超深地层高温高压，长井筒具有井口-井底温差、压差显著的特点，钻井期间流体相态变化机制复杂。相态预测对流体物性计算具有重要意义。针对钻井期间超深井筒内流体存在气、液、超临界以及钻井液相的多组分流动特点，建立超深井钻井井筒流体多组分多相平衡模型。基于塔里木YH区块超深井典型产出流体组分展开相态实验与模型验证，模型精度达97.71%。分析超深井钻井井筒多组分流体相态时空演化规律。结果表明：井筒温压范围内干气未出现气液两相区，仅以气相形式流动；湿气、高含二氧化碳气与凝析气在井筒不同位置以气态、液态、气液两相和超临界态4种状态存在；井筒压力梯度、地温梯度和钻井液排量的增加使相变点位置更靠近井口，其中压力梯度影响较大；气体突破相变点后密度降低是气侵具有强隐蔽性的直接原因。实例井计算结果表明，研究方法使超深钻井井筒压力计算精度提高2.81%，可为超深井钻井安全提供理论支撑。

Ultra-deep formations exhibit high-temperature and high-pressure conditions, with extended wellbores characterized by significant wellhead-to-bottomhole temperature and pressure differentials, leading to complex fluid phase behavior mechanisms during drilling. Phase-state prediction is critical for accurate fluid property characterization. To address the multicomponent flow dynamics involving gas, liquid, supercritical phases, and drilling fluids in ultra-deep wellbores, a multicomponent multiphase equilibrium model was developed. Phase behavior experiments and model validation were conducted using representative fluid compositions from ultra-deep wells in the Tarim YH Block, achieving a model accuracy of 97.71%. The spatiotemporal evolution law of multi-component fluid phase states in ultra deep well drilling wellbore was analyzed. The results show that there is no gas-liquid two-phase zone in the dry gas within the temperature and pressure range of the wellbore, and it only flows in the form of gas phase. Moisture, high carbon dioxide gas, and condensate gas exist in four states at different locations in the wellbore: gaseous, liquid, gas-liquid two-phase, and supercritical. The increase in wellbore pressure gradient, geothermal gradient, and drilling fluid displacement brings the phase transition point closer to the wellhead, with the pressure gradient having a greater impact. The direct reason for the strong concealment of gas invasion is the decrease in density after the gas breaks through the phase transition point. The calculation results of the example well show that the research method improves the accuracy of wellbore pressure calculation in ultra deep drilling by 2.81%, which can provide theoretical support for the safety of ultra deep drilling.