The Double Cantilever Beam (DCB) test method standardized in ANSI NACE TM0177 is increasingly applied as a quality assurance test to specify the performance of carbon and low alloy steels for sour service. The DCB test method has been modified and specified tightly from the view point of specimen geometry test environment and initial stress intensity factor controlled by arm displacement to obtain highly repeatable test results.NACE TM0177 2016 method D has various types of starter notch configurations on DCB specimens. Crack start position shifted change specimen of EDM notch has been in accordance with NACE TM0177 since 2016 and the distance from a pin hole to a crack starter has been different.Previous research the influence of crack starter position on K1SSC has been revealed using Finite Element Analysis (FEA) and DCB tests. In this paper in order to clarify the applicability of compliance curve in TM0177-2016 and propose the new compliance curves FEA and experimental approach was performed. K1SSC of DCB tests should be evaluated in the same crack start positions from the view point of a fracture mechanics.

Integrity of materials in Oil & Gas production wells is critical to meet the objectives of design and the lifecycle performance of wells. This is significant value both in economic terms and health safety and environment. Subsurface uncertainties Aging fields EOR activities and also the quality of procured equipment add to the difficulties in preventing equipment failures in wells. Failures that are especially unforeseen or unanticipated provide crucial feedback to operators and lessons to be learnt. It is imperative for operators to learn improve processes and avoid recurrence of failures.Petroleum Development Oman (PDO) as a large operator with more than 10000 wells has gained important experience and lessons from many such failures. This has contributed significantly to improve the company standards material selection reset the operating envelope and procedures enhance surveillance and improve upon quality assurance and control of new equipment.This paper is a compilation of some of the important lessons learnt from such incidents in the recent past. It discusses the operational experience and learning from different subsurface materials from CS to nickel alloys used in different components such as casing tubing packers and X-trees. 

CO2 corrosion has become a problem that can not be ignored for the deepwater natural gas pipeline. At present this is difficult to simulate the low water content and the high gas flow velocity for natural gas field in the deep water by the traditional evaluation method of corrosion inhibitor in the laboratory and the accuracy of experimental results is questionable. In this paper laboratory simulation of actual natural gas field conditions was carried out using traditional rotating cylinder electrodes and self-made wet gas flow loop via considering the wall shear stress and mass transfer function as the hydrodynamic parameters to equivalent actual working conditions and laboratory conditions. The effect of corrosion inhibitor in high gas flow velocity was evaluated by using the weight loss test the Microcor ER probe and the self-made electrochemical probe respectively. By comparing the evaluation results of above methods the advantages and disadvantages of each method are analyzed at same time the most suitable method and process for the evaluation of corrosion inhibitors are screened and formulated in deepwater natural gas pipelines. In addition it provides the theory and data support for the evaluation of the corrosion inhibitor in deepwater natural gas field.