A method for evaluating the applicability of nickel-based alloy tubing/casing in high-temperature,high-pressure,and high-sulfur gas wells
Due to the complex and harsh corrosion environment of deep,high-temperature,high-pressure,and high-sulfur gas reservoirs,the rational selection of materials for pipe string is crucial to ensuring wellbore integrity and safety.The current materials selection solely based on environmental cracking and corrosion rate as core indicators is limited to some extent.In this paper,a high-temperature and high-pressure reactor was used to simulate the service environment of a high-sulfur gas well in a high-sulfur reservoir in the northeastern Sichuan Basin,and a hierarchical structure model was constructed with indicators such as corrosion rate,stress corrosion damage degree,collapse resistance,burst resistance,tensile strength,and cost,to evaluate the applicability of nickel-based alloy tubing/casing.With this model,the BG2532,G3,and SM2550 nickel-based alloy pipes were evaluated for their corrosion resistance,stress corrosion damage,and strength degradation under harsh conditions,and their applicabilities were quantified.The results show that,under simulated working conditions,the corrosion rates of BG2532,G3,and SM2550 all meet the oilfield control indices,with SM2550 exhibiting the best corrosion resistance and a corrosion rate of 0.008 3 mm/a.After stress corrosion testing,the yield strength,tensile strength,elongation after fracture,section shrinkage,hardening index,and fracture toughness of BG2532,G3,and SM2550 declined,with SM2550 demonstrating the smallest decline and thus relatively stable mechanical properties.Based on the quantitative evaluation of applicability,the recommended order of materials to be selected for pipes in high-sulfur gas wells in the northeastern Sichuan Basin is as follows:SM2550＞BG2532＞G3 for tubing,and G3＞SM2550＞BG2532 for casing.It is concluded that the proposed new method for evaluating the applicability of nickel-based alloy tubing/casing in high-temperature,high-pressure,and high-sulfur gas wells is instrumental for selecting materials for tubing/casing to be used in harsh conditions,thereby facilitating the safe,green and beneficial development of(extra-)high-sulfur gas.
Deep and ultra-deep strataHigh-sulfur gas reservoirNickel-based alloy tubing/casingEvaluation indicatorCorrosion rateStrength degradationStress corrosion
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