变形介质凝析气藏油气相态特征研究

RESEARCH ON OIL/GAS PHASE BEHAVIOR OF DEFORMABLE MEDIUM CONDENSATE GAS RESERVOIRS

变形介质凝析气藏因储层岩石颗粒细、孔隙小,储层界面效应极为突出。同时,降压开采过程中储层变形作用明显,因而其相态特征不同于常规凝析气藏。考虑吸附、毛细凝聚和毛细管力等界面效应和储层变形作用对油气体系相态特征的影响,建立了变形介质凝析气藏油气体系真实露点预测模型和衰竭开采过程中气藏的反凝析液饱和度预测模型。将该模型用于Q69井的露点和反凝析油饱和度的预测,其计算结果表明孔隙介质界面现象和储层变形作用不仅会导致气藏的露点升高,而且会加剧地层反凝析作用。考虑孔隙介质界面效应和储层变形作用影响后,地层反凝析油饱和度比常规模拟方法的预测结果更大,并且储层渗透率越低、变形作用越大,地层反凝析油饱和度增加就越显著。因此,与常规凝析气藏相比,变形介质凝析气藏在衰竭开采过程中反凝析现象将提前,反凝析污染也将更加严重。

Due to fine grain and small pores of reservoir rock of deformable medium condensate gas reserve, interface effect is obvious. Meanwhile, reservoir deformation during pressure drop period of production is so evident that the phase behavior differs from conventional condensate gas reservoir. The paper establishes true dew point prediction model for deformable medium condensate reservoir system and anti-condensate saturation prediction model for gas reservoir during production decline by considering interface effects such as absorption, capillary coacervation and capillary force as well as reservoir deformation. The application of the models in the Well Q69 predicting the dew point and anti-condensate oil saturation has indicated that interface effects and reservoir deformation will surely lead to dew point increase of gas reservoir and intensify formation anti-condensation effect, thus predicted formation anti-condensate saturation is larger than the predicted value by conventional modeling. Also, it shows the tendency that the lower the reservoir permeability, the greater the deformation effect and the more obvious the increase of anti-condensation saturation. Compared with conventional gas reservoirs, it is concluded that as for deformable medium condensate gas reservoirs, anti-condensation phenomena appears much earlier during production depletion process and anti-condensation contamination is relatively severer.