Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Developing a model to understand the growth mechanism of different forms of the sour corrosion product is essential in predicting corrosion rates and mitigating scale formation in sour environment. This paper presents a new approach wherein the nanocrystalline iron sulphide (mackinawite) scale formation is modeled by the nucleation and growth of the scale crystals. Ignoring any solid state reactions that could form iron sulphide in undersaturated solutions, the supersaturation level quantified the extent of nucleation followed by diffusion controlled crystal growth. The scale morphology in terms of the volumetric porosity and their influence on the predicted sour corrosion rates were studied under stagnant conditions.
- Europe > Norway > Norwegian Sea (0.24)
- North America > United States > Texas (0.18)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
ABSTRACT This paper presents a new approach to model the growth mechanism of the sweet corrosion product (i.e. iron carbonate scale) and to study the influence of the corrosion product morphology on the uniform corrosion rates. Corrosion rates were defined as the iron ion flux rate leaving the metal surface which is governed by the thickness and volumetric porosity of the corrosion product (scale). Nucleation and crystal growth were treated as the two committed steps in forming the scale. The population number and the critical size of the iron carbonate nuclei were determined using the classical nucleation theory. Supersaturation level was quantified by the effusion of iron ions from the metal surface and infusion of carbonate ions from the bulk solution. Crystal growth, followed by nucleation and termination of the supersaturation condition, was modeled using a moving boundary approach solving Fick’s diffusion equations in spherical coordinates. Under stagnant conditions, the formed scale layer thickness and the volumetric porosity were obtained based upon the crystal shape and size. Also, the time-dependent iron ion flux/corrosion rates were predicted. Further, the effects of operating parameters such as pressure and temperature on the competition between the nucleation rate and the growth rate of crystal nuclei were examined.
INTRODUCTION ABSTRACT: A mechanistic model was developed to predict uniform corrosion rates in sour liquid petroleum pipelines. The model incorporates the transient chemical reactions which occur in the bulk of the corrosive fluid, the transport of the active species to and away from the surface, and the electrochemical reactions occurring at the surface of the metal. In addition, the technical complications of coupling a scale growth model applicable to multiple scale types such as FeCO3 and FeS, with a corrosion simulation were discussed in detail. It was proposed to remedy these issues by separating the scale growth and corrosion modeling procedures. The results of examining scale formation can be stored in a correlated database to be imported later into the corrosion simulation using the approach presented in this paper. This method helped to incorporate the effect of FeS film growth on the variation of the corrosion rate. All the assumptions and simplifications of the model are discussed and shown to be appropriate for solving this problem. Several simulations were performed, and the predictions were compared with available experimental data in different operating conditions. In general, results agreed well with the corresponding experimental values tending to justify the approach presented. The worldwide consumption of oil and gas is increasing and, as a consequence, so is the number of sour production fields. Operating in these environments inflicts higher costs for the material, safety requirements, and due to the more frequent shutdowns. In these environments, scales form much faster and can quickly become the prominent rate limiting phenomenon. There is a huge potential for cutting down the cost of operation in sour environments via obtaining a better knowledge of the general/pitting corrosion and scale growth mechanisms. This has motivated Broadsword Corrosion Engineering(1) to develop a comprehensive and up-to-date model suitable for these environments.
- North America > Canada (0.28)
- North America > United States > Texas (0.17)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Simulation And Analysis of the Effect of Different Design Parameters On the General Corrosion In the Annular Space of Flexible Pipes
Fardisi, Sina (Broadsword Corrosion Engineering Ltd.) | Tajallipour, Nima (Broadsword Corrosion Engineering Ltd.) | Teevens, Patrick J. (Broadsword Corrosion Engineering Ltd.)
