Internal Corrosion Prevention of Sea Lines for South Pars Phase 2&3

For South Pars Phase 2&3 corrosion prevention has a very high priority because ofthe wet full stream scheme to be implemented. South Pars reservoir fluids contain, in volume 0.5% H2S and 1.8% CO2 which when combined with condensed water are known to be corrosive. This Paper is a study on different methods fur intemal corrosion mitigation ofsea lines. With the implementation ofthe wet full stream scheme, internal corrosion control ofthe sea line is normally by pH stabilisation, using a mixture of glycol (used for hydrate inhibition) andMDEA. The back-up solution fur hydrate inhibition and corrosion inhibitor when the MEG system is not available consists ofthe injection offshore ofLow Dosage Hydrate Inhibitor (LDHI) and Corrosion Inhibitor (CI). The role ofMDEA is to capture Wions. thereby increasing the bicarbonate content ofthe medium and raising the pH. By raising pH corrosive power offluid is reduced. The advantages is that the pH stabilizer is recalculated with the MEG and since in a steady state regime there is no addition ofa consumable. it's is more cost effective. Presence of calcium is due to reservoir acid-stimulation effect wet scheme by CaC03 precipitation and enriched MEG loop with salt. To over come this problem acid cleaning of sea lines has been done but with no satisfactory result and finally a MEG reclaiming unit was installed to remove the calcium and reduced the chlorine content in MEG loop. Corrosion risk in South Pars fluid was known as: 1. C02 & H2S corrosion which contabts: )0 Sulfide stress corrosion cracking )0 Hydrogen induced cracking )0 Acid corrosion by C02 To overcome any risk ofH2S embrittlement, all carbon steel in contact with sam fluids are complied with NACE MR0175. 2. Top ofUne corrosion (TOL) TOL corrosion occurs in pipelines transporting wet acid gas at temperature much higher than ambient temperature. It occurs at the top ofpipe. where water condenses in contact with a cold pipe wall. TOL corrosion is provoked by massive water condensation, which is controlled below risk limit by: )0 Use ofpolyurethane heat insulation on doglegs )0 Use of6mm corrosion coating )0 Concrete weight coating on pipelines.3. Erosion corrosion It can be happen due to pure fluid velocity and abrasion risk due to solid particle production.

Keywords:

Corrosion , pH stabilizer , MEG (monoethyleneglaycol) , MDEA (methyldiethanolamin) , CI (corrosion inhibitor) , Low Dosage Hydrate Inhibitor (LDHI)