Environmental assisted cracking and strength attenuation effect computing on the mechanical properties of casing steel P110 for industrial revolution 5.0 applications in sour well environments

Casing steel is prone to reduced mechanical properties and occurred environmentally assisted cracking finally in sour well environment containing H2S and CO2. The paper mainly researched on the relationship between mechanical properties and hydrogen permeation, exposed casing steel P110 to air, NACE A solution, and simulated formation water containing H2S and CO2 with a stress of 80% yield strength at 60 degrees C for 168 h, testing its mechanical properties shown strain-aging phenomenon and ductile-brittle transition. The lowest mechanical properties are occurred in the sour well environment, its yield strength, and tensile strength, respectively, reduction 5.0% and 4.7%, while a loss of 41.4% in fracture toughness. With temperature increased from 25 to 60 degrees C, the hydrogen diffusion coefficient increases by 1.59 times, and there is a mutation in mechanical properties of P110, when the hydrogen diffusion coefficient is 1.64 x 10(-4) cm(2)/s and the subsurface hydrogen concentration is.1.653 x 10(-5)%. The steel P110 has shown a ductile fracture with toughnest exposed in the air and shown cleavage fracture characteristics exposed to sour environments, indicating that hydrogen permeation has changed the fracture mode from ductile to brittle. This method can be used to test and compute the strength attenuation effect of casing P110 serviced in sour well environments.