Subsea Engineering

Course — SUBS 6360: Materials and Corrosion

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Term: 

Usually offered in the Spring Semester.

Description: 

This course provides an overview of materials and corrosion for subsea production systems. It sets out principles and practices of materials selection. Hence, materials used in the construction and deployment in subsea production systems are covered. The basics of corrosion with emphasis on the type of corrosion and materials degradation that can occur in oil and gas production are included. Corrosion processes become of concern with the reliability and health and safety requirements of subsea systems. Materials addressed include metallic, non-metallic, and coatings. Erosion, a problem associated with high rate production encountered in subsea production will be addressed. API specifications that govern subsea oil and gas production projects are used in the class so the metallurgical principles codified in these specifications are understood.

At the end of this course the student will have a framework for materials development and selection. The materials of construction for a variety of oilfield operations will have been explained and principles of materials selection developed. The student will be an informed user and purchaser of subsea equipment, capable of asking strategic questions and enlisting the correct subject matter experts.

Topics Covered: 

Basics of Metallurgy: This part of the course introduces basic properties of engineering alloys, melting, forming, welding and heat treatment to get to the products used in drilling, production, and distribution of oil and gas. Metallurgical aspects and mechanical properties of alloy families from carbon steel to corrosion resistant alloys, and their use in the oilfield will be addressed. Welding and fabrication will also be included.

Corrosion: The principles of corrosion, both chemical and electrochemical will be covered. It will be focused to the types of corrosion found in the oilfield with emphasis on the effects of acid gases (CO2and H2S). Introduction of the effect of organic acid on the corrosion of carbon steel for the oil and gas fields will be covered. Corrosion aspects of subsea systems are emphasized along with strategies to address problems. Hydrogen embrittlement, an indirect result of corrosion, and sulfide stress corrosion cracking will be covered in detail using NACE MR0175. Testing on this topic is included. Approaches to mitigate corrosion based on corrosive species and operating conditions will be highlighted. Principles of erosion and solids production will be addressed. Laboratory methodologies to evaluate chemical products (corrosion inhibitors, scale inhibitors, oxygen scavenger, H2S scavenger, biocides) for oilfield application will be reviewed. This last section is usually complemented with a field trip.

Material Selection: Operational integrity during the lifetime of the production system are provided by the appropriate material selection for subsea production systems. Subsea material selection shall have improved grades with the aim of avoiding failure risks, minimize difficulties and high cost associated with inspection, maintenance and intervention. However, the diversity of materials along the entire system should be minimized without affecting integrity. In this unit, material selection for drilling, downhole and pipeline operations will be covered.

Course Grading: 

The course grade will be based on homework, project, quizzes and final exam.

Project: 

Each project will cover a different corrosion related problem. These projects are presented at the end of the semester. The report shall include description of the material degradation mechanisms, identification of components sensitive to damage, most-common examples of failures, mitigation options -including discussion of pros and cons-, inspection and monitoring. Experienced engineers might come to evaluate and comment the group project presentations.