Abstract
Polymer liners, especially polyethylene liners are commonly used in carbon steel lined pipe for water injection service. Historical seawater/produced water applications have a typical design temperature of 60°C or less and are usually operated from 30 to 40°C. Handling of oilfield water, in the operating temperature range between 60°C to 90°C becomes a challenge. Very limited applications have been reported at elevated temperature and details of specific operational conditions are not known to validate safe and reliable performance at high temperatures.
This paper explores the current state of the art for the increased temperature limits of high density polyethylene liners and identifies the most credible failure modes to be mitigated. A testing campaign was conducted on commercial grade high density polyethylene to de-risk the application of the liners to operating temperatures up to 80°C. A series of small scale testing were performed to understand the material properties under different conditions (temperature, oil saturation, oil/water concentration etc.).
Performance properties of typical high-density polyethylene were benchmarked against a proposed raised temperature polyethylene grade. The material properties were used as an input to a finite element analysis tool to evaluate the strains experienced by the liner at various locations such as a weld bead, flange connection and vent location. The testing and analysis provides increased confidence to expand the operational envelope of polyethylene liners to higher temperatures in produced water service. A condition monitoring plan has been developed to record the liner condition during operation.
