AMPP Annual Conference & Expo

Effect Of Oxygen Concentrations on Localized Corrosion of Martensitic and Super Martensitic Stainless Steels

by Suresh Divi, PhD, PE and Bruce Craig, PhD, PE

Monday, March 20, 2023  |  1:50pm – 2:15pm
Martensitic stainless steel material, 13Cr (UNS 42000) and Super ​S13Cr-6Ni-2Mo (UNS S41426), tubing is used in ​producing oil and gas wells ​due to their corrosion resistance compared to low alloy steels. However, the ​industry is often anxious to turn these producing wells around for seawater injection or saltwater disposal in which case the presence of oxygen must be considered which significantly influences the corrosion behavior. The risk for localized corrosion ​(i.e., pitting and crevice corrosion) in highly concentrated chloride environments is dependent on the dissolved oxygen level, temperature, and chloride content.

Keywords: Martensitic stainless steel, pitting, localized corrosion, dissolved oxygen.

Laboratory Study of Internal Corrosion and Cathodic Protection Concerns Related to Offshore Monopile Structures

by Suresh Divi, PhD, PE, Adam Rowe, PE and Dan Efird, PE

Wednesday, March 22, 2023  |  1:10pm – 1:35pm
Cathodic protection is one of the primary methods considered by designers and operators to protect internal surfaces within the immersed portion of offshore monopile foundations. There is an industry need to better understand the use of cathodic protection inside offshore monopile foundations. A laboratory study was conducted to explore several aspects related to internal corrosion and cathodic protection of offshore monopile steel structures. Electrochemical and immersion corrosion tests were performed on structural steel in ASTM D1141 simulated seawater and a variety of temperature, aeration, and pH conditions in order to establish fundamental trends. The effect of these parameters on free corrosion rates, cathodic protection, acidification, and hydrogen gas generation were measured. The impacts of slight chromium additions and different sacrificial anode compositions were also explored.

Keywords: Monopile, Cathodic Protection, Offshore, Corrosion, pH, Seawater, Sacrificial Anode, Wind Energy.

Internal Corrosion of L80 Tubing in Permian Basin Oil and Gas Wells-Case Studies (Lab Study)

by Suresh Divi, PhD, PE, and Michael Newman - BPX Energy

Thursday, March 23, 2023  |  10:10pm – 10:35pm
Production of oil and gas from shale wells formations located in the Permian Basin, West Texas, has increased due to high demand. It is estimated that approximately 30 billion barrels of oil and 75 trillion cubic feet of natural gas of been produced from Permian wells since the 1920s. Due to global demand for oil and gas, Permian production is once again growing and is estimated to continue to break production records by 2027.

During oil and gas production, API 5CT L80 production tubing is commonly used. Due to the exposure to the production of oil, gas and produced water, and other chemicals the internal surface of the tubing experiences wear and corrosion. Lately, L80 tubing failures due to various corrosion mechanisms were observed. This paper presents two case studies of L80 corrosion failures and associated corrosion mechanism(s) via lab failure analysis.

Keywords: L80, tubing, failure analysis, metallurgical examination, Permian basin.

Ghost Pearlite In External Corrosion Of Buried Pipeline

by Sri Krishna Chimbli

Wednesday, March 22, 2023  |  3:25pm – 3:50pm
A recent failure analysis of buried API 5L Grade X42 pipeline that leaked exhibited ghost pearlite in the corrosion deposits. The 12.75-inch OD and 0.25-inch wall pipeline was installed in 1949 and was in natural gas service. The work scope for the pipeline failure analysis included visual examination, metallography, energy dispersive X-Ray spectroscopy (EDS), X-Ray diffraction (XRD) analysis, Vickers hardness and tensile tests to determine the mechanism that led to the perforation. This paper provides the pipeline failure analysis results and the damage mechanism. Ghost pearlite is not typically observed in external corrosion products of buried pipelines and presents a unique case to share the findings.

Failure Analysis of a 4-Inch 25Cr-35Ni Welded Fitting

by Sudhakar Mahajanam, PhD, MBA, PE; Scott Harding, PhD, PE; Christopher Miller

Thursday, March 23, 2023  |  9:00 am – 9:25 am
In this case study, a 4-inch HP-modified fitting that cracked in the weld between the pipe and the reducer was examined. The fitting was operating in a cracking/pyrolysis operation (carburizing/reducing environment) with hydrocarbon (gas phase) on the inside surface and furnace atmosphere on the outside surface. Several examinations of the fitting were performed including visual inspection, fractography, metallography, chemical analysis and hardness testing. It was found that the crack occurred in the reducer side heat affected zone (HAZ) region of the girth weld from stress relaxation cracking (SRC). SRC is known to occur at high temperatures (500-700°C) in thick-walled, austenitic stainless steels and nickel-based alloys in the HAZ regions, where high residual stresses exist. The crack morphology was intergranular/interdendritic and chromium/niobium carbides were identified at the austenite dendrite boundaries.