Test Protocol for Corrosion Resistant Alloys and Application to Material Selection for Ultra Sour Reservoir Containing Elemental Sulphur, in Continuation of SPE-203337-MS

Abstract

Abstract Building upon the work detailed inSPE-203337-MS, the present work reports test results for the G3 alloy beyond the 4D limits defined by ISO 15156-3:2015/ NACE MR0175. Corrosion of Oil Country Tubular Goods (OCTG) is a traditional concern in the Oil and Gas industry, as it represents a major component of well integrity management. Various corrosion mechanisms may affect the performance of materials in downhole applications, especially in corrosive environments containing large amounts of H2S, CO2, and Chlorides. In high sour environments, elemental Sulphur may also be present, in which case, it will act as a strong oxidizer, affecting the performance of the material selected. In this paper, a test methodology was developed to select a techno economical fit for purpose material for application in the development of a Ultra Sour Reservoir Containing Elemental Sulphur. This methodology consisted in evaluation of the SCC (Stress Corrosion Cracking) behavior of Corrosion Resistant Alloys (CRA) of group 4D, as per ISO15156-3/ NACE MR0175-3, at the border between 4D and 4E environmental limits including the simultaneous presence of dissolved and elemental Sulphur in the fluid. A testing set-up was developed to ensure the contact of elemental S with the material to ensure the strong oxidizing reaction at the surface of the material. The behavior of the materials was assessed by Slow Strain rate testing (SSRT), C-Ring Sulphide stress cracking and Crevice corrosion test, conducted on UNS N06985. CRAs have a greater CAPEX due to the content of costly chemical elements: Chromium, Nickel, Molybdenum, etc. However, they may be cost effective in a life cycle cost analysis by preventing workovers, assuring a higher HSE and well integrity level.