Abstract
In this study, a large number of fracture systems with various types and morphologies are described by the discrete element method. Further, using the point source function theory and the dual-system matrix superposition method, a semi-analytical seepage model of the reservoir surrounding the volume-fractured vertical well in the Laplace space is established. The proposed model is tested based on the oilfield well testing data. Accordingly, the discrete elements are used to calculate the flow rate and the characteristic curve, the fluid flow stages in the reservoir around the volume-fractured vertical well are identified. The sensitivity analysis of the fracture morphology coefficient reflects the influence of different types of fracture morphology and distribution characteristics on the fluid flow stages in the reservoir. The results show that in the seven flow stages, multiple linear flow patterns appear continuously. The four fracture morphology coefficients reflect the existence or duration of different linear flow stages. Among them, the increase of number Ns and Vd will make the characteristics of natural fracture linear flow and linear flow stage of connected fractures more obvious, respectively. The increase of number Nd will significantly prolong the duration of the natural fracture bilinear flow stage while significantly shortening the duration of the formation linear flow stage. The increase of number Ma will shorten the multi-linear flow stage. Overall, this work provides useful insights on improving the volume-fractured reservoir production and describing the reservoir fracture morphology.
•In this paper, the coupling method of discrete units and dual systems is used to describe a large number of fracture networks with complex morphology.•In the paper, due to the existence of different types of fracture units in the calculation model, the fluid flow process in the reservoir is clearer. This can assist in identifying the flow stages.•In this paper, the calculation model can provide new methods in predicting the effect of fracturing and restoring the real fracture morphology in the reservoir.