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.

There is a significant use of Nickel based alloys in the oil and gas industry for high strength / high corrosion resistance applications yet there has been a lack of understanding of fracture toughness of these Ni alloys under seawater / Cathodic Protection (CP) environments. Furthermore this class of alloys has demonstrated a weakness following high profile failures where the failing mechanism identified was Hydrogen Assisted Cracking (HAC). This study examines several Precipitation Hardened (PH) Nickel alloys by the J-R Curve method (ASTM E1820) using side-grooved single edged notched bend (SENB) fatigue pre-cracked test samples in a simulated seawater environment under CP. The Ni alloys evaluated a good representation of those associated with the in-service failures reported in the past were UNS N07718 UNS N07716 and UNS N07725 together with other alloys more recently developed such as UNS N09945 and UNS N09955.The materials were tested in a 3.5%NaCl solution with applied potentials of -1.1V and -1.4V vs SCE at room temperature at a loading rate of 0.005 Nmm-3/2. The overall response of the alloys in laboratory air was elastic-plastic in nature while the behavior in environment shifted towards a linear-elastic response most likely associated with the embrittlement caused by the hydrogen adsorbed during CP. Scanning electron microscopy analysis was performed to obtain insights on the fracture morphologies. Amongst the alloys tested UNS N07718 showed the least reduction in fracture toughness in the environment in relation to air while alloy UNS N07716 showed the most susceptibility to the environment with the lowest performance.Key words: Ni Alloys Fracture Toughness J-R Curve Method CP environment seawater.

NACE TM0177 Method D corrosion test is used on low alloyed steels in sour environments. A DCB testing program has been performed on 125 ksi grade sour service casings and couplings in 0.07 bar H2S gas for solving these issues and for providing meaningful KISSC values.