Complex barite filter cake removal using in-situ generated acids by thermochemicals.

Area of Science:

• Petroleum Engineering
• Drilling Fluids Technology
• Wellbore Chemistry

Background:

• Filter cake formation in sandstone wells impedes removal due to quartz particle integration.
• Existing methods struggle with quartz layers and polymer coatings, reducing wellbore cleanup efficiency.

Purpose of the Study:

• To develop and evaluate a novel multi-stage chemical formulation for effective filter cake removal.
• To address challenges posed by quartz and polymer components in filter cakes.

Main Methods:

• A two-stage chemical treatment was developed: Stage 1 uses ammonium fluoride (NH4F) and sodium bromate (NaBrO3) for an exothermic reaction generating HF acid.
• Stage 2 employs chelating agents and catalysts to dissolve barite-based filter cakes.
• Solubility experiments were conducted at 300 ºF and 500 psi to assess efficiency.

Main Results:

• The NH4F and NaBrO3 formulation successfully generated HF in-situ, dissolving quartz minerals and removing polymer coatings.
• The multi-stage approach demonstrated effectiveness in breaking down complex filter cake structures.
• Experimental results validated the chemical formulation's ability to enhance filter cake removal.

Conclusions:

• The novel multi-stage formulation provides an effective solution for challenging filter cake removal in sandstone formations.
• In-situ HF generation is a key mechanism for overcoming quartz and polymer impediments.
• This method improves wellbore cleanup efficiency and drilling fluid performance.