This paper presents corrosion management of a wet sour gas carbon steel export pipeline using continuous and batch corrosion inhibitors with mono-ethylene-glycol (MEG) as the hydrate mitigation strategy operating in NACE MR 0175/ ISO 15156 region 3 (severe sour).1 The wet sour gas carbon steel export pipeline corrosion management via continuous corrosion inhibitor (CI) and batch inhibitors with closed loop MEG regeneration system is rare worldwide. This is especially challenging when the said pipeline is likely be the longest offshore wet sour gas, large diameter carbon steel pipeline, approximately 207 km × 812 mm in the world thus far.
Pipeline corrosion management and hydrate management aspects when being reviewed holistically, it could potentially provide significant cost savings yet safeguarding the overall technical integrity of the pipeline. The overall corrosion management leverages on company many years of involvements in JIP and own operating experience in sour service including the pipeline material specification, corrosion management, inspection, and maintenance philosophy. Reliable correlation between reservoir properties and uncertainties in severe sour service, flow assurance, chemical behaviors, operating experiences, etc. were considered to best represent the operating envelope for this wet sour gas carbon steel pipeline. This includes the comprehensive testing and selection of continuous CI and batch inhibitor, corrosion monitoring, operational pigging, maintenance, and inspection requirements throughout the pipeline field life.
Project A is being developed by the company with two fields about 220 km distance from Bintulu, Sarawak. The fields are classified as sour with estimated H2S concentration up to 5,000 ppm and 3.8 mol% CO2. The two fields are mainly Field A1 and Field A2 with approximately 20km apart. Field A1 will have two dry xmas trees, drilled from the Platform A while Field A2 will be developed with 2 subsea wells and supporting subsea infrastructures. The platform will be designed for 20 years field life with a gas throughput of about 800 MMscf/d and the platform will house subsea ancillaries, power, chemical injection, and pipeline pigs launching facilities. The wet sour gas will then be transported from the offshore platform through a 207 km × 812 mm NACE rated carbon steel (CS) export pipeline with 140 m water depth to an Onshore Gas Processing (OGP) plant in Bintulu.
