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.

The integrity of oil well cement sheaths is closely related to the long-term production safety of oil and gas wells. The primary material used to form a cement sheath is brittle. In order to reduce the brittleness of oil well cement and improve its flexibility and resistance to stress damage, nano-silica was used to modify polymer elastic particles, and their properties were analyzed. The influence of the modified polymer particles on the properties of oil well cement-based composite materials was studied, and the microstructure of the polymer particle cement sample was analyzed. The results showed that nano-silica effectively encapsulates polymer particles, improves their hydrophilicity, and achieves a maximum temperature resistance of 415 °C. The effect of the modified polymer particles on the compressive strength of cement sample is reduced. Polymer particles with different dosages can effectively reduce the elastic modulus of cement paste, improve the deformation and elasticity of cement paste, and enhance the toughness of cement paste. Microstructural analysis showed that the polymer particles are embedded in the hydration products, which is the main reason for the improvement in the elasticity of cement paste. At the same time, polymer particle cement slurry can ensure the integrity of the cement sample after it is impacted, which helps to improve the ability of oil well cement-based composite materials to resist stress damage underground.

Oil well cement is prone to corrosion and damage in carbon dioxide (CO₂) acidic gas wells. In order to improve the anti-corrosion ability of oil well cement, polymer resin was used as the anti-corrosion material. The effect of polymer resin on the mechanical and corrosion properties of oil well cement was studied. The corrosion law of polymer anti-corrosion cement in an acidic gas environment was studied. The long-term corrosion degree of polymer anti-corrosion cement was evaluated using an improved neural network model. The cluster particle algorithm (PSO) was used to improve the accuracy of the neural network model. The results indicate that in acidic gas environments, the compressive strength of polymer anti-corrosion cement was reduced under the effect of CO₂, and the corrosion depth was increased. The R² of the prediction model PSO-BPNN3 is 0.9970, and the test error is 0.0136. When corroded for 365 days at 50 °C and 25 MPa pressure of CO₂, the corrosion degree of the polymer anti-corrosion cement was 43.6%. The corrosion depth of uncorroded cement stone is 76.69%, which is relatively reduced by 33.09%. The corrosion resistance of cement can be effectively improved by using polymer resin. Using the PSO-BP neural network to evaluate the long-term corrosion changes of polymer anti-corrosion cement under complex acidic gas conditions guides the evaluation of its corrosion resistance.

Magnesium oxychloride has excellent early strength, lightweight and environmentally friendly properties, and excellent application value. However, insufficient water resistance affects its engineering application. This paper uses fly ash to improve the water resistance of magnesium oxychloride cement (MOC). The response surface method was used to optimize the ratio of magnesium oxychloride cement. The influence of fly ash content, magnesium oxychloride cement ratio, and their interaction on the water resistance of magnesium oxychloride cement was studied using a response surface experiment. The fly ash content and magnesium oxychloride cement ratio were optimized to form magnesium oxychloride cement with good water-resistance. The experimental results show that the fitting efficiency of the response surface model is R² = 0.9951; the model reflects the relationship between the factors of magnesium oxychloride cement and water resistance well. The magnesium oxychloride cement has a maximum softening coefficient of 0.898 when the amount of fly ash added is 21.94%, and the molar ratio of magnesium oxychloride cement is 11.49: 1:11.77. The magnesium oxychloride cement has good water resistance by optimizing the ratio based on external fly ash and response surface methodology. The study provides a reference for improving the water resistance of magnesium oxychloride cement.