A hybrid semi-analytical model for production from heterogeneous tight oil reservoirs with fractured horizontal well

Abstract

Fracture networks induced by hydraulic fracturing are highways for fluid flow into the horizontal wellbore in tight formations. Pressure and rate transient responses of fractured horizontal wells in a heterogeneous reservoir are commonly simulated with numerical models by fined grids around the fractures. An alternative to full-scale numerical simulation in heterogeneous formations has been the use of semi-analytical methods for relatively simple forms of heterogeneity, such as composite and compartmental reservoirs. However, flow within the fracture networks is not considered in current semi-analytical models. This paper presents an efficient hybrid method for modeling fluid flow in fractured heterogeneous reservoirs. In this approach, the reservoir is divided into locally homogenous blocks where bounded Green-function solution is employed and coupled at the boundaries between adjacent substructures of reservoir. Green-function solution is employed and coupled at the boundaries between adjacent substructures of reservoir. Locally dual porosity models are implemented to characterize the heterogeneity of small-scale natural fractures, and large-scale fractures are represented explicitly by discrete fracture models. The flow within fracture networks is solved via the finite element method. With a simple direct discretization of the fractures and boundaries, the proposed hybrid model is shown to accurately capture the flow behavior with high computational efficiency. The validation of the approach is demonstrated in comparison to numerical solutions in heterogeneous reservoirs. On the basis of the model, detailed analysis of the flow behavior of a fractured horizontal production well in heterogeneous reservoir are provided. Finally, a field case is investigated to highlight the applicability and computational convenience of the proposed method.