Fracture acidizing of carbonate formations is a proven method for increasing hydrocarbon production. It can also be used in sandstone formation with acid solubility greater than 75%. Acid gelling agents effectively improve the fluid efficiency of an acid and increase the treating distance (fracture conductivity) of these treatments. Surfactants and polyacrylamides are used to develop stable viscosities for acidizing.

Gelling Agents

AGA-150 - Blend of cationic surfactants that viscosifies HCl acid by forming a macromolecular structure of oriented micelles. Used at temperatures to 150°F (66°C). Normal concentrations range from 20 to -40 gal/1,000 gal (20 to 40 L/m³).

AGA-400ME - Cationic, high-molecular weight, polyacrylamide copolymer that viscosifies HCl acid and is the main component in a self-diverting, cross-linked acid system designed for use in high permeability limestones and dolomites up to 300°F (149°C). Concentration range is 15 to 40 gal/1,000 gal (15 to 40 L/m³). The other additives in the system include a cross-linker, AGA-XL-1; pH buffer, AGA-Buffer-1; iron control agent, ICA-720

Cross-linkers and Stabilizers

AGA-Buffer 1 - Low-pH solution of a proprietary organic buffer, used in the AGA-400ME cross-linked acid system, to “lock” the pH at the proper range for complete cross-link. Usually used at 1 to 2 gal/1,000 gal (1 to 2 L/m³) of gelled acid up to 300°F (149°C).

AGA-XL-1 - Low pH solution of a proprietary metal chloride cross-linker that reacts with the polymer in AGA-400ME to form longer polymer chains and increase the apparent viscosity of the gelled acid. System cross-links at pH 2.5 to 3.0 and breaks to initial viscosity as the pH continues to rise to 4.0 to 5.0. Normal concentration is 4 to 5 gal/1,000 gal (4 to 5 L/m³) of gelled acid up to 300°F (149°C).

AGA-XL-3 - Low pH solution of a proprietary metal chloride (non-iron) cross-linker that reacts with the polymer in AGA-400ME as the pH increases to increase the apparent viscosity and divert the live acid. Normal concentration is 4 to 5 gal/1,000 gal (4 to 5 L/m³) of gelled acid up to 300°F (149°C).

ICA-720 - Organic acid sodium salt that functions as an iron reducing agent and oxygen scavenger. It also provides pH stabilization in AGA-400ME cross-linked acid system. Normal concentration is 4 to 10 pounds/1,000 gal (0.48 to 1.2 kg/m³) up to 300°F (149°C).