Corrosion Assessment of High Strength Carbon Steel Grades P-110, Q-125, 140 and 150 for H2S Containing Producing Well Environments

In recent times, the increase in pressure, depth and diameter of wells requires Oil Country Tubular Goods (OCTG) with higher yield strength. Because Sulphide Stress Cracking (SSC) can occur when high strength steel is exposed to wet sour gas, SSC characterization of such materials must be addressed to avoid failures in sour wells.A test program was designed, using modified NACE TM0177 Method A, in order to assess the high strength carbon steel alloys grades P-110, Q-125, 140 and 150. This was in order to determine the risk in the use of such steel grades for production casing in H2S containing well environment.

The results from this test program revealed that the higher the yield strength the lower the SSC performance. Steel grade P-110, in fact, has the largest window of applicability compared to steel grades Q-125, 140 and 150. Tests performed on steel grade Q-125 in a ppH2S of 1 bar using modified NACE TM0177 Method A, solution A at the elevated test temperature of 80°C produced no SSC failure. A threshold temperature was determined by means of NACE TM0177 method C for steel grade 140 (90 °C).