Abstract:
Objective This study aims to prepare a high-temperature resistant, low-corrosion, and solid-free well control sluid system suitable for ultra-deep wells, and clarify its temperature resistance, corrosion resistance performances.
Method Firstly, two well control fluid systems were prepared using potassium formate and composite salt weighting agents as the basis, supplemented with solubilizers, oxygen scavengers, corrosion inhibitors, etc. Secondly, the low-corrosion resistant performance for these systems was evaluated using electrochemical methods, the high-temperature resistant performance was evaluated using hot rolling test, corrosion weight loss experiment of P110 steel in wellbore working condition was simulated by high temperature and high pressure autoclave, and the corrosion product film’s forms and components were analysed by SEM、EDS、XRD methods.
Result Both JSY-1 and FHY-1 well control fluid systems with the density up to 1.6 g/cm3 could withstand temperatures up to 180 ℃. After corrosion in 180 ℃、2 MPa CO2 pressure dividing wellbore condition, P110 steel corrosion rate in two well control fluid were both below 0.060 mm/a.The corrosion products in potassium formate system JSY-1 were Fe3O4 and FeCO3, and that in composite salt system FHY-1 were Fe3O4、Fe2O3 and CaCO3.
Conclusion The developed high-density well conrol fluid has high-temperature resistance、 low-corrosion and solid-free characteristics, which can meet the requirement of well control in ultra deep well.
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