Materials for Use in Oil & Gas: CO2 (sweet), H2S (sour) & Chloride (Cl-)

This course principally addresses environmental embrittlement mechanisms active in sour gas production operations, as opposed to sour gas processing and sour oil refining.

Sulfide Stress Cracking (SSC) is one of several “environmental embrittlement” mechanisms whereby a metal or alloy exposed to an aqueous or moist gaseous environment containing hydrogen sulfide (H₂S) – a “sour environment” – can fail catastrophically.  The term “SSC” is applied to the failure of carbon and low alloy steels (CS and LAS) and corrosion-resistant alloys (CRAs).

Objectives

• Creating awareness of recent developments in materials science and technology
• Learning about new materials used in the petroleum and petrochemical industries
• Issues and Concerns (Problem): i.e., occurrences in pipelines and pressure vessels handling sour gas and oil (upstream and downstream operations), gas transmission pipelines, etc.

Presentation Topics

• Definitions of SSC, HSC, SCC and “Sour Service”.
• Mechanism of, and Factors Affecting Environmental Cracking (EC) in Carbon Steels (CS), Low Alloy Steels (LAS) & Corrosion-Resistant Alloys (CRAs).
• EC in Other Metals and Alloys.
• Effects of Welding on Environmental Cracking.
• Restrictions on Materials for Sour Service.
• Laboratory Testing Methods.
• Corrosion in Sour Environnements.
• Failure Examples

Factors Affecting Environmental Cracking:

1. Metallurgy factors
2. Environment factor, and
3. State of stress factor

ENVIRONMENTAL CRACKING AVOIDANCE: MR0175, MR0103 AND ISO 15156.

Note: Materials standards have been developed by industry consensus (producers, manufacturers, engineering contractors [design and construction], consultants and government licensing bodies) for avoiding EC in sour systems.  Inevitably, the need for consensus to go forward resulted in some interested parties having to compromise on their opinions concerning the suitability of a material or its metallurgical condition, etc. for sour service.

Understanding these factors is of great importance to minimize and control corrosion problem in many industrial applications. Since the environment play an important role in materials corrosion, petroleum and chemical industries revealed many corrosion problems as, localised corrosion, corrosion fatigue, sulfide stress cracking (SSC), stress corrosion cracking (SCC), intergranular corrosion, etc. Many of the corrosion failure problems can be prevented by a proper attention from the early stage of material manufacturing, processing, treatment and machining.