In light of the potential feasibility of gas injection for the development of high-temperature， high-pressure， low-permeability oil reservoirs in the western South China Sea and the imperative to enhance oilfield recovery efficiency， this study embarked on a series of laboratory experiments. These experiments were conducted with a focus on two gas types： carbon dioxide （CO₂） and hydrocarbon-associated gas. Under high-temperature and high-pressure conditions， fine-tube experiments and long-core displacement tests were meticulously carried out.A comparative analysis of the oil displacement efficiency of the two gases was undertaken， leading to a comprehensive evaluation of their development performance. The research findings indicate that under high-temperature and high-pressure conditions， CO₂ injection achieved a maximum oil displacement efficiency of 88.8%. Among various injection strategies， the alternating gas-water injection method yielded the highest displacement efficiency of 87.4%. The injection angle was found to have a maximum impact of 3.2% on the displacement efficiency. Hydrocarbon gas flooding and CO₂ injection technologies are deemed applicable to the high-temperature， high-pressure， low-permeability oil reservoirs in the western South China Sea.