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裂缝性凝析气藏油气渗流机理与常规凝析气藏不同，在循环注气开发过程中将表现出不同的开采特征，因而如何准确地描述裂缝性凝析气藏循环注气过程中 “裂缝—岩块”质量交换机理和岩块中的驱替效率，对于高效开发裂缝性凝析气藏具有一定的指导意义。文章利用多相多组分渗流理论，首次建立了考虑裂缝油气毛管力影响的裂缝性凝析气藏循环注气数学模型，利用该模型研究了裂缝性凝析气藏循环注气特征。结果表明，在利用气体驱替凝析油的过程中，毛管力表现出阻力作用；裂缝性凝析气藏循环注气开发时，凝析油采收率随注采比增加呈现先增后降的变化趋势，这与常规凝析气藏循环注气开发凝析油采收率变化趋势相异；采用较低的注采比更有利于提高裂缝性凝析气藏开发效果。

RESEARCH AND APPLICATION OF MATHEMATICAL MODEL FOR FRACTURED CONDENSATE RESERVOIRS TO INJECT GAS CYCLICALLY 1)

Oil/gas percolation mechanism of fractured condensate reservoirs is different from that of conventional condensate reservoirs, which will result in different production performance in the process of cycle gas injection. Therefore, it has the guiding significance for efficiently developing fractured condensate reservoirs how to exactly describe the mass exchange mechanism between fractures and rock blocks and the displacement efficiency in the rock blocks. Based on the percolation theory of multi-phase and multi-components, considering the influence of capillary pressure, the mathematical model is first established for fractured condensate reservoirs to inject gas cyclically. With the model, the characteristics of cycle gas injection are studied for fractured condensate reservoirs. The results show the capillary pressure produces resistance effect when condensate oil is driven by gas. When developing fractured condensate reservoirs by cycle gas injection, the recovery factor of condensate oil increases first, then decreases as the ratio of injection and production increases, which is different from that of conventional condensate reservoirs. It is more favor to improve the development benefit of fractured condensate reservoirs using lower injection-production ratio. (Financed by the National Science Fund Project, No. 90210018)