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. Notably, a significant decline in displacement efficiency was observed when the injection pressure dropped below 30 MPa, with the lower injection pressures correlating with an increased oil production capacity upon gas breakthrough.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, demonstrating efficacy in enhancing formation energy and holding substantial potential for widespread application.