砂岩渗透率实验与动态网络模拟研究——以枫丹白露砂岩为例

Permeability experiment and dynamic network simulation of sandstones:a case study of the Fontainebleau sandstone

用氮气和盐水,在室温条件下开展了28块不含黏土的枫丹白露砂岩样品实验测试,并将氮气和盐水测得的渗透率结果进行了对比.实验结果表明,克式校后,氮气所测得的渗透率值大于液体所测得的渗透率值,其中液体渗透率值是克式校正后的氮气渗透率值的0.5976倍.通过驱替实验后的SEM图片发现,造成这个现象的原因是,当用盐水为测量流体介质时,盐水与枫丹白露砂岩内部表面形成液膜且驱替过程中产生的次生颗粒堵塞岩石内部孔喉的共同作用减小了有效流动路径.最后,采用孔隙尺度网络模型用以模拟枫丹白露砂岩样品的渗透率值,并将其与N_(2)的渗透率测量结果进行了比较.从模拟结果可以看出,克式校正后的气体渗透率更能准确表征枫丹白露砂岩的固有属性参数,更能准确评价实际开发过程中的油气开采难易程度与开采效果.

In this study,the impact of testing fluid on permeability was investigated using perm-plug method under room condition.28 pieces of clay-free core samples from Fontainebleau sandstones were employed in this experimental study in order to remove the impacts of clay swelling and clay/fluid interaction on the results.The Klinkenberg-corrected permeability results measured by N_(2)and brine were compared.The results showed that the N_(2)permeability values are larger than those measured by brine,where the liquid permeability are 0.5976 times of the Klinkenberg-corrected N_(2)permeability values.The primary reason can be interpreted to be the formation of water films on the pore surface caused by the fluid adhering to the matrix of Fontainebleau sandstones,which efficiently reduces the effective pore width for brine.In this work,we simulated the permeability values of Fontainebleau core samples using pore-scale network model for brine and compared the results with those measured by N_(2).The results indicated that the Klinkenberg-corrected N_(2)permeability values are more representative compared to the vales of liquid permeability,in terms of assessing the extent of difficulty and effectiveness of oil and gas production.