Materials Selection and Corrosion
Management in Oil Field Environments
Tuesday, February 7, 2017
Kingwood Country Club, Kingwood, TX
7:00AM-8:00 AM Breakfast and Check-in
8:00 AM- 8:45 AM Keynote: Corrosion – It’s About Time
Bruce Craig, PhD, PE, Stress Engineering Services
The science and practice of corrosion engineering has been based entirely on measurement of corrosion rate and that of corrosion science on corrosion rate prediction. We measure corrosion rate and we predict it using values like mpy and mm/y which denote uniform loss and likewise crack growth rates for environmental cracking. We then take such numbers to design equipment or predict remaining life but is this adequate? Is it correct? In actual fact what we mean is how long will it last? It’s really about time not rate and most often we don’t have a good answer. This lecture will present examples from the oil and gas industry that underline our misapplications of corrosion rates and environmental cracking and provide insight into better methods and concepts for defining design and remaining life of equipment.
8:45 AM-9:15 AM Stress Corrosion Cracking forecasting of time to failure based on pit growth kinetics
Raymundo Case, Texas A and M University
To assess the susceptibility of series 300 stainless steels to stress corrosion cracking (SCC) under both sour and non-sour service conditions a stochastical model is developed. The model is based in the hypothesis that the critical conditions for crack initiation and propagation are satisfied by the presence of metastable pit regime.
The underlying criteria for the model developed is that the transition from meta stable pit to crack follows using the slip dissolution model, in which the crack growth rate is controlled by the crack tip strain rate produced by the remote applied stress and can be described using the Cogleton’s correlation1-2 considering the Tsujikawa 3 criteria as a boundary condition.
The results of the analysis suggest that metastable pits should show a minimum frequency of pitting events in order to be able to induce SCC, this critical pit frequency is defined as:
, where: (1)
Where τ0 is the base meta stable pit propagation time ω0=1/τ0 and i0 the base pit current (with no stress applied), σ is the applied external stress, is the density, z is the charge transfer number, F is the Faraday constant and M is molecular weight for the alloy, ), α=0.5 and β=5 are material related parameters, whose particular values for stainless steel are obtained from the literature4, E is Young’s modulus, which is equal to 200 Gpa, y is the material’s yield strength, =0.33 is the Poisson ratio and εf is the fracture strain for the oxide passive layer, which is taken to be εf=8×10-4 for stainless steel1.
Thus the likelihood meta stable pit propagating into cracks is controlled by the pit propagation time (τ0) which is considered as a distributed variable, that based on experimental evidence5-6, it is assumed it follows a Poisson type of probability distribution function described as:
, where (2)
The model determines the probability of cracking Pcracking by evaluating using the Tsujikawa border condition in conjunction with crack propagation algorithm1 . The forecasting for the most likely time to failure is assessed from the elapsed time to achieve sustained crack growth using the hazard function derived from the pit survival probability distribution function, shown in Eq. (2).
To validate the model, actual field cases of stress corrosion cracking were simulated experimentally. Using weak potentiostatical polarization methods the meta stable pit transients where analyzed using a current deconvolution algorithim5 . The model forecasts for the time to failure were in agreement with typical field times to failure within 95% certainty in all the occasions evaluated.
The evaluation of the correlation between the experimentally obtained values of ω0 and the pitting event frequency calculated using the identified threshold stress for SCC were found to be in agreement with relationship indicated in Eq. (1)
9:15 AM -9:45 AM Hydrogen Embrittlement: A Duplex Stainless HISC Case History
Herman Amaya, Schlumberger
Hydrogen embrittlement is one of the main challenges to metallic materials in Oil & Gas subsea production. This type of embrittlement is known as Hydrogen Induced Stress Cracking (HISC) and is caused by the ingress of hydrogen produced by the cathodic protection system. For failure or embrittlement, the material must either have a susceptible microstructure or design stresses that act to trap the hydrogen.
This presentation will highlight some of the effects of HISC thru the exposition of a representative failure analysis case history of a duplex stainless steel stab plate that regulates hydraulic fluids in subsea control systems. This particular failure was complex in nature and is an example of the challenges of how interrelated factors can combine to create failures, which are difficult to analyze.
