Abstract:

Associated gas booster reinjection flooding is an important measure to achieve carbon emission reduction in oil and gas exploitation, but the associated gas is a CO₂/CH₄ mixture, the composition fluctuates violently, and the properties of CO₂ near the critical point are extremely unstable, which poses a severe challenge to the stability of the gas injection compressor. In order to clarify the trans-critical pressurization characteristics of CO₂/CH₄ mixture, the PR equation of the physical properties of the mixture was constructed, the physical properties and phase changes of the mixture were calculated, and the safe pressurization path was clarified. Based on this, the theoretical trans-critical pressurization thermodynamic model of CO₂/CH₄ mixture was constructed, and the p-V diagram, valve movement law and indication power of the mixture trans-critical pressurization process were obtained, and the influence mechanism of component concentration on physical properties and thermal performance of the compressor was compared and analyzed. The results show that with the increase of CO₂ concentration, the saturated gas phase moves to the high temperature region, the critical temperature increases, the inlet and exhaust pressure loss increases during the pressurization process, and the compressor power consumption decreases by 22.93% when the CO₂ concentration increases from 20% to 100%. The relevant research results can provide a theoretical basis for the design and reliable operation of the trans-critical supercharging compressor of CO₂/CH₄ mixture.

Key words: supercritical carbon dioxide, gas injection compressor, trans-critical pressurization, mathematical model, boost simulation

摘要：

伴生气增压回注驱油是油气开采中实现碳减排的重要措施，但伴生气主成分为CO₂/CH₄混合物，组分波动剧烈，且CO₂在临界点附近性质极不稳定，这对注气压缩机的稳定性提出了严峻挑战。为厘清CO₂/CH₄混合物跨临界增压特性，构建了混合物物性PR方程，计算了混合物物性及相态变化规律，明确了安全增压路径。据此构建了CO₂/CH₄混合物理论跨临界增压热力学模型，得到了混合物跨临界增压过程p-V图、阀片运动规律及指示功率，并对比分析了组分浓度对物性特征及压缩机热力性能的影响机理。研究结果表明：随着CO₂浓度升高，饱和气相线向高温区移动，临界温度升高，增压过程中进排气压力损失增大，CO₂浓度从20%增加到100%过程中压缩机功耗降低22.93%。相关研究结果可为CO₂/CH₄混合物跨临界增压压缩机的设计和可靠运行提供理论依据。

关键词: 超临界二氧化碳, 注气压缩机, 跨临界增压, 数学模型, 增压模拟