Comprehensive risk assessment of high sulfur-containing gas well

Well integrity has been a growing concern of oil and gas industry, especially in the years of cheap oil. The failure of well integrity may cause undesirable events or even devastating consequences such as safety hazards or loss of containment. In this paper, a novel calculation model of wellbore integrity comprehensive risk has been presented. Firstly, the risk hazard associated with well barrier failure modes are identified based on the relevant literature. The risk factors of well integrity in production phase are investigated in detail. The risk matrix based on Borda number analytical method and Analytic Hierarchy Process (AHP) is then presented to assess the risks of well integrity in production safety. Finally, the case of XX high sour gas well is empirically investigated to validate the model. The results indicate that 27 risk factors are identified for XX gas well in production. In addition, it is found that the XX gas well is prone to suffer damage in presence of H2S and CO2, furthermore, the Borda number analytical results also show that the most important factor affecting the well integrity is effect of string corrosion, followed by the corrosion of string sealing accessories and the corrosion environment of material applicability. Therefore, the appropriate measures should be taken to reduce the corrosion of string and sealing accessories, thus prolonging the service life of the equipment. The case of XX high sour gas field verifies the feasibility and applicability of the risk matrix method in wellbore integrity risk assessment. The innovative assessment method provides methodological reference and guidance for the application of the limited resources, in addition, it also has practical information for well integrity engineers to improve the performance of safety management, thus ensuring well safety during production.