凝析气藏压力衰竭过程中凝析油微观赋存形态

为了研究凝析气藏开发过程中凝析油的形成机理和微观赋存状态，开展碎屑岩储层多孔介质和碳酸盐岩储层缝洞介质凝析气藏压力衰竭实验，对不同压力衰竭阶段的储层岩心进行微米CT扫描，并对CT扫描图像中的油/气/岩石骨架进行识别和分割，得到油、气在孔隙和缝洞中的三维空间分布状态，通过图像处理和计算结果分析，对凝析气藏不同储层不同开发阶段凝析油赋存形态和位置进行表征。研究表明:在碎屑岩储层多孔介质内，衰竭过程中形成的凝析油主要以单孔状态和油膜状态赋存(占比超过90%)，多孔状油占比很少，没有网络状油，整体来说，油相高度分散在孔隙和喉道中；而在碳酸盐岩储层缝洞介质内，压力衰竭过程中形成的凝析油主要以网络状和多孔状赋存(占比超过85%)，油相分布相对集中，网络状和多孔状凝析油通过油膜连接，压力衰竭过程主要是油相由多孔状、单孔状和油膜状向网络状转变的过程；在压力衰竭过程中，随着凝析油增多，油相会向岩石壁面靠近，当凝析油开始产出，油相会远离岩石壁面，随着油相的产出，油相减少，凝析油在表面张力的作用下向岩石壁面靠近。本研究为凝析气藏开发方案制定和提高凝析气藏采收率提供了理论支撑。

Study on the microscopic occurrence forms of condensate oil in the pressure depletion process of condensate gas reservoirs

In order to research the formation mechanisms and microscopic occurrence states of condensate oil in the development process of condensate gas reservoirs, an experimental study was carried out on the pressure depletion of the condensate gas reservoir in the porous media of clastic reservoir and in the fractured-vuggy media of carbonate reservoir. Micrometer CT scanning was performed on the reservoir cores in different stages of pressure depletion. The oil/gas/rock skeleton in the CT scanning images were identified and divided to determine the distribution state of oil and gas in pores, fractures and vugs in the three-dimensional space. In addition, the occurrence forms and locations of condensate oil in different reservoirs of condensate gas reservoirs in different development stages were characterized by means of image processing and calculation result analysis. It is indicated that the condensate oil formed in the porous media of clastic reservoir during pressure depletion is existed mainly in the form of single pore and oil film (over 90%), the proportion of the condensate oil in the form of multiple pore is quite low and there is no network-form condensate oil. On the whole, oil phase is mainly dispersed in pores and throats. The condensate oil formed in the fractured-vuggy media of carbonate reservoir during pressure depletion is mainly existed in the form of network and multiple pore (over 85%). The distribution of oil phase is relatively concentrated. The condensate oil in the form of network and multiple pore is connected through oil film. The pressure depletion process is the transformation process of oil phase from multiple pore, single pore and oil film to network. In the process of pressure depletion, oil phase will approach the rock wall as the condensate oil increases. When the condensate oil is produced, the oil phase will move away from the rock wall. With the production of oil phase, oil phase reduces and condensate oil approaches the rock wall under the action of surface tension. This study provides the theoretical support for the formulation of condensate gas reservoir development scheme and the improvement of the recovery factor of condensate gas reservoir.