Study on the Distribution Characteristics of Remaining Oil of Typical Fault Block Reservoir in Ordos Basin

Oilfield development is significantly hampered by a complex geological characteristics, a difficulty of recovering a residual oil, and a high recovery costs. The geological elements as well as microscopic residual oil distribution of Chang 9 block in this region were systematically investigated in this paper using a combination of environmental scanning electron microscope, mercury indentation experiment, NMR analysis and testing methods. The experimental data demonstrated that target oil-bearing formation consists primarily of dark gray, gray-green, gray medium grain arkosic sandstone, and fine grain debris arkosic sandstone. A formation porosity of 3∼14% and a rock permeability parameters of 0.1∼1 mD indicated a typical tight formation. A quality proportion of the working solution in rock cores of different reservoir types after water flooding was studied by the nuclear magnetic resonance experiment of the core flooding oil. Class Ⅰ reservoirs had a uniform and reticular displacements. The class Ⅱ reservoir had dendritic displacement, and the Class Ⅲ reservoir had serpentine displacement. Especially, Class Ⅱ reservoirs had micro residual oil primarily concentrated in corners with small distribution ranges, whereas type 3 reservoirs had micro residual oil concentrated in areas with sharp pore throat changes.