Flow Assurance in High-Pressure Water Injection Flowlines using GRE Composite Lined API 5CT Threaded and Coupled Tubing

Abstract

In a first ever case within Shell assets worldwide, Badr Petroleum Company (Bapetco) - a Shell Joint Venture Company in Egypt, has embarked on a project of replacing a 20 km Water Injection network, originally constructed with Welded API 5L carbon steel pipe, with fiberglass lined API 5CT Threaded and Coupled tubing. The original network is a conventional pipeline system of welded pipes transferring brine from 3 Water Source wells to 23 Water Injectors through the Egyptian Western Desert. The water is of a high salinity of 180,000 ppm saturated with dissolved oxygen up to 1,000 ppb before chemical treatment. After injecting oxygen scavenger the concentration of the dissolved oxygen is 100 ppb. As a result, Bapetco has been facing severe corrosion related failures in Water Injection flowlines. The 20 km surface pipeline network had to be totally replaced approximately once every two years. Many of the Water Source and Water Injection wells in this network were completed using GRE lined tubing for internal corrosion protection. However, corrosion by-products from the carbon steel flowline were a cause for concern given the risk of plugging the reservoir. Basic remedial solutions such as clamps, chemical inhibitions, patches etc. were carried out on the flowline. Nevertheless a more manageable approach was sought especially after reviewing the life cycle costs of maintaining the network and the impact of frequent drops in injection rates on the overall production from the field. Bapetco embarked on an ambitious plan to use API 5CT Threaded and Coupled Steel Tubing internally lined with fiberglass for corrosion protection to replace the bare Carbon Steel pipeline. Shell's confidence in GRE lining has been established over 20 years of using GRE lined tubing downhole in 11 countries. This endeavor also helps Bapetco utilize unused inventory of tubing instead of additional capex required for flowline replacement with API 5L pipes manufactured from more exotic steel. The integration of API 5CT specification threaded and coupled tubulars into Pipeline Engineering design, considering flow dynamics and make up compatibility with standard valves and fittings, is a huge challenge given the lack of applicable design codes, standards and Engineering common ground. Special components were engineered to provide a transition between GRE lined tubulars and plain end unlined fittings and flanges. Also, pressure testing, pigging and connection make-up procedures were reviewed and/or revised to accommodate the use of GRE lined API 5CT pipes in flowlines. This paper chronicles the history of the Water Flood project, the nature, reasons and consequences of the multiple corrosion failures and the failed corrosion mitigation strategies. Furthermore, the paper will shed light on the techno-commercial analysis and engineering that forms the basis for this mammoth effort.