The influence of hydrogen sulfide on internal pressure strength of carbon steel production casing in the gas well

The production casing strength design of gas well containing hydrogen sulfide is deeply complicated because of corrosion and hydrogen damage increase. In general, API 5C3: 2018 yield strength design criterion is the main standard to calculate casing string strength that satisfies casing materials selection. There are two kinds of production casing materials C110 and P110SS in the experiment, according to API 5C3: 2018 yield strength design criterion combining with fracture toughness measured by NACE TM0177: 2016 method D (Double Cantilever Beam Test) to evaluate casing string internal pressure strength. The relationship between fracture toughness and internal pressure strength is discussed in the room environment, NACE Standard TM0177-2016 Test Solution D and the special sour environment containing hydrogen sulfide with annuals protection solution. The results show that the fracture toughness of production casing string decreases with the severity of harsh environments. Thus, annulus protection fluid has a positive effect on improving the internal pressure strength of the production casing that enhances wellbore integrity performance to resist the sour environment risk. These research results can provide an important reference for strength design and specification optimization of carbon steel production casing in the gas well with hydrogen sulfide.