水驱砂岩气藏型地下储气库气水二相渗流机理

Gas-water percolation mechanism in an underground storage built on a water-drive sandstone gas reservoir

水驱砂岩气藏型地下储气库的渗流机理具有特殊性及复杂性,并客观上决定了地下储气库多周期运行的注采效果。为此,针对其储层特征,开展了多轮次气、水互驱物理模拟实验,研究了储气库储层气、水二相渗流特征,分析了储气库储层孔隙空间可利用率的变化规律,并揭示了该类储气库建设及运行的主要影响因素。研究表明:①该类储气库经长期注采运行,水相渗流能力相应增强,导致边水运移越发活跃,储层孔隙空间出现大量残余气、束缚水,气相渗流阻力相应增加,气库扩容及注采效果受到影响;②储气库运行中边水往复运移造成储层空间形成大量死气区,导致储层孔隙空间利用效果变差,库容可利用率降低,储层孔隙空间可利用率介于40%～70%;③该类储气库建设及运行过程中应重视储层含水量的变化,并采取相应措施以降低水侵对储气库运行效果的影响。

The percolation mechanism of an underground gas storage(UGS) built on a water-drive sandstone gas reservoir is unique and complex,which decides the injection-production effect of multi-period operation of the UGS.This paper hereby performs several rounds of gas-water drive physical simulation,studies the characteristics of gas-water percolation mechanism,analyzes the changing rules of the availability of reservoir pore space,and reveals the main influencing factors for the UGS construction and operation.The experiment results show that for the long-term injection-production operation at the UGS,the water percolation ability is relatively enhanced,accordingly the edge water migration becomes increasingly active,a great deal of residual air and irreducible water appears at the reservoir pore space,gas percolating resistance increases relatively,the UGS expansion and injection-production efficiency are both badly affected.In addition,the edge water migration results in large died gas zones,which results in the worse utilization effect of the reservoir pore space,the lower degree of the availability of the UGS space,and the availability degree of reservoir pore space being 40%-70%.Besides,more attention should be paid to the water content of a reservoir during the construction and operation of this type of UGS built on a water-drive sandstone gas reservoir and appropriate measures should be taken to reduce negative effects caused by water invasion on the operation of the UGS.