| Abstrakt: |
Unconventional oil and gas reservoirs are characterised by low porosity, low permeability and low natural deliverability. At present, horizontal wells staged fracturing is an effective development method. However, in the case of staged hydraulic fracturing in horizontal wells, stress interference occurs between multiple fractures, leading to fracture deformation and even inhibiting the formation of fractures, thereby affecting reservoir production. In this paper, based on the extended finite element method (XFEM), considering the fluid flow in the fracture and fracturing fluid filtration, we analyse the effects of fracturing fluid pumping rate, fracture spacing and elastic modulus on horizontal in-situ stress, fracture parameters and fracture extension pattern during different fracturing initiation processes. The results show that the induced stress generated by the action of fracturing fluid changes the direction of horizontal in-situ stress in the elliptical region around the fracture. In the mode of simultaneous fracture initiation (TFIS), the extension of two symmetrical fractures is "repulsive"; in the mode of two fractures initiated at different times (TFIDT), the extension direction is "mutual attraction". A large pumping rate and small elastic modulus are conducive to fracture propagation. In the TFIS mode, two fractures alternately expand, while in the TFIDT mode, the impact of rock mechanical properties and construction parameters on fracture propagation will be amplified. The extension of subsequent fractures will be restrained, especially when the fracture spacing is less than 10 m. The width of the previously created fracture will be severely affected, even causing a partial closure and becoming elongated fractures. [ABSTRACT FROM AUTHOR] |