ABSTRACT: Flexible pipes are made of steel wires covered with a minimum of two polymer sheaths from inside (to protect the line from the bore flow) and outside (to protect the line from sea water). The space between the inner and outer polymer sheaths form an annular where corrosive species such as H2S, CO2, and H2O can penetrate, condense and accumulate. Corrosion in such conditions features some unique characteristics that are very different from conventional production lines. The amount of the electrolyte is very limited in these applications. This causes the electrolyte to become saturated with the corrosion products and disturbs the chemical reactions that ultimately cause corrosion. Broadsword Corrosion Engineering decided to develop a comprehensive and up-to-date model suitable for these applications. The model incorporates the effect of transport processes, the chemical reactions occurring in the electrolyte, and the electrochemical and precipitation reactions that occur at the surface of the metal. The model was validated using the client’s third-party laboratory testing and other experimental data. Several simulations were performed and the effects of pressure, temperature, and volume-to-surfacearea were investigated and discussed in details. INTRODUCTION Flexible pipe technology is an attractive alternative for offshore applications. “These pipes transport oil produced from deepwater subsea templates to the FPSO (Floating Production, Storage and Offloading) unit for processing and storage. Once sufficient oil is gathered, it will be shipped from the FPSO unit to the main land using a tanker. Corrosion in flexible pipes, which is the main focus of the current contribution, features some unique characteristics that are very different from conventional production lines.” As shown in Fig. 1, these pipes are composed of several steel layers covered by a minimum of two polymer layers that protect the internal metallic parts from the outside sea water and the bore flow.1
- North America > Canada (0.28)
- North America > United States > Texas (0.18)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Floating production systems (1.00)
A Mechanistic Model For Predicting Localized Pitting Corrosion In a Brine Water-CO2 System
Zhu, Zhenjin (MCIC Broadsword Corrosion Engineering, Ltd.) | Tajallipour, Nima (MCIC Broadsword Corrosion Engineering, Ltd.) | Teevens, Patrick J. (MCIC Broadsword Corrosion Engineering, Ltd.) | Xue, Huibin (Department of Mechanical and Manufacturing Engineering University of Calgary) | Cheng, Frank Y.F. (Department of Mechanical and Manufacturing Engineering University of Calgary)
ABSTRACT: This paper proposes a Finite-Element-Analysis-based mechanistic model to predict internal localized pitting corrosion rates of petroleum pipelines in sweet (CO2) production environments. In this model, the computational domain consisted of a hemispherical pit and a thin boundary layer of an electrolyte solution. The mesh was generated using quadratic triangular elements in the Cartesian coordinate system whereas a moving mesh method was utilized to track the dynamic pitting propagation. The flux rate of each participating chemical ionic species was computed by solving the Nernst-Planck equation. Specifically, the convection was obtained by solving the Navier-Stokes equations. The electric field in the electrolyte solution was computed based on the Poisson equation with electroneutrality whereas a Debye-Hückel approximation was applied to describe the variation of potential at the metal-solution interface by reason of the existence of the electrical double layer. The ionic concentration distribution was solved using Fick's Second Law. Consequently, the growth rate of a pre-existing pit was predicted. Meanwhile, laboratory tests were conducted to validate the proposed model, demonstrating that the developed model agrees well with experimental data. Furthermore, numerical studies were performed to characterize the effects of convection and chloride ion concentration on pitting corrosion rates. Hence, the model presented herein is able to predict localized pitting corrosion rates and incubation times for its onset in a given sweet system set of operating conditions as well as the onset of pit passivation incubation time. The technical benefits to be gained by the corrosion engineering community and pipeline operators include a better understanding of when to batch chemically treat a pipeline before pitting becomes autocatalytic and when it may be impossible to “turn-off” the pitting excursions due to operationally delaying proper corrosion inhibition practices. INTRODUCTION Localized pitting corrosion is an insidious degradation process of a metal. It primarily manifests as deep cavernous voids which when interconnected have a negative direct impact on the remaining fitness-for-service life of a pipeline. The localized defects can be induced by mechanical breakdown or chemical dissolution (e.g. mineral acids) damage. Pits can also be attributable to other effects of external stress during installation, solids impingement in operation, micro-structural phase heterogeneity during manufacturing, dissimilar expansion/shrinkage rates between scale and metal, as well as chloride anions attack. Upon initiation of the defect, a voltage difference (i.e. potential gradient) occurs between the uncorroded metal and the neighboring adjacent surface, leading to the establishment of an anode at the bottom of the defect but a cathode at the surrounding surface. The generated iron ions tend to effuse into the electrolyte solution. Due to a restricted confined volume inside the defect, ionic transportation (i.e. diffusion or more aptly, mass transfer) is retarded. As ferrous ions are accumulated, Fe²+ hydrolysis takes place under the catalysis by chloride ions, which produces hydrogen ions, depresses pH levels within the defect, and leads to a steep Tafel slope [1]. When an electrochemical reaction appears, a smaller anode dissipates the current as required for the reduction reaction at the cathode, elevating anodic current density.
- North America > United States > Texas (0.46)
- North America > Canada > Alberta (0.29)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)