考虑地层水的凝析气井注CO_2相态机理评价

EVALUATION ON PHASE - STATE MECHANISM OF GAS CONDENSATE WELL CONSIDERING FORMATION WATER BY CO_2 INJECTION

为评价含水凝析气井注CO2消除近井带反凝析污染的相态机理,基于气液液三相相平衡热力学理论,并结合PR状态方程、HV混合规则和活度系数模型,建立CO2-烃-水相平衡热力学计算模型及评价方法。并对一个实际含水凝析气井注CO2吞吐的相态机理进行评价,研究CO2注入时机对反凝析液饱和度、采收率曲线和CO2注入量对反凝析液饱和度、采收率、露点压力及凝析液储量的影响规律。研究表明:最大反凝析压力之前CO2吞吐效果更好,注入量越多效果越好;不同注入时机,凝析液采收率曲线都会出现中间相交,都会降低反凝析液量和露点压力;相同注入量时,随注入时机的推迟,凝析液储量增加。

In order to evaluate the phase-state mechanism of CO2 Injection to eliminate retrograde condensate pollution of the near borehole zones for gas condensate well considering formation water,based on the three phase equilibrium thermodynamic theory,PR state equation,HV mixed rule and activity coefficient model,the CO2 hydrocarbon-water phase equilibrium thermodynamic calculation model and evaluation method have been established.With the model and method,the phase-state mechanism of CO2 Injection is evaluated for a real gas condensate well considering formation water.The effects of the CO2 injection time on retrograde condensed liquid saturation,recovery curve and the CO2 injection volume on retrograde condensed liquid saturation,recovery,dew point pressure,condensed liquid reserve are studied.Research results show that: the CO2 injection is more effective when it performed before the maximum retrograde condensation pressure;the more the injected volume is,the better the result is;While CO2 are injected in different injection times,the condensed liquid recovery curve will intersect,and the retrograde condensed liquid volume and the dew point pressure will decline;While CO2 are injected with the same volume,the condensed liquid reserve will increase as the injection time is delayed.