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油气开采过程中的蜡质和沥青质等固相沉积问题，是目前国内外研究的热点和难点。在油气生产的各个环节，随着温度、压力和轻质组分逸出等热力学条件的变化所产生的有机固相沉积问题，给油气田生产造成了严重的危害；特别是在注气提高采收率过程中，由于相间传质诱发的石蜡和沥青等固相沉积，将会改变油藏岩石的渗透性和润湿性，从而影响采收率的提高和注气开采效果。本采用状态方程描述气相和液相的相态，根据正规溶液理论校正固相混合物的非理想性；将以状态方程为基础的气—液平衡模型和以溶液理论为基础的液-因平衡模型有机地统一，建立了气下液-固三相相平衡热力学模型。将该气-液-固三相相平衡热力学模型应用于某一油气体系的蜡固相沉积模拟研究，模拟结果表明，在温度、压力改变过程中，出现了气液固三相相态转换；压力对石蜡沉积点温度和石蜡沉积量均有一定程度的影响；压力对蜡沉积点温度的影响在低于饱和压力下更为显。

The Prediction Method for Wax Precipitation

Wax and asphalt solid precipitation in oil and gas recovering process is a problem considering very much at home and abroad in the petroleum industry.The organic solid precipitation happening in the recovering process along with the changes of thermodynamic conditions,such as temperature, pressure and composition,influences the oil and gas production severely.Especially in the process of gas injection for enhancing oil recovery,the wax and asphalt solid precipitation resulting from molecular transferring among phases may change permeability and wet ability in the porous media and influence the improvement of recovering rate and the effect of gas injection.The article uses the state equation to describe the phase behavior of both gas and liquid phases,and the solution theory to correct the non ideality of the solid phase.Then a thermodynamic model of gas liquid solid three phases is developed combining the gas liquid balance model basing on the state equation and the liquid solid balance model basing on the solution theory.The gas liquid solid three phases balance model is used to study the wax solid precipitation for an oil and gas system.The calculation results demonstrate that the state conversion of gas liquid solid three phases happens as temperature and pressure changes.Pressure affects both the wax precipitation temperature and the amount of wax precipitation.The influence of pressure on wax precipitation temperature is much higher when the pressure is lower than the saturation pressure.