Barium Sulphate Scaling

Barium Sulphate Scaling

Why can chemical flooding increase the risk of BaSO₄ (Barium Sulphate) scale compared with conventional water flooding?
Because changing the injected fluid changes the chemical interactions, mobility, IFT, adsorption, and ion transport within the reservoir.

How Barium Sulphate Forms

Scale forms when:
Ba²⁺ + SO₄²⁻ → BaSO₄(s)
During chemical EOR, injected fluids can alter the movement and mixing of formation brine and injected water, increasing the potential for precipitation.

What Controls Scale Severity?

Important factors include:
• Mobility ratio
• Oil-water IFT
• Chemical adsorption
• Polymer inaccessible pore volume (IPV)
• Brine composition and ion transport
These factors influence where Ba²⁺ and SO₄²⁻ meet and where precipitation occurs.

Where Does Scale Go?

Barium and sulphate can be co-produced and precipitate in different parts of the system.
Scale may deposit:
• Inside the reservoir
• Near the producer
• In the wellbore
Grid refinement in reservoir simulation can also significantly affect predicted precipitation and deposition patterns.

Scale Inhibition

Scale inhibitor squeeze treatments are used to control BaSO₄ deposition.
A key design parameter is the:
Minimum Inhibitor Concentration (MIC)
The treatment must maintain inhibitor concentration above the MIC after breakthrough.
Treatment frequency and inhibitor return profiles are therefore critical for maintaining production.

EOR Performance + Economics

Different flooding strategies can produce very different recovery and economic outcomes.
The study compares:
• Surfactant Type III
• Surfactant-Polymer (SP) Type II-ME
Chemical costs considered:
Surfactant = $2.75/lb
Polymer = $1/lb
The economic analysis evaluates NPV at $25, $50, and $75/bbl oil prices.

Summary

Chemical EOR is not only about increasing recovery.
It also changes:
Fluid Properties → Ion Transport → Precipitation → Scale Risk → Production → Economics
Understanding BaSO₄ scaling and designing effective inhibitor treatments can be critical to achieving the expected value from chemical flooding.

Reference

https://onepetro.org/SPEOCC/proceedings-abstract/19OCC/19OCC/D021S008R003/218720