Super martensitic stainless steels are widely in use in oil & gas production environments providing a cost-effective alternative to more expensive corrosion resistant alloys (CRA) for mitigation of general corrosion due to the presence of CO2 in the produced fluids. However there is little agreement on the service limits when exposed in environments that contain H2S particularly in relation to the susceptibility to sulfide stress cracking (SSC).This paper presents a review on the published literature in relation to the susceptibility to SSC of super martensitic stainless steels in production environments with the aim to evaluate the service limits of these materials from both the empirical and mechanistic approaches. The conclusion of this review is that an adequate assessment of the susceptibility to SSC for the super martensitic stainless steels can only be accomplished by using testing methods that account for: a) the role of the passive layer and b) the formation of metastable pits and their propagation in H2S-containing environments.This paper recommends the adoption of study methodology based on the characterization of the passive layer resistance in super martensitic stainless steels using point defect modeling techniques to identify the role of critical variables on the pit induction time distribution which can be used to describe the susceptibility to SSC. These critical variables include both material

Corrosion resistant alloys (CRAs) have been used in exploration and production fields which contain high pressure high temperature and significant amounts of hydrogen sulfide carbon dioxide and chloride ion. As exploration for High-Pressure High-Temperature (HPHT) hydrocarbon reservoirs with corrosive environments has been increasing the industry needs corrosion resistant alloys (CRAs) for HPHT corrosive deeper well applications. It is highly profitable to apply CRA’s (corrosion resistant alloys) to sour gas environment.　It can be thought that CRA shows the benefit for well development of these conditions from the point of minimization of life-cycle cost.With regard to the surface film formation mandatory elements of CRAs are chromium nickel and molybdenum because it is assumed that chromium forms oxide at the surface of the material and nickel and molybdenum assist the formation of the film in the condition. In this study the surface films on CRA of conventional UNS N08535 are analyzed. The film which is formed after the long term exposure in the actual well is compared with the one formed after the corrosion testing at laboratory.The surface film structure after the exposure in the actual well was composed of sulfides and oxides. This thin layer structure is consistent with laboratory results using small-scale specimens during a short exposure time (720 hours). These results clearly prove the effectiveness of the proposed corrosion resistant mechanism against corrosive environment and the validity of the original material selection.

Sulfide stress cracking has special importance in the Oil and Gas (O&G) industry due to the considerable amount of hydrogen sulfide that may be present in the processed fluids. Furthermore the increasing interest of the O&G industry on high grade tubulars to work at high pressure make of the sulfide stress cracking phenomenon an important issue in the safe operational conditions assessment of Oil country Tubular Goods (OCTG).Consequently the adequate determination of fracture toughness value (i.e.: K-mat) is of fundamental importance for fitness for purpose evaluation. Particularly the fracture toughness of OCTG materials in aggressive media is usually determined using DCB specimens and the obtained K-limit values are the employed for fracture assessment. Although Method D using DCB specimens has been and is the recognized testing methodology for QA/QC purposes in pipes manufacturing  its validity as a fracture resistance parameter for burst pressure estimation of flawed pipes (FAD) remains uncertain and therefore alternative methods are being assessed.In the present paper an experimental program is described on C110 and T95 materials testedin aggressive environments. K-limit from conventional DCB tests and K-threshold from SENT specimens under constant loading are compared and discussed. The K-mat obtained from both testing techniques are employed to calculate the burst pressure of flawed pipes using API 579 equations and compared against the failure pressure from API PRAC III full scale test result (Work Group 2315). The presented results and discussion allow to incorporate a further insight on an alternative testing method and specimens geometry for brittle burst assessment of flawed pipes in an aggressive media.