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Fitness-for-Purpose Research of OCTG for Underground Gas Storage Applications in H2/CO2 Environments

In China, some underground gas storages (UGS) would be built to reserve the gaseous coal gas (CO, H2, CO2, H2O, etc.). Gaseous hydrogen induced hydrogen embrittlement (HE) and CO2 corrosion could possess great threat to the safety of OCTG in UGS. Fitness-for-purpose research of OCTG materials is urgently expected to screen out the suitable material for tubing application in UGS.
HE resistance and CO2 corrosion of OCTG materials (C110, 3Cr-90S, 13Cr-110 and 13Cr-110S) were investigated by slow strain rate testing and weight loss tests in UGS environments containing CO2 and H2. SSRT results show that both elongation ratio and reduction in area ratio of C110, 13Cr-110 and 13Cr-110S were more than 80%, except for 3Cr-90S. In addition, 3Cr-90S and 13Cr-110 tested in H2/CO2 environments possessed embrittled regions and secondary cracks, respectively. Weight loss test results show that C110 and 3Cr-90S exhibited high corrosion rates, which were classified as severe corrosion followed by qualitative categorization of corrosion rates for oil production systems in NACE RP0775. For stainless steels (13Cr-110 and 13Cr-110S), the corrosion rates were very low (low corrosion). Combined with the above results, 13Cr-110S could be the suitable OCTG material for UGS containing gaseous coal gas.

Product Number: 51320-14698-SG
Author: Yameng Qi, Zhonghua Zhang
Publication Date: 2020
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Impact of O2 Content on Corrosion Behavior of X65 Mild Steel in Gaseous, Liquid and Supercritical CO2 environments

Product Number: 51320-14433-SG
Author: Xiu Jiang, Dingrong Qu , Xiaoliang Song
Publication Date: 2020
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CO2 stream in CCS system usually contains impurities, such as water, O2, SO2, NO2, H2S, and other trace substances, which could pose a threat to internal corrosion and integrity of CO2 transportation pipelines. The general and localized corrosion behavior of API 5L X65 mild steel were evaluated using an autoclave both in water-saturated CO2 and CO2-saturated water environments in the presence of varying concentrations of O2. Experiments were performed at 25 °C and 35 °C, 8 MPa and 35 °C, 4 MPa to simulate the conditions encountered during dense, supercritical and gaseous CO2 transport. General corrosion rates were obtained by weight-loss method. The surface morphology of the coupons was examined by scanning electron microscopy (SEM). Results indicated that general corrosion rates at each O2 concentration in CO2-saturated water environment were much higher than those in water-saturated CO2 environment. The corrosion rates did not increase with increasing O2 concentration from 0 to 2000 ppm; instead the corrosion rate reached a maximum with 1000 ppm O2 at 25 °C, 8 MPa and 50 ppm O2 at 35 °C, 8 MPa in water-saturated CO2 environment and 50 ppm at 25 °C, 8 MPa and 100 ppm at 35 °C, 8 MPa in CO2-saturated water environment. However, the change trend of general corrosion rate with O2 content at 35 °C, 4 MPa was different from that in 25 °C and 35 °C, 8 MPa both in water-saturated CO2 and CO2-saturated water environments. Localized corrosion or general corrosion rate of over 0.1 mm/y was identified at each test condition both in a water-saturated CO2 and CO2-saturated water environments. When O2 was added, coupon surfaces were covered by a more porous corrosion product scale. A final series of tests conducted with the addition of 100 ppm and 2000 ppm O2 in CO2 environment with 60% relative humidity (RH) and 80% RH revealed that no localized corrosion was observed and the general corrosion rates were lower than 0.1 mm/y at 25 °C and 35 °C, 8