Synchronous vertical fracture propagation of multi-layer radial wells for enhancing stimulated height in shale oil reservoir

The diversity of interlayers in shale oil reservoir leads to a low degree of vertical reconstruction. This paper aims to propose a method to guide the synchronous initiation of hydraulic fractures in different layers by drilling multi-layer radial wells in spatial positions, and to form a fracture network that satisfies the vertical propagation range and complexity. In this paper, a 3D (three-dimensional) multi-layer radial well fracturing model considering fluid-mechanics coupling is established and the properties of shale oil reservoir are characterized according to the field geological profile. The influences of radial well spacing, fracturing fluid injection rate, and fracturing fluid viscosity on vertical fracture communication in multi-layer radial wells are investigated. The results show that the radial well has the characteristics of guiding fracture penetrating interlayers. Reducing radial well spacing and appropriately increasing injection rate and viscosity are beneficial to improving vertical fracture propagation ability. However, high fracture fluid viscosity under the same displacement will lead to a significant increase in fracture aperture and weaken the total fracture area. In addition, if the stress interference around the radial wells is low, the radial well can be located in the middle of each layer to minimize the fracture height limitation. This study can provide a solution idea for vertical propagation limitation of hydraulic fractures in shale oil reservoir.