ARTIFICIAL LIFT, NITROGEN CONCENTRATION AND METAL CORROSION
The use of nitrogen injection among artificial lift technologies is currently subject to discussion, particularly with regard to nitrogen concentration levels.
As is well known, liquid nitrogen produced via cryogenic processes provides a very high level of purity, minimizing residual oxygen content, which is identified as a potential corrosion driver in critical oil & gas sour service applications.
However, liquid nitrogen supply is not always readily available in remote areas and may be exposed to price fluctuations driven also by commercial dynamics linked to ancillary services (transport, equipment rental, etc.).
These factors open further considerations regarding the possibility of on-site nitrogen generation using technologies different from cryogenic separation.
In this context, the issue of residual oxygen concentration in the pressurized injected nitrogen stream becomes relevant again and must be addressed through dedicated engineering analysis. The acceptable threshold, meaning the oxygen level that minimizes the risk of corrosive effects on metals, is not uniquely defined, as it depends on several variables, including:
- Partial pressure of H₂S
- Temperature
- Presence of free water
- Salinity
- Hydrogen sulfide content
- Type of metallic materials
- Exposure time
The classification and evaluation of these parameters open the scenario to the use of alternative technologies to cryogenics for low-oxygen nitrogen production, ensuring suitability for the application.
Nitrogen purities between 99.9% and 99.99%, with continuous oxygen monitoring and achievable respectively through membrane and PSA technologies, can be considered acceptable across a wide range of sour service applications.
Only in super-critical cases does the recommended specification remain O₂ < 10 ppm in gaseous nitrogen, achievable through cryogenic production.
Sinergia S.p.A. can provide consulting services aimed at evaluating the above-mentioned factors and identifying the most appropriate technological solution to minimize corrosion risk.
Its modular on-site nitrogen generation systems, developed using membrane and PSA technologies, besides offering all advantages related to production autonomy under continuous operation in extreme environmental conditions, ensure the quality required to effectively minimize corrosive effects, preserving the integrity of the well and installed equipment.
