CO_2作垫层气时储气库敏感性参数分析

The Impact of Reservoir Properties and Operating Conditions on Mixing of CO_2 Cushion and Natural Gas in Storage Reservoirs

天然气地下储气库在能源结构调整及天然气的调峰中起着决定性的作用。用CO_2作储气库垫层气既可实现碳的地质埋存,又可提高天然气采收率,节约资金。在储气库注采运行过程中,储气库储层压力、流体饱和度等会发生周期性变化,流体渗流能力不断变化,作垫层气的CO_2气体与天然气的混气问题将不可避免。为指导储气库最优运行控制,必须研究垫层气与天然气混气现象的生成与发展,分析其主要影响参数及影响方式。采用数值模拟方法建立储气库机理模型,对垫层气注入方式、注入比例、储层渗透率等主要因素对垫层气与天然气的影响进行分析。结果表明,垫层气注入量、混气压力、注采速度等因素对混气有着明显的影响。研究结果对于储气库的最优运行控制,避免过度混气,影响采出气质量具有指导意义。

Natural gas is a kind of national strategic resource, so underground gas storage is significant for the guarantee of national economic development and national energy security. Using CO 2 as cushion gas of gas storage is beneficial to CO 2 geological sequestration, enhance natural gas recovery and conserve resources. But the mixture of CO 2 and natural gas is inevitable. In this study, the inert gas mixing problem is investigated in storage reservoirs by using a reservoir simulator based on the equation of state. The degree of mixing between the two dissimilar gases was found by the amount of inert cushion that is produced along with the withdrawn gas. Reservoir parameters like the volume of inert, porosity, permeability, pressure and temperature were varied to study their effect on mixing. This paper studies the sensitivity of the mixing between CO 2 and natural gas by numerical simulation, finds out the main factors influencing the mixing, proves the great influence of dynamic injection-production on mixing. It s shown that it s better to inject cushion gas from the side of reservoirs.