9:45-10:15 AM Analyzing SCC through EIS
J.I. Barraza Fiero, Texas A and M University
Engineering structures and components are designed according to accepted industry standards, and recommendations, however, stress corrosion cracking (SCC) may lead to nucleation and catastrophic propagation of cracks due to the synergy between susceptible materials, tensile stresses, and a corrosive environment. SCC occurs well below the design stress and is the most insidious form of corrosion because its mechanisms are unclear and its occurrence unpredictable. In general, SCC susceptibility is analyzed by simply characterizing mechanical failure of a material in a corrosive environment, while the emerging electrochemical characteristics are ignored. Here we characterize the electrochemical behavior via Electrochemical Impedance Spectroscopy (EIS) and Electrochemical Frequency Modulation (EFM), of a material that is subjected to chemo-mechanical loading. These techniques provided unprecedented view of all the interfacial phenomena affecting SCC.
Break 10:15-10:30 AM
10:30-11:00 AM The Use of Reinforced Thermoplastic Pipe to Rehabilitate Pipelines to Restore Integrity and to Eliminate On-going Corrosion Concerns
James Wright, Specialty RTP
Many onshore and offshore pipelines exhibit severe corrosion creating pipeline integrity issues resulting in the complete replacement or abandonment of the line. With the low pricing for oil and gas, abandonment is currently the more frequent solution. By installing reinforced thermoplastic piping inside of the existing pipeline, the line can have complete integrity restored and no ongoing corrosion inhibitor costs, for a fraction of the cost of traditional replacement options. The presentation will focus on the process of rehabilitation from sizing of the pipe for “today’s” production through installation and will emphasize the proper testing criteria to determine what are the correct polymers and reinforcement for the application. This would include chemical compatibility, permeation, static and cyclic strength, and the impact of temperature. The presentation will also provide methodology for in service pipeline integrity management. The presentation will use an offshore rehabilitation of two pipelines in the Gulf of Mexico flowing hydrocarbons, brine and H2S to highlight the process.
11:00-11:30 AM Full Scale Testing of Composite Pipeline Repairs for Use in Advanced Applications
Colton Sheets, Stress Engineering Services
Over the past two decades, a significant amount of research has been conducted on the use of composite materials for the repair and reinforcement of pipelines. This has led to vast improvements in the quality of composite systems used for pipeline repair and has increased the range of applications for which they are viable solutions (including corrosion and mechanical damage). Although this research has led to substantial advancements in technology, questions have remained regarding the effectiveness of composite repair systems for new and complex applications. A Joint Industry Program (JIP) was recently undertaken by Stress Engineering Services Inc. and several composite repair manufacturers to investigate the use of composites in many of these applications. As a part of the JIP, proof-of-concept testing with both fiberglass (e-glass) and carbon fiber based repair systems acting as pipeline crack arrestors was conducted, as well as testing to reinforce wrinkle bends and crack-like defects. It was shown that composites have significant potential in these areas and outperformed samples with no composite reinforcement. Continuing to build upon the foundation of this testing could lead to composite repair of these pipeline anomalies being as widely accepted as corrosion is today.
This presentation will briefly touch on the advancement of composite pipeline repairs over the last two decades including their development into industry standards such as ASME PCC-2 and ISO 24817. Additionally, the full-scale testing and results of these recent JIP initiatives will be presented. Finally, the presentation will discuss areas of future investigation and applications for composite pipeline repairs.
11:30 AM -12:00 PM Identifying surface breaking cracks and corrosion under insulation and overwrap repair using microwave NDE
Donald McNichol, Evisive
Microwave NDE inspection is being deployed more and more frequently to ascertain the volumetric integrity of non metallic and composite materials and their bond integrity to a metallic substrate. The high frequencies employed by the microwave technique overcomes the difficulties faced when trying to inspect these materials, or through the material to the substrate, using conventional techniques.
The patented technique has been, or is in process of being recognized, by ASNT, ASME, ASTM, EPRI, ISO, NATA and other regulatory or approval bodies, worldwide.
