Abstract:

 The present paper is aim at a deeper study  on  the microseepage flow and the influencing factors of displacement efficiency  of Chang6 reservoir of Triassic Yanchang Formation in the area of Heshui, in the Ordos Basin in order to  provide a scientific basis for increasing the recovery ratio. Take the real sandstone micromodel experiment as the main method in this study, and  combined with  the checkup of slices, SEM, mercury penetration etc.  to study the pore structure, the composition of the rocks. The results show that the waterdrive patterns in the reservoirs of Chang6 in this area are mainly homogeneous seepage and reticular seepage, the finger like seepage is few. The homogeneous seepage gets the highest final oil saturation and final displacement efficiency, the models of reticular seepage are lower, the models of the finger like seepage are the lowest. As to the physical properties, the permeability is the first factor affecting the displacement efficiency, the porosity is the second; the displacement efficiency can be increased effectively by increasing the drive pressure advisably; the displacement efficiency also can be increased by increasing the multiple volume of driving water, finally the  heterogeneity also is one of the affecting factors.

Key words:  Heshui, ultralow permeability, microflow characteristics, oil displacement efficiency, physical property of reservoir, drive pressure, heterogeneity, Ordos Basin