凝析气藏型地下储气库多周期运行盘库方法

地下储气库多周期运行盘库过程，是对气库库存量、库容量、工作气量以及气垫气量的全过程实施跟踪的过程，是研究气库运行规律、漏失分析以及进一步提高气库运行效率、降低运行成本的关键环节。为此，针对凝析气藏型地下储气库库内凝析气与注入干气混气的特点，从库存量的定义入手，利用摩尔体积权衡混合流体密度计算方法和气体状态方程，提出了定容和弱边底水凝析气藏型地下储气库多周期运行系列盘库计算的数学模型。所建立的盘库计算模型（库存量计算模型、注气末气体孔隙体积和库容量计算模型、采气末气垫气量计算模型、采气阶段工作气量计算模型）通过实例验证有两个显著特点：一是充分考虑了库内混合流体性质改变的影响；二是以注气过程分析含气孔隙体积和库容量变化，同时将该过程求得的含气孔隙体积作为下一采气过程分析气垫气量和工作量的主要依据，依次交替计算从而使盘库系列数据的规律性和可靠性大大增强。应用实表明该数学模型具有较高的准确性。

The multi-cycle working inventory methods of underground gas storages based on condensate gas reservoirs

Making inventory is a process which tracks down inventory, storage capacity, working gas volume and cushion gas volume in multi cycle operation of underground gas storage （UGS）. This process is a key step to study the UGS operation rule, analyze the gas loss, improve the operating efficiency, and reduce the cost. According to the character of condensate gas and the injected dry gas inside the UGS based on condensate gas reservoirs, the paper puts forward a mathematical model of multi cycle working inventory for constant volume and weak water bearing condensate gas reservoir by the mixed fluid density calculation method with molar volume balance and the gas equation of state. The established calculation models for making inventory, including the inventory calculation model, the calculation model for gas pore volume at the end of gas injection and storage capacity, the calculation model for cushion gas volume at the end of gas withdrawal, the calculation model for the working gas volume at the gas withdrawal stage, presented two distinct features by actual examples. First, the effect of the changing property of the mixed fluids is fully taken into account. Second, the change of gas pore volume and storage capacity is analyzed in the process of gas injection. Meanwhile, the calculated gas pore volume is regarded as the main basis for the analysis of the cushion gas volume and working gas volume in the gas withdrawal process. Therefore, the alternate calculations will help improve the regularity and reliability of a series of inventory making data. This mathematical model has been proved to be of relatively high accuracy by many examples.