sensitive locations. The enhanced filter-cake breaker is engineered to achieve improved bio-degradation with reduced toxicity and environmental footprint, while offering less corrosion potential than hydrochloric acid (HC1). Meanwhile, it maintains the high reaction rate with metal ions that is critical for efficient filter-cake removal.

Chelating agents are chemicals that are used to control undesirable reactions of metal ions. Treatment with chelate-based fluids has been successfully applied in the past for numerous well stimulations, for iron control during acidizing and for filter-cake breaker fluids in a variety of formations. A novel polyacidic chelate (NPC) breaker has been developed. The chelate-based fluid effectively dissolves calcium carbonate (CaCO3), yet has a low corrosion potential and is easy to apply.

From an environmental standpoint, NPC is readily biodegradable and is a renewable raw material. NPC has low animal and aquatic toxicity. As a replacement for live mineral acids, NPC is significantly safer to the environment and humans and is less corrosive.

This paper describes laboratory studies comparing the effectiveness of NPC in removing the acid soluble content of the filter cake versus conventional breaker systems that contain formic, lactic and acetic acid precursors. Additionally, application challenges in terms of corrosion potential, usage volumes, fluid preparation, and conformance to discharge regulations in various locations are reviewed.

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