Test Devices to Assess SCC in Ultra High Pressure of H_2S

摘要

The exploitation of fields with high H_2S and/or CO_2 content is nowadays of growing importance for oil companies. The presence of H_2S and/or sulphur in production fluids can be responsible for both general and localized corrosion. In application, users can combine experience with suggestions from standards and regulations. A good deal of knowledge is available to predict corrosion rates for CO_2 containing hydrocarbons, but the effect of high pressure H_2S is less known, also due to the difficulty of performing laboratory tests in such challenging conditions. Re-injection wells are, for instance, in contact with dry (or low water content) supercritical fluids, whose corrosion properties are not fully known. Accepted international standards for materials selection are based on laboratory data where specimens are immersed in a water solution, mainly at low pH, in equilibrium with much lower total and partial gas pressures. Venezia Tecnologie has labs equipped with test devices specifically conceived to perform tests at ultra high pressure in sour environments, mainly consisting of: 1. Slow strain rate and ripple slow strain rate test equipment, operating at a pressure up to 760 bar in H_2S 2. An autoclave designed to test up to a total pressure of 1000 bar of H_2S and/or other gas mixtures. Water can be added to fully simulate the service environment. Preliminary tests were performed to assess the capability of the testing apparatus, in conditions simulating extreme field of interest. Preliminary results on steels and corrosion resistant alloys (CRA) are presented in this paper, and discussed with reference to conventional low pressure/low pH tests.