New Single-Phase Retarded Acid System Boosts Production after Acid Fracturing in Kazakhstan

TLDR

Conventional acid systems in high‑temperature, fast‑reactive carbonate reservoirs limit matrix acidizing and acid fracturing effectiveness, and while retarded acids are recommended, they typically dissolve less rock, create higher friction, and are more complex to mix. The study introduces a new single‑phase retarded acid designed to overcome these drawbacks. The acid treatments were applied to exploration wells in carbonate fields of the pre‑Caspian and Mangystau provinces in West Kazakhstan. The new acid produced a sustained increase in productivity index after acid fracturing and matrix acidizing under high‑pressure, high‑temperature conditions.

Abstract

Abstract The use of conventional acid systems in high-temperature, fast-reactive carbonate reservoirs limits the effectiveness of matrix acidizing and acid fracturing. Therefore, during acid stimulation in such conditions, acids with retarded reaction are usually recommended. Industry-employed retarded acid systems have several significant drawbacks—they either dissolve lower rock volume or have higher friction and are more complex to mix than the standard hydrochloric acid system. The introduction of a new single-phase retarded acid enabled minimizing these drawbacks. The sustained increase in productivity index (PI) after the acid fracturing and matrix acidizing treatments under high-pressure/high-temperature conditions was achieved. The treatments were performed on exploration wells drilled in carbonate oil fields of the pre-Caspian and Mangystau oil-bearing provinces of West Kazakhstan.