A Special N-80 Steel Tubing Developed in France To Resist Sulfide Stress Corrosion in Sour Gas Wells★

Abstract

Abstract The presence of hydrogen sulfide in the Lacq gas field in France resulted in a number of equipment failures. It was found advisable to use a steel tubing having the N-80 grade steel mechanical properties but having a better sulfide stress corrosion resistance under the action of hydrogen sulfide than the conventional N-80 steel. The steel developed for this purpose was designated APS 10 M4 and was a chromium-aluminum-molybdenum alloy which had been heat treated in such a manner as to obtain a thermodynamically stable structure of carbon-free ferrite with highly dispersed fine carbides. Specimens of the newly developed steel were subjected to a number of laboratory tests including the Jones Test, Cantilever Beam Test, U-Bend Test, Expansion Test, and Tensile Test. Extensive data are given from these tests. It was found that appropriately heat treated APS 10 M4 steel had a very high resistance to hydrogen sulfide as compared with other materials in general and with the conventional N-80 steel in particular. Field tests were made on 23/⅜-inch tubing made from APS 10 M4 steel. After six months of testing it was found that the steel was sufficiently resistant to hydrogen sulfide to be satisfactory for use at the Lacq field. 3.2.2