This paper develops a well testing model for horizontal wells with continuum and discrete fracture networks. The proposed model has the capability to analyze the pressure behavior by considering complex fracture networks and natural fractures efficiently. The proposed model includes three domains:
matrix,
natural fracture networks, and
discrete hydraulic fracture networks.
The pressure transient solution of these diffusivity equation is obtained by using Laplace transforms and superposition principle. It is found that there are some interesting flow behaviors in shale reservoirs like bilinear flow, "V-shape" caused by fracture supply, pseudo boundary-dominated flow, impact of natural fractures, etc. The pseudo boundary-dominated flow provides us the information about how large the area covered by hydraulic fracture networks. This work provides a throughout understanding of transient pressure behaviors in shale reservoirs and guidelines for the producer optimize field development and well economics
Because of geological activities, high fluid pressure, thermal loading, etc, natural fractures are commonly seen in some shale reservoirs (Kuchuk and Biryukov, 2015). Meanwhile, lots of large-scale hydraulic fracturing treatments are implemented to ensure commercial production rate. Thus, it is very common that shale reservoirs comprise a huge number of natural and hydraulic fractures. However, it is neither practical nor advantageous to use numerical models to analyze the pressure transient behaviors. First, how to address the natural fractures is the primary work to investigate the transient behaviors in those reservoirs.
Huge amount of literatures have reported the pressure transient analysis in naturally fractured reservoirs (Barenblatt et al., 1960; Warren and Root, 1963; Kazimi, 1969; de Swaan, 1976; Teimoori et al., 2003; Dershowitz et al., 2000; Araujo et al., 2004). Unfortunately, the explicitly of natural fractures cannot be reflected clearly. With the gridding approaches (Palagi and Aziz, 1994; Karimi-Fard et al., 2003; Xu et al., 2017), fracture flow, matrix flow, and matrix-fracture flow are comprehensively captured. Although more accurate results can be obtained, the application of gridding approaches is time-consuming, expensive, and site-specific. Therefore, modelling thousands of fractures in numerical DFM is unpractical.
