API(1) 5CT Grade L80, type 1 oil country tubular goods (OCTG), e.g. production tubing & casing, in non-sour, natural gas wells in East Texas failed after relatively short exposure times upon being placed in service. Laboratory failure analysis of failed tubing and casing from several wells determined that the L80 tubing failed from environmental cracking initiating in the body on the annular (O.D.) side of the tubing/casing. The laboratory testing also showed that the failed tubing and casing met compositional and mechanical requirements of API 5CT L80 and NACE MR0175/ISO15156 requirements for sour service. This paper describes in detail three case histories of L80 downhole environmental cracking failures and summarizes two cases of N80 casing failures, the production environments the tubing/casing were exposed to and the influence of material heat treatment and well treatment chemicals and production/stimulation environments on the susceptibility to environmental cracking.
Lyublinski, Efim (Northern Technologies International Corporation) | Vaks, Yefim (Northern Technologies International Corporation) | Natale, Terry (Northern Technologies International Corporation) | Singh, Ronnie (ZERUST) | Tanabe, Edwardo (ZERUST) | Schultz, Marcelo (Petrobras)
Corrosion protection of large equipment’s internal surfaces (distillation towers, pipelines, tanks, boilers, heat exchangers, etc.) during storage, transportation/shipping and long term mothballing (up to 10 years) is a worldwide problem1-18. In many cases, well-known technology for replacement of the environment with nitrogen gases cannot be applied and is not always efficient enough. In addition to their limited protection ability, this approach can be cumbersome, complicated, labor intensive, very expensive and create safety issues. This paper describes a system that reduces the environment corrosiveness by decreasing the relative humidity (RH) to a level that allows achieving corrosion protection of different metals in any sealed enclosure. In addition, this new system delivers the volatile corrosion inhibitors (VCI) into enclosures that increases the corrosion protection efficiency and decreases the corrosion if the enclosures have some leakage. This system quickly creates the required RH and concentration of VCI. The equipment and can be easily moved for applying corrosion protection in different locations. This paper will present a mobile system that can be used for many kinds of equipment in different facilities. Application experience of a system that was utilized to provide corrosion protection of mothballed equipment in a refinery will be presented.
Murugan, Pulikesi (Weatherford Edmonton Research and Development Centre) | Duane, Treybig (Weatherford Edmonton Research and Development Centre) | Worsley, Kenneth (Weatherford Edmonton Research and Development Centre) | Smith, Clayton (Weatherford Edmonton Research and Development Centre)
Crude oil and natural gas with condensate production can contain varying ratios of acid gases which are extremely corrosive to metal surfaces. Because of its corrosiveness, sour production may require specialized production equipment such as Inconel metallurgy to mitigate the severe environment; hence the control of sour corrosion is a major concern in the oil and gas industry today. Currently, most sour corrosion inhibitors are based on alkyl pyridine (AP) chemistries and typical treatment rates for critical sour environments range from 200-1000 ppm based on brine production.
The objective of this work is to develop an alternative sour corrosion inhibitor to replace alkyl pyridine formulations. This paper investigates the effect of different operating parameters such as temperature (300C, 500C, 800C and 1200C), salinity (low, medium and high), H2S composition (10%, 20%, 35%), CO2 composition (4% and 10%) and brine to oil ratio (90:10, 70:30, and 50:50) on the performance of the new inhibitor chemistry.
In this paper a non-alkyl pyridine corrosion inhibitor (NAP CI) formulation was developed to prevent corrosion in critical sour systems. In the lab testing conditions used the unmitigated corrosion rates ranged from 30-50 mpy with varying degrees of pitting. The non-alkyl pyridine chemistry treatment ranges of 200-300 ppm demonstrate an excellent reduction in both the synthetic brine and gas phase corrosion rates. This was supported by corrosion rates of less than 3 mpy and no observed pits.
Conventional(1) 13%-Chrome Martensitic Stainless Steels (MSS) have been selectively used as Oil Country Tubular Goods (OCTG) in sour environments as unexpected failures occurred by cracking in some cases. Accordingly, restricted sour service environment has been recommended for use of 13%Cr MSS tubulars in oil & gas production by the standard i.e., ANSI/NACE MR0175/ISO 15156(2).
However, variables & their limits responsible for cracking of 13%Cr MSS tubulars, are probably not exhaustively defined yet; sometimes operating companies devise and follow their own qualification programs to select 13%Cr MSS for application in sour environments.
Likewise, a material qualification program was taken up for API 5CT L80 13Cr(3) steel for the application of downhole tubulars in several sour production environments. Along with other observations, unexpected failures of the material were observed in testing within the specified limits currently mentioned in the standard.
This technical paper details the test program and evaluation of the test results to define a further reliable domain for use of L80 13Cr MSS in sour service as downhole tubulars, including need to revisit limits indicated in the standard.
