关键词: 二类油层, 注采类型, 聚合物驱, 非均质, 调整时机

Abstract:

Compared with main layers in Daqing oilfield, the class II oil layer is characterized by severe interlayer heterogeneity that makes features of its polymer injection and oil production combination quite different from the main layer. Commingled injection in the class II oil layer can not well solve the problem of interlayer production because thin and poor layers could be hardly recovered and water fingering in thick layers occurs frequently, so the effect of polymer flooding is still not highly satisfactory. It is important to define the optimal adjustment moment of polymer flooding for different injection-production types of the class II oil layer in Daqing oilfield. There are four types of the injection-production combination for the class II oil layer in Daqing oilfield, i.e. thick-layer injection with thick-layer production, thick-layer injection with thin-layer production, thin-layer injection with thin-layer production, and thin-layer injection with thick-layer production. Through isobaric polymer flooding experiments on parallel models of the four types, we obtained the optimal adjustment moment for these four different types, namely the polymer volume at the optimal adjustment moment is 740 PV·mg/L, 780 PV·mg/L, 810 PV·mg/L and 860 PV·mg/L respectively. Ceasing polymer injection at the optimal moment for each injection-production well type could make the oil increment per ton polymer maximum and reservoir recovery the most effective. Therefore, ceasing polymer injection at the optimal adjustment moment and taking further measures in time to enhance oil recovery can make the injection amount of each well type efficient and economical. By comparing displacement effects between the thick-layer injection with thin-layer production and the thin-layer injection with thick-layer production, we concluded that the pattern of injection in a high-permeable zone and production in a low-permeable zone was the most favorable and effective way of the horizontal heterogeneous reservoir development.

Key words: class II oil layer, injection-production type, polymer flooding, heterogeneity, adjustment moment