A numerical approach for pressure transient analysis of a vertical well with complex fractures

• DOI: 10.1007/s10409-016-0568-0
• Publication Date: 2016-05-25T12:22:12Z
• Authors: Yizhao Wan; Yuewu Liu; Wenchao Liu; Guofeng Han; Congcong Niu
• Keywords: Complex fracture; Wedge (geometry); Matrix (chemical analysis); Transient (computer programming)

A new well test model for a vertical fractured well is developed based on a discrete-fracture model in which the fractures are discretized as one dimensional (1-D) entities. The model overcomes the weakness of complex meshing, a large number of grids, and instability in conventional stripe-fracture models. Then, the discrete-fracture model is implemented using a hybrid element finite-element method. Triangular elements are used for matrix and line elements for the fractures. The finite element formulation is validated by comparing with the semi-analytical solution of a single vertical fractured well. The accuracy of the approach is shown through several examples with different fracture apertures, fracture conductivity, and fracture amount. Results from the discrete-fracture model agree reasonably well with the stripe-fracture model and the analytic solutions. The advantages of the discrete-fracture model are presented in mesh generation, computational improvement, and abilities to handle complex fractures like wedge-shaped fractures and fractures with branches. Analytical results show that the number of grids in the discrete-fracture model is 10 % less than stripe-fracture model, and computational efficiency increases by about 50 %. The more fractures there are, the more the computational efficiency increases.