Carbonate Acidizing: A New Insight into Wormhole Propagation under Low Flow Rates

Area of Science:

• Geochemistry
• Petroleum Engineering
• Geological CO2 Storage

Background:

• Wormholes, formed by acid dissolution of carbonate rock, are vital for fluid flow in petroleum engineering and CO2 storage.
• Wormhole formation at low flow rates is under-explored, despite its occurrence in field operations.
• Existing models inaccurately predict wormhole behavior at low flow rates with concentrated acids.

Purpose of the Study:

• Investigate wormhole formation and morphology at low flow rates.
• Determine the pore volume to breakthrough (PVBt) under these conditions.
• Address the limitations of current models in predicting wormhole behavior.

Main Methods:

• Conducted acidizing experiments at low flow rates.
• Employed partial acidizing due to minimal pressure drop.
• Utilized micro-CT imaging to analyze wormhole morphology and estimate PVBt.

Main Results:

• Traditional models overestimate PVBt at low flow rates; breakthrough occurs earlier than predicted.
• A trend of PVBt stabilization was observed at lower flow rates.
• This stabilization occurs at a stoichiometrically derived limit, contradicting indefinite increase predictions.

Conclusions:

• Current models require revision to accurately predict wormhole breakthrough at low flow rates.
• Findings enhance understanding of reactive flow dynamics in carbonate systems.
• The study provides crucial data for optimizing acidizing treatments and CO2 storage.