Study on the Oil Well Cement-Based Composites to Prevent Corrosion by Carbon Dioxide and Hydrogen Sulfide at High Temperature

Complex wells with high temperature and the presence of carbon dioxide and hydrogen sulfide acid gas require the use of high-temperature and high-density anti-corrosion cement slurry for cementing operations, and conventional cement slurry does not have the advantages of high density, high-temperature resistance, or corrosion resistance. In order to avoid the severe corrosion of cement slurry by carbon dioxide and hydrogen sulfide at high temperatures, solid phase particles with different particle sizes are combined with polymer materials to form a dense, high-density, high-temperature- and corrosion-resistant cement slurry. In this paper, we consider the use of manganese ore powder weighting agent, composite high-temperature stabilizer, inorganic preservative slag and organic preservative resin to improve the corrosion resistance of cement slurry, design a high-density cement slurry that is resistant to high temperature and carbon dioxide and hydrogen sulfide corrosion, and evaluate the performances of the cement slurry at 180 °C. The results show that the manganese ore powder weighting agent effectively improves the density of the cement slurry. Using composite silica fume with different particle sizes as a high-temperature stabilizer can ensure the rheology of the cement slurry and improve the ability of the cement sample to resist high-temperature damage. The use of slag and resin as preservatives can effectively reduce the corrosion degree in cement slurry. The high-temperature corrosion-resistant cement slurry systems with different densities designed using these materials exhibit good rheological properties, with water loss of less than 50 mL and a thickening time of more than four hours. The compressive strength decreased by less than 5.8% after 28 days at high temperatures. After being corroded by hydrogen sulfide and carbon dioxide (total pressure 30 MPa, 16.7% hydrogen sulfide and 6.7% carbon dioxide) under high temperature (180 °C) for 30 days, the corrosion depth of the cement sample was less than 2 mm, the reduction of compressive strength was low, and the corrosion resistance was strong. These research results can be used for cementing operations of high-temperature oil and gas wells containing hydrogen sulfide and dioxide.