Abstract

The objective of most acidizing treatments in older wells is to eliminate wellbore damage caused by fines migration during the producing life of those wells. Acid is injected into a pay zone where a dissolving action enlarges existing voids and thereby increases the productivity of the zone or dissolves the damage near wellbore. The basic methods of acid stimulation are dependent on various techniques and materials.

Basically, acidizing treatments are characterized by injection rates and pressure. Injection rates below fracture pressure are classified as matrix acidizing, while those above fracture pressure are termed as fracture acidizing. Two-stage acidizing (or microacidizing) has been conducted in several wells in the Pendopo Old Area of South Sumatra. Two of these treated wells were producing naturally after the stimulation treatment, and the other wells were producing well above pretreatment rates.

The two-stage acidizing procedure is used for removing and delaying formation damage. Field evaluation of this procedure indicates that sufficient amounts of acid injected into the formation in the first stage significantly improves the stimulation response of the treatment. Properly selected chemicals or additives (based on a formation damage diagnosis) in the second-stage treatment aid in delays and reducing future formation damage.