低渗透岩性气藏局部建设储气库库容量的确定

Keywords Determination of underground gas storage capacity for local low-permeability lithological gas reservoirs

库容量是地下储气库工作气量设计的前提和基础,根据国家能源战略需求,计划在鄂尔多斯盆地榆林气田南区下二叠统山西组山2段气藏建设地下储气库。该气藏的北部与榆林气田长北合作区储层连通,榆林气田南区山2段储层则为大面积分布砂体的一部分,在此建设储气库面临两个难点:①低渗透岩性气藏动态储量如何准确评价;②榆林气田南区局部建库,为防止气体外溢到长北区,如何在边界处设置缓冲区,从而确保南区储气库的可用库容量。为此,首先在获取准确的动态资料基础上,利用压降法、物质平衡法和产量不稳定分析法等综合评价了南区的动态储量,然后通过气藏工程方法、数值模拟方法以及现场动态监测试验研究了压力传播速度,明确了缓冲区距离及库区范围,最终确定了榆林南区储气库库容量:一年一周期建设储气库容量×1,两年一周期建设储气库容量×2,三年一周期建设储气库容量×3。

The storage capacity is the foundation and prerequisite for the design of working gas capacity of an underground gas storage(UGS).According to the demand of national energy strategy,the UGS will be constructed at the Shan 23 reservoir of the southern Yulin Gas Field,the northern part of which is connected to the Changbei Block.Because this reservoir is a part of blanket sand body,there are two difficulties to construct the UGS at this site.One is how to evaluate the dynamic reserves of low-permeability lithological gas reservoir accurately.The other is how to set the buffer area at the boundary to prevent the gas from escaping to the Changbei Block,so as to guarantee the available storage capacity of the southern UGS.For this purpose,based on the accurate dynamic data,dynamic reserves at the southern Yulin are evaluated comprehensively by using the P/Z method,the material balance method,and the rate-transient analysis method,etc.After that,the propagation velocity of pressure is studied by using the gas reservoir engineering,numerical simulation and field monitoring.Furthermore,the range of buffer zone and underground gas storage are clarified and the gas storage capacity of the southern Yulin Gas Field is determined.All the above provide foundations for the design of UGS projects.