Abstract
Produced water injection systems are an integral part of many oilfields. Typically they transport produced water from a central pumping facility to a number of injection wells. The two main purposes of produced water systems are to maintain voidage in the reservoir and to maintain reservoir pressure.
The subject produced water system was installed in the early 1970’s and was originally internally coated with cement mortar lining (CML). This lining was applied to the main injection lines, laterals and risers. Failures began to occur after about 15 years of service and were due to cracking, spalling and degradation of the CML. These leaks resulted in environmental damage and excessive spill clean up and repair costs. An extensive program to rehabilitate the system was undertaken. The main pipeline sections were re-lined with high-density polyethylene (HDPE); spools and risers were internally coated with fusion bond epoxy (FBE).
After about ten years, failures began to occur in the refurbished pipe spools coated with FBE. Coating failures were attributed to inadequate surface preparation, inconsistent coating thickness and improperly installed flange gaskets led to other failures. Due to environmental impact and high clean up costs, and resulting management and regulatory pressure, it was decided to replace all buried spool pieces. Various alternatives such as corrosion resistant alloys, weld overlays and internal lining with HDPE were considered. Organic coatings were again chosen because of their overall past performance and cost.
A “holistic” approach was taken to the rehabilitation program. This included the fabrication of complex pieces to make them more “coater friendly”, process changes by the applicator to enable more consistent coating application and a more rigorous specification and inspection program.
