Scale squeeze
- Also known as
- squeeze treatment
A scale squeeze is a treatment in which scale inhibitor is pumped down a producing well and into the surrounding formation, where it is retained on the rock and then released slowly into the produced water, protecting the well and near-wellbore area from mineral scale for months.
What is a scale squeeze?
Mineral scale often starts forming in the formation near the wellbore and in the tubing, where pressure and temperature change. Adding inhibitor continuously at the surface cannot protect the formation itself. A squeeze places a supply of scale inhibitor out in the rock, where the problem begins.
How a squeeze works
A typical treatment has several stages:
- Preflush, to prepare the formation and sometimes improve inhibitor retention.
- Main treatment, a concentrated inhibitor solution pumped into the formation.
- Overflush, pushing the inhibitor deeper into the rock, away from the wellbore.
- Shut-in, a period with the well closed to let the inhibitor adsorb onto rock surfaces or precipitate in the pores.
When the well returns to production, the retained inhibitor gradually dissolves or desorbs into the produced water, keeping its concentration high enough to prevent scale.
Squeeze lifetime
A squeeze lasts until the inhibitor concentration in the produced water falls below the minimum inhibitor concentration needed to prevent scale. Lifetime depends on:
- How strongly the inhibitor is retained by the rock.
- Water production rate. More water depletes the inhibitor faster.
- Scaling severity and the inhibitor’s effectiveness.
Operators monitor inhibitor levels in produced water to decide when to re-squeeze.
Considerations
- Formation damage, such as emulsions or changes in wettability from treatment chemicals.
- Lost production during the shut-in.
- Compatibility of the inhibitor with formation water and rock.
Frequently asked questions
Continuous injection at the surface protects surface equipment and sometimes tubing, but it cannot reach the formation or the near-wellbore area where scale may first form.
It varies widely, from months to more than a year, depending on the inhibitor, rock and water production.
Sources
- squeeze; scale inhibitor, SLB Energy Glossary
- Scale inhibitor squeeze treatments, SPE PetroWiki, Society of Petroleum Engineers