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Evaluation Of Hydrogen Embrittlement Of Nickel-Based Alloys In Cesium Formate With H2S/CO2

Cesium formate (CsFo) brines have been used as the drilling and/or completion fluids in oil and gas wells in need of high-density fluids.1,2 Multiple studies on corrosion of steels and corrosion resistance alloys (CRA) in formate environments have been reported in the literature.2-8 It was known that the formate brines could undergo significant decomposition to form hydrogen when in contact with catalytic surfaces which CRA can act as. Therefore, there have been concerns that the CRA may catalyze the decomposition of formate brines to accelerate the generation of hydrogen which in turn may embrittle certain CRAs and endanger the relevant well equipment.

Product Number: 51322-18024-SG
Author: Xiaoji Li, Ramgopal Thodla
Publication Date: 2022
Industry: Oil and Gas
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Because of hydrogen generation from thermal decomposition of cesium formate, there were concerns that the use of cesium formate in certain applications may induce hydrogen embrittlement to CRA equipment after extensive exposure to elevated temperatures followed by cooling to low temperature under stress. This study focused on evaluating the severity of hydrogen embrittlement of seven nickelbased alloys at room temperature following exposure at elevated temperature to cesium formate of H2S/CO2 acid gases and consequently reduced pH. Unstressed slow strain rate (SSR) test specimens were previously exposed in an autoclave of cesium formate saturated with H2S/CO2 at an elevated temperature of 275 °F for 90 days. After exposure, significant hydrogen uptakes were observed under the tested conditions by measurement of total hydrogen concentration. The hydrogen-charged SSR specimens were then tested in air with 1 x 10-6 in./in./s strain rate at room temperature and compared with performance of the pristine specimens. In addition, three charged CRA alloys were also heated in furnace to release dissolved hydrogen and then tested in air. Two of the seven CRAs were also strained in situ in cesium formate at 275 °F.

Because of hydrogen generation from thermal decomposition of cesium formate, there were concerns that the use of cesium formate in certain applications may induce hydrogen embrittlement to CRA equipment after extensive exposure to elevated temperatures followed by cooling to low temperature under stress. This study focused on evaluating the severity of hydrogen embrittlement of seven nickelbased alloys at room temperature following exposure at elevated temperature to cesium formate of H2S/CO2 acid gases and consequently reduced pH. Unstressed slow strain rate (SSR) test specimens were previously exposed in an autoclave of cesium formate saturated with H2S/CO2 at an elevated temperature of 275 °F for 90 days. After exposure, significant hydrogen uptakes were observed under the tested conditions by measurement of total hydrogen concentration. The hydrogen-charged SSR specimens were then tested in air with 1 x 10-6 in./in./s strain rate at room temperature and compared with performance of the pristine specimens. In addition, three charged CRA alloys were also heated in furnace to release dissolved hydrogen and then tested in air. Two of the seven CRAs were also strained in situ in cesium formate at 275 °F.

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