Abstract: Offshore oil fields usually adopt a large-interval commingled production strategy. Interlayer interference is relatively serious. To evaluate this phenomenon correctly, based on the theory of seepage mechanics, an interlayer interference evaluation numerical model considering the number of layers, thickness, permeability, porosity, viscosity, formation pressure, supply radius, and so on, was established. The model considered four aspects of the interlayer interference mechanism, including the interlayer heterogeneity, initial pressure gradient, wellbore connectivity, and liquid transfer. Based on the mathematical model, the productivity of each layer and the entire well during commingled production, the productivity of each layer and the entire well during separate production, and the interlayer interference coefficient were calculated. The productivity under the conditions of commingled and separate production was analyzed. The results show that the contributions of the permeability difference ratio, test operation procedures, water saturation stage, hydrostatic pressure, and other parameters to the interlayer interference were 50%, 25%, 15%, and 10%, respectively. Interlayer interference is mainly controlled by interlayer heterogeneity. During the commingling of multiple layers, if the permeability ratio is less than 4, the interlayer interference coefficient can be guaranteed to be less than 0.6. If the permeability ratio is less than 10, the interference coefficient can be guaranteed to be less than 0.6.

Key words: multi-layer reservoir, commingled production, separate production, interlayer interference, mathematical simulation