Clark, Jennifer E. (The Lubrizol Corporation) | Minch, Britt (The Lubrizol Corporation) | Faber, Ben (The Lubrizol Corporation) | Boothe, David (The Lubrizol Corporation) | Hadler, Amelia (The Lubrizol Corporation) | Koenig, Miranda (The Lubrizol Corporation) | Rodeheaver, Eric (The Lubrizol Corporation)
Traditional rust preventives utilize wax and oils to leave a thin, temporary coating on a metal surface. The waxes used in traditional rust preventives are petroleum waxes typically from Group I refineries. Ongoing research has started investigating alternative waxes such as natural waxes and synthetic waxes. Because these waxes have varying melt point and structures in comparison to petroleum waxes, a wax solubilizer is needed. This study will compare rust preventives made with natural waxes and synthetic waxes to the traditional petroleum wax rust preventives. This study will also examine the differences in performance of alternative wax rust preventives with and without wax solubilizers.
Liu, Yingkun (University of Science and Technology Beijing) | Zhang, Lei (University of Science and Technology Beijing) | Cui, Wei (Safetech Research Institute) | Li, Huixin (University of Science and Technology Beijing) | Lu, Minxu (University of Science and Technology Beijing)
The inhibition effect of a kind of imidazoline base inhibitor on the corrosion of carbon steel under various conditions of pre-corrosion was studied using autoclave. Scanning electron microscopy (SEM) was used to characterize the steel surface. The results indicate the influence of pre-corrosion status on the corrosion rate and the effectiveness of corrosion inhibitor. Different kinds of corrosion products on the steel surface will play an important role on and significantly affect the inhibition effect.
Jiang, Xiu (SINOPEC Qingdao Research Institute of Safety Engineering) | Qu, Dingrong (SINOPEC Qingdao Research Institute of Safety Engineering) | Song, Xiaoliang (SINOPEC Qingdao Research Institute of Safety Engineering) | Liu, Xiaohui (SINOPEC Qingdao Research Institute of Safety Engineering) | Zhang, Yanling (SINOPEC Qingdao Research Institute of Safety Engineering)
CO2 could be transported by pipelines in gaseous, liquid or supercritical phase according to the operating temperature and pressure. Safety concerns might arise from supercritical CO2 transportation pipeline, especially crossing the densely populated areas. Short-distance gaseous CO2 pipeline was designed and constructed for an energy company. Water content is critical to understand the corrosion mechanism of CO2 pipeline. Corrosion behavior of API 5L X65 mild steel exposed to CO2 stream with different relative humidities (RH), temperatures and pressures was investigated by weight-loss method to determine maximum allowable water content in CO2 pipeline. The surface morphology of the coupons was examined by scanning electron microscopy (SEM). The results showed that general corrosion rate was stable with increased RH before a separate water phase was observed, and significantly increased when free water was formed for all the test conditions. Localized corrosion or serious general corrosion was observed when the relative humidity was beyond 60%. The upper limit of water content for CO2 stream should be set at 60% RH for the safety concern of API 5L X65 pipeline on the basis of corrosion study.
Microbiologically influenced corrosion (MIC) is one of many potential corrosion threats faced by onshore and offshore pipeline operators. Experience has shown that effective management of the MIC threat is often more elusive and problematic for operators than the control of other internal corrosion threats. In this paper the application of corrosion management principles is shown to identify a clear path for managing MIC in for example crude oil transport, multiphase gathering and water injection pipeline systems. The basic steps of corrosion threat assessment, mitigation selection and application, and implementation of appropriate monitoring methods, are employed. This systematic corrosion management approach provides meaningful and measurable data that can drive key performance indicators (KPIs). Improved confidence in corrosion threat management contributes to overall pipeline integrity and asset reliability.
Carbon dioxide (CO2) corrosion is one of the most serious corrosion problems in oil and gas industry for many years. The corrosion scale formed during CO2 corrosion process plays an important role in the corrosion mechanism of pipeline steels. In this study, the formation mechanism of corrosion scale on X65 pipeline steel, as well as its protective characteristic to steel, were investigated in NaCl solution at 80 0C and 1 MPa. Immersion experiments were conducted with different time: 0.5h, 2h, 8h, 12h, 24h, 50h, 96h, 168h. The weight loss tests showed that before the immersion of 50h, the weight loss increased dramatically with the increasing immersion time, while after 50 h, the weight loss slightly increased with the increase of immersion time. The surface morphology of corrosion scale and EIS results indicated that, FeCO3 corrosion scale formed between 24 h and 50 h immersion, corresponding to the transition point of weight loss after which the increasing rate of weight loss was decreased significantly. The formation of FeCO3 corrosion scale decreased the corrosion rate of X65 steel significantly.
With the continued development of offshore production in ultra-deepwater (UDW), more and more wells are exposed to extremely high pressure and temperature (xHPHT) under anoxic condition. In order to better predict scale formation, scale solubility under these extreme conditions need to be accurate. Knowledge of the thermodynamic and kinetic properties of this mineral under xHPHT conditions is important for the solubility studies. Research to expand the amount of data and models for such minerals at these conditions will reduce offshore production risk and improve human safety in ultra-deepwater production.
A novel flow-through apparatus has been developed to perform scale solubility, dissolution and precipitation studies of various minerals under high pressure (up to 24,000 psig), high temperature (up to 250 0C), and high total dissolved solids (TDS, up to 360,000 mg/L). This research focused on the solubility of siderite under strictly anoxic (<<1 ppb O2) xHPHT conditions. This study increased our understanding of the formation of passive layers (Fe3O4 and FeCO3) and their phase transitions as temperature increases, as has been observed in corrosion research. In this work, effects of reaction conditions, including temperature and pressure have been investigated.