Top Integrity Challenges: Oil and Gas Surface Facilities

Introduction

This article summarizes a comprehensive survey conducted by the Research & Development Center (R&DC) of Saudi Aramco to understand top corrosion damage mechanisms experienced by its operating onshore surface facilities. Particular focus was placed on environmentally assisted cracking (EAC), namely hydrogen-induced cracking (HIC), stepwise cracking (SWC), stress corrosion cracking (SCC), and sulfide stress cracking (SSC). The survey identified hydrogen-related damage (in particular, HIC and SWC) and general corrosion — including sulfidation — as the most frequently reported (“top”) integrity damage mechanisms followed by coating failures and carbon dioxide (CO₂) corrosion. Corrosion mitigation and inspection methods employed by these facilities were also identified.

This article also highlights the long-term value of NDE data for developing and validating credible damage growth rate models. Better damage models and monitoring practices enable more effective life cycle management of equipment.

Environmentally assisted cracking (EAC) is defined as the brittle fracture of a normally ductile material in which the corrosive effect of the environment is a causative factor. EAC can occur with a wide variety of metals and alloys and includes the following: hydrogen-induced cracking (HIC), stepwise cracking (SWC), stress corrosion cracking (SCC), and sulfide stress cracking (SSC).  A combination of tensile stresses — applied or residual — and a specific corrosive environment is commonly the cause of sudden cracking-type failures of metal structures. Proper design is the most important consideration to avoid EAC, in conjunction with adequate material selection for the environment. Gradually increasing levels of hydrogen sulfide (H₂S) may occur as a producing field ages. If material selection did not account for souring in the design stage, EAC is likely to become a significant problem in the future.