凝析气藏注气过程中露点压力变化特征研究

在凝析气藏循环注气和注气吞吐解除近井带反凝析堵塞的注气过程中,凝析气流体的露点压力变化较大,而在目前的凝析气藏开发过程中,对凝析气露点压力变化考虑较少.作者利用Nemeth.L.K和Kennedy.H.T.的露点压力计算经验公式,研究了向凝析气中注入N2、甲烷、CO2和丙烷等介质的过程中露点压力变化规律,并分析了衰竭式开发和注气过程中凝析气井近井带露点压力变化特征.结果表明,注甲烷使露点压力有较小幅度的减小;注入CO2和丙烷均可使凝析气露点压力有较大幅度降低;而注入N2将使露点压力升高.在凝析气藏衰竭式开发过程中,当近井带压力下降至露点压力以下时,距井筒越近,凝析气中重质组分含量越低,露点压力也越低.在注气吞吐的焖井阶段,反蒸发作用会引起凝析气中重质组分增加,露点压力将升高.

CHANGING OF DEWPOINT PRESSURE FOR CONDENSATE GAS IN GAS INJECTION

Dewpoint pressure of condensate gas changes greatly during gas cycling and huff ＂n＂ puff,which is not often considered in the development of gas condensate reservoirs.Using empirical model of Nemeth.L.K and Kennedy.H.T,this research is conducted to investigate the effects of injecting different media,including methane,CO2,propane and N2 on the gas condensate dewpoint pressure.The changing characteristic of dewpoint is studied during depletion and different gases injection.The injected methane could reduce the dewpoint pressure of condensate gas slightly,while CO2 or propane can decreases it obviously,otherwise the dewpoint increase during N2 injection.When reservoir pressure is lower than dewpoint,the composition of heavier components increase during the gas flows towards near-wellbore-zone.During gas huff ＂n＂ puff process the condensate gas dewpoint increases due to heavy components increases with condensate evaporation in the soak stage.