An Empirical Model for Indication ofM13Cr-110 NACE Method A Test Acceptability

摘要

Martensitic stainless steels have been used extensively in the oil and gas industry for over twenty years, yet only a few application limits exist to provide materials selection guidance in sour service production environments or if reservoir souring has to be considered. Fitness-for-service testing is required to verify sufficient sulfide stress cracking (SSC) resistance exists when these materials are exposed to low H_2S partial pressure environments with variations in pH and chloride concentrations not addressed by current industry guidelines. As the first stage of a project to provide broader materials selection guidelines for the industry, a review of published NACE TM 0177 Method A test data on 110 ksi grade modified 13Cr martensitic stainless steels (referred to as "13-5-2" martensitic stainless steels by ISO 13680) has been undertaken with the aim to support the development of SSC application limits. Open literature data was compiled from several from different mills and third party laboratories and then analyzed using H_2S partial pressure, chloride content and pH as inputs. Acceptable chloride concentrations were determined to be a function of both H_2S and pH, with pH having a significant influence at the test temperature of 25°C (75°F). Evaluation of these findings allows th ese test results to be separated into three different regions: No SSC Expected, SSC Possible, and SSC Probable. These limits and regions have subsequently been converted into a versatile system that provides an empirical model that indicates if a NACE Method A test is expected to pass for a modified 13Cr stainless steel in multiple different H_2S and chloride containing environments at 25°C (75°F).