Acidizing is a well stimulation technique in which acid is injected into a wellbore to dissolve formation minerals, remove damage, and enhance permeability, improving the flow of oil and gas.

Types of Acidizing Processes

1. Matrix Acidizing:

Acid is injected at a pressure below the fracture pressure to dissolve formation damage (e.g., drilling mud, scale, or clays).

Common acids used: Hydrochloric acid (HCl) for carbonate formations and Hydrofluoric acid (HF) for sandstone formations.

This method helps remove near-wellbore damage and improve production.

2. Fracture Acidizing (Acid Fracturing):

Acid is injected at a pressure above the fracture pressure, creating fractures in the formation.

The acid reacts with the rock (mainly carbonates) to etch the fracture faces, keeping them open for improved hydrocarbon flow.

This technique is mostly used in limestone and dolomite reservoirs.

Acidizing Process Steps

1. Pre-flush – Removes unwanted materials and ensures effective acid penetration.

2. Acid Injection – Acid is pumped into the well to react with the formation.

3. Post-flush – Pushes the spent acid away from the wellbore and prevents formation damage.

4. Flowback – The well is allowed to flow, removing dissolved materials and enhancing production.

Applications of Acidizing in the Petroleum Industry

Enhances oil and gas well productivity.

Removes formation damage caused by drilling, cementing, or completion fluids.

Improves permeability in low-permeability reservoirs.