Chemical injection policy for internal corrosion prevention of South Pars sea-pipeline: A case study

Ten phases of south pars in five independent gas processing plants (GPP) are located on the Iranian coast of the Persian Gulf. In each phase, raw gas is taken from the on-veil platform and transferred in a multi-phase form through 32-inch submarine pipeline at a distance of 110 km from shore. In GPP No 1 or Phase 1, gas is daily extracted from two on-veil platforms and the gas-water separation as dehydration policy is performed on the platform. In order to preserve the pipes and avoid hydrate and corrosion, Mono Ethylene Glycol (MEG) accompanied by corrosion inhibitor as corrosion inhibition policy (in GPP No. 3, 5) or MDEA as pH stabilization policy (in GPP No. 2, 4) is transferred to the platforms via two 4.5-inch pipelines and injected into the submarine pipeline. Sludge and scale deposits formed within the pipeline as byproducts of the corrosion inhibition and PH stabilization techniques, respectively. The derivation of the field partitioning of MEG, ferrous ion, calcium, chloride, pH and weight loss coupons provide useful information concerning the sealine corrosion and scale accumulation. Heat transfer analyses of submarine pipeline show that the water condensation rate and top of the line corrosion can occur with the loose concrete and any pipe coating defects. The results show that the pH stabilization with the separation of brine water which is located in offshore has better performance than corrosion inhibition policy.