Justification of technologies selected to protect difficult production wells

The paper explores ESP shaft failures, occurring in difficult wells. It also presents protection technology for downhole pumping equipment to prevent failures.
Materials and methods
Review of well operation modes, chemical and metallographic study of ESPs with broken shafts.
Results
Broken shafts of ESPs operating in difficult wells have been effectively studied. It has been revealed that one of the causes ofbroken ESP shafts is related to deposition of scale and solids around ESP units, which leads to sticking and failing.
Сonclusions
The following recommendations have been developed to reduce such failures:
- injection of small amount of scale inhibitors into the bottomhole area with pre-slug of mutual solvent and oil wetting agent;
- sequential injection of scale inhibitor and acid compound and squeezing the composition into the formation, in order to increase inhibitor performance and to remove scaling from the surface of downhole equipment;
- adding scale inhibitors to well-killing fluids;
- use of acid compounds containing scale inhibitor for ESP flushing;
- preventive calculation of scale concentration potential based on production rate, water-cut, and gas/oil ratio.
Implementation of these scale-preventing recommendations and actions will significantly reduce the number of shaft failures in downhole pumping equipment and improve ESP efficiency.