While performing field inspection work, it was noted in the composite/substrate interface detail that corrosion especially had a characteristic “signature” that was identifiably different from a simple disbond. This lead to investigation of the suitability of the technique for the detection of CUI and thence to surface breaking cracks.
This presentation gives an overview of how microwave inspection works, provides an update on progress to identify and characterize surface breaking cracks under insulation/composite reinforcement and has a number of illustrations of identifying and generally sizing CUI in real world application.
Lunch 12:00-1:00 PM
1:00-1:45 PM Keynote: Turbulent flow, How it Relates to Corrosion and Why that is Important
K. Daniel Efird, PE, Stress Engineering Services
Corrosion is a surface phenomenon, and as such, what goes on at the metal surface has a profound effect on corrosion. Many detailed aspects of fluid dynamics directly relate to and define the interactions of a fluid with the metal surface that are important to corrosion. When a fluid flows over a solid surface, the flow is characterized as either laminar or turbulent. In most situations where the effect of fluid flow on corrosion is important the flow is turbulent; so the physical structure of turbulent flow is a primary consideration. This lecture will detail the fluid dynamics characteristics of turbulent flow as they relate to micro and macro corrosion processes.
1:45-2:15 PM The Seven Deadly Sins of Corrosion Prevention
Michael Pendley, Villares Metals
Mistakes made in corrosion prevention can have devastating consequences. In a humorous but memorable fashion, the author examines the seven most common mistakes made in corrosion prevention including:
- Unnatural relations – Galvanic corrosion resulting from placing dissimilar metals in contact.
- Preoccupation – Concentrating on general corrosion and failing to consider other modes of corrosion such as pitting, SCC, etc.
- Laxity – Failure to observe changes in the environment and react accordingly.
- Negligence- Not accounting for trace chemicals, water, dilute aqueous solutions, alklaines, or other process variables.
- And more!
The author will discuss how to avoid these mistakes and how to effectively manage a corrosion prevention program. The format will be similar to last year’s presentation by the same author “The Seven Deadly Sins of Failure Analysis.”
2:15-2:45 PM DNA Speciation and Microbiologically Influenced Corrosion (MIC) in Produced Water Systems
Amilcar Oberto, BP GoM
Microbiologically influenced corrosion (MIC) is corrosion affected by the presence or activity of microorganism in corroding material. Many materials including most metals and some non-metals can be degraded by bacteria metabolism by-products altering rates and types of electrochemical reactions in a corrosion cell. Microbial corrosion can also apply to plastic and concrete, and many other materials. Two examples are Nylon eating bacteria and Plastic-eating bacteria.
Bacteria can also be classified based on oxygen requirement ( Aerobic, Anaerobic and Facultative), aerobic bacteria like Thiobacillus that commonly cause biogenic sulfide corrosion or anaerobic microorganisms like Sulfate Reducing Bacteria (SRB) produce hydrogen sulphide. These bacterial can result in a corrosive environment detrimental to carbon steel piping, and even corrosion resistant alloys. Failure to control and mitigate growth of these types of bacterial can result in accelerated localized corrosion.
A case study involving localized corrosion on an Offshore production platform due to MIC will be presented. The MIC occurred on a carbon steel piping associated with a separation vessel. DNA speciation, as well as standard metallurgical forensic tools were used to determine which bacteria species were active in different produced water chemistries. These findings lead us to understand the bacteria adaptability in favourable and adverse environments, and better mitigate the MIC in this system.
2:45-3:15 PM Material Selection Aspects for Oil and Gas equipment
Rashmi Bhavsar, Schlumberger
With restriction on OD and ID for downhole tools it becomes challenging to select materials that are compatible to downhole tubing. Various consideration will be discussed for low alloy steel, stainless steels and nickel based alloys. The mission profile for tools used for drilling, completion and surface equipment are different and long term reliability for these tools require proper material selection, especially for HPHT applications. Various corrosion testing techniques used for evaluating these alloys are being discussed. The presentation will also discuss aspects of industry standards such as NACE and API in material selection of these tools.
