致密多孔介质中凝析气定容衰竭实验及相态特征

凝析气藏衰竭开发方案的制定依赖于PVT相态实验，而常规PVT相态实验忽略了多孔介质对凝析气相态的影响，导致实验结果与实际存在偏差。基于常规PVT定容衰竭实验原理，建立了致密多孔介质中凝析气定容衰竭模拟装置及实验方法，模拟研究了凝析气在裂缝性致密储层中的衰竭开发动态，分析了衰竭速度及多孔介质的作用对凝析气藏开发效果的影响，明确了致密多孔介质中凝析气相态特征。研究结果表明，衰竭速度是影响凝析气藏开发的主要原因，天然气采收率随衰竭速度的增快而降低，但凝析油采收率则表现出相反规律；致密多孔介质中凝析气的露点压力比PVT筒中的测量值提高9.42%。此外，裂缝能够有效增大泄油面积，减小渗流阻力，提高天然气和凝析油采收率。

Constant volume depletion experiment and phase characteristics of condensate gas in dense porous media

The development plan of condensate gas reservoir depletion depends on pressure-volume-temperature (PVT)phase behavior experiment, while the conventional PVT phase behavior experiment neglects the influence of porous media on the condensate gas phase behavior, resulting in deviations from the actual results. Based on the principle of constant volume depletion (CVD)experiment under a conventional PVT mode, this paper establishes a device for simulating the constant volume depletion of condensate gas in dense porous media and its experimental method; it also stimulates and studies the dynamic depletion development of condensate gas in fractured tight reservoirs, analyzes the effects of depletion rate and porous media on the condensate gas development, and clarifies the phase characteristics of condensate gas in dense porous media. The results show that the depletion rate is the main reason that affects the development of condensate gas reservoirs. The natural gas recovery factor decreases with the increase of depletion rate, but the condensate recovery factor shows the opposite. The dew point pressure of condensate gas in dense porous media is 9.42% higher than that measured in the PVT cell. In addition, the fracture can effectively increase the drainage area, reduce the seepage resistance, and improve the recovery of natural gas and condensate oil.