A combined laboratory and field study was conducted to evaluate the susceptibility of Endicott Kekiktuk formation to acid stimulation treatments and to optimize treatment performance.

Endicott crude oil causes severe sludging and emulsion problems when mixed with concentrated acids. Iron concentration aggravates emulsion and sludging problems, especially ferric ion. However, the associated permeability damage can be effectively reduced with the addition of proper antisludge/demulsification chemicals in acids and by reduction in acid strength and complexation or reduction of ferric ion. Laboratory geological analyses, acid solubility tests, and acid core flow tests further indicated that half strength mud acid gives similar stimulation performance than full strength mud acid with less weakening of rock strength and fewer fines migration problems following acid treatments.

Actual field acidizing treatments conducted at Endicott Field using 80 gal/ft half strength mud acid with proper additives have shown good productivity increases with better balanced production profiles. No evidence of fines migration has been observed in the post treatment production well testing.

Selection of the acid treatment compatible with reservoir fluids and lithology will minimize formation damage and lead to increases in production.

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