采用室内研究的方法，对CO₂ 含量分别为10%，30%，50%，70%，90%，100% 的天然气样品做了3 个 不同温度（20 ℃，30 ℃，40 ℃）下的恒组成膨胀实验测试研究。结果表明：随CO₂含量由10% 增大到100%， 天然气样品的临界温度由-69.86 ℃ 增高到31.4 ℃，临界压力由4.85 MPa 增高到7.38 MPa；温度不变， 压力一定时，随着天然气中CO₂含量的增高，天然气样品的相对体积呈增大的趋势，不同CO₂含量的天然 气样品随压力降低其体积膨胀规律表现出了类似CO₂超临界状态的特征。以上认识对CO₂和天然气混 合气体驱油施工及今后更进一步的研究具有一定的借鉴意义。

The constant composition expansion experiments on natural gas with CO₂ content of 10%, 30%, 50%, 70%, 90%, 100% under three different temperatures （20 ℃, 30 ℃, 40 ℃） are conducted respectively. The results showthat with the CO₂ content increasing from10% to 100%, the critical temperature of natural gas samples increases from - 69.86℃ to 31.4 ℃, and the critical pressure increases from 4.85 MPa to 7.38 MPa. When the temperature and pressure is constant, with the increasing of CO₂ content in natural gas, the relative volume of natural gas samples shows an increase, and with the decreasing of pressure, the volume expansion lawof natural gas samples with different CO₂ content shows a similar phenomenon in the supercritical CO₂ characteristics. This cognition is significant for the further study on oil displacement by mixture of CO₂ and natural gas.