Perforated fracturing is an effective way to stimulate production of deep tight reservoir. However, some problems, high fracture pressure, complex fracture geometry, and premature screen-out, arise during perforated fracturing operation, because of deep tight reservoir characteristics, such as deep burial, high density and so on. Whereas, effective design of perforation parameters is supposed to reduce fracture pressure and fracture complexity. In order to design perforation parameters for high effective fracturing, the effect of different perforation parameters (shot density, shot length, and shot diameter) on fracture initiation and propagation in the horizontal well has been studied based on lots of true tri-axial laboratory experiments. The experimental results reveal that: two types of fracture geometries are observed in perforated horizontal well under different perforation parameters. A single flat fracture is created in more initiated perforations with good connection, whereas, spiral-shape fracture is made by big shot diameter or high shot density. Furthermore, there is no change in fracture geometry due to the change of shot length. Ultimately, big shot diameter and high shot density should be designed to improve the effect of perforated fracturing, resulting in low burst pressure and simple fracture geometry near wellbore in deep tight reservoir.
Perforated fracturing was used frequently to stimulate deep tight formation in recent year, because of their specific rock properties (Hou et al., 2017). Non-planar propagation of fracture caused some problems during perforated fracturing operation, such as high treatment pressure, high friction near wellbore, and premature screen-out. One of the mechanism causing above issues was the existence of perforation, which caused new stress distribution near wellbore.
Daneshy (1973) claimed that the existence of perforation affected fracture morphology and fracture pressure for the first time. Behrman and Elbel (1991) determined that different fracture pressure was created based on perforation orientation. Van de Ketterrij and de Pater (1997) indicated that perforation phase of 90° resulted in poor connection among induced fractures. Moreover, small perforation spacing facilitated that connection. Fallahzadeh et al. (2010) demonstrated that perforation orientation had an impact on fracture initiation pressure in a deviated borehole.
