致密砂岩气藏含气饱和度影响因素分析

摘要

The article analyses the overburden pressure impact on rock porosity and permeability by measuring permeability changes of different grain size samples under different overburden pressure, the gas saturation of tight sandstone reservoir by measuring gas saturation of different grain size samples under critical injection pressure, the relationship between porosity and gas saturation in tight sandstone reservoir by measuring Kuqa foreland basin of deep tight sandstone core porosity and permeability parameters. Experiments show that there is a positive correlation between the reservoir permeability and rock grain size, that is, the smaller rock grain size, the lower reservoir permeability, and there is a negative correlation between overburden pressure and reservoir permeability, that is, the greater overburden pressure, the smaller reservoir permeability (but the overburden pressure has little effect on reservoir permeability, when it increases to a certain extent), and there is a negative correlation between reservoir gas saturation and reservoir grain size and permeability, that is, the smaller the grain size and lower reservoir permeability, the higher gas saturation. And according to the results of physical simulation, we propose two conceptions which are permeability class change and permeability differential of tight sandstone. Lastly, it concludes that reservoir inhomogeneity and reservoir permeability differential of tight sandstone reservoir are the main controlling factors on reservoir gas saturation, that is, the better reservoir homogeneity, the higher reservoir gas saturation, and the smaller permeability differential, the higher reservoir gas saturation.%对库车前陆盆地深层致密砂岩岩芯孔渗参数测定,分析致密砂岩储层孔渗性与含气饱和度的关系,结果表明:储层渗透率与岩石颗粒粒级存在正相关性,即粒级越小,渗透率越低；储层渗透率与上覆压力存在负相关性,即上覆压力越大,渗透率越小,但上覆压力增大到一定程度后,对渗透率的影响很小；储层合气饱和度与岩石颗粒粒级、储层渗透率之间存在负相关性,即粒级越小、渗透率越低,含气饱和度越高.根据物理模拟实验的结果,初步提出了致密砂岩的渗透率级变和渗透率级变系数的概念.综合分析认为,致密砂岩的非均质性和渗透率级变系数是决定其成藏规模与含气饱和度的主要控制因素,均质性较好的致密砂岩,含气饱和度较高,且局部孔隙度和渗透率相对较好的砂体更容易富集成藏；渗透率级变系数越小含气饱和度会越高,渗透率级变系数越大含气饱和度会越低.