Abstract:

The oil recovery rate has great impact on the development effects of the water drive reservoir in the period of extra-high water cut. During this period, the water saturation is further increased. The reservoir is subjected to the flooding, scour and erosion of the long-term water injection. Along the main line of the injection and mining, and under the long-term effect of the large pressure gradient, the loose particles of the reservoir will gradually peel off and move with the oil and water flow to the well. The pore structure of the reservoir is well remodeled in the wellbore near the well area. All these lead to the profound change of the microscopic pore structure of the reservoir. What's more serious is that a secondary dominant channel will form, which causes the abrupt change of the characteristics of the oil and water seepage. So there arises a non-linear characteristic of the oil-water infiltration ratio curve. Based on this feature, we established the relation between the oil recovery rate, and the reservoir characteristics, water cut, water saturation and the water cut increasing rate by using the water diversion equation to show the inner links between the oil recovery rate and the factors above. We also analyzed the influence of the various factors on the oil recovery rate. Compared with the previous methods, this new method has obvious advantages in the application of the reservoirs with the high water cut.

Key words: extra-high water cut period, production oil rate, water cut, increasing rate of water cut, relative permeability curve