页岩凝析气藏反凝析及油气流动特征

Retrograde condensation and hydrocarbon flow characteristics in condensate shale gas reservoirs

乔润伟 张士诚 王金伟 王飞 李凤霞 李宁

Runwei QIAO Shicheng ZHANG Jinwei WANG Fei WANG Fengxia LI Ning LI

四川盆地复兴地区下侏罗统自流井组东岳庙段页岩凝析气藏压裂后开发时出现反凝析现象和严重水锁伤害。为定量研究页岩凝析气藏压裂后开发凝析气反凝析特征及油、气、水三相共存和共渗特征，进行了考虑压裂液滞留的页岩岩心反凝析实验，用氮气作为对照组排除页岩应力敏感性对实验结果的干扰。通过气测渗透率和采出油、气组分测试，评价了岩心反凝析伤害和采出油、气组成变化特征。开展岩心尺度反凝析特征模拟，定性、定量分析岩心内油、气、水三相赋存及渗流特征。研究结果表明：①无压裂液时反凝析伤害使气相有效渗透率下降40 %，有压裂液时反凝析伤害使气相有效渗透率下降30 %。水相优先占据小孔喉，削弱油相占据小孔喉的能力，导致凝析油临界可流动饱和度降低。②反凝析过程中重质组分滞留在岩心中，部分C—C烃类中间质组分因反凝析作用进入油相。随着压降过程再次“溶解”到凝析气中。③岩心内发生反凝析后，凝析油不是无限堆积而是很快突破至临界可流动饱和度。凝析气单相渗流区域较小，油、气共渗区域较大。

Retrograde condensation and severe water block were observed during the post-fracturing exploitation of condensate shale gas reservoirs in the Dongyuemiao Member of the Lower Jurassic Ziliujing Formation in the Fuxing area， Sichuan Basin. To quantitatively investigate the retrograde condensation and the coexistence and flow characteristics of oil， gas， and water during post-fracturing exploitation of these reservoirs， we conduct retrograde condensation experiments on a shale core while considering fracturing fluid retention， with N flooding used as the control group to eliminate the stress-sensitive interference of shale. Based on gas permeability tests and the compositional analyses of produced oil and gas， we assess the retrograde condensation and the compositional variations in the produced oil and gas. Additionally， core-scale numerical simulations of retrograde condensation are conducted to qualitatively and quantitatively analyze the occurrence and flow characteristics of oil， gas， and water in the core. The results indicate that the damage of retrograde condensation decreases the effective gas permeability by 40 % in the absence of fracturing fluids and by 30 % in their presence. The water phase preferentially occupies small pore throats， weakening the oil phase’s ability to occupy these spaces and lowering the critical saturation of gas condensate. During retrograde condensation process， heavy components are retained in the core， while certain intermediate components （C—C） initially enter the oil phase due to retrograde condensation effect and then dissolve into condensate gas again as the pressure drops. After retrograde condensation occurs in the core， gas condensate rapidly reaches its critical saturation rather than accumulating indefinitely. Moreover， the period of post-retrograde condensation is characterized by a small single-phase seepage zone of condensate gas but a large oil-gas co-seepage zone.

10.11743/ogg20250219