Oil & Gas flowlines are paramount for safe and reliable production of hydrocarbons, ensuring their integrity is one of the key tasks for all operators. Petroleum Development of Oman (PDO) manages around 11,000 Km of flowlines and connects to production stations more than 400 wells across more than 50 fields every year. Applications for these flowlines vary from the traditional Oil & Gas transmission to other applications such as water injection, polymer flood and steam injection. All these diverse applications involve multiple operation environments ranging from benign fields with low CO2 < 0.5 mole% and minimum H2S to very aggressive environments with CO2 and H2S concentrations well above 10 mole%, combined with a wide range of salinities and water cuts, with chlorides concentrations ranging from 5,000 to 200,000 ppm and water cuts from almost nil to more than 95%. The challenges encountered in safe and economic development of these assets across such a wide range of conditions are numerous; therefore, the material selection and designed methods to manage flowlines integrity are complex with no single solution approach to address the myriad of different conditions. This paper present two cases of metallic and non-metallic materials installed in PDO flowlines showing their historical field performance and discusses the strategy adopted for the material selection of flowlines.  

Duplex Stainless steel (22Cr) also known as corrosion resistant alloy (CRA) has been extensively used in oil and gas industry for critical applications such as wet gas production flow lines and pipelines. A number of new sour Oil &amp; Gas projects with high salinity (exceeding 200000ppm NaCl) will be developed in the coming years in Petroleum Development Oman (PDO). So far DSS material is qualified upto 10mbar partial pressure of H2S (ppH2S) in 160000ppm chloride levels. The operating conditions of these new projects are outside these current material operating limits of 22Cr DSS. The objective of the study was to enable wider use of 22 Cr DSS grades (lower cost CRA) in highly sour projects in high chloride environments instead of selecting more expensive CRA materials like 25 Cr super duplex alloy 825 or alloy 625. Pitting crevice and stress corrosion cracking tests were conducted on both parent metal and representative welds in high ppH2S and in high chloride environments. The results established the new threshold sour service limits of DSS material which resulted in significant cost savings for various projects. The paper will present the test results and discuss the opportunities for DSS application.

Quality assurance and procurement & construction challenges associated with DSS materials and operational best practices to ensure integrity and meet intended design life cycle of DSS components.