In-situ oil shale retort; thermocouple well failure analysis

Technical Report · Tue May 01 04:00:00 EDT 1979

OSTI ID:6024600

Douglas, D L

A plain-carbon steel pipe, 3/4-in. diam., was used as a thermocouple well during field tests of in-situ oil-shale retorts near Vernal, Utah. The pipe had nearly completely corroded during service stated to be for long periods of time in the temperature range 1000 to 2000/sup 0/F. One leg of the chromel--alumel thermocouple, the chromel branch, had corroded, and the Inconel 600 sheath was partially corroded. X-ray energy dispersive analysis in a scanning electron microscope revealed that the steel had oxidized to a mixture of iron oxides and/or iron--calcium silicates. A minor amount of iron sulfide was detected. The insulation of the thermocouple had been infiltrated by either liquid nickel sulfide or a eutectic of Ni/sub 3/S/sub 2/ and Ni. The corroded chromel wire had been converted to Cr/sub 2/O/sub 3/ and a nickel sulfide. Intergranular formation of Cr/sub 3/S/sub 4/ in the exterior of the Inconel 600 sheath was noted also. The observations showed that oxidation was the major cause of failure and was selectively assisted by sulfidation, e.g., the thermocouple. The results are consistent with the known products of in-situ retorting of oil shale. Plain-carbon steel is not an oxidation-resistant material and is not suited for high-temperature use. The extensive oxidation clearly showed that the steel was used at much too high a temperature (generally not suited for temperatures above about 900/sup 0/F) for excessive time periods. The highly corrosive atmosphere of the gases produced by the in-situ combustion of shale oil requires a chromium-rich alloy such as ferritic or austentic stainless steels, both of which are considerably more expensive than plain-carbon steel. The only alternative to upgrading the material would be to use an aluminum coating. Various coatings are suggested.

• Research Organization: Sandia Labs., Albuquerque, NM (USA)
• DOE Contract Number: EY-76-C-04-0789
• OSTI ID: 6024600
• Report Number(s): SAND-79-0742
• Country of Publication: United States
• Language: English

Related Subjects

04 OIL SHALES AND TAR SANDS
040401* -- Oil Shales & Tar Sands-- In Situ Methods
True & Modified
36 MATERIALS SCIENCE
360105 -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
BITUMINOUS MATERIALS
CARBON STEELS
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
CHEMICAL REACTORS
CORROSION
ENERGY SOURCES
FAILURES
FOSSIL FUELS
FUELS
IN-SITU PROCESSING
IN-SITU RETORTING
IRON ALLOYS
IRON BASE ALLOYS
MEASURING INSTRUMENTS
OIL SHALES
PROCESSING
RETORTING
RETORTS
STEELS
THERMOCOUPLES