For traditional dual porosity/permeability model, the fracture system is assumed to remains a steady state which the width, length, density of the fractures in reservoir does not change during the whole production, and it is not possible to simulate fractures variation effect with these models. Hower, the above assumption does not hold in low permeability fractured reservoir where the fracture system will change with the formation pressure.

In order to simulate the unsteady state of fracture system, an improved approach to simulate low-permeability fractured reservoirs is proposed in this paper which a dynamic transitivity tensor model is overlapped to dual porosity model. It is assumed that the fracture network is the primary continuum for fluid flow, and the matrix of high storability is considered to be a sink or source to the fracture. In this approach, the fluid exchange between the matrix and the fracture is expressed by an exchange term, and the variation of fractured system is described by dynamic permeability, which is a function of pressure, stress, density of fractures.

The paper will detail the dynamic hybrid dual-porosity model such as its assumptions, equations, mechanisms and also its applications in the fractured reservoirs simulation. The simulation results show that the dynamic hybrid model has high potential to accurately simulate the dynamic fracture network for low-permeability resevoirs.

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