Break 3:15-3:30 PM
3:30-4:00 PM Minimizing the Risk of Casing Failures in Multi-Frac Horizontal Shale Wells Based on Historical Lessons Learned
Mario Guerra, Viking Engineering
Hydraulic fracturing induces high stresses in tubular components used in the construction of multi-frac horizontal shale wells. Ever since this process was adopted by the oil and gas industry to produce from tight shale formations there have been numerous very expensive failures that occur during these hydraulic fracturing operations. Many of these failures have been attributed to environmentally assisted cracking (EAC) of high strength API 5CT steel tubulars such as grade P110 casing and couplings. Some factors that aggravated these casing failures when exposed to high cyclic frac loads and corrosive environments was the lack of proper manufacturing processes, poor quality assurance and inspection plans, and the use of standard API connections with inherently high make-up stresses.
Over the years the industry has learned from these failures and some operators have adopted lessons learned to well designs in order to minimize the risk of future failures. However, adopting these learnings into well designs can substantially increase the cost of completing these wells and operators often struggle between cost and optimal well design. Some of the main well design modifications include the use of lower make-up stress connections, specifying lower yield strength materials, including a well-defined pipe purchasing process with a detailed pipe/manufacturing process specification and an ITP and QA plan (inspection and testing plan and quality assurance plan).
This presentation will illustrate several failure analysis case histories related to EAC and corrosion fatigue of standard API and modified buttress connections. The operational state of stress on some of these connections will also be discussed. Additionally, some recommended best practices related to connection selection, enhanced API 5CT material specification requirements and quality assurance as it relates to OCTG manufacturing will be discussed as well.
4:00-4:30 PM Processing Aluminum 6061 by Equal Channel Angular Extrusion (ECAE) for the oilfield
Ramatou Ly, Texas A and M University
Aluminum 6061 is used in Oilfield structures (offshore platform tubes, equipment) and tools (drill pipes) where high strength and good corrosion resistance are required. Equal Channel Angular Extrusion (ECAE) is a severe plastic deformation process by which high strength nanostructured aluminum 6061 is formed. Our research explores the potential use of high strength extruded aluminum 6061 in replacement of common 6061-T6 in the Oilfield. We found that after room temperature ECAE (3 passes) followed by ageing at 100C, the microstructure, the texture and the mechanical properties of the extruded material differ. Indeed there is a significant grain refinement and a redistribution of the intermetallic particles AlFeSi and the hardening precipitates Mg2Si in the aluminum matrix. Our research shows by electrochemical testing (potentiodynamic and potentiostatic polarization) in 1M NaCl that room temperature ECAE also changes the pitting corrosion resistance of aluminum 6061. The attack is characterized by formation of pits (less deep than those in commercial 6061-T6 Al) with a selective dissolution of the grain along the textured microstructure. The standardized test ISO 11846 (Method B) used to assess the intergranular corrosion (IGC) susceptibility of heat treatable aluminum alloys also demonstrates that ECAE makes aluminum 6061 susceptible to IGC. The IGC follow the textured microstructure as well. By Electron Backscatter Diffraction (EBSD) and microscopic characterizations, we found that the grain boundary characteristics after ECAE are preferential sites for precipitation during ageing, making extruded 6061-Al stronger than commercial 6061-T6 but susceptible to IGC. With a material-by-design approach for corrosion resistance, we investigated the optimal ageing time that gives the optimal strength/corrosion resistance combination for extruded 6061 Al.
4:30-5:00 PM The Potential Impact of Non-essential Variables in GTAW-Hotwire Overlays
Nathan Sumrall, Superior Cladding
Welding is considered both a science and an art form. Much of the art form is tribal knowledge, or welding know-how that is rarely conveyed in welding procedures. Depending on joint geometries and positions, sometimes this knowledge is vital to produce satisfactory welds, even though all essential and supplementary-essential variables were maintained per relevant code. One of the most prevalent joints plagued with this phenomenon is the overlaid ring groove, utilizing GTAW-Hotwire. Therefore, a study was conducted to evaluate the potential impact of four non-essential variables in GTAW-Hotwire